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Siddiq S, Murray V, Tyagi N, Borman P, Gui C, Crane C, Wu C, Otazo R. MR signature matching (MRSIGMA) implementation for true real-time free-breathing volumetric imaging with sub-200 ms latency on an MR-Linac. Magn Reson Med 2024; 92:1162-1176. [PMID: 38576131 PMCID: PMC11209806 DOI: 10.1002/mrm.30097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 02/20/2024] [Accepted: 03/14/2024] [Indexed: 04/06/2024]
Abstract
PURPOSE Develop a true real-time implementation of MR signature matching (MRSIGMA) for free-breathing 3D MRI with sub-200 ms latency on the Elekta Unity 1.5T MR-Linac. METHODS MRSIGMA was implemented on an external computer with a network connection to the MR-Linac. Stack-of-stars with partial kz sampling was used to accelerate data acquisition and ReconSocket was employed for simultaneous data transmission. Movienet network computed the 4D MRI motion dictionary and correlation analysis was used for signature matching. A programmable 4D MRI phantom was utilized to evaluate MRSIGMA with respect to a ground-truth translational motion reference. In vivo validation was performed on patients with pancreatic cancer, where 15 patients were employed to train Movienet and 7 patients to test the real-time implementation of MRSIGMA. Dice coefficients between real-time MRSIGMA and a retrospectively computed 4D reference were used to evaluate motion tracking performance. RESULTS Motion dictionary was computed in under 5 s. Signature acquisition and matching presented 173 ms latency on the phantom and 193 ms on patients. MRSIGMA presented a mean error of 1.3-1.6 mm for all phantom experiments, which was below the 2 mm acquisition resolution along the motion direction. The Dice coefficient over time between MRSIGMA and reference contours was 0.88 ± 0.02 (GTV), 0.87 ± 0.02(duodenum-stomach), and 0.78 ± 0.02(small bowel), demonstrating high motion tracking performance for both tumor and organs at risk. CONCLUSION The real-time implementation of MRSIGMA enabled true real-time free-breathing 3D MRI with sub-200 ms imaging latency on a clinical MR-Linac system, which can be used for treatment monitoring, adaptive radiotherapy and dose accumulation mapping in tumors affected by respiratory motion.
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Affiliation(s)
- Saad Siddiq
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Victor Murray
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Neelam Tyagi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Pim Borman
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Chengcheng Gui
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Christopher Crane
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Can Wu
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Ricardo Otazo
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
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Oliver PAK, Yip E, Tari SY, Wachowicz K, Reynolds M, Burke B, Warkentin B, Fallone BG. Skin dose investigations on a 0.5 T parallel rotating biplanar linac-MR using Monte Carlo simulations and measurements. Med Phys 2024. [PMID: 38873942 DOI: 10.1002/mp.17246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 05/06/2024] [Accepted: 05/30/2024] [Indexed: 06/15/2024] Open
Abstract
BACKGROUND The Alberta rotating biplanar linac-MR has a 0.5 T magnetic field parallel to the beamline. When developing a new linac-MR system, interactions of charged particles with the magnetic field necessitate careful consideration of skin dose and tissue interface effects. PURPOSE To investigate the effect of the magnetic field on skin dose using measurements and Monte Carlo (MC) simulations. METHODS We develop an MC model of our linac-MR, which we validate by comparison with ion chamber measurements in a water tank. Additionally, MC simulation results are compared with radiochromic film surface dose measurements on solid water. Variations in surface dose as a function of field size are measured using a parallel plate ion chamber in solid water. Using an anthropomorphic computational phantom with a 2 mm-thick skin layer, we investigate dose distributions resulting from three beam arrangements. Magnetic field on and off scenarios are considered for all measurements and simulations. RESULTS For a 20 × 20 cm2 field size,D 0.2 c c ${D_{0.2cc}}$ (the minimum dose to the hottest contiguous 0.2 cc volume) for the top 2 mm of a simple water phantom is 72% when the magnetic field is on, compared to 34% with magnetic field off (values are normalized to the central axis dose maximum). Parallel plate ion chamber measurements demonstrate that the relative increase in surface dose due to the magnetic field decreases with increasing field size. For the anthropomorphic phantom,D ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ (minimum skin dose in the hottest 1 × 1 × 1 cm3 cube) shows relative increases of 20%-28% when the magnetic field is on compared to when it is off. With magnetic field off, skinD ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ is 71%, 56%, and 21% for medial-lateral tangents, anterior-posterior beams, and a five-field arrangement, respectively. For magnetic field on, the corresponding skinD ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ values are 91%, 67%, and 25%. CONCLUSIONS Using a validated MC model of our linac-MR, surface doses are calculated in various scenarios. MC-calculated skin dose varies depending on field sizes, obliquity, and the number of beams. In general, the parallel linac-MR arrangement results in skin dose enhancement due to charged particles spiraling along magnetic field lines, which impedes lateral motion away from the central axis. Nonetheless, considering the results presented herein, treatment plans can be designed to minimize skin dose by, for example, avoiding oblique beams and using a larger number of fields.
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Affiliation(s)
- Patricia A K Oliver
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
- Dept. of Medical Physics, Nova Scotia Health and Dept. of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Eugene Yip
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Shima Y Tari
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Keith Wachowicz
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Michael Reynolds
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
| | - Ben Burke
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Brad Warkentin
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Biagio G Fallone
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
- MagnetTx Oncology Solutions, Edmonton, Alberta, Canada
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Hobson MA, Hu Y, Caldwell B, Cohen GN, Glide-Hurst C, Huang L, Jackson PD, Jang S, Langner U, Lee HJ, Levesque IR, Narayanan S, Park JC, Steffen J, Wu QJ, Zhou Y. AAPM Task Group 334: A guidance document to using radiotherapy immobilization devices and accessories in an MR environment. Med Phys 2024; 51:3822-3849. [PMID: 38648857 DOI: 10.1002/mp.17061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 11/13/2023] [Accepted: 03/28/2024] [Indexed: 04/25/2024] Open
Abstract
Use of magnetic resonance (MR) imaging in radiation therapy has increased substantially in recent years as more radiotherapy centers are having MR simulators installed, requesting more time on clinical diagnostic MR systems, or even treating with combination MR linear accelerator (MR-linac) systems. With this increased use, to ensure the most accurate integration of images into radiotherapy (RT), RT immobilization devices and accessories must be able to be used safely in the MR environment and produce minimal perturbations. The determination of the safety profile and considerations often falls to the medical physicist or other support staff members who at a minimum should be a Level 2 personnel as per the ACR. The purpose of this guidance document will be to help guide the user in making determinations on MR Safety labeling (i.e., MR Safe, Conditional, or Unsafe) including standard testing, and verification of image quality, when using RT immobilization devices and accessories in an MR environment.
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Affiliation(s)
- Maritza A Hobson
- Department of Radiation Oncology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Yanle Hu
- Department of Radiation Oncology, Mayo Clinic Arizona, Phoenix, Arizona, USA
| | - Barrett Caldwell
- School of Industrial Engineering, Purdue University, West Lafayette, Indiana, USA
- School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana, USA
| | - Gil'ad N Cohen
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
| | - Carri Glide-Hurst
- Department of Human Oncology, University of Wisconsin--Madison, Madison, Wisconsin, USA
- Department of Medical Physics, University of Wisconsin--Madison, Madison, Wisconsin, USA
| | - Long Huang
- Department of Radiation Oncology, University of Utah, Salt Lake City, Utah, USA
| | - Paul D Jackson
- Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan, USA
| | - Sunyoung Jang
- Department of Radiation Oncology, Penn State College of Medicine, Hershey, Pennsylvania, USA
| | - Ulrich Langner
- Department of Radiation Oncology, Rhode Island Hospital, Providence, Rhode Island, USA
| | - Hannah J Lee
- Corewell Health William Beaumont University Hospital, Royal Oak, Michigan, USA
| | - Ives R Levesque
- Gerald Bronfman Department of Oncology and Medical Physics Unit, McGill University, Montreal, QC, Canada
- Department of Medical Physics, McGill University Health Centre, Cedars Cancer Centre, Montreal, QC, Canada
| | - Sreeram Narayanan
- Department of Radiation Oncology, Virginia Mason Cancer Institute, Seattle, Washington, USA
| | - Justin C Park
- Division of Medical Physics, Department of Radiation Oncology, Mayo Clinic, Jacksonville, Florida, USA
| | | | - Q Jackie Wu
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA
| | - Yong Zhou
- Department of Radiology Services, Corewell Health, Grand Rapids, Michigan, USA
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Yoon YH, Chun J, Kiser K, Marasini S, Curcuru A, Gach HM, Kim JS, Kim T. Inter-scanner super-resolution of 3D cine MRI using a transfer-learning network for MRgRT. Phys Med Biol 2024; 69:115038. [PMID: 38663411 DOI: 10.1088/1361-6560/ad43ab] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 04/25/2024] [Indexed: 05/30/2024]
Abstract
Objective. Deep-learning networks for super-resolution (SR) reconstruction enhance the spatial-resolution of 3D magnetic resonance imaging (MRI) for MR-guided radiotherapy (MRgRT). However, variations between MRI scanners and patients impact the quality of SR for real-time 3D low-resolution (LR) cine MRI. In this study, we present a personalized super-resolution (psSR) network that incorporates transfer-learning to overcome the challenges in inter-scanner SR of 3D cine MRI.Approach: Development of the proposed psSR network comprises two-stages: (1) a cohort-specific SR (csSR) network using clinical patient datasets, and (2) a psSR network using transfer-learning to target datasets. The csSR network was developed by training on breath-hold and respiratory-gated high-resolution (HR) 3D MRIs and their k-space down-sampled LR MRIs from 53 thoracoabdominal patients scanned at 1.5 T. The psSR network was developed through transfer-learning to retrain the csSR network using a single breath-hold HR MRI and a corresponding 3D cine MRI from 5 healthy volunteers scanned at 0.55 T. Image quality was evaluated using the peak-signal-noise-ratio (PSNR) and the structure-similarity-index-measure (SSIM). The clinical feasibility was assessed by liver contouring on the psSR MRI using an auto-segmentation network and quantified using the dice-similarity-coefficient (DSC).Results. Mean PSNR and SSIM values of psSR MRIs were increased by 57.2% (13.8-21.7) and 94.7% (0.38-0.74) compared to cine MRIs, with the reference 0.55 T breath-hold HR MRI. In the contour evaluation, DSC was increased by 15% (0.79-0.91). Average time consumed for transfer-learning was 90 s, psSR was 4.51 ms per volume, and auto-segmentation was 210 ms, respectively.Significance. The proposed psSR reconstruction substantially increased image and segmentation quality of cine MRI in an average of 215 ms across the scanners and patients with less than 2 min of prerequisite transfer-learning. This approach would be effective in overcoming cohort- and scanner-dependency of deep-learning for MRgRT.
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Affiliation(s)
- Young Hun Yoon
- Department of Radiation Oncology, Yonsei Cancer Center, Heavy Ion Therapy Research Institute, Yonsei University College of Medicine, Seoul, Republic of Korea
- Medical Physics and Biomedical Engineering Lab (MPBEL), Yonsei University College of Medicine, Seoul, Republic of Korea
- Department of Radiation Oncology, Washington University in St. Louis, St Louis, MO, United States of America
| | | | - Kendall Kiser
- Department of Radiation Oncology, Washington University in St. Louis, St Louis, MO, United States of America
| | - Shanti Marasini
- Department of Radiation Oncology, Washington University in St. Louis, St Louis, MO, United States of America
| | - Austen Curcuru
- Department of Radiation Oncology, Washington University in St. Louis, St Louis, MO, United States of America
| | - H Michael Gach
- Department of Radiation Oncology, Washington University in St. Louis, St Louis, MO, United States of America
- Departments of Radiology and Biomedical Engineering, Washington University in St. Louis, St Louis, MO, United States of America
| | - Jin Sung Kim
- Department of Radiation Oncology, Yonsei Cancer Center, Heavy Ion Therapy Research Institute, Yonsei University College of Medicine, Seoul, Republic of Korea
- Medical Physics and Biomedical Engineering Lab (MPBEL), Yonsei University College of Medicine, Seoul, Republic of Korea
- Oncosoft Inc., Seoul, Republic of Korea
| | - Taeho Kim
- Department of Radiation Oncology, Washington University in St. Louis, St Louis, MO, United States of America
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Lakshmanan K, Wang B, Walczyk J, Collins CM, Brown R. Three-row MRI receive array with remote circuitry to preserve radiation transparency. Phys Med Biol 2024; 69:10.1088/1361-6560/ad388c. [PMID: 38537307 PMCID: PMC11071057 DOI: 10.1088/1361-6560/ad388c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Accepted: 03/27/2024] [Indexed: 04/18/2024]
Abstract
Objective.Up to this point, 1.5 T linac-compatible coil array layouts have been restricted to one or two rows of coils because of the desire to place radiation-opaque circuitry adjacent to the coils and outside the window through which the linac beam travels. Such layouts can limit parallel imaging performance. The purpose of this work was to design and build a three-row array in which remotely located circuits permitted a central row of coils while preserving the radiolucent window.Approach.The remote circuits consisted of a phase shifter to cancel the phase introduced by the coaxial link between the circuit and coil, followed by standard components for tuning, matching, detuning, and preamplifier decoupling. Tests were performed to compare prototype single-channel coils with remote or local circuits, which were followed by tests comparing two and three-row arrays .Main results.The single-channel coil with the remote circuit maintained 85% SNR at depths of 30 mm or more as compared to a coil with local circuit. The three-row array provided similar SNR as the two-row array, along with geometry factor advantages for parallel imaging acceleration in the head-foot direction.Significance.The remote circuit strategy could potentially support future MR-linac arrays by allowing greater flexibility in array layout compared to those confined by local circuits, which can be leveraged for parallel imaging acceleration.
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Affiliation(s)
- Karthik Lakshmanan
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
| | - Bili Wang
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
| | - Jerzy Walczyk
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
| | - Christopher M. Collins
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
| | - Ryan Brown
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States
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Orlando N, Crosby J, Glide-Hurst C, Culberson W, Keller B, Sarfehnia A. Experimental determination of magnetic field quality conversion factors for eleven ionization chambers in 1.5 T and 0.35 T MR-linac systems. Med Phys 2024; 51:2998-3009. [PMID: 38060696 DOI: 10.1002/mp.16858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 10/05/2023] [Accepted: 11/02/2023] [Indexed: 01/05/2024] Open
Abstract
BACKGROUND The static magnetic field present in magnetic resonance (MR)-guided radiotherapy systems can influence dose deposition and charged particle collection in air-filled ionization chambers. Thus, accurately quantifying the effect of the magnetic field on ionization chamber response is critical for output calibration. Formalisms for reference dosimetry in a magnetic field have been proposed, whereby a magnetic field quality conversion factor kB,Q is defined to account for the combined effects of the magnetic field on the radiation detector. Determination of kB,Q in the literature has focused on Monte Carlo simulation studies, with experimental validation limited to only a few ionization chamber models. PURPOSE The purpose of this study is to experimentally measure kB,Q for 11 ionization chamber models in two commercially available MR-guided radiotherapy systems: Elekta Unity and ViewRay MRIdian. METHODS Eleven ionization chamber models were characterized in this study: Exradin A12, A12S, A28, and A26, PTW T31010, T31021, and T31022, and IBA FC23-C, CC25, CC13, and CC08. The experimental method to measure kB,Q utilized cross-calibration against a reference Exradin A1SL chamber. Absorbed dose to water was measured for the reference A1SL chamber positioned parallel to the magnetic field with its centroid placed at the machine isocenter at a depth of 10 cm in water for a 10 × 10 cm2 field size at that depth. Output was subsequently measured with the test chamber at the same point of measurement. kB,Q for the test chamber was computed as the ratio of reference dose to test chamber output, with this procedure repeated for each chamber in each MR-guided radiotherapy system. For the high-field 1.5 T Elekta Unity system, the dependence of kB,Q on the chamber orientation relative to the magnetic field was quantified by rotating the chamber about the machine isocenter. RESULTS Measured kB,Q values for our test dataset of ionization chamber models ranged from 0.991 to 1.002, and 0.995 to 1.004 for the Elekta Unity and ViewRay MRIdian, respectively, with kB,Q tending to increase as the chamber sensitive volume increased. Measured kB,Q values largely agreed within uncertainty to published Monte Carlo simulation data and available experimental data. kB,Q deviation from unity was minimized for ionization chamber orientation parallel or antiparallel to the magnetic field, with increased deviations observed at perpendicular orientations. Overall (k = 1) uncertainty in the experimental determination of the magnetic field quality conversion factor, kB,Q was 0.71% and 0.72% for the Elekta Unity and ViewRay MRIdian systems, respectively. CONCLUSIONS For a high-field MR-linac, the characterization of ionization chamber performance as angular orientation varied relative to the magnetic field confirmed that the ideal orientation for output calibration is parallel. For most of these chamber models, this study represents the first experimental characterization of chamber performance in clinical MR-linac beams. This is a critical step toward accurate output calibration for MR-guided radiotherapy systems and the measured kB,Q values will be an important reference data source for forthcoming MR-linac reference dosimetry protocols.
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Affiliation(s)
- Nathan Orlando
- Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Jennie Crosby
- Carbone Cancer Center, Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Carri Glide-Hurst
- Carbone Cancer Center, Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Wesley Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Brian Keller
- Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Arman Sarfehnia
- Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
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Sherwani MK, Gopalakrishnan S. A systematic literature review: deep learning techniques for synthetic medical image generation and their applications in radiotherapy. FRONTIERS IN RADIOLOGY 2024; 4:1385742. [PMID: 38601888 PMCID: PMC11004271 DOI: 10.3389/fradi.2024.1385742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 03/11/2024] [Indexed: 04/12/2024]
Abstract
The aim of this systematic review is to determine whether Deep Learning (DL) algorithms can provide a clinically feasible alternative to classic algorithms for synthetic Computer Tomography (sCT). The following categories are presented in this study: ∙ MR-based treatment planning and synthetic CT generation techniques. ∙ Generation of synthetic CT images based on Cone Beam CT images. ∙ Low-dose CT to High-dose CT generation. ∙ Attenuation correction for PET images. To perform appropriate database searches, we reviewed journal articles published between January 2018 and June 2023. Current methodology, study strategies, and results with relevant clinical applications were analyzed as we outlined the state-of-the-art of deep learning based approaches to inter-modality and intra-modality image synthesis. This was accomplished by contrasting the provided methodologies with traditional research approaches. The key contributions of each category were highlighted, specific challenges were identified, and accomplishments were summarized. As a final step, the statistics of all the cited works from various aspects were analyzed, which revealed that DL-based sCTs have achieved considerable popularity, while also showing the potential of this technology. In order to assess the clinical readiness of the presented methods, we examined the current status of DL-based sCT generation.
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Affiliation(s)
- Moiz Khan Sherwani
- Section for Evolutionary Hologenomics, Globe Institute, University of Copenhagen, Copenhagen, Denmark
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Rusu DN, Cunningham JM, Arch JV, Chetty IJ, Parikh PJ, Dolan JL. Impact of intrafraction motion in pancreatic cancer treatments with MR-guided adaptive radiation therapy. Front Oncol 2023; 13:1298099. [PMID: 38162503 PMCID: PMC10756668 DOI: 10.3389/fonc.2023.1298099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 11/27/2023] [Indexed: 01/03/2024] Open
Abstract
Purpose The total time of radiation treatment delivery for pancreatic cancer patients with daily online adaptive radiation therapy (ART) on an MR-Linac can range from 50 to 90 min. During this period, the target and normal tissues undergo changes due to respiration and physiologic organ motion. We evaluated the dosimetric impact of the intrafraction physiological organ changes. Methods Ten locally advanced pancreatic cancer patients were treated with 50 Gy in five fractions with intensity-modulated respiratory-gated radiation therapy on a 0.35-T MR-Linac. Patients received both pre- and post-treatment volumetric MRIs for each fraction. Gastrointestinal organs at risk (GI-OARs) were delineated on the pre-treatment MRI during the online ART process and retrospectively on the post-treatment MRI. The treated dose distribution for each adaptive plan was assessed on the post-treatment anatomy. Prescribed dose volume histogram metrics for the scheduled plan on the pre-treatment anatomy, the adapted plan on the pre-treatment anatomy, and the adapted plan on post-treatment anatomy were compared to the OAR-defined criteria for adaptation: the volume of the GI-OAR receiving greater than 33 Gy (V33Gy) should be ≤1 cubic centimeter. Results Across the 50 adapted plans for the 10 patients studied, 70% were adapted to meet the duodenum constraint, 74% for the stomach, 12% for the colon, and 48% for the small bowel. Owing to intrafraction organ motion, at the time of post-treatment imaging, the adaptive criteria were exceeded for the duodenum in 62% of fractions, the stomach in 36%, the colon in 10%, and the small bowel in 48%. Compared to the scheduled plan, the post-treatment plans showed a decrease in the V33Gy, demonstrating the benefit of plan adaptation for 66% of the fractions for the duodenum, 95% for the stomach, 100% for the colon, and 79% for the small bowel. Conclusion Post-treatment images demonstrated that over the course of the adaptive plan generation and delivery, the GI-OARs moved from their isotoxic low-dose region and nearer to the dose-escalated high-dose region, exceeding dose-volume constraints. Intrafraction motion can have a significant dosimetric impact; therefore, measures to mitigate this motion are needed. Despite consistent intrafraction motion, plan adaptation still provides a dosimetric benefit.
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Affiliation(s)
- Doris N. Rusu
- Department of Radiation Oncology, Wayne State University, Detroit, MI, United States
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, United States
| | - Justine M. Cunningham
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, United States
| | - Jacob V. Arch
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, United States
| | - Indrin J. Chetty
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, United States
- Department of Radiation Oncology, Cedars Sinai Medical Center, Los Angeles, CA, United States
| | - Parag J. Parikh
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, United States
| | - Jennifer L. Dolan
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, United States
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Hickey S, Reichert A, Ptacek W, Bielak L, Reiss S, Fischer J, Gunashekar DD, Bortfeld T, Bock M. Simultaneous T 2 -weighted real-time MRI of two orthogonal slices. Magn Reson Med 2023; 90:2388-2399. [PMID: 37427459 DOI: 10.1002/mrm.29795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 07/11/2023]
Abstract
PURPOSE MR guidance is used during therapy to detect and compensate for lesion motion. T2 -weighted MRI often has a superior lesion contrast in comparison to T1 -weighted real-time imaging. The purpose of this work was to design a fast T2 -weighted sequence capable of simultaneously acquiring two orthogonal slices, enabling real-time tracking of lesions. METHODS To generate a T2 contrast in two orthogonal slices simultaneously, a sequence (Ortho-SFFP-Echo) was designed that samples the T2 -weighted spin echo (S- ) signal in a TR-interleaved acquisition of two slices. Slice selection and phase-encoding directions are swapped between the slices, leading to a unique set of spin-echo signal conditions. To minimize motion-related signal dephasing, additional flow-compensation strategies are implemented. In both the abdominal breathing phantom and in vivo experiments, a time series was acquired using Ortho-SSFP-Echo. The centroid of the target was tracked in postprocessing steps. RESULTS In the phantom, the lesion could be identified and delineated in the dynamic images. In the volunteer experiments, the kidney was visualized with a T2 contrast at a temporal resolution of 0.45 s under free-breathing conditions. A respiratory belt demonstrated a strong correlation with the time course of the kidney centroid in the head-foot direction. A hypointense saturation band at the slice overlap did not inhibit lesion tracking in the semi-automatic postprocessing steps. CONCLUSION The Ortho-SFFP-Echo sequence delivers real-time images with a T2 -weighted contrast in two orthogonal slices. The sequence allows for simultaneous acquisition, which could be beneficial for real-time motion tracking in radiotherapy or interventional MRI.
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Affiliation(s)
- Samantha Hickey
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Andreas Reichert
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Lars Bielak
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- German Cancer Consortium (DKTK), Partner Site Freiburg, Freiburg, Germany
| | - Simon Reiss
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Johannes Fischer
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Deepa Darshini Gunashekar
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Thomas Bortfeld
- Division of Radiation Biophysics, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Michael Bock
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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10
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Lee D, Renz P, Oh S, Hwang MS, Pavord D, Yun KL, Collura C, McCauley M, Colonias A(T, Trombetta M, Kirichenko A. Online Adaptive MRI-Guided Stereotactic Body Radiotherapy for Pancreatic and Other Intra-Abdominal Cancers. Cancers (Basel) 2023; 15:5272. [PMID: 37958447 PMCID: PMC10648954 DOI: 10.3390/cancers15215272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 10/31/2023] [Accepted: 11/01/2023] [Indexed: 11/15/2023] Open
Abstract
A 1.5T MRI combined with a linear accelerator (Unity®, Elekta; Stockholm, Sweden) is a device that shows promise in MRI-guided stereotactic body radiation treatment (SBRT). Previous studies utilized the manufacturer's pre-set MRI sequences (i.e., T2 Weighted (T2W)), which limited the visualization of pancreatic and intra-abdominal tumors and organs at risk (OAR). Here, a T1 Weighted (T1W) sequence was utilized to improve the visualization of tumors and OAR for online adapted-to-position (ATP) and adapted-to-shape (ATS) during MRI-guided SBRT. Twenty-six patients, 19 with pancreatic and 7 with intra-abdominal cancers, underwent CT and MRI simulations for SBRT planning before being treated with multi-fractionated MRI-guided SBRT. The boundary of tumors and OAR was more clearly seen on T1W image sets, resulting in fast and accurate contouring during online ATP/ATS planning. Plan quality in 26 patients was dependent on OAR proximity to the target tumor and achieved 96 ± 5% and 92 ± 9% in gross tumor volume D90% and planning target volume D90%. We utilized T1W imaging (about 120 s) to shorten imaging time by 67% compared to T2W imaging (about 360 s) and improve tumor visualization, minimizing target/OAR delineation uncertainty and the treatment margin for sparing OAR. The average time-consumption of MRI-guided SBRT for the first 21 patients was 55 ± 15 min for ATP and 79 ± 20 min for ATS.
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Affiliation(s)
- Danny Lee
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
- College of Medicine, Radiologic Sciences/Drexel University, Philadelphia, PA 19129, USA
| | - Paul Renz
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
| | - Seungjong Oh
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
- College of Medicine, Radiologic Sciences/Drexel University, Philadelphia, PA 19129, USA
| | - Min-Sig Hwang
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
- College of Medicine, Radiologic Sciences/Drexel University, Philadelphia, PA 19129, USA
| | - Daniel Pavord
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
- College of Medicine, Radiologic Sciences/Drexel University, Philadelphia, PA 19129, USA
| | - Kyung Lim Yun
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
| | - Colleen Collura
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
| | - Mary McCauley
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
| | - Athanasios (Tom) Colonias
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
| | - Mark Trombetta
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
- College of Medicine, Radiologic Sciences/Drexel University, Philadelphia, PA 19129, USA
| | - Alexander Kirichenko
- Radiation Oncology, Allegheny Health Network, Pittsburgh, PA 15012, USA; (P.R.); (S.O.); (M.-S.H.); (D.P.); (K.L.Y.); (C.C.); (M.M.); (M.T.); (A.K.)
- College of Medicine, Radiologic Sciences/Drexel University, Philadelphia, PA 19129, USA
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11
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Lawrence LSP, Chan RW, Chen H, Stewart J, Ruschin M, Theriault A, Myrehaug S, Detsky J, Maralani PJ, Tseng CL, Soliman H, Jane Lim-Fat M, Das S, Stanisz GJ, Sahgal A, Lau AZ. Diffusion-weighted imaging on an MRI-linear accelerator to identify adversely prognostic tumour regions in glioblastoma during chemoradiation. Radiother Oncol 2023; 188:109873. [PMID: 37640160 DOI: 10.1016/j.radonc.2023.109873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 07/12/2023] [Accepted: 08/20/2023] [Indexed: 08/31/2023]
Abstract
BACKGROUND AND PURPOSE Survival in glioblastoma might be extended by escalating the radiotherapy dose to treatment-resistant tumour and adapting to tumour changes. Diffusion-weighted imaging (DWI) on MRI-linear accelerators (MR-Linacs) could be used to identify a dose escalation target, but its prognostic value must be demonstrated. The purpose of this study was to determine whether MR-Linac DWI can assess treatment response in glioblastoma and whether changes in DWI show greater prognostic value than changes in the contrast-enhancing gross tumour volume (GTV). MATERIALS AND METHODS Seventy-five patients with glioblastoma were treated with chemoradiotherapy, of which 32 were treated on a 1.5 T MRI-linear accelerator (MR-Linac). Patients were imaged with simulation MRI scanners (MR-sim) at treatment planning and weeks 2, 4, and 10 after treatment start. Twenty-eight patients had additional MR-Linac DWI sequences. Cox modelling was used to evaluate the correlation of overall and progression-free survival (OS and PFS) with clinical variables and volumetric changes in the GTV and low-ADC regions (ADC < 1.25 µm2/ms within GTV). RESULTS In total, 479 MR-Linac DWI and 289 MR-sim DWI datasets were analyzed. MR-Linac low-ADC changes between weeks 2 and 5 inclusive were prognostic for OS (hazard ratio lower limits ≥ 1.2, p-values ≤ 0.02). MR-sim low-ADC changes showed greater correlation with OS and PFS than GTV changes (e.g., OS hazard ratio at week 2 was 3.4 (p <0.001) for low-ADC versus 2.0 (p = 0.022) for GTV). CONCLUSION MR-Linac DWI can measure low-ADC tumour volumes that correlate with OS and PFS better than contrast-enhancing GTV. Low-ADC regions could serve as dose escalation targets.
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Affiliation(s)
| | - Rachel W Chan
- Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Hanbo Chen
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - James Stewart
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Mark Ruschin
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Aimee Theriault
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Sten Myrehaug
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Jay Detsky
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Pejman J Maralani
- Medical Imaging, University of Toronto, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
| | - Chia-Lin Tseng
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Hany Soliman
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Mary Jane Lim-Fat
- Division of Neurology, Department of Medicine, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Sunit Das
- Keenan Chair in Surgery, St. Michael's Hospital, Division of Neurosurgery, University of Toronto, Toronto, Ontario, Canada
| | - Greg J Stanisz
- Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada; Department of Neurosurgery and Paediatric Neurosurgery, Medical University, Lublin, Poland
| | - Arjun Sahgal
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Angus Z Lau
- Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada.
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12
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Chen S, Eldeniz C, Fraum TJ, Ludwig DR, Gan W, Liu J, Kamilov US, Yang D, Gach HM, An H. Respiratory motion management using a single rapid MRI scan for a 0.35 T MRI-Linac system. Med Phys 2023; 50:6163-6176. [PMID: 37184305 DOI: 10.1002/mp.16469] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 04/27/2023] [Accepted: 04/27/2023] [Indexed: 05/16/2023] Open
Abstract
BACKGROUND MRI has a rapidly growing role in radiation therapy (RT) for treatment planning, real-time image guidance, and beam gating (e.g., MRI-Linac). Free-breathing 4D-MRI is desirable in respiratory motion management for therapy. Moreover, high-quality 3D-MRIs without motion artifacts are needed to delineate lesions. Existing MRI methods require multiple scans with lengthy acquisition times or are limited by low spatial resolution, contrast, and signal-to-noise ratio. PURPOSE We developed a novel method to obtain motion-resolved 4D-MRIs and motion-integrated 3D-MRI reconstruction using a single rapid (35-45 s scan on a 0.35 T MRI-Linac. METHODS Golden-angle radial stack-of-stars MRI scans were acquired from a respiratory motion phantom and 12 healthy volunteers (n = 12) on a 0.35 T MRI-Linac. A self-navigated method was employed to detect respiratory motion using 2000 (acquisition time = 5-7 min) and the first 200 spokes (acquisition time = 35-45 s). Multi-coil non-uniform fast Fourier transform (MCNUFFT), compressed sensing (CS), and deep-learning Phase2Phase (P2P) methods were employed to reconstruct motion-resolved 4D-MRI using 2000 spokes (MCNUFFT2000) and 200 spokes (CS200 and P2P200). Deformable motion vector fields (MVFs) were computed from the 4D-MRIs and used to reconstruct motion-corrected 3D-MRIs with the MOtion Transformation Integrated forward-Fourier (MOTIF) method. Image quality was evaluated quantitatively using the structural similarity index measure (SSIM) and the root mean square error (RMSE), and qualitatively in a blinded radiological review. RESULTS Evaluation using the respiratory motion phantom experiment showed that the proposed method reversed the effects of motion blurring and restored edge sharpness. In the human study, P2P200 had smaller inaccuracy in MVFs estimation than CS200. P2P200 had significantly greater SSIMs (p < 0.0001) and smaller RMSEs (p < 0.001) than CS200 in motion-resolved 4D-MRI and motion-corrected 3D-MRI. The radiological review found that MOTIF 3D-MRIs using MCNUFFT2000 exhibited the highest image quality (scoring > 8 out of 10), followed by P2P200 (scoring > 5 out of 10), and then motion-uncorrected (scoring < 3 out of 10) in sharpness, contrast, and artifact-freeness. CONCLUSIONS We have successfully demonstrated a method for respiratory motion management for MRI-guided RT. The method integrated self-navigated respiratory motion detection, deep-learning P2P 4D-MRI reconstruction, and a motion integrated reconstruction (MOTIF) for 3D-MRI using a single rapid MRI scan (35-45 s) on a 0.35 T MRI-Linac system.
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Affiliation(s)
- Sihao Chen
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Cihat Eldeniz
- Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Tyler J Fraum
- Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Daniel R Ludwig
- Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Weijie Gan
- Department of Computer Science & Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jiaming Liu
- Department of Electrical & Systems Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Ulugbek S Kamilov
- Department of Computer Science & Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
- Department of Electrical & Systems Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Deshan Yang
- Department of Radiation Oncology, Duke University, Durham, North Carolina, USA
| | - H Michael Gach
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
- Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Hongyu An
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
- Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Department of Electrical & Systems Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
- Department of Neurology, Washington University in St. Louis, St. Louis, Missouri, USA
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13
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Fahad HM, Dorsch S, Zaiss M, Karger CP. Multi-parametric optimization of magnetic resonance imaging sequences for magnetic resonance-guided radiotherapy. Phys Imaging Radiat Oncol 2023; 28:100497. [PMID: 37869476 PMCID: PMC10585385 DOI: 10.1016/j.phro.2023.100497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 09/15/2023] [Accepted: 09/29/2023] [Indexed: 10/24/2023] Open
Abstract
Background and purpose Magnetic Resonance Imaging (MRI) is widely used in oncology for tumor staging, treatment response assessment, and radiation therapy (RT) planning. This study proposes a framework for automatic optimization of MRI sequences based on pulse sequence parameter sets (SPS) that are directly applied on the scanner, for application in RT planning. Materials and methods A phantom with seven in-house fabricated contrasts was used for measurements. The proposed framework employed a derivative-free optimization algorithm to repeatedly update and execute a parametrized sequence on the MR scanner to acquire new data. In each iteration, the mean-square error was calculated based on the clinical application. Two clinically relevant optimization goals were pursued: achieving the same signal and therefore contrast as in a target image, and maximizing the signal difference (contrast) between specified tissue types. The framework was evaluated using two optimization methods: a covariance matrix adaptation evolution strategy (CMA-ES) and a genetic algorithm (GA). Results The obtained results demonstrated the potential of the proposed framework for automatic optimization of MRI sequences. Both CMA-ES and GA methods showed promising results in achieving the two optimization goals, however, CMA-ES converged much faster as compared to GA. Conclusions The proposed framework enables for automatic optimization of MRI sequences based on SPS that are directly applied on the scanner and it may be used to enhance the quality of MRI images for dedicated applications in MR-guided RT.
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Affiliation(s)
- Hafiz Muhammad Fahad
- German Cancer Research Center (DKFZ), Medical Physics in Radiation Oncology, Heidelberg, Germany
- University of Heidelberg, Faculty of Medicine, Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Stefan Dorsch
- German Cancer Research Center (DKFZ), Medical Physics in Radiation Oncology, Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
- Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany
| | - Moritz Zaiss
- Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Institute of Neuroradiology, University Hospital Erlangen, Erlangen, Germany
- Magnetic Resonance Center, Max- Planck Institute for Biological Cyberrnetics, Tübingen, Germany
| | - Christian P. Karger
- German Cancer Research Center (DKFZ), Medical Physics in Radiation Oncology, Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
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14
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Subashi E, Segars P, Veeraraghavan H, Deasy J, Tyagi N. A model for gastrointestinal tract motility in a 4D imaging phantom of human anatomy. Med Phys 2023; 50:3066-3075. [PMID: 36808107 PMCID: PMC10561541 DOI: 10.1002/mp.16305] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 01/26/2023] [Accepted: 01/29/2023] [Indexed: 02/23/2023] Open
Abstract
BACKGROUND Gastrointestinal (GI) tract motility is one of the main sources for intra/inter-fraction variability and uncertainty in radiation therapy for abdominal targets. Models for GI motility can improve the assessment of delivered dose and contribute to the development, testing, and validation of deformable image registration (DIR) and dose-accumulation algorithms. PURPOSE To implement GI tract motion in the 4D extended cardiac-torso (XCAT) digital phantom of human anatomy. MATERIALS AND METHODS Motility modes that exhibit large amplitude changes in the diameter of the GI tract and may persist over timescales comparable to online adaptive planning and radiotherapy delivery were identified based on literature research. Search criteria included amplitude changes larger than planning risk volume expansions and durations of the order of tens of minutes. The following modes were identified: peristalsis, rhythmic segmentation, high amplitude propagating contractions (HAPCs), and tonic contractions. Peristalsis and rhythmic segmentations were modeled by traveling and standing sinusoidal waves. HAPCs and tonic contractions were modeled by traveling and stationary Gaussian waves. Wave dispersion in the temporal and spatial domain was implemented by linear, exponential, and inverse power law functions. Modeling functions were applied to the control points of the nonuniform rational B-spline surfaces defined in the reference XCAT library. GI motility was combined with the cardiac and respiratory motions available in the standard 4D-XCAT phantom. Default model parameters were estimated based on the analysis of cine MRI acquisitions in 10 patients treated in a 1.5T MR-linac. RESULTS We demonstrate the ability to generate realistic 4D multimodal images that simulate GI motility combined with respiratory and cardiac motion. All modes of motility, except tonic contractions, were observed in the analysis of our cine MRI acquisitions. Peristalsis was the most common. Default parameters estimated from cine MRI were used as initial values for simulation experiments. It is shown that in patients undergoing stereotactic body radiotherapy for abdominal targets, the effects of GI motility can be comparable or larger than the effects of respiratory motion. CONCLUSION The digital phantom provides realistic models to aid in medical imaging and radiation therapy research. The addition of GI motility will further contribute to the development, testing, and validation of DIR and dose accumulation algorithms for MR-guided radiotherapy.
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Affiliation(s)
- Ergys Subashi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Paul Segars
- Department of Radiology, Duke University Medical Center, Durham, North Carolina
| | - Harini Veeraraghavan
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Joseph Deasy
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Neelam Tyagi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
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15
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Chuong MD, Palm RF, Tjong MC, Hyer DE, Kishan AU. Advances in MRI-Guided Radiation Therapy. Surg Oncol Clin N Am 2023; 32:599-615. [PMID: 37182995 DOI: 10.1016/j.soc.2023.02.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
Abstract
Image guidance for radiation therapy (RT) has evolved over the last few decades and now is routinely performed using cone-beam computerized tomography (CBCT). Conventional linear accelerators (LINACs) that use CBCT have limited soft tissue contrast, are not able to image the patient's internal anatomy during treatment delivery, and most are not capable of online adaptive replanning. RT delivery systems that use MRI have become available within the last several years and address many of the imaging limitations of conventional LINACs. Herein, the authors review the technical characteristics and advantages of MRI-guided RT as well as emerging clinical outcomes.
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Affiliation(s)
- Michael D Chuong
- Department of Radiation Oncology, Miami Cancer Institute, 8900 North Kendall Drive, Miami, FL 33176, USA.
| | - Russell F Palm
- Department of Radiation Oncology, Moffitt Cancer Center, 12902 USF Magnolia Drive, Tampa, FL 33612, USA
| | - Michael C Tjong
- Department of Radiation Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Boston, MA 02215, USA
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Dr, Iowa City, IA 52242, USA
| | - Amar U Kishan
- Department of Radiation Oncology, University of California Los Angeles, 1338 S Hope Street, Los Angeles, CA 90015, USA
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16
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Begg J, Jelen U, Moutrie Z, Oliver C, Holloway L, Brown R. ACPSEM position paper: dosimetry for magnetic resonance imaging linear accelerators. Phys Eng Sci Med 2023; 46:1-17. [PMID: 36806156 PMCID: PMC10030536 DOI: 10.1007/s13246-023-01223-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2023] [Indexed: 02/23/2023]
Abstract
Consistency and clear guidelines on dosimetry are essential for accurate and precise dosimetry, to ensure the best patient outcomes and to allow direct dose comparison across different centres. Magnetic Resonance Imaging Linac (MRI-linac) systems have recently been introduced to Australasian clinics. This report provides recommendations on reference dosimetry measurements for MRI-linacs on behalf of the Australiasian College of Physical Scientists and Engineers in Medicine (ACPSEM) MRI-linac working group. There are two configurations considered for MRI-linacs, perpendicular and parallel, referring to the relative direction of the magnetic field and radiation beam, with different impacts on dose deposition in a medium. These recommendations focus on ion chambers which are most commonly used in the clinic for reference dosimetry. Water phantoms must be MR safe or conditional and practical limitations on phantom set-up must be considered. Solid phantoms are not advised for reference dosimetry. For reference dosimetry, IAEA TRS-398 recommendations cannot be followed completely due to physical differences between conventional linac and MRI-linac systems. Manufacturers' advice on reference conditions should be followed. Beam quality specification of TPR20,10 is recommended. The configuration of the central axis of the ion chamber relative to the magnetic field and radiation beam impacts the chamber response and must be considered carefully. Recommended corrections to delivered dose are [Formula: see text], a correction for beam quality and [Formula: see text], for the impact of the magnetic field on dosimeter response in the magnetic field. Literature based values for [Formula: see text] are given. It is important to note that this is a developing field and these recommendations should be used together with a review of current literature.
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Affiliation(s)
- Jarrad Begg
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia.
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.
| | - Urszula Jelen
- St Vincents Clinic, GenesisCare, Darlinghurst, NSW, 2010, Australia
| | - Zoe Moutrie
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia
| | - Chris Oliver
- Primary Standards Dosimetry Laboratory, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, 3085, Australia
| | - Lois Holloway
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
- Institute of Medical Physics, University of Sydney, Camperdown, NSW, 2505, Australia
| | - Rhonda Brown
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, 3085, Australia
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Cook N, Shelton N, Gibson S, Barnes P, Alinaghi-Zadeh R, Jameson MG. ACPSEM position paper: the safety of magnetic resonance imaging linear accelerators. Phys Eng Sci Med 2023; 46:19-43. [PMID: 36847966 PMCID: PMC10030425 DOI: 10.1007/s13246-023-01224-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2023] [Indexed: 03/01/2023]
Abstract
Magnetic Resonance Imaging linear-accelerator (MRI-linac) equipment has recently been introduced to multiple centres in Australia and New Zealand. MRI equipment creates hazards for staff, patients and others in the MR environment; these hazards must be well understood, and risks managed by a system of environmental controls, written procedures and a trained workforce. While MRI-linac hazards are similar to the diagnostic paradigm, the equipment, workforce and environment are sufficiently different that additional safety guidance is warranted. In 2019 the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) formed the Magnetic Resonance Imaging Linear-Accelerator Working Group (MRILWG) to support the safe clinical introduction and optimal use of MR-guided radiation therapy treatment units. This Position Paper is intended to provide safety guidance and education for Medical Physicists and others planning for and working with MRI-linac technology. This document summarises MRI-linac hazards and describes particular effects which arise from the combination of strong magnetic fields with an external radiation treatment beam. This document also provides guidance on safety governance and training, and recommends a system of hazard management tailored to the MRI-linac environment, ancillary equipment, and workforce.
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Affiliation(s)
- Nick Cook
- Christchurch Hospital, Christchurch, New Zealand
| | - Nikki Shelton
- Olivia Newton-John Cancer Wellness and Research Centre, Heidelberg, VIC, Australia
| | | | | | - Reza Alinaghi-Zadeh
- Olivia Newton-John Cancer Wellness and Research Centre, Heidelberg, VIC, Australia
| | - Michael G Jameson
- GenesisCare, Sydney, NSW, Australia.
- University of New South Wales, Sydney, Australia.
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Olberg S, Choi BS, Park I, Liang X, Kim JS, Deng J, Yan Y, Jiang S, Park JC. Ensemble learning and personalized training for the improvement of unsupervised deep learning-based synthetic CT reconstruction. Med Phys 2023; 50:1436-1449. [PMID: 36336718 DOI: 10.1002/mp.16087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 08/22/2022] [Accepted: 10/19/2022] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND The growing adoption of magnetic resonance imaging (MRI)-guided radiation therapy (RT) platforms and a focus on MRI-only RT workflows have brought the technical challenge of synthetic computed tomography (sCT) reconstruction to the forefront. Unpaired-data deep learning-based approaches to the problem offer the attractive characteristic of not requiring paired training data, but the gap between paired- and unpaired-data results can be limiting. PURPOSE We present two distinct approaches aimed at improving unpaired-data sCT reconstruction results: a cascade ensemble that combines multiple models and a personalized training strategy originally designed for the paired-data setting. METHODS Comparisons are made between the following models: (1) the paired-data fully convolutional DenseNet (FCDN), (2) the FCDN with the Intentional Deep Overfit Learning (IDOL) personalized training strategy, (3) the unpaired-data CycleGAN, (4) the CycleGAN with the IDOL training strategy, and (5) the CycleGAN as an intermediate model in a cascade ensemble approach. Evaluation of the various models over 25 total patients is carried out using a five-fold cross-validation scheme, with the patient-specific IDOL models being trained for the five patients of fold 3, chosen at random. RESULTS In both the paired- and unpaired-data settings, adopting the IDOL training strategy led to improvements in the mean absolute error (MAE) between true CT images and sCT outputs within the body contour (mean improvement, paired- and unpaired-data approaches, respectively: 38%, 9%) and in regions of bone (52%, 5%), the peak signal-to-noise ratio (PSNR; 15%, 7%), and the structural similarity index (SSIM; 6%, <1%). The ensemble approach offered additional benefits over the IDOL approach in all three metrics (mean improvement over unpaired-data approach in fold 3; MAE: 20%; bone MAE: 16%; PSNR: 10%; SSIM: 2%), and differences in body MAE between the ensemble approach and the paired-data approach are statistically insignificant. CONCLUSIONS We have demonstrated that both a cascade ensemble approach and a personalized training strategy designed initially for the paired-data setting offer significant improvements in image quality metrics for the unpaired-data sCT reconstruction task. Closing the gap between paired- and unpaired-data approaches is a step toward fully enabling these powerful and attractive unpaired-data frameworks.
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Affiliation(s)
- Sven Olberg
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Byong Su Choi
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Medical Physics and Biomedical Engineering Lab (MPBEL), Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea
| | - Inkyung Park
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Medical Physics and Biomedical Engineering Lab (MPBEL), Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea
| | - Xiao Liang
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Jin Sung Kim
- Medical Physics and Biomedical Engineering Lab (MPBEL), Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea
- Oncosoft Inc., Seoul, South Korea
| | - Jie Deng
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Yulong Yan
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Steve Jiang
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Justin C Park
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Medical Physics and Biomedical Engineering Lab (MPBEL), Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea
- Department of Radiation Oncology, Mayo Clinic, Jacksonville, Florida, USA
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van der Heide U, Thwaites DI. Integrated MRI-linac systems: The new paradigm for precision adaptive radiotherapy and biological image-guidance? Radiother Oncol 2022; 176:249-250. [PMID: 36446519 DOI: 10.1016/j.radonc.2022.08.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 08/14/2022] [Indexed: 11/29/2022]
Affiliation(s)
- Uulke van der Heide
- Department of Radiation Oncology, the Netherlands Cancer Institute, Amsterdam, the Netherlands.
| | - David I Thwaites
- Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW, Australia; Radiotherapy Research Group, Leeds Institute of Medical Research, St James's Hospital and University of Leeds, Leeds, UK.
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Chu VWS, Kan MWK, Lee LKY, Wong KCW, Chan ATC. Magnetic-field-modulated radiotherapy (MagMRT) in inhomogeneous medium and its potential applications. Biomed Phys Eng Express 2022; 8. [PMID: 36130477 DOI: 10.1088/2057-1976/ac9390] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 09/21/2022] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To study the effects of magnetic field gradients on the dose deposition in an inhomogeneous medium and to present the benefits offered by magnetic-field-modulated radiotherapy (MagMRT) under multiple radiation beams. APPROACH Monte Carlo simulations were performed using the Geant4 simulation toolkit with a 7 MV photon beam from an Elekta Unity system. A water cuboid embedded with material slabs of water, bone, lung or air was used to study the effects of MagMRT within inhomogeneous medium. Two cylindrical water phantoms, with and without a toroidal lung insert embedded, were used to study the effects of MagMRT under single, opposing or four cardinal radiation beams. Optimized magnetic field variations in the form of a wavelet were used to induce dose modulation within the material slabs or at the iso-center of the phantoms. MAIN RESULTS The magnitudes of the dose enhancement and reduction induced by the magnetic field gradients become more prominent in a medium of lower density. A maximum dose increase of 6.5% and a decrease of 4.8% were found inside bone, while an increase of 20.4% and a decrease of 13.9% were found in lung tissue. Under multiple radiation beams, the dose enhancement can be induced at the iso-center while the dose reduction occurs in regions around the tumor. For the case with four cardinal beams irradiating a homogeneous water cylinder, an 8.4% of dose enhancement and a 2.4% of dose reduction were found. When a toroidal lung insert was embedded, a maximum dose enhancement of 9.5% and a reduction of 17.0% were produced for anterior-posterior opposing fields. SIGNIFICANCE With an optimized magnetic field gradient, MagMRT can induce a dose boost to the target while producing a better sparing to the surrounding normal tissue, resulting in a sharper dose fall-off in all directions outside the target volume.
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Affiliation(s)
- Vivien W S Chu
- Clinical Oncology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, 000, HONG KONG
| | - Monica W K Kan
- Clinical Oncology, Prince of Wales Hospital, 30-32 Ngan Shing Street, Shatin, New Territories, Hong Kong, 000, HONG KONG
| | - Louis K Y Lee
- CUHK Medical Centre, 12 Chak Cheung Street, Ma Liu Shui, Shatin, New Territories, Hong Kong, 000, HONG KONG
| | - Kenneth C W Wong
- Clinical Oncology, Prince of Wales Hospital, 30-32 Ngan Shing Street, Shatin, New Territories, Hong Kong, 000, HONG KONG
| | - Anthony T C Chan
- Clinical Oncology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, 000, HONG KONG
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MRI-guided Radiotherapy (MRgRT) for treatment of Oligometastases: Review of clinical applications and challenges. Int J Radiat Oncol Biol Phys 2022; 114:950-967. [PMID: 35901978 DOI: 10.1016/j.ijrobp.2022.07.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 07/18/2022] [Accepted: 07/19/2022] [Indexed: 11/23/2022]
Abstract
PURPOSE Early clinical results on the application of magnetic resonance imaging (MRI) coupled with a linear accelerator to deliver MR-guided radiation therapy (MRgRT) have demonstrated feasibility for safe delivery of stereotactic body radiotherapy (SBRT) in treatment of oligometastatic disease. Here we set out to review the clinical evidence and challenges associated with MRgRT in this setting. METHODS AND MATERIALS We performed a systematic review of the literature pertaining to clinical experiences and trials on the use of MRgRT primarily for the treatment of oligometastatic cancers. We reviewed the opportunities and challenges associated with the use of MRgRT. RESULTS Benefits of MRgRT pertaining to superior soft-tissue contrast, real-time imaging and gating, and online adaptive radiotherapy facilitate safe and effective dose escalation to oligometastatic tumors while simultaneously sparing surrounding healthy tissues. Challenges concerning further need for clinical evidence and technical considerations related to planning, delivery, quality assurance (QA) of hypofractionated doses, and safety in the MRI environment must be considered. CONCLUSIONS The promising early indications of safety and effectiveness of MRgRT for SBRT-based treatment of oligometastatic disease in multiple treatment locations should lead to further clinical evidence to demonstrate the benefit of this technology.
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22
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Zijlema SE, Breimer W, Gosselink MWJM, Bruijnen T, Arteaga de Castro CS, Tijssen RHN, Lagendijk JJW, Philippens MEP, van den Berg CAT. A mask-compatible, radiolucent, 8-channel head and neck receive array for MRI-guided radiotherapy treatments and pre-treatment simulation. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac6ebd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 05/11/2022] [Indexed: 11/11/2022]
Abstract
Abstract
Immobilization masks are used to prevent patient movement during head and neck (H&N) radiotherapy. Motion restriction is beneficial both during treatment, as well as in the pre-treatment simulation phase, where magnetic resonance imaging (MRI) is often used for target definition. However, the shape and size of the immobilization masks hinder the use of regular, close-fitting MRI receive arrays. In this work, we developed a mask-compatible 8-channel H&N array that consists of a single-channel baseplate, on which the mask can be secured, and a flexible 7-channel anterior element that follows the shape of the mask. The latter uses high impedance coils to achieve its flexibility and radiolucency. A fully-functional prototype was manufactured, its radiolucency was characterized, and the gain in imaging performance with respect to current clinical setups was quantified. Dosimetry measurements showed an overall dose change of −0.3%. Small, local deviations were up to −2.7% but had no clinically significant impact on a full treatment plan, as gamma pass rates (3%/3 mm) only slightly reduced from 97.9% to 97.6% (clinical acceptance criterion: ≥95%). The proposed H&N array improved the imaging performance with respect to three clinical setups. The H&N array more than doubled (+123%) and tripled (+246%) the signal-to-noise ratio with respect to the clinical MRI-simulation and MR-linac setups, respectively. G-factors were also lower with the proposed H&N array. The improved imaging performance resulted in a clearly visible signal-to-noise ratio improvement of clinically used TSE and DWI acquisitions. In conclusion, the 8-channel H&N array improves the imaging performance of MRI-simulation and MR-linac acquisitions, while dosimetry suggests that no clinically significant dose changes are induced.
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Keall PJ, Brighi C, Glide-Hurst C, Liney G, Liu PZY, Lydiard S, Paganelli C, Pham T, Shan S, Tree AC, van der Heide UA, Waddington DEJ, Whelan B. Integrated MRI-guided radiotherapy - opportunities and challenges. Nat Rev Clin Oncol 2022; 19:458-470. [PMID: 35440773 DOI: 10.1038/s41571-022-00631-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2022] [Indexed: 12/25/2022]
Abstract
MRI can help to categorize tissues as malignant or non-malignant both anatomically and functionally, with a high level of spatial and temporal resolution. This non-invasive imaging modality has been integrated with radiotherapy in devices that can differentially target the most aggressive and resistant regions of tumours. The past decade has seen the clinical deployment of treatment devices that combine imaging with targeted irradiation, making the aspiration of integrated MRI-guided radiotherapy (MRIgRT) a reality. The two main clinical drivers for the adoption of MRIgRT are the ability to image anatomical changes that occur before and during treatment in order to adapt the treatment approach, and to image and target the biological features of each tumour. Using motion management and biological targeting, the radiation dose delivered to the tumour can be adjusted during treatment to improve the probability of tumour control, while simultaneously reducing the radiation delivered to non-malignant tissues, thereby reducing the risk of treatment-related toxicities. The benefits of this approach are expected to increase survival and quality of life. In this Review, we describe the current state of MRIgRT, and the opportunities and challenges of this new radiotherapy approach.
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Affiliation(s)
- Paul J Keall
- ACRF Image X Institute, The University of Sydney, Sydney, New South Wales, Australia.
| | - Caterina Brighi
- ACRF Image X Institute, The University of Sydney, Sydney, New South Wales, Australia
| | - Carri Glide-Hurst
- Department of Human Oncology, University of Wisconsin, Madison, WI, USA
| | - Gary Liney
- Ingham Institute of Applied Medical Research, Sydney, New South Wales, Australia
| | - Paul Z Y Liu
- ACRF Image X Institute, The University of Sydney, Sydney, New South Wales, Australia
| | - Suzanne Lydiard
- ACRF Image X Institute, The University of Sydney, Sydney, New South Wales, Australia
| | - Chiara Paganelli
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Trang Pham
- Faculty of Medicine and Health, The University of New South Wales, Sydney, New South Wales, Australia
| | - Shanshan Shan
- ACRF Image X Institute, The University of Sydney, Sydney, New South Wales, Australia
| | - Alison C Tree
- The Royal Marsden NHS Foundation Trust and the Institute of Cancer Research, London, UK
| | - Uulke A van der Heide
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, Netherlands
| | - David E J Waddington
- ACRF Image X Institute, The University of Sydney, Sydney, New South Wales, Australia
| | - Brendan Whelan
- ACRF Image X Institute, The University of Sydney, Sydney, New South Wales, Australia
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Begg J, Jelen U, Keall P, Liney G, Holloway L. Experimental characterisation of the magnetic field correction factor,kB⃗,for Roos chambers in a parallel MRI-linac. Phys Med Biol 2022; 67. [PMID: 35413694 DOI: 10.1088/1361-6560/ac66b8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 04/12/2022] [Indexed: 12/15/2022]
Abstract
Objective.Reference dosimetry on an MRI-linac requires a chamber specific magnetic field correction factor,kB⃗.This work aims to measure the correction factor for a parallel plate chamber on a parallel MRI-linac.Approach.kB⃗is defined as the ratio of the absorbed dose to water calibration coefficient in the presence of the magnetic field,ND,wB⃗relative to that under 0 T conditions,ND,w0T.kB⃗was measured via aND,wtransfer to a field chamber at each magnetic field strength from a chamber with knownND,wandkB⃗.This was achieved on the parallel MRI-linac by moving the measurement set-up between a high magnetic field strength region at the MRI-isocentre and a low magnetic field strength region at the end of the bore whilst maintaining consistent set-up and scatter conditions. Three PTW 34001 Roos chambers were investigated as well as a PTW 30013 Farmer used to validate methodology.Main Results.The beam quality used for the measurements ofkB⃗wasTPR20/10 = 0.632. ThekB⃗for the PTW Farmer chamber at 1 T on a parallel MRI-linac was 0.993 ± 0.013 (k = 1). The averagekB⃗factor measured for the three Roos chambers on a 1 T parallel MRI-linac was 0.999 ± 0.014 (k = 1).Significance.The results presented are the first measurements ofkB⃗for a Roos chamber on a parallel MRI-linac. The Roos chamber results demonstrate the potential for the chamber as a reference dosimeter in parallel MRI-linacs.
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Affiliation(s)
- Jarrad Begg
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia
| | - Urszula Jelen
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Paul Keall
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,Image X Institute, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, 2005, Australia
| | - Gary Liney
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Lois Holloway
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Institute of Medical Physics, University of Sydney, Camperdown, NSW, 2005, Australia
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Ding S, Liu H, Li Y, Wang B, Li R, Huang X. Dosimetric Accuracy of MR-Guided Online Adaptive Planning for Nasopharyngeal Carcinoma Radiotherapy on 1.5 T MR-Linac. Front Oncol 2022; 12:858076. [PMID: 35463359 PMCID: PMC9022004 DOI: 10.3389/fonc.2022.858076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 03/11/2022] [Indexed: 12/04/2022] Open
Abstract
Purpose The aim of this study is to evaluate the dose accuracy of bulk relative electron density (rED) approach for application in 1.5 T MR-Linac and assess the reliability of this approach in the case of online adaptive MR-guided radiotherapy for nasopharyngeal carcinoma (NPC) patients. Methods Ten NPC patients formerly treated on conventional linac were included in this study, with their original planning CT and MRI collected. For each patient, structures such as the targets, organs at risk, bone, and air regions were delineated on the original CT in the Monaco system (v5.40.02). To simulate the online adaptive workflow, firstly all contours were transferred to MRI from the original CT using rigid registration in the Monaco system. Based on the structures, three different types of synthetic CT (sCT) were generated from MRI using the bulk rED assignment approach: the sCTICRU uses the rED values recommended by ICRU46, the sCTtailor uses the patient-specific mean rED values, and the sCTHomogeneity uses homogeneous water equivalent values. The same treatment plan was calculated on the three sCTs and the original CT. Dose calculation accuracy was investigated in terms of gamma analysis, point dose comparison, and dose volume histogram (DVH) parameters. Results Good agreement of dose distribution was observed between sCTtailor and the original CT, with a gamma passing rate (3%/3 mm) of 97.81% ± 1.06%, higher than that of sCTICRU (94.27% ± 1.48%, p = 0.005) and sCTHomogeneity (96.50% ± 1.02%, p = 0.005). For stricter criteria 1%/1 mm, gamma passing rates for plans on sCTtailor, sCTICRU, and sCTHomogeneity were 86.79% ± 4.31%, 79.81% ± 3.63%, and 77.56% ± 4.64%, respectively. The mean point dose difference in PTVnx between sCTtailor and planning CT was −0.14% ± 1.44%, much lower than that calculated on sCTICRU (−8.77% ± 2.33%) and sCTHomogeneity (1.65% ± 2.57%), all with p < 0.05. The DVH differences for the plan based on sCTtailor were much smaller than sCTICRU and sCTHomogeneity. Conclusions The bulk rED-assigned sCT by adopting the patient-specific rED values can achieve a clinically acceptable level of dose calculation accuracy in the presence of a 1.5 T magnetic field, making it suitable for online adaptive MR-guided radiotherapy for NPC patients.
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Affiliation(s)
- Shouliang Ding
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Hongdong Liu
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Yongbao Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Bin Wang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Rui Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Xiaoyan Huang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
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Subashi E, Dresner A, Tyagi N. Longitudinal assessment of quality assurance measurements in a 1.5 T MR-linac: Part II-Magnetic resonance imaging. J Appl Clin Med Phys 2022; 23:e13586. [PMID: 35332990 PMCID: PMC9398228 DOI: 10.1002/acm2.13586] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 02/05/2022] [Accepted: 02/25/2022] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To describe and report longitudinal quality assurance (QA) measurements for the magnetic resonance imaging (MRI) component of the Elekta Unity MR-linac during the first year of clinical use in our institution. MATERIALS AND METHODS The performance of the MRI component of Unity was evaluated with daily, weekly, monthly, and annual QA testing. The measurements monitor image uniformity, signal-to-noise ratio (SNR), resolution/detectability, slice position/thickness, linearity, central frequency, and geometric accuracy. In anticipation of routine use of quantitative imaging (qMRI), we characterize B0/B1 uniformity and the bias/reproducibility of longitudinal/transverse relaxation times (T1/T2) and apparent diffusion coefficient (ADC). Tolerance levels for QA measurements of qMRI biomarkers are derived from weekly monitoring of T1, T2, and ADC. RESULTS The 1-year assessment of QA measurements shows that daily variations in each MR quality metric are well below the threshold for failure. Routine testing procedures can reproducibly identify machine issues. The longitudinal three-dimensional (3D) geometric analysis reveals that the maximum distortion in a diameter of spherical volume (DSV) of 20, 30, 40, and 50 cm is 0.4, 0.6, 1.0, and 3.1 mm, respectively. The main source of distortion is gradient nonlinearity. Maximum peak-to-peak B0 inhomogeneity is 3.05 ppm, with gantry induced B0 inhomogeneities an order of magnitude smaller. The average deviation from the nominal B1 is within 2%, with minimal dependence on gantry angle. Mean ADC, T1, and T2 values are measured with high reproducibility. The median coefficient of variation for ADC, T1, and T2 is 1.3%, 1.1%, and 0.5%, respectively. The median bias for ADC, T1, and T2 is -0.8%, -0.1%, and 3.9%, respectively. CONCLUSION The MRI component of Unity operates within the guidelines and recommendations for scanner performance and stability. Our findings support the recently published guidance in establishing clinically acceptable tolerance levels for image quality. Highly reproducible qMRI measurements are feasible in Unity.
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Affiliation(s)
- Ergys Subashi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Alex Dresner
- Philips Healthcare MR Oncology, Cleveland, Ohio, USA
| | - Neelam Tyagi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York, USA
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Pham TT, Whelan B, Oborn BM, Delaney GP, Vinod S, Brighi C, Barton M, Keall P. Magnetic resonance imaging (MRI) guided proton therapy: A review of the clinical challenges, potential benefits and pathway to implementation. Radiother Oncol 2022; 170:37-47. [DOI: 10.1016/j.radonc.2022.02.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 02/09/2022] [Accepted: 02/25/2022] [Indexed: 10/18/2022]
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Yano M, Araki F, Ohno T. Monte Carlo study of small-field dosimetry for an ELEKTA Unity MR-Linac system. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2022.110036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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29
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Causer TJ, Rosenfeld AB, Metcalfe PE, Oborn BM. A portable magnet for radiation biology and dosimetry studies in magnetic fields. Med Phys 2022; 49:1924-1931. [PMID: 35023145 DOI: 10.1002/mp.15447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 11/01/2021] [Accepted: 12/14/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND AND PURPOSE In the current and rapidly evolving era of real-time MRI-guided radiotherapy, our radiation biology and dosimetry knowledge is being tested in a novel way. This paper presents the successful design and implementation of a portable device used to generate strong localized magnetic fields. These are ideally suited for small scale experiments that mimic the magnetic field environment inside an MRI-linac system, or more broadly MRI-guided particle therapy as well. MATERIALS AND METHODS A portable permanent magnet based device employing an adjustable steel yoke and magnetic field focusing cones has been designed, constructed and tested. The apparatus utilises two banks of Nd2 Fe14 B permanent magnets totalling around 50 kg in mass to generate a strong magnetic field throughout a small volume between two pole tips. The yoke design allows adjustment of the pole tip gap and exchanging of the focusing cones. Further to this, beam portal holes are present in the yoke and focusing cones, allowing for radiation beams of up to 5 x 5 cm2 to pass through the region of high magnetic field between the focusing cone tips. Finite element magnetic modelling was performed to design and characterise the performance of the device. Automated physical measurements of the magnetic field components at various locations were measured to confirm the performance. The adjustable pole gap and interchangeable cones allows rapid changing of the experimental set-up to allow different styles of measurements to be performed. RESULTS A mostly uniform magnetic field of 1.2 T can be achieved over a volume of at least 3 x 3 x 3 cm3 . This can be reduced in strength to 0.3 T but increased in volume to 10 x 10 x 10 cm3 via removal of the cone tips and/or adjustment of the steel yoke. Although small, these volumes are sufficient to house radiation detectors, cell culture dishes and various phantom arrangements targeted at examining small radiation field dosimetry inside magnetic field strengths that can be changed with ease. Most important is the ability to align the magnetic field both perpendicular to, or inline with the radiation beam. To date, the system has been successfully used to conduct published research in the areas of radiation detector performance, lung phantom dosimetry, and how small clinical electron beams behave in these strong magnetic fields. CONCLUSIONS A portable, relatively inexpensive, and simple to operate device has successfully been constructed and used for performing radiation oncology studies around the theme of MRI-guided radiotherapy. This can be in either inline and perpendicular magnetic fields of up to 1.2 T with x-ray and particle beams.
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Affiliation(s)
- Trent J Causer
- Illawarra Cancer Care Centre, Wollongong, NSW, 2500, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
| | | | - Peter E Metcalfe
- Illawarra Cancer Care Centre, Wollongong, NSW, 2500, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Bradley M Oborn
- Illawarra Cancer Care Centre, Wollongong, NSW, 2500, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
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Tan H, Stewart J, Ruschin M, Wang MH, Myrehaug S, Tseng CL, Detsky J, Husain Z, Chen H, Sahgal A, Soliman H. Inter-fraction dynamics during post-operative 5 fraction cavity hypofractionated stereotactic radiotherapy with a MR LINAC: a prospective serial imaging study. J Neurooncol 2022; 156:569-577. [PMID: 34981300 DOI: 10.1007/s11060-021-03938-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 12/27/2021] [Indexed: 11/30/2022]
Abstract
PURPOSE/OBJECTIVE(S) This study examined changes in the clinical target volume (CTV) and associated clinical implications on a magnetic resonance imaging linear accelerator (MR LINAC) during hypofractionated stereotactic radiotherapy (HSRT) to resected brain metastases. In addition, the suitability of using T2/FLAIR (T2f) sequence to define CTV was explored by assessing contouring variability between gadolinium-enhanced T1 (T1c) and T2f sequences. MATERIALS/METHODS Fifteen patients treated to either 27.5 or 30 Gy with five fraction HSRT were imaged with T1c and T2f sequences during treatment; T1c was acquired at planning (FxSim), and fraction 3 (Fx3), and T2f was acquired at FxSim and all five fractions. The CTV were contoured on all acquired images. Inter-fraction cavity dynamics and CTV contouring variability were quantified using absolute volume, Dice similarity coefficient (DSC), and Hausdorff distance (HD) metrics. RESULTS The median CTV on T1c and T2f sequences at FxSim were 12.0cm3 (range, 1.2-30.1) and 10.2cm3 (range, 2.9-27.9), respectively. At Fx3, the median CTV decreased in both sequences to 9.3cm3 (range, 3.7-25.9) and 8.6cm3 (range, 3.3-22.5), translating to a median % relative reduction of - 11.4% on T1c (p = 0.009) and - 8.4% on T2f (p = 0.032). We observed a median % relative reduction in CTV between T1c and T2f at FxSim of - 6.0% (p = 0.040). The mean DSC was 0.85 ± 0.10, and the mean HD was 5.3 ± 2.7 mm when comparing CTV on T1c and T2f at FxSim. CONCLUSION Statistically significant reductions in cavity CTV was observed during HSRT, supporting the use of MR image guided radiation therapy and treatment adaptation to mitigate toxicity. Significant CTV contouring variability was seen between T1c and T2f sequences. Trial registration NCT04075305 - August 30, 2019.
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Affiliation(s)
- Hendrick Tan
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
- GenesisCare, Perth, WA, Australia
| | - James Stewart
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
| | - Mark Ruschin
- Department of Radiation Oncology, University of Toronto, Toronto, Canada
- Department of Medical Physics, Sunnybrook Odette Cancer Centre, Toronto, Canada
| | - Michael H Wang
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
| | - Sten Myrehaug
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Canada
| | - Chia-Lin Tseng
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Canada
| | - Jay Detsky
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Canada
| | - Zain Husain
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Canada
| | - Hanbo Chen
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Canada
| | - Arjun Sahgal
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Canada
| | - Hany Soliman
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
- Department of Radiation Oncology, University of Toronto, Toronto, Canada.
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Hall WA, Paulson E, Li XA, Erickson B, Schultz C, Tree A, Awan M, Low DA, McDonald BA, Salzillo T, Glide-Hurst CK, Kishan AU, Fuller CD. Magnetic resonance linear accelerator technology and adaptive radiation therapy: An overview for clinicians. CA Cancer J Clin 2022; 72:34-56. [PMID: 34792808 PMCID: PMC8985054 DOI: 10.3322/caac.21707] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 09/01/2021] [Accepted: 09/22/2021] [Indexed: 12/25/2022] Open
Abstract
Radiation therapy (RT) continues to play an important role in the treatment of cancer. Adaptive RT (ART) is a novel method through which RT treatments are evolving. With the ART approach, computed tomography or magnetic resonance (MR) images are obtained as part of the treatment delivery process. This enables the adaptation of the irradiated volume to account for changes in organ and/or tumor position, movement, size, or shape that may occur over the course of treatment. The advantages and challenges of ART maybe somewhat abstract to oncologists and clinicians outside of the specialty of radiation oncology. ART is positioned to affect many different types of cancer. There is a wide spectrum of hypothesized benefits, from small toxicity improvements to meaningful gains in overall survival. The use and application of this novel technology should be understood by the oncologic community at large, such that it can be appropriately contextualized within the landscape of cancer therapies. Likewise, the need to test these advances is pressing. MR-guided ART (MRgART) is an emerging, extended modality of ART that expands upon and further advances the capabilities of ART. MRgART presents unique opportunities to iteratively improve adaptive image guidance. However, although the MRgART adaptive process advances ART to previously unattained levels, it can be more expensive, time-consuming, and complex. In this review, the authors present an overview for clinicians describing the process of ART and specifically MRgART.
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MESH Headings
- History, 20th Century
- History, 21st Century
- Humans
- Magnetic Resonance Imaging, Interventional/history
- Magnetic Resonance Imaging, Interventional/instrumentation
- Magnetic Resonance Imaging, Interventional/methods
- Magnetic Resonance Imaging, Interventional/trends
- Neoplasms/diagnostic imaging
- Neoplasms/radiotherapy
- Particle Accelerators
- Radiation Oncology/history
- Radiation Oncology/instrumentation
- Radiation Oncology/methods
- Radiation Oncology/trends
- Radiotherapy Planning, Computer-Assisted/history
- Radiotherapy Planning, Computer-Assisted/instrumentation
- Radiotherapy Planning, Computer-Assisted/methods
- Radiotherapy Planning, Computer-Assisted/trends
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Affiliation(s)
- William A. Hall
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Eric Paulson
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - X. Allen Li
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Beth Erickson
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Christopher Schultz
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Alison Tree
- The Royal Marsden National Health Service Foundation Trust and the Institute of Cancer Research, London, United Kingdom
| | - Musaddiq Awan
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Daniel A. Low
- Department of Radiation Oncology, University of California-Los Angeles, Los Angeles, California
| | - Brigid A. McDonald
- Department of Radiation Oncology, The University of Texas, MD Anderson Cancer Center, Houston, Texas
| | - Travis Salzillo
- Department of Radiation Oncology, The University of Texas, MD Anderson Cancer Center, Houston, Texas
| | - Carri K. Glide-Hurst
- Department of Radiation Oncology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Amar U. Kishan
- Department of Radiation Oncology, University of California-Los Angeles, Los Angeles, California
| | - Clifton D. Fuller
- Department of Radiation Oncology, The University of Texas, MD Anderson Cancer Center, Houston, Texas
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Li Y, Xiao F, Liu B, Qi M, Lu X, Cai J, Zhou L, Song T. Deep learning-based 3D in vivodose reconstruction with an electronic portal imaging device for magnetic resonance-linear accelerators: a proof of concept study. Phys Med Biol 2021; 66. [PMID: 34798623 DOI: 10.1088/1361-6560/ac3b66] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 11/19/2021] [Indexed: 11/11/2022]
Abstract
Objective.To develop a novel deep learning-based 3Din vivodose reconstruction framework with an electronic portal imaging device (EPID) for magnetic resonance-linear accelerators (MR-LINACs).Approach.The proposed method directly back-projected 2D portal dose into 3D patient coarse dose, which bypassed the complicated patient-to-EPID scatter estimation step used in conventional methods. A pre-trained convolutional neural network (CNN) was then employed to map the coarse dose to the final accurate dose. The electron return effect caused by the magnetic field was captured with the CNN model. Patient dose and portal dose datasets were synchronously generated with Monte Carlo simulation for 96 patients (78 cases for training and validation and 18 cases for testing) treated with fixed-beam intensity-modulated radiotherapy in four different tumor sites, including the brain, nasopharynx, lung, and rectum. Beam angles from the training dataset were further rotated 2-3 times, and doses were recalculated to augment the datasets.Results.The comparison between reconstructed doses and MC ground truth doses showed mean absolute errors <0.88% for all tumor sites. The averaged 3Dγ-passing rates (3%, 2 mm) were 97.42%±2.66% (brain), 98.53%±0.95% (nasopharynx), 99.41%±0.46% (lung), and 98.63%±1.01% (rectum). The dose volume histograms and indices also showed good consistency. The average dose reconstruction time, including back projection and CNN dose mapping, was less than 3 s for each individual beam.Significance.The proposed method can be potentially used for accurate and fast 3D dosimetric verification for online adaptive radiotherapy using MR-LINACs.
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Affiliation(s)
- Yongbao Li
- Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, People's Republic of China
| | - Fan Xiao
- School of Biomedical Engineering, Southern Medical University, Guangzhou, People's Republic of China
| | - Biaoshui Liu
- Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, People's Republic of China
| | - Mengke Qi
- School of Biomedical Engineering, Southern Medical University, Guangzhou, People's Republic of China
| | - Xingyu Lu
- School of Biomedical Engineering, Southern Medical University, Guangzhou, People's Republic of China
| | - Jiajun Cai
- School of Biomedical Engineering, Southern Medical University, Guangzhou, People's Republic of China
| | - Linghong Zhou
- School of Biomedical Engineering, Southern Medical University, Guangzhou, People's Republic of China
| | - Ting Song
- School of Biomedical Engineering, Southern Medical University, Guangzhou, People's Republic of China
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33
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White I, Hunt A, Bird T, Settatree S, Soliman H, Mcquaid D, Dearnaley D, Lalondrelle S, Bhide S. Interobserver variability in target volume delineation for CT/MRI simulation and MRI-guided adaptive radiotherapy in rectal cancer. Br J Radiol 2021; 94:20210350. [PMID: 34723622 PMCID: PMC8631009 DOI: 10.1259/bjr.20210350] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 09/19/2021] [Accepted: 09/23/2021] [Indexed: 12/02/2022] Open
Abstract
OBJECTIVES Quantify target volume delineation uncertainty for CT/MRI simulation and MRI-guided adaptive radiotherapy in rectal cancer. Define optimal imaging sequences for target delineation. METHODS Six experienced radiation oncologists delineated clinical target volumes (CTVs) on CT and 2D and 3D-MRI in three patients with rectal cancer, using consensus contouring guidelines. Tumour GTV (GTVp) was also contoured on MRI acquired week 0 and 3 of radiotherapy. A STAPLE contour was created and volume and interobserver variability metrics were analysed. RESULTS There were statistically significant differences in volume between observers for CT and 2D-MRI-defined CTVs (p < 0.05). There was no significant difference between observers on 3D-MRI. Significant differences in volume were seen between observers for both 2D and 3D-MRI-defined GTVp at weeks 0 and 3 (p < 0.05). Good interobserver agreement (IOA) was seen for CTVs delineated on all imaging modalities with best IOA on 3D-MRI; median Conformity index (CI) 0.74 for CT, 0.75 for 2D-MRI and 0.77 for 3D-MRI. IOA of MRI-defined GTVp week 0 was better compared to CT; CI 0.58 for CT, 0.62 for 2D-MRI and 0.7 for 3D-MRI. MRI-defined GTVp IOA week three was worse compared to week 0. CONCLUSION Delineation on MRI results in smaller volumes and better IOA week 0 compared to CT. 3D-MRI provides the best IOA in CTV and GTVp. MRI-defined GTVp on images acquired week 3 showed worse IOA compared to week 0. This highlights the need for consensus guidelines in GTVp delineation on MRI during treatment course in the context of dose escalation MRI-guided rectal boost studies. ADVANCES IN KNOWLEDGE Optimal MRI sequences for CT/MRI simulation and MRI-guided adaptive radiotherapy in rectal cancer have been defined.
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Affiliation(s)
| | - Arabella Hunt
- The Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, UK
| | - Thomas Bird
- University Hospitals Bristol NHS Foundation Trust, Bristol, UK
| | - Sarah Settatree
- The Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, UK
| | - Heba Soliman
- The Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, UK
| | - Dualta Mcquaid
- The Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, UK
| | - David Dearnaley
- The Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, UK
| | - Susan Lalondrelle
- The Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, UK
| | - Shree Bhide
- The Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, UK
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34
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de Leon J, Woods A, Twentyman T, Meade M, Sproule V, Chandran S, Christiansen J, Kennedy N, Marney M, Barooshian K, Plit M, Lynch J, Jagavkar R, Ormandy H, Christodouleas J, Pietzsch F, Chan M, Jameson MG. Analysis of data to Advance Personalised Therapy with MR-Linac (ADAPT-MRL). Clin Transl Radiat Oncol 2021; 31:64-70. [PMID: 34646950 PMCID: PMC8495756 DOI: 10.1016/j.ctro.2021.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 09/08/2021] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND Analysis of Data to Advance Personalised Therapy with MR-Linac (ADAPT-MRL) is a multi-site, multinational, observational cohort registry designed to collect data on the use of the magnetic resonance linear accelerator (MR-Linac) for radiation therapy and patient outcomes. The registry will provide a linked repository of technical and clinical data that will form a platform for prospective studies and technology assessment. METHODS Design: This registry aims to include an estimated 10,000 eligible participants across Australia and other countries over a 7- to 10-year period. Participants will undergo treatment and assessments in accordance with standard practice. Toxicity and survival outcomes will be assessed at baseline, during treatment, and with 3 monthly follow-up until 24 months, patient reported outcome measures will also be collected. Participants with a variety of cancers will be included. DISCUSSION Data obtained from the ADAPT-MRL registry is expected to provide evidence on the safety and efficacy of the MR-Linac, a new technical innovation in radiation oncology. We expect this registry will generate data that will be used to optimise treatment techniques, MR-Linac software algorithms, evaluate participants' outcomes and toxicities and to create a repository of adapted plans, anatomical and functional MR sequences linked to participants' outcomes.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - John Christodouleas
- Elekta AB, Stockholm, Sweden
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, USA
| | | | | | - Michael G Jameson
- GenesisCare, Sydney, Australia
- University of New South Wales, Sydney, Australia
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35
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Chu VWS, Kan MWK, Wong KCW, Lee LKY, Chan ATC. Towards magnetic-field-modulated radiotherapy (MagMRT) with an MR-LINAC-a Monte Carlo study. Phys Med Biol 2021; 66. [PMID: 34587609 DOI: 10.1088/1361-6560/ac2b83] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 09/29/2021] [Indexed: 11/12/2022]
Abstract
Objective.The feasibility of magnetic-field-modulated radiotherapy (MagMRT) with an MR-LINAC was investigated by studying the effects of dose enhancement and reduction using a transverse magnetic field with a longitudinal gradient applied along a photon radiation beam.Approach.Geant4 simulation toolkit was used to perform Monte Carlo simulations on a water phantom with the energy spectrum of a 7 MV flattening-filter-free photon beam from an Elekta Unity system as the source of radiation. Linear magnetic field gradients with magnitudes ranged from 1 to 6 T cm-1and spatial extents of 1-3 cm were used to study the dependence of dose modulation on these two parameters. The effects of radiation field size and the ability of dose modulation through optimizing the waveform of magnetic field variation were also explored.Main results.Our results show that dose enhancement and reduction can be achieved by applying a transverse magnetic field with a longitudinal field gradient along a photon beam. The steeper the gradient, the more prominent is the effect. A dose enhancement of 33% and a dose reduction of 22% are found for a magnetic gradient of 6 T cm-1and -6 T cm-1respectively. The spatial extent of the dose modulation effect which is greater than 3% is found to be around 1-2 cm. Both the dose enhancement and reduction effects are independent of the radiation field sizes, but they exhibit different behaviors with the spatial extents of the gradient. Multiple locations of dose enhancement and reduction can be produced by modulating the waveform of the magnetic field variation along the radiation beam, demonstrating a vast degree of freedom in the modulation aspect of MagMRT.Significance.MagMRT is a conceptually feasible and promising new radiotherapy modulation technique along the direction of the radiation beam.
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Affiliation(s)
- Vivien W S Chu
- Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong SAR, People's Republic of China.,Department of Clinical Oncology, The Chinese University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Monica W K Kan
- Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong SAR, People's Republic of China.,Department of Clinical Oncology, The Chinese University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Kenneth C W Wong
- Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong SAR, People's Republic of China.,Department of Clinical Oncology, The Chinese University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Louis K Y Lee
- CUHK Medical Centre, Hong Kong SAR, People's Republic of China
| | - Anthony T C Chan
- Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong SAR, People's Republic of China.,Department of Clinical Oncology, The Chinese University of Hong Kong, Hong Kong SAR, People's Republic of China.,State Key Laboratory of Translational Oncology, Sir YK Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong SAR, People's Republic of China
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36
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Olberg S, Chun J, Su Choi B, Park I, Kim H, Kim T, Sung Kim J, Green O, Park JC. Abdominal synthetic CT reconstruction with intensity projection prior for MRI-only adaptive radiotherapy. Phys Med Biol 2021; 66. [PMID: 34530421 DOI: 10.1088/1361-6560/ac279e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 09/16/2021] [Indexed: 11/11/2022]
Abstract
Objective. Owing to the superior soft tissue contrast of MRI, MRI-guided adaptive radiotherapy (ART) is well-suited to managing interfractional changes in anatomy. An MRI-only workflow is desirable, but producing synthetic CT (sCT) data through paired data-driven deep learning (DL) for abdominal dose calculations remains a challenge due to the highly variable presence of intestinal gas. We present the preliminary dosimetric evaluation of our novel approach to sCT reconstruction that is well suited to handling intestinal gas in abdominal MRI-only ART.Approach. We utilize a paired data DL approach enabled by the intensity projection prior, in which well-matching training pairs are created by propagating air from MRI to corresponding CT scans. Evaluations focus on two classes: patients with (1) little involvement of intestinal gas, and (2) notable differences in intestinal gas presence between corresponding scans. Comparisons between sCT-based plans and CT-based clinical plans for both classes are made at the first treatment fraction to highlight the dosimetric impact of the variable presence of intestinal gas.Main results. Class 1 patients (n= 13) demonstrate differences in prescribed dose coverage of the PTV of 1.3 ± 2.1% between clinical plans and sCT-based plans. Mean DVH differences in all structures for Class 1 patients are found to be statistically insignificant. In Class 2 (n= 20), target coverage is 13.3 ± 11.0% higher in the clinical plans and mean DVH differences are found to be statistically significant.Significance. Significant deviations in calculated doses arising from the variable presence of intestinal gas in corresponding CT and MRI scans result in uncertainty in high-dose regions that may limit the effectiveness of adaptive dose escalation efforts. We have proposed a paired data-driven DL approach to sCT reconstruction for accurate dose calculations in abdominal ART enabled by the creation of a clinically unavailable training data set with well-matching representations of intestinal gas.
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Affiliation(s)
- Sven Olberg
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States of America.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63110, United States of America
| | - Jaehee Chun
- Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Byong Su Choi
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States of America.,Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Inkyung Park
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States of America.,Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Hyun Kim
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, MO 63110, United States of America
| | - Taeho Kim
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, MO 63110, United States of America
| | - Jin Sung Kim
- Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Olga Green
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, MO 63110, United States of America
| | - Justin C Park
- Medical Artificial Intelligence and Automation (MAIA) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States of America
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Lawrence LSP, Chan RW, Chen H, Keller B, Stewart J, Ruschin M, Chugh B, Campbell M, Theriault A, Stanisz GJ, MacKenzie S, Myrehaug S, Detsky J, Maralani PJ, Tseng CL, Czarnota GJ, Sahgal A, Lau AZ. Accuracy and precision of apparent diffusion coefficient measurements on a 1.5 T MR-Linac in central nervous system tumour patients. Radiother Oncol 2021; 164:155-162. [PMID: 34592363 DOI: 10.1016/j.radonc.2021.09.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/20/2021] [Accepted: 09/22/2021] [Indexed: 12/14/2022]
Abstract
BACKGROUND AND PURPOSE MRI linear accelerators (MR-Linacs) may allow treatment adaptation to be guided by quantitative MRI including diffusion-weighted imaging (DWI). The aim of this study was to evaluate the accuracy and precision of apparent diffusion coefficient (ADC) measurements from DWI on a 1.5 T MR-Linac in patients with central nervous system (CNS) tumours through comparison with a diagnostic scanner. MATERIALS AND METHODS CNS patients were treated using a 1.5 T Elekta Unity MR-Linac. DWI was acquired during MR-Linac treatment and on a Philips Ingenia 1.5 T. The agreement between the two scanners on median ADC over the gross tumour/clinical target volumes (GTV/CTV) and in brain regions (white/grey matter, cerebrospinal fluid (CSF)) was computed. Repeated scans were used to estimate ADC repeatability. Daily changes in ADC over the GTV of high-grade gliomas were characterized from MR-Linac scans. RESULTS DWI from 59 patients was analyzed. MR-Linac ADC measurements showed a small bias relative to Ingenia measurements in white matter, grey matter, GTV, and CTV (bias: -0.05 ± 0.03, -0.08 ± 0.05, -0.1 ± 0.1, -0.08 ± 0.07 μm2/ms). ADC differed substantially in CSF (bias: -0.5 ± 0.3 μm2/ms). The repeatability of MR-Linac ADC over white/grey matter was similar to previous reports (coefficients of variation for median ADC: 1.4%/1.8%). MR-Linac ADC changes in the GTV were detectable. CONCLUSIONS It is possible to obtain ADC measurements in the brain on a 1.5 T MR-Linac that are comparable to those of diagnostic-quality scanners. This technical validation study adds to the foundation for future studies that will correlate brain tumour ADC with clinical outcomes.
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Affiliation(s)
- Liam S P Lawrence
- Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | - Rachel W Chan
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada
| | - Hanbo Chen
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Brian Keller
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - James Stewart
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Mark Ruschin
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Brige Chugh
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada; Department of Physics, Ryerson University, Toronto, Canada
| | - Mikki Campbell
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Aimee Theriault
- Department of Medical Biophysics, University of Toronto, Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada; Department of Neurosurgery and Paediatric Neurosurgery, Medical University, Lublin, Poland
| | - Greg J Stanisz
- Department of Medical Biophysics, University of Toronto, Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada; Department of Neurosurgery and Paediatric Neurosurgery, Medical University, Lublin, Poland
| | - Scott MacKenzie
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Sten Myrehaug
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Jay Detsky
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Pejman J Maralani
- Medical Imaging, University of Toronto, Sunnybrook Health Sciences Centre, Toronto, Canada
| | - Chia-Lin Tseng
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Greg J Czarnota
- Department of Medical Biophysics, University of Toronto, Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada; Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Arjun Sahgal
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
| | - Angus Z Lau
- Department of Medical Biophysics, University of Toronto, Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada.
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Subashi E, Lim SB, Gonzalez X, Tyagi N. Longitudinal assessment of quality assurance measurements in a 1.5T MR-linac: Part I-Linear accelerator. J Appl Clin Med Phys 2021; 22:190-201. [PMID: 34505349 PMCID: PMC8504604 DOI: 10.1002/acm2.13418] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/16/2021] [Accepted: 08/29/2021] [Indexed: 01/04/2023] Open
Abstract
Purpose To describe and report longitudinal quality assurance (QA) measurements for the mechanical and dosimetric performance of an Elekta Unity MR‐linac during the first year of clinical use in our institution. Materials and methods The mechanical and dosimetric performance of the MR‐linac was evaluated with daily, weekly, monthly, and annual QA testing. The measurements monitor the size of the radiation isocenter, the MR‐to‐MV isocenter concordance, MLC and jaw position, the accuracy and reproducibility of step‐and‐shoot delivery, radiation output and beam profile constancy, and patient‐specific QA for the first 50 treatments in our institution. Results from end‐to‐end QA using anthropomorphic phantoms are also included as a reference for baseline comparisons. Measurements were performed in water or water‐equivalent plastic using ion chambers of various sizes, an ion chamber array, MR‐compatible 2D/3D diode array, portal imager, MRI, and radiochromic film. Results The diameter of the radiation isocenter and the distance between the MR/MV isocenters was (μ ± σ) 0.39 ± 0.01 mm and 0.89 ± 0.05 mm, respectively. Trend analysis shows both measurements to be well within the tolerance of 1.0 mm. MLC and jaw positional accuracy was within 1.0 mm while the dosimetric performance of step‐and‐shoot delivery was within 2.0%, irrespective of gantry angle. Radiation output and beam profile constancy were within 2.0% and 1.0%, respectively. End‐to‐end testing performed with ion‐chamber and radiochromic film showed excellent agreement with treatment plan. Patient‐specific QA using a 3D diode array identified gantry angles with low‐pass rates allowing for improvements in plan quality after necessary adjustments. Conclusion The MR‐linac operates within the guidelines of current recommendations for linear accelerator performance, stability, and safety. The analysis of the data supports the recently published guidance in establishing clinically acceptable tolerance levels for relative and absolute measurements.
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Affiliation(s)
- Ergys Subashi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Seng Boh Lim
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | | | - Neelam Tyagi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
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The effect of the magnetic fields from three different configurations of the MRIgRT systems on the dose deposition from lateral opposing photon beams in a laryngeal geometry – A Monte Carlo study. RADIATION MEDICINE AND PROTECTION 2021. [DOI: 10.1016/j.radmp.2021.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Spadea MF, Maspero M, Zaffino P, Seco J. Deep learning based synthetic-CT generation in radiotherapy and PET: A review. Med Phys 2021; 48:6537-6566. [PMID: 34407209 DOI: 10.1002/mp.15150] [Citation(s) in RCA: 82] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 06/06/2021] [Accepted: 07/13/2021] [Indexed: 01/22/2023] Open
Abstract
Recently,deep learning (DL)-based methods for the generation of synthetic computed tomography (sCT) have received significant research attention as an alternative to classical ones. We present here a systematic review of these methods by grouping them into three categories, according to their clinical applications: (i) to replace computed tomography in magnetic resonance (MR) based treatment planning, (ii) facilitate cone-beam computed tomography based image-guided adaptive radiotherapy, and (iii) derive attenuation maps for the correction of positron emission tomography. Appropriate database searching was performed on journal articles published between January 2014 and December 2020. The DL methods' key characteristics were extracted from each eligible study, and a comprehensive comparison among network architectures and metrics was reported. A detailed review of each category was given, highlighting essential contributions, identifying specific challenges, and summarizing the achievements. Lastly, the statistics of all the cited works from various aspects were analyzed, revealing the popularity and future trends and the potential of DL-based sCT generation. The current status of DL-based sCT generation was evaluated, assessing the clinical readiness of the presented methods.
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Affiliation(s)
- Maria Francesca Spadea
- Department Experimental and Clinical Medicine, University "Magna Graecia" of Catanzaro, Catanzaro, 88100, Italy
| | - Matteo Maspero
- Division of Imaging & Oncology, Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan, Utrecht, The Netherlands.,Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, Heidelberglaan, Utrecht, The Netherlands
| | - Paolo Zaffino
- Department Experimental and Clinical Medicine, University "Magna Graecia" of Catanzaro, Catanzaro, 88100, Italy
| | - Joao Seco
- Division of Biomedical Physics in Radiation Oncology, DKFZ German Cancer Research Center, Heidelberg, Germany.,Department of Physics and Astronomy, Heidelberg University, Heidelberg, Germany
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Guerreiro F, Svensson S, Seravalli E, Traneus E, Raaymakers BW. Intra-fractional per-beam adaptive workflow to mitigate the need for a rotating gantry during MRI-guided proton therapy. Phys Med Biol 2021; 66. [PMID: 34298523 DOI: 10.1088/1361-6560/ac176f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 07/23/2021] [Indexed: 11/12/2022]
Abstract
The integration of real-time magnetic resonance imaging (MRI)-guidance and proton therapy would potentially improve the proton dose steering capability by reducing daily uncertainties due to anatomical variations. The use of a fixed beamline coupled with an axial patient couch rotation would greatly simplify the proton delivery with MRI-guidance. Nonetheless, it is mandatory to assure that the plan quality is not deteriorated by the anatomical deformations due to patient rotation. In this work, an in-house tool allowing for intra-fractional per-beam adaptation of intensity-modulated proton plans (BeamAdapt) was implemented through features available in RayStation. A set of three MRIs was acquired for two healthy volunteers (V1, V2): (1) no rotation/static, (2) rotation to the right and (3) left. V1 was rotated by 15º, to simulate a clinical pediatric abdominal case and V2 by 45º, to simulate an extreme patient rotation case. For each volunteer, a total of four intensity-modulated pencil beam scanning plans were optimized on the static MRI using virtual abdominal targets and 2-3 posterior-oblique beams. Beam angles were defined according to the angulations on the rotated MRIs. With BeamAdapt, each original plan was first converted into separate plans with one beam per plan. In an iterative order, individual beam doses were non-rigidly deformed to the rotated anatomies and re-optimized accounting for the consequent deformations and the beam doses delivered so far. For evaluation, the final adapted dose distribution was propagated back to the static MRI. Planned and adapted dose distributions were compared by computing relative differences between dose-volume histogram (DVH) metrics. Absolute target dose differences were on average below 1% and mean dose organs-at-risk differences were below 3%. With BeamAdapt, not only intra-fractional per-beam proton plan adaptation coupled with axial patient rotation is possible but also the need for a rotating gantry during MRI-guidance might be mitigated.
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Affiliation(s)
- Filipa Guerreiro
- Department of Radiotherapy, University Medical Center Utrecht Imaging Division, Utrecht, NETHERLANDS
| | | | - Enrica Seravalli
- Department of Radiotherapy, University Medical Center Utrecht Imaging Division, Utrecht, NETHERLANDS
| | - Erik Traneus
- RaySearch Laboratories AB, Stockholm, Stockholm, SWEDEN
| | - Bas W Raaymakers
- Department of Radiotherapy, University Medical Center Utrecht Imaging Division, Utrecht, NETHERLANDS
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Hyer DE, Cai B, Rong Y. Future mainstream platform for online adaptive radiotherapy will be using on-board MR rather than on-board (CB) CT images. J Appl Clin Med Phys 2021; 22:4-9. [PMID: 34278681 PMCID: PMC8292695 DOI: 10.1002/acm2.13352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 06/18/2021] [Indexed: 01/18/2023] Open
Affiliation(s)
- Daniel E Hyer
- Radiation Oncology, University of Iowa, Iowa City, IA, USA
| | - Bin Cai
- Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yi Rong
- Radiation Oncology, Mayo Clinic Arizona, Phoenix, AZ, USA
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Liu X, Li Z, Rong Y, Cao M, Li H, Jia C, Shi L, Lu W, Gong G, Yin Y, Qiu J. A Comparison of the Distortion in the Same Field MRI and MR-Linac System With a 3D Printed Phantom. Front Oncol 2021; 11:579451. [PMID: 34150605 PMCID: PMC8209415 DOI: 10.3389/fonc.2021.579451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 04/30/2021] [Indexed: 11/13/2022] Open
Abstract
PURPOSE A 3D printed geometric phantom was developed that can be scanned with computed tomography (CT) and magnetic resonance imaging (MRI) to measure the geometric distortion and determine the relevant dose changes. MATERIALS AND METHODS A self-designed 3D printed photosensitive resin phantom was used, which adopts grid-like structures and has 822 1 cm2 squares. The scanning plan was delivered by three MRI scanners: the Elekta Unity MR-Linac 1.5T, GE Signa HDe 1.5T, and GE Discovery-sim 750 3.0T. The geometric distortion comparison was concentrated on two 1.5T MRI systems, whereas the 3.0T MRI was used as a supplemental experiment. The most central transverse images in each dataset were selected to demonstrate the plane distortion. Some mark points were selected to analyze the distortion in the 3D direction based on the plane geometric distortion. A treatment plan was created with the off-line Monaco system. RESULTS The distortion increases gradually from the center to the outside. The distortion range is 0.79 ± 0.40 mm for the Unity, 1.31 ± 0.56 mm for the GE Signa HDe, and 2.82 ± 1.48 mm for the GE Discovery-sim 750. Additionally, the geometric distortion slightly affects the actual planning dose of the radiotherapy. CONCLUSION Geometric distortion increases gradually from the center to the outside. The distortion values of the Unity were smaller than those of the GE Signa HDe, and the Unity has the smallest geometric distortion. Finally, the Unity's dose variation best matched with the standard treatment plan.
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Affiliation(s)
- Xuechun Liu
- Medical Engineering and Technology Research Center, Department of Radiology, Shandong First Medical University & Shandong Academy of Medical Sciences, Tai’an, China
- Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
| | - Zhenjiang Li
- Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
| | - Yi Rong
- Department of Radiation Oncology, University of California Davis Comprehensive Cancer Center, Sacramento, CA, United States
| | - Minsong Cao
- Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA, United States
| | - Hongyu Li
- Academy of Marine Science and Engineering, Shandong University of Science and Technology, Qingdao, China
| | - Chuntao Jia
- Academy of Marine Science and Engineering, Shandong University of Science and Technology, Qingdao, China
| | - Liting Shi
- Medical Engineering and Technology Research Center, Department of Radiology, Shandong First Medical University & Shandong Academy of Medical Sciences, Tai’an, China
| | - Weizhao Lu
- Medical Engineering and Technology Research Center, Department of Radiology, Shandong First Medical University & Shandong Academy of Medical Sciences, Tai’an, China
| | - Guanzhong Gong
- Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
| | - Yong Yin
- Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
| | - Jianfeng Qiu
- Medical Engineering and Technology Research Center, Department of Radiology, Shandong First Medical University & Shandong Academy of Medical Sciences, Tai’an, China
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Calculations of magnetic field correction factors for ionization chambers in a transverse magnetic field using Monte Carlo code TOPAS. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2021.109405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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de Pooter J, Billas I, de Prez L, Duane S, Kapsch RP, Karger CP, van Asselen B, Wolthaus J. Reference dosimetry in MRI-linacs: evaluation of available protocols and data to establish a Code of Practice. Phys Med Biol 2021; 66:05TR02. [PMID: 32570225 DOI: 10.1088/1361-6560/ab9efe] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
With the rapid increase in clinical treatments with MRI-linacs, a consistent, harmonized and sustainable ground for reference dosimetry in MRI-linacs is needed. Specific for reference dosimetry in MRI-linacs is the presence of a strong magnetic field. Therefore, existing Code of Practices (CoPs) are inadequate. In recent years, a vast amount of papers have been published in relation to this topic. The purpose of this review paper is twofold: to give an overview and evaluate the existing literature for reference dosimetry in MRI-linacs and to discuss whether the literature and datasets are adequate and complete to serve as a basis for the development of a new or to extend existing CoPs. This review is prefaced with an overview of existing MRI-linac facilities. Then an introduction on the physics of radiation transport in magnetic fields is given. The main part of the review is devoted to the evaluation of the literature with respect to the following subjects: • beam characteristics of MRI-linac facilities; • formalisms for reference dosimetry in MRI-linacs; • characteristics of ionization chambers in the presence of magnetic fields; • ionization chamber beam quality correction factors; and • ionization chamber magnetic field correction factors. The review is completed with a discussion as to whether the existing literature is adequate to serve as basis for a CoP. In addition, it highlights subjects for future research on this topic.
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Ding S, Liu H, Li Y, Wang B, Li R, Liu B, Ouyang Y, Wu D, Huang X. Assessment of dose accuracy for online MR-guided radiotherapy for cervical carcinoma. JOURNAL OF RADIATION RESEARCH AND APPLIED SCIENCES 2021. [DOI: 10.1080/16878507.2021.1888243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Shouliang Ding
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
- Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Hongdong Liu
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Yongbao Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Bin Wang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Rui Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Biaoshui Liu
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Yi Ouyang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Dehua Wu
- Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Xiaoyan Huang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
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Whelan B, Leghissa M, Amrei P, Zaitsev M, Heinrich B, Fahrig R, Rohdjess H. Magnetic modeling of actively shielded rotating MRI magnets in the presence of environmental steel. Phys Med Biol 2021; 66:045004. [PMID: 33264755 DOI: 10.1088/1361-6560/abd010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Rotating MRI systems could enable novel integrated medical devices such as MRI-Linacs, MRI-xray-angiography systems, and MRI-proton therapy systems. This work aimed to investigate the feasibility of rotating actively shielded superconducting MRI magnets in the presence of environmental steel-in particular, construction steel in the floor of the installation site. Two magnets were investigated: a 1.0 T split bore magnet, and a 1.5 T closed bore magnet. Each magnet was scaled to emulate field strengths of 0.5, 1.0, and 1.5 T. Finite Element Modeling was used to simulate these magnets in the presence of a 3 × 4 m steel plate located 1250 mm or 1400 mm below the isocenter. There are two possible rotation directions: around the longitudinal (z) axis or around the transverse (x) axis. Each model was solved for rotation angles between 0 and 360° in 30° intervals around each of these axes. For each simulation, a 300 mm DSV was extracted and decomposed into spherical harmonics. For the closed-bore magnet, total induced perturbation for the zero degree rotation angle was 223, 432, and 562 μT peak-to-peak (pk-pk) for the 0.5, 1.0, and 1.5 T models respectively (steel at 1250 mm). For the split-bore magnet, the same numbers were 1477, 16747, and 1766 μT. The substantially higher perturbation for the split-bore magnet can be traced to its larger fringe field. For rotation around the z-axis, total perturbation does not change as a function of angle but is exchanged between different harmonics. For rotation around the x-axis, total perturbation is different at each rotation angle. For the closed bore magnet, maximum perturbations occurred for a 90° rotation around the transverse axis. For the split-bore magnet, the opposite was observed, with the same 90° rotation yielding total perturbation lower than the conventional position. In all cases, at least 95% of the total perturbation was composed of 1st and 2nd order harmonics. The presence of environmental steel poses a major challenge to the realization of an actively shielded rotating superconducting MRI system, requiring some novel form of shimming. Possible shimming strategies are discussed at length.
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Affiliation(s)
- Brendan Whelan
- Innovation, Advanced Therapies, Siemens Healthineers GmbH, Forchheim, Germany. ACRF Image X Institute, Sydney School of Health Sciences, University of Sydney, Australia
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Otazo R, Lambin P, Pignol JP, Ladd ME, Schlemmer HP, Baumann M, Hricak H. MRI-guided Radiation Therapy: An Emerging Paradigm in Adaptive Radiation Oncology. Radiology 2020; 298:248-260. [PMID: 33350894 DOI: 10.1148/radiol.2020202747] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Radiation therapy (RT) continues to be one of the mainstays of cancer treatment. Considerable efforts have been recently devoted to integrating MRI into clinical RT planning and monitoring. This integration, known as MRI-guided RT, has been motivated by the superior soft-tissue contrast, organ motion visualization, and ability to monitor tumor and tissue physiologic changes provided by MRI compared with CT. Offline MRI is already used for treatment planning at many institutions. Furthermore, MRI-guided linear accelerator systems, allowing use of MRI during treatment, enable improved adaptation to anatomic changes between RT fractions compared with CT guidance. Efforts are underway to develop real-time MRI-guided intrafraction adaptive RT of tumors affected by motion and MRI-derived biomarkers to monitor treatment response and potentially adapt treatment to physiologic changes. These developments in MRI guidance provide the basis for a paradigm change in treatment planning, monitoring, and adaptation. Key challenges to advancing MRI-guided RT include real-time volumetric anatomic imaging, addressing image distortion because of magnetic field inhomogeneities, reproducible quantitative imaging across different MRI systems, and biologic validation of quantitative imaging. This review describes emerging innovations in offline and online MRI-guided RT, exciting opportunities they offer for advancing research and clinical care, hurdles to be overcome, and the need for multidisciplinary collaboration.
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Affiliation(s)
- Ricardo Otazo
- From the Departments of Medical Physics (R.O.) and Radiology (R.O., H.H.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; The D-Lab, Department of Precision Medicine, Department of Radiology & Nuclear Medicine, GROW-School for Oncology, Maastricht University Medical Centre, Maastricht, the Netherlands (P.L.); Department of Radiation Oncology, Dalhousie University, Halifax, Canada (J.P.P.); Divisions of Medical Physics in Radiology (M.E.L.), Radiology (H.P.S.), and Radiation Oncology/Radiobiology (M.B.), German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy (M.E.L.) and Faculty of Medicine (M.E.L., M.B.), Heidelberg University, Heidelberg, Germany; and OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany (M.B.)
| | - Philippe Lambin
- From the Departments of Medical Physics (R.O.) and Radiology (R.O., H.H.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; The D-Lab, Department of Precision Medicine, Department of Radiology & Nuclear Medicine, GROW-School for Oncology, Maastricht University Medical Centre, Maastricht, the Netherlands (P.L.); Department of Radiation Oncology, Dalhousie University, Halifax, Canada (J.P.P.); Divisions of Medical Physics in Radiology (M.E.L.), Radiology (H.P.S.), and Radiation Oncology/Radiobiology (M.B.), German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy (M.E.L.) and Faculty of Medicine (M.E.L., M.B.), Heidelberg University, Heidelberg, Germany; and OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany (M.B.)
| | - Jean-Philippe Pignol
- From the Departments of Medical Physics (R.O.) and Radiology (R.O., H.H.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; The D-Lab, Department of Precision Medicine, Department of Radiology & Nuclear Medicine, GROW-School for Oncology, Maastricht University Medical Centre, Maastricht, the Netherlands (P.L.); Department of Radiation Oncology, Dalhousie University, Halifax, Canada (J.P.P.); Divisions of Medical Physics in Radiology (M.E.L.), Radiology (H.P.S.), and Radiation Oncology/Radiobiology (M.B.), German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy (M.E.L.) and Faculty of Medicine (M.E.L., M.B.), Heidelberg University, Heidelberg, Germany; and OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany (M.B.)
| | - Mark E Ladd
- From the Departments of Medical Physics (R.O.) and Radiology (R.O., H.H.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; The D-Lab, Department of Precision Medicine, Department of Radiology & Nuclear Medicine, GROW-School for Oncology, Maastricht University Medical Centre, Maastricht, the Netherlands (P.L.); Department of Radiation Oncology, Dalhousie University, Halifax, Canada (J.P.P.); Divisions of Medical Physics in Radiology (M.E.L.), Radiology (H.P.S.), and Radiation Oncology/Radiobiology (M.B.), German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy (M.E.L.) and Faculty of Medicine (M.E.L., M.B.), Heidelberg University, Heidelberg, Germany; and OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany (M.B.)
| | - Heinz-Peter Schlemmer
- From the Departments of Medical Physics (R.O.) and Radiology (R.O., H.H.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; The D-Lab, Department of Precision Medicine, Department of Radiology & Nuclear Medicine, GROW-School for Oncology, Maastricht University Medical Centre, Maastricht, the Netherlands (P.L.); Department of Radiation Oncology, Dalhousie University, Halifax, Canada (J.P.P.); Divisions of Medical Physics in Radiology (M.E.L.), Radiology (H.P.S.), and Radiation Oncology/Radiobiology (M.B.), German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy (M.E.L.) and Faculty of Medicine (M.E.L., M.B.), Heidelberg University, Heidelberg, Germany; and OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany (M.B.)
| | - Michael Baumann
- From the Departments of Medical Physics (R.O.) and Radiology (R.O., H.H.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; The D-Lab, Department of Precision Medicine, Department of Radiology & Nuclear Medicine, GROW-School for Oncology, Maastricht University Medical Centre, Maastricht, the Netherlands (P.L.); Department of Radiation Oncology, Dalhousie University, Halifax, Canada (J.P.P.); Divisions of Medical Physics in Radiology (M.E.L.), Radiology (H.P.S.), and Radiation Oncology/Radiobiology (M.B.), German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy (M.E.L.) and Faculty of Medicine (M.E.L., M.B.), Heidelberg University, Heidelberg, Germany; and OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany (M.B.)
| | - Hedvig Hricak
- From the Departments of Medical Physics (R.O.) and Radiology (R.O., H.H.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; The D-Lab, Department of Precision Medicine, Department of Radiology & Nuclear Medicine, GROW-School for Oncology, Maastricht University Medical Centre, Maastricht, the Netherlands (P.L.); Department of Radiation Oncology, Dalhousie University, Halifax, Canada (J.P.P.); Divisions of Medical Physics in Radiology (M.E.L.), Radiology (H.P.S.), and Radiation Oncology/Radiobiology (M.B.), German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy (M.E.L.) and Faculty of Medicine (M.E.L., M.B.), Heidelberg University, Heidelberg, Germany; and OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany (M.B.)
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Kooreman ES, van Houdt PJ, Keesman R, Pos FJ, van Pelt VWJ, Nowee ME, Wetscherek A, Tijssen RHN, Philippens MEP, Thorwarth D, Wang J, Shukla-Dave A, Hall WA, Paulson ES, van der Heide UA. ADC measurements on the Unity MR-linac - A recommendation on behalf of the Elekta Unity MR-linac consortium. Radiother Oncol 2020; 153:106-113. [PMID: 33017604 PMCID: PMC8327388 DOI: 10.1016/j.radonc.2020.09.046] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 09/23/2020] [Accepted: 09/23/2020] [Indexed: 01/23/2023]
Abstract
BACKGROUND AND PURPOSE Diffusion-weighted imaging (DWI) for treatment response monitoring is feasible on hybrid magnetic resonance linear accelerator (MR-linac) systems. The MRI scanner of the Elekta Unity system has an adjusted design compared to diagnostic scanners. We investigated its impact on measuring the DWI-derived apparent diffusion coefficient (ADC) regarding three aspects: the choice of b-values, the spatial variation of the ADC, and scanning during radiation treatment. The aim of this study is to give recommendations for accurate ADC measurements on Unity systems. MATERIALS AND METHODS Signal-to-noise ratio (SNR) measurements with increasing b-values were done to determine the highest bvalue that can be measured reliably. The spatial variation of the ADC was assessed on six Unity systems with a cylindrical phantom of 40 cm diameter. The influence of gantry rotation and irradiation was investigated by acquiring DWI images before and during treatment of 11 prostate cancer patients. RESULTS On the Unity system, a maximum b-value of 500 s/mm2 should be used for ADC quantification, as a trade-off between SNR and diffusion weighting. Accurate ADC values were obtained within 7 cm from the iso-center, while outside this region ADC values deviated more than 5%. The ADC was not influenced by the rotating linac or irradiation during treatment. CONCLUSION We provide Unity system specific recommendations for measuring the ADC. This will increase the consistency of ADC values acquired in different centers on the Unity system, enabling large cohort studies for biomarker discovery and treatment response monitoring.
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Affiliation(s)
- Ernst S Kooreman
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Petra J van Houdt
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Rick Keesman
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Floris J Pos
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Vivian W J van Pelt
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Marlies E Nowee
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Andreas Wetscherek
- Joint Department of Physics, The Institute of Cancer Research, and The Royal Marsden NHS Foundation Trust, London, United Kingdom
| | - Rob H N Tijssen
- Department of Radiotherapy, University Medical Center Utrecht, The Netherlands
| | | | - Daniela Thorwarth
- Section for Biomedical Physics, Department of Radiation Oncology, University of Tübingen, Germany
| | - Jihong Wang
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, United States
| | - Amita Shukla-Dave
- Departments of Medical Physics and Radiology, Memorial Sloan Kettering Cancer Center, New York, United States
| | - William A Hall
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, United States
| | - Eric S Paulson
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, United States
| | - Uulke A van der Heide
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
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50
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Ingle M, Lalondrelle S. Current Status of Anatomical Magnetic Resonance Imaging in Brachytherapy and External Beam Radiotherapy Planning and Delivery. Clin Oncol (R Coll Radiol) 2020; 32:817-827. [PMID: 33169690 DOI: 10.1016/j.clon.2020.10.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 10/06/2020] [Accepted: 10/08/2020] [Indexed: 02/06/2023]
Abstract
Radiotherapy planning and delivery have dramatically improved in recent times. Imaging is key to a successful three-dimensional and increasingly four-dimensional based pathway with computed tomography embedded as the backbone modality. Computed tomography has significant limitations for many tumour sites where soft-tissue discrimination is suboptimal, and where magnetic resonance imaging (MRI) has largely superseded in the diagnostic arena. MRI is increasingly used together with computed tomography in the radiotherapy planning pathway and is now established as a prerequisite for several tumours. With the advent of combined MRI and linear accelerator (MR-linac) systems, a transition to MRI-based radiotherapy planning is becoming reality, with increasing experience and research involving these new platforms. In this overview, we aim to highlight how magnetic resonance-guided imaging has improved radiotherapy, using gynaecological malignancies to illustrate, in both external beam radiotherapy and image-guided brachytherapy, and will assess the early evidence for magnetic resonance-guided radiotherapy using combined MR-linac systems.
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Affiliation(s)
- M Ingle
- Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK; Institute of Cancer Research, London, UK
| | - S Lalondrelle
- Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK; Institute of Cancer Research, London, UK.
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