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Gregg KW, Ruff C, Koenig G, Penev KI, Shepard A, Kreissler G, Amatuzio M, Owens C, Nagpal P, Glide-Hurst CK. Development and first implementation of a novel multi-modality cardiac motion and dosimetry phantom for radiotherapy applications. Med Phys 2024. [PMID: 39042362 DOI: 10.1002/mp.17315] [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: 12/18/2023] [Revised: 05/11/2024] [Accepted: 06/19/2024] [Indexed: 07/24/2024] Open
Abstract
BACKGROUND Cardiac applications in radiation therapy are rapidly expanding including magnetic resonance guided radiation therapy (MRgRT) for real-time gating for targeting and avoidance near the heart or treating ventricular tachycardia (VT). PURPOSE This work describes the development and implementation of a novel multi-modality and magnetic resonance (MR)-compatible cardiac phantom. METHODS The patient-informed 3D model was derived from manual contouring of a contrast-enhanced Coronary Computed Tomography Angiography scan, exported as a Stereolithography model, then post-processed to simulate female heart with an average volume. The model was 3D-printed using Elastic50A to provide MR contrast to water background. Two rigid acrylic modules containing cardiac structures were designed and assembled, retrofitting to an MR-safe programmable motor to supply cardiac and respiratory motion in superior-inferior directions. One module contained a cavity for an ion chamber (IC), and the other was equipped with multiple interchangeable cavities for plastic scintillation detectors (PSDs). Images were acquired on a 0.35 T MR-linac for validation of phantom geometry, motion, and simulated online treatment planning and delivery. Three motion profiles were prescribed: patient-derived cardiac (sine waveform, 4.3 mm peak-to-peak, 60 beats/min), respiratory (cos4 waveform, 30 mm peak-to-peak, 12 breaths/min), and a superposition of cardiac (sine waveform, 4 mm peak-to-peak, 70 beats/min) and respiratory (cos4 waveform, 24 mm peak-to-peak, 12 breaths/min). The amplitude of the motion profiles was evaluated from sagittal cine images at eight frames/s with a resolution of 2.4 mm × 2.4 mm. Gated dosimetry experiments were performed using the two module configurations for calculating dose relative to stationary. A CT-based VT treatment plan was delivered twice under cone-beam CT guidance and cumulative stationary doses to multi-point PSDs were evaluated. RESULTS No artifacts were observed on any images acquired during phantom operation. Phantom excursions measured 49.3 ± 25.8%/66.9 ± 14.0%, 97.0 ± 2.2%/96.4 ± 1.7%, and 90.4 ± 4.8%/89.3 ± 3.5% of prescription for cardiac, respiratory, and cardio-respiratory motion profiles for the 2-chamber (PSD) and 12-substructure (IC) phantom modules respectively. In the gated experiments, the cumulative dose was <2% from expected using the IC module. Real-time dose measured for the PSDs at 10 Hz acquisition rate demonstrated the ability to detect the dosimetric consequences of cardiac, respiratory, and cardio-respiratory motion when sampling of different locations during a single delivery, and the stability of our phantom dosimetric results over repeated cycles for the high dose and high gradient regions. For the VT delivery, high dose PSD was <1% from expected (5-6 cGy deviation of 5.9 Gy/fraction) and high gradient/low dose regions had deviations <3.6% (6.3 cGy less than expected 1.73 Gy/fraction). CONCLUSIONS A novel multi-modality modular heart phantom was designed, constructed, and used for gated radiotherapy experiments on a 0.35 T MR-linac. Our phantom was capable of mimicking cardiac, cardio-respiratory, and respiratory motion while performing dosimetric evaluations of gated procedures using IC and PSD configurations. Time-resolved PSDs with small sensitive volumes appear promising for low-amplitude/high-frequency motion and multi-point data acquisition for advanced dosimetric capabilities. Illustrating VT planning and delivery further expands our phantom to address the unmet needs of cardiac applications in radiotherapy.
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Affiliation(s)
- Kenneth W Gregg
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Chase Ruff
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Grant Koenig
- Modus Medical Devices, Inc. (IBA QUASAR), London, Ontario, Canada
| | - Kalin I Penev
- Modus Medical Devices, Inc. (IBA QUASAR), London, Ontario, Canada
| | - Andrew Shepard
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Grace Kreissler
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Margo Amatuzio
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Cameron Owens
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Prashant Nagpal
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Carri K Glide-Hurst
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
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Tsai CY, Tsai SCS, Shen GQ, Guo GLR, Tsui ZLG, Hsieh MY, Yuan C, Lin FCF. Simulation education utilizing phantom and angle reference guide in pulmonary nodule CT localization. Heliyon 2023; 9:e18329. [PMID: 37539172 PMCID: PMC10395521 DOI: 10.1016/j.heliyon.2023.e18329] [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: 11/16/2022] [Revised: 07/11/2023] [Accepted: 07/13/2023] [Indexed: 08/05/2023] Open
Abstract
Objective The incidence of sub-centimeter pulmonary nodules has been increasing along with the use of low-dose computed tomography (LDCT) as a screening tool for early lung cancer detection. In our institution, pulmonary nodule computed tomography-guided localization (PNCL) is performed preoperatively with the laser angle guided assembly (LAGA), an angle reference device. This study aims to investigate the efficacy of postgraduate education in a phantom simulation of PNCL, with or without LAGA. Setting design This prospective study was conducted in an academic hospital in Taiwan. Seven thoracic surgery residents and three experienced senior physicians were recruited to perform PNCL using a phantom simulation, with or without LAGA, for five nodules each and complete a questionnaire. Performance data were collected. χ2 tests, Mann-Whitney U test, univariate and multivariate linear regression were used for statistical analyses. Results The confidence level increased from median 7[range 1, 9] to 8, range [6,9] (p = 0.001) before and after the simulation education course. The scores of enhanced PNCL ability and course satisfaction were as high as 8 [5,9], and 9 [7,9]. LAGA enabled broader puncture angles (with 27.5° [0°,80°]; without 14° [0°, 80°], p = 0.003), a lower puncture frequency (with 1 [1,4]; without 2 [1,5], p < 0.001), and a smaller angle deviation (with 3°[ 0°,8°]; without 5°[ 0°,19°], p = 0.002). Pleural depth in millimeters was associated with increased puncture frequency (0.019[0,010,0.028]) and procedure time (0.071'[ 0.018,0.123']. The PNCL-experienced physicians performed the procedure in less time (-2.854'[-4.646',1.061']. The traverse direction toward the mediastinum diminished the frequency (toward 1[ 1,3]; away 1 [1,5], p = 0.003) and time (toward 7.5'[2',18]'; away 9'[ 3',31'], p = 0.027). The learning curve did not improve procedure performance after ten PNCL simulation rounds. Conclusions The phantom PNCL simulation education course increased the confidence level, enhanced residents' skill acquisition, and promoted learning satisfaction. The angle reference device helped improve the outcomes of the puncture frequency and reduced angle deviation.
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Affiliation(s)
- Chiao-Yun Tsai
- Department of Thoracic Surgery, Chung Shan Medical University Hospital, Taichung, Taiwan
- Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Stella Chin-Shaw Tsai
- Superintendents' Office, Tungs' Taichung MetroHarbor Hospital, Taichung, Taiwan
- Department of Postbaccalaureate Medicine, School of Medicine, National Chung Hsing University, Taichung, Taiwan
| | - Guang-Qian Shen
- Department of Mechanical and Computer-Aided Engineering, Feng Chia University, Taichung, Taiwan
| | - Guan-Liang Robert Guo
- Department of Mechanical and Computer-Aided Engineering, Feng Chia University, Taichung, Taiwan
| | - Zhe-Luen Gerald Tsui
- Department of Mechanical and Computer-Aided Engineering, Feng Chia University, Taichung, Taiwan
| | - Ming-Yu Hsieh
- Department of Pediatric Surgery, Chung Shan Medical University Hospital, Taichung, Taiwan
- School of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Cadmus Yuan
- Department of Mechanical and Computer-Aided Engineering, Feng Chia University, Taichung, Taiwan
| | - Frank Cheau-Feng Lin
- Department of Thoracic Surgery, Chung Shan Medical University Hospital, Taichung, Taiwan
- Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan
- School of Medicine, Chung Shan Medical University, Taichung, Taiwan
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Laidlaw J, Earl N, Shavdia N, Davis R, Mayer S, Karaman D, Richtsmeier D, Rodesch PA, Bazalova-Carter M. Design and CT imaging of casper, an anthropomorphic breathing thorax phantom. Biomed Phys Eng Express 2023; 9. [PMID: 36724499 DOI: 10.1088/2057-1976/acb7f7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 02/01/2023] [Indexed: 02/03/2023]
Abstract
The goal of this work was to build an anthropomorphic thorax phantom capable of breathing motion with materials mimicking human tissues in x-ray imaging applications. The thorax phantom, named Casper, was composed of resin (body), foam (lungs), glow polyactic acid (bones) and natural polyactic acid (tumours placed in the lungs). X-ray attenuation properties of all materials prior to manufacturing were evaluated by means of photon-counting computed tomography (CT) imaging on a table-top system. Breathing motion was achieved by a scotch-yoke mechanism with diaphragm motion frequencies of 10-20 rpm and displacements of 1 to 2 cm. Casper was manufactured by means of 3D printing of moulds and ribs and assembled in a complex process. The final phantom was then scanned using a clinical CT scanner to evaluate material CT numbers and the extent of tumour motion. Casper CT numbers were close to human CT numbers for soft tissue (46 HU), ribs (125 HU), lungs (-840 HU) and tumours (-45 HU). For a 2 cm diaphragm displacement the largest tumour displacement was 0.7 cm. The five tumour volumes were accurately assessed in the static CT images with a mean absolute error of 4.3%. Tumour sizes were either underestimated for smaller tumours or overestimated for larger tumours in dynamic CT images due to motion blurring with a mean absolute difference from true volumes of 10.3%. More Casper information including a motion movie and manufacturing data can be downloaded from http://web.uvic.ca/~bazalova/Casper/.
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Affiliation(s)
- Josie Laidlaw
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Nicolas Earl
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Nihal Shavdia
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Rayna Davis
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Sarah Mayer
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Dmitri Karaman
- Axolotl Bioscience, Victoria, British Columbia V8W 2Y2, Canada
| | - Devon Richtsmeier
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Pierre-Antoine Rodesch
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Magdalena Bazalova-Carter
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
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Lis M, Newhauser W, Donetti M, Wolf M, Steinsberger T, Paz A, Graeff C. Dosimetric Validation of a System to Treat Moving Tumors Using Scanned Ion Beams That Are Synchronized With Anatomical Motion. Front Oncol 2021; 11:712126. [PMID: 34568041 PMCID: PMC8456027 DOI: 10.3389/fonc.2021.712126] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 08/16/2021] [Indexed: 12/25/2022] Open
Abstract
Purpose The purpose of this study was to validate the dosimetric performance of scanned ion beam deliveries with motion-synchronization to heterogenous targets. Methods A 4D library of treatment plans, comprised of up to 10 3D sub-plans, was created with robust and conventional 4D optimization methods. Each sub-plan corresponded to one phase of periodic target motion. The plan libraries were delivered to a test phantom, comprising plastic slabs, dosimeters, and heterogenous phantoms. This phantom emulated range changes that occur when treating moving tumors. Similar treatment plans, but without motion synchronization, were also delivered to a test phantom with a stationary target and to a moving target; these were used to assess how the target motion degrades the quality of dose distributions and the extent to which motion synchronization can improve dosimetric quality. The accuracy of calculated dose distributions was verified by comparison with corresponding measurements. Comparisons utilized the gamma index analysis method. Plan quality was assessed based on conformity, dose coverage, overdose, and homogeneity values, each extracted from calculated dose distributions. Results High pass rates for the gamma index analysis confirmed that the methods used to calculate and reconstruct dose distributions were sufficiently accurate for the purposes of this study. Calculated and reconstructed dose distributions revealed that the motion-synchronized and static deliveries exhibited similar quality in terms of dose coverage, overdose, and homogeneity for all deliveries considered. Motion-synchronization substantially improved conformity in deliveries with moving targets. Importantly, measurements at multiple locations within the target also confirmed that the motion-synchronized delivery system satisfactorily compensated for changes in beam range caused by the phantom motion. Specifically, the overall planning and delivery approach achieved the desired dose distribution by avoiding range undershoots and overshoots caused by tumor motion. Conclusions We validated a dose delivery system that synchronizes the movement of the ion beam to that of a moving target in a test phantom. Measured and calculated dose distributions revealed that this system satisfactorily compensated for target motion in the presence of beam range changes due to target motion. The implication of this finding is that the prototype system is suitable for additional preclinical research studies, such as irregular anatomic motion.
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Affiliation(s)
- Michelle Lis
- Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany.,Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, United States
| | - Wayne Newhauser
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, United States.,Department of Radiation Physics, Mary Bird Perkins Cancer Center, Baton Rouge, LA, United States
| | - Marco Donetti
- Research and Development Department, CNAO National Center for Oncological Hadrontherapy, Pavia, Italy
| | - Moritz Wolf
- Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany
| | - Timo Steinsberger
- Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany.,Institute of Condensed Matter Physics, Technical University of Darmstadt, Darmstadt, Germany
| | - Athena Paz
- Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany
| | - Christian Graeff
- Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany
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Lennie E, Tsoumpas C, Sourbron S. Multimodal phantoms for clinical PET/MRI. EJNMMI Phys 2021; 8:62. [PMID: 34436671 PMCID: PMC8390737 DOI: 10.1186/s40658-021-00408-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 08/10/2021] [Indexed: 12/02/2022] Open
Abstract
Phantoms are commonly used throughout medical imaging and medical physics for a multitude of applications, the designs of which vary between modalities and clinical or research requirements. Within positron emission tomography (PET) and nuclear medicine, phantoms have a well-established role in the validation of imaging protocols so as to reduce the administration of radioisotope to volunteers. Similarly, phantoms are used within magnetic resonance imaging (MRI) to perform quality assurance on clinical scanners, and gel-based phantoms have a longstanding use within the MRI research community as tissue equivalent phantoms. In recent years, combined PET/MRI scanners for simultaneous acquisition have entered both research and clinical use. This review explores the designs and applications of phantom work within the field of simultaneous acquisition PET/MRI as published over the period of a decade. Common themes in the design, manufacture and materials used within phantoms are identified and the solutions they provided to research in PET/MRI are summarised. Finally, the challenges remaining in creating multimodal phantoms for use with simultaneous acquisition PET/MRI are discussed. No phantoms currently exist commercially that have been designed and optimised for simultaneous PET/MRI acquisition. Subsequently, commercially available PET and nuclear medicine phantoms are often utilised, with CT-based attenuation maps substituted for MR-based attenuation maps due to the lack of MR visibility in phantom housing. Tissue equivalent and anthropomorphic phantoms are often developed by research groups in-house and provide customisable alternatives to overcome barriers such as MR-based attenuation correction, or to address specific areas of study such as motion correction. Further work to characterise materials and manufacture methods used in phantom design would facilitate the ability to reproduce phantoms across sites.
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Affiliation(s)
- Eve Lennie
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK
| | - Charalampos Tsoumpas
- Biomedical Imaging Science Department, University of Leeds, Leeds, UK
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Steven Sourbron
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK
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Black DG, Yazdi YO, Wong J, Fedrigo R, Uribe C, Kadrmas DJ, Rahmim A, Klyuzhin IS. Design of an anthropomorphic PET phantom with elastic lungs and respiration modeling. Med Phys 2021; 48:4205-4217. [PMID: 34031896 DOI: 10.1002/mp.14998] [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: 12/27/2020] [Revised: 05/06/2021] [Accepted: 05/10/2021] [Indexed: 11/11/2022] Open
Abstract
PURPOSE Respiratory motion during positron emission tomography (PET) scans can be a major detriment to image quality in oncological imaging. The impact of motion on lesion quantification and detectability can be assessed using phantoms with realistic anatomy representation and motion modeling. In this work, we develop an anthropomorphic phantom for PET imaging that combines anatomic fidelity and a realistic breathing mechanism with deformable lungs. METHODS We start from a previously developed anatomically accurate but static phantom of a human torso, and add elastic lungs with a highly controllable actuation mechanism which replicates the physics of breathing. The space outside the lungs is filled with a radioactive water solution. To maintain anatomical accuracy and realistic gamma ray attenuation in the torso, all motion mechanisms and actuators are positioned outside of the phantom compartment. The actuation mechanism can produce custom respiratory waveforms with breathing rates up to 25 breaths per minute and tidal volumes up to 1200 mL. RESULTS Several tests were performed to validate the performance of the phantom assembly, in which the phantom was filled with water and given respiratory waveforms to execute. All parts demonstrated expected performance. Force requirements were not exceeded and no leaks were detected, although continued use of the phantom is required to evaluate wear. The motion of the lungs was determined to be within a reasonable realistic range. CONCLUSIONS The full mechanical design is described in this paper, as well as a software application with graphical user interface which was developed to plan and visualize respiratory patterns. Both are available online as open source files. The developed phantom will facilitate future work in evaluating the impact of respiratory motion on lesion quantification and detectability in clinical practice.
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Affiliation(s)
- David G Black
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - Yas Oloumi Yazdi
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - Jeremy Wong
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - Roberto Fedrigo
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada.,BC Cancer Research Institute, Vancouver, BC, Canada
| | - Carlos Uribe
- Department of Functional Imaging, BC Cancer, Vancouver, BC, Canada.,Department of Radiology, University of British Columbia, Vancouver, BC, Canada
| | - Dan J Kadrmas
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, USA
| | - Arman Rahmim
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada.,BC Cancer Research Institute, Vancouver, BC, Canada.,Department of Radiology, University of British Columbia, Vancouver, BC, Canada
| | - Ivan S Klyuzhin
- BC Cancer Research Institute, Vancouver, BC, Canada.,Department of Radiology, University of British Columbia, Vancouver, BC, Canada
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Kroll C, Dietrich O, Bortfeldt J, Kamp F, Neppl S, Belka C, Parodi K, Baroni G, Paganelli C, Riboldi M. Integration of spatial distortion effects in a 4D computational phantom for simulation studies in extra-cranial MRI-guided radiation therapy: Initial results. Med Phys 2020; 48:1646-1660. [PMID: 33220073 DOI: 10.1002/mp.14611] [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: 10/01/2019] [Revised: 09/15/2020] [Accepted: 09/16/2020] [Indexed: 12/18/2022] Open
Abstract
PURPOSE Spatial distortions in magnetic resonance imaging (MRI) are mainly caused by inhomogeneities of the static magnetic field, nonlinearities in the applied gradients, and tissue-specific magnetic susceptibility variations. These factors may significantly alter the geometrical accuracy of the reconstructed MR image, thus questioning the reliability of MRI for guidance in image-guided radiation therapy. In this work, we quantified MRI spatial distortions and created a quantitative model where different sources of distortions can be separated. The generated model was then integrated into a four-dimensional (4D) computational phantom for simulation studies in MRI-guided radiation therapy at extra-cranial sites. METHODS A geometrical spatial distortion phantom was designed in four modules embedding laser-cut PMMA grids, providing 3520 landmarks in a field of view of (345 × 260 × 480) mm3 . The construction accuracy of the phantom was verified experimentally. Two fast MRI sequences for extra-cranial imaging at 1.5 T were investigated, considering axial slices acquired with online distortion correction, in order to mimic practical use in MRI-guided radiotherapy. Distortions were separated into their sources by acquisition of images with gradient polarity reversal and dedicated susceptibility calculations. Such a separation yielded a quantitative spatial distortion model to be used for MR imaging simulations. Finally, the obtained spatial distortion model was embedded into an anthropomorphic 4D computational phantom, providing registered virtual CT/MR images where spatial distortions in MRI acquisition can be simulated. RESULTS The manufacturing accuracy of the geometrical distortion phantom was quantified to be within 0.2 mm in the grid planes and 0.5 mm in depth, including thickness variations and bending effects of individual grids. Residual spatial distortions after MRI distortion correction were strongly influenced by the applied correction mode, with larger effects in the trans-axial direction. In the axial plane, gradient nonlinearities caused the main distortions, with values up to 3 mm in a 1.5 T magnet, whereas static field and susceptibility effects were below 1 mm. The integration in the 4D anthropomorphic computational phantom highlighted that deformations can be severe in the region of the thoracic diaphragm, especially when using axial imaging with 2D distortion correction. Adaptation of the phantom based on patient-specific measurements was also verified, aiming at increased realism in the simulation. CONCLUSIONS The implemented framework provides an integrated approach for MRI spatial distortion modeling, where different sources of distortion can be quantified in time-dependent geometries. The computational phantom represents a valuable platform to study motion management strategies in extra-cranial MRI-guided radiotherapy, where the effects of spatial distortions can be modeled on synthetic images in a virtual environment.
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Affiliation(s)
- C Kroll
- Department of Medical Physics, Ludwig-Maximilians University, Garching, 85748, Germany
| | - O Dietrich
- Department of Radiology, University Hospital, LMU Munich, Munich, 81377, Germany
| | - J Bortfeldt
- Department of Medical Physics, Ludwig-Maximilians University, Garching, 85748, Germany.,European Organization for Nuclear Research (CERN), Geneva 23, 1211, Switzerland
| | - F Kamp
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, 81377, Germany
| | - S Neppl
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, 81377, Germany
| | - C Belka
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, 81377, Germany.,German Cancer Consortium (DKTK), Munich, 81377, Germany
| | - K Parodi
- Department of Medical Physics, Ludwig-Maximilians University, Garching, 85748, Germany
| | - G Baroni
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, 20133, Italy.,Bioengineering Unit, Centro Nazionale di Adroterapia Oncologica, Pavia, 27100, Italy
| | - C Paganelli
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, 20133, Italy
| | - M Riboldi
- Department of Medical Physics, Ludwig-Maximilians University, Garching, 85748, Germany
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Respiratory Motion Detection and Correction for MR Using the Pilot Tone: Applications for MR and Simultaneous PET/MR Examinations. Invest Radiol 2020; 55:153-159. [PMID: 31895221 DOI: 10.1097/rli.0000000000000619] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES The aim of this study was to develop a method for tracking respiratory motion throughout full MR or PET/MR studies that requires only minimal additional hardware and no modifications to the sequences. MATERIALS AND METHODS Patient motion that is caused by respiration affects the quality of the signal of the individual radiofrequency receive coil elements. This effect can be detected as a modulation of a monofrequent signal that is emitted by a small portable transmitter placed inside the bore (Pilot Tone). The frequency is selected such that it is located outside of the frequency band of the actual MR readout experiment but well within the bandwidth of the radiofrequency receiver, that is, the oversampling area. Temporal variations of the detected signal indicate motion. After extraction of the signal from the raw data, principal component analysis was used to identify respiratory motion. The approach and potential applications during MR and PET/MR examinations that rely on a continuous respiratory signal were validated with an anthropomorphic, PET/MR-compatible motion phantom as well as in a volunteer study. RESULTS Respiratory motion detection and correction were presented for MR and PET data in phantom and volunteer studies. The Pilot Tone successfully recovered the ground-truth respiratory signal provided by the phantom. CONCLUSIONS The presented method provides reliable respiratory motion tracking during arbitrary imaging sequences throughout a full PET/MR study. All results can directly be transferred to MR-only applications as well.
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Pösse S, Büther F, Mannweiler D, Hong I, Jones J, Schäfers M, Schäfers KP. Comparison of two elastic motion correction approaches for whole-body PET/CT: motion deblurring vs gate-to-gate motion correction. EJNMMI Phys 2020; 7:19. [PMID: 32232687 PMCID: PMC7105551 DOI: 10.1186/s40658-020-0285-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 03/03/2020] [Indexed: 12/27/2022] Open
Abstract
Background Respiratory motion in PET/CT leads to well-known image degrading effects commonly compensated using elastic motion correction approaches. Gate-to-gate motion correction techniques are promising tools for improving clinical PET data but suffer from relatively long reconstruction times. In this study, the performance of a fast elastic motion compensation approach based on motion deblurring (DEB-MC) was evaluated on patient and phantom data and compared to an EM-based fully 3D gate-to-gate motion correction method (G2G-MC) which was considered the gold standard. Methods Twenty-eight patients were included in this study with suspected or confirmed malignancies in the thorax or abdomen. All patients underwent whole-body [18F]FDG PET/CT examinations applying hardware-based respiratory gating. In addition, a dynamic anthropomorphic thorax phantom was studied with PET/CT simulating tumour motion under controlled but realistic conditions. PET signal recovery values were calculated from phantom scans by comparing lesion activities after motion correction to static ground truth data. Differences in standardized uptake values (SUV) and metabolic volume (MV) between both reconstruction methods as well as between motion-corrected (MC) and non motion-corrected (NOMC) results were statistically analyzed using a Wilcoxon signed-rank test. Results Phantom data analysis showed high lesion recovery values of 91% (2 cm motion) and 98% (1 cm) for G2G-MC and 83% (2 cm) and 90% (1 cm) for DEB-MC. The statistical analysis of patient data found significant differences between NOMC and MC reconstructions for SUV max, SUV mean, MV, and contrast-to-noise ratio (CNR) for both reconstruction algorithms. Furthermore, both methods showed similar increases of 11–12% in SUV max and SUV mean after MC. The statistical analysis of the MC/NOMC ratio found no significant differences between the methods. Conclusion Both motion correction techniques deliver comparable improvements of SUV max, SUV mean, and CNR after MC on clinical and phantom data. The fast elastic motion compensation technique DEB-MC may thereby be a valuable alternative to state-of-the art motion correction techniques.
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Affiliation(s)
- Stefanie Pösse
- European Institute for Molecular Imaging, University of Münster, Waldeyerstr. 15, Münster, 48149, Germany.
| | - Florian Büther
- European Institute for Molecular Imaging, University of Münster, Waldeyerstr. 15, Münster, 48149, Germany.,Department of Nuclear Medicine, University Hospital of Münster, Albert-Schweitzer-Campus 1, Münster, 48149, Germany
| | - Dirk Mannweiler
- European Institute for Molecular Imaging, University of Münster, Waldeyerstr. 15, Münster, 48149, Germany
| | - Inki Hong
- Molecular Imaging, Siemens Medical Solutions Inc., Knoxville, Knoxville, USA
| | - Judson Jones
- Molecular Imaging, Siemens Medical Solutions Inc., Knoxville, Knoxville, USA
| | - Michael Schäfers
- European Institute for Molecular Imaging, University of Münster, Waldeyerstr. 15, Münster, 48149, Germany.,Department of Nuclear Medicine, University Hospital of Münster, Albert-Schweitzer-Campus 1, Münster, 48149, Germany
| | - Klaus Peter Schäfers
- European Institute for Molecular Imaging, University of Münster, Waldeyerstr. 15, Münster, 48149, Germany
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Abstract
Three-dimensional (3D) printing of human tissues and organs has been an exciting area of research for almost three decades [Bonassar and Vacanti. J Cell Biochem. 72(Suppl 30-31):297-303 (1998)]. The primary goal of bioprinting, presently, is achieving printed constructs with the overarching aim toward fully functional tissues and organs. Technology, in hand with the development of bioinks, has been identified as the key to this success. As a result, the place of computer-aided systems (design and manufacturing-CAD/CAM) cannot be underestimated and plays a significant role in this area. Unlike many reviews in this field, this chapter focuses on the technology required for 3D bioprinting from an initial background followed by the exciting area of medical imaging and how it plays a role in bioprinting. Extraction and classification of tissue types from 3D scans is discussed in addition to modeling and simulation capabilities of scanned systems. After that, the necessary area of transferring the 3D model to the printer is explored. The chapter closes with a discussion of the current state-of-the-art and inherent challenges facing the research domain to achieve 3D tissue and organ printing.
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Rigie D, Vahle T, Zhao T, Czekella B, Frohwein LJ, Schäfers K, Boada FE. Cardiorespiratory motion-tracking via self-refocused rosette navigators. Magn Reson Med 2019; 81:2947-2958. [PMID: 30615208 DOI: 10.1002/mrm.27609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 09/27/2018] [Accepted: 10/22/2018] [Indexed: 11/09/2022]
Abstract
PURPOSE To develop a flexible method for tracking respiratory and cardiac motions throughout MR and PET-MR body examinations that requires no additional hardware and minimal sequence modification. METHODS The incorporation of a contrast-neutral rosette navigator module following the RF excitation allows for robust cardiorespiratory motion tracking with minimal impact on the host sequence. Spatial encoding gradients are applied to the FID signal and the desired motion signals are extracted with a blind source separation technique. This approach is validated with an anthropomorphic, PET-MR-compatible motion phantom as well as in 13 human subjects. RESULTS Both respiratory and cardiac motions were reliably extracted from the proposed rosette navigator in phantom and patient studies. In the phantom study, the MR-derived motion signals were additionally validated against the ground truth measurement of diaphragm displacement and left ventricle model triggering pulse. CONCLUSION The proposed method yields accurate respiratory and cardiac motion-state tracking, requiring only a short (1.76 ms) additional navigator module, which is self-refocusing and imposes minimal constraints on sequence design.
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Affiliation(s)
- David Rigie
- Bernard and Irene Schwartz Center for Biomedical Imaging, NYU School of Medicine, New York, New York
| | | | - Tiejun Zhao
- Siemens Medical Solutions, New York, New York
| | - Björn Czekella
- European Institute for Molecular Imaging, Münster, Germany
| | | | - Klaus Schäfers
- European Institute for Molecular Imaging, Münster, Germany
| | - Fernando E Boada
- Bernard and Irene Schwartz Center for Biomedical Imaging, NYU School of Medicine, New York, New York
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12
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Trnková P, Knäusl B, Actis O, Bert C, Biegun AK, Boehlen TT, Furtado H, McClelland J, Mori S, Rinaldi I, Rucinski A, Knopf AC. Clinical implementations of 4D pencil beam scanned particle therapy: Report on the 4D treatment planning workshop 2016 and 2017. Phys Med 2018; 54:121-130. [PMID: 30337001 DOI: 10.1016/j.ejmp.2018.10.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 09/18/2018] [Accepted: 10/02/2018] [Indexed: 12/14/2022] Open
Abstract
In 2016 and 2017, the 8th and 9th 4D treatment planning workshop took place in Groningen (the Netherlands) and Vienna (Austria), respectively. This annual workshop brings together international experts to discuss research, advances in clinical implementation as well as problems and challenges in 4D treatment planning, mainly in spot scanned proton therapy. In the last two years several aspects like treatment planning, beam delivery, Monte Carlo simulations, motion modeling and monitoring, QA phantoms as well as 4D imaging were thoroughly discussed. This report provides an overview of discussed topics, recent findings and literature review from the last two years. Its main focus is to highlight translation of 4D research into clinical practice and to discuss remaining challenges and pitfalls that still need to be addressed and to be overcome.
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Affiliation(s)
- Petra Trnková
- HollandPTC, P.O. Box 5046, 2600 GA Delft, the Netherlands; Erasmus MC, P.O. Box 5201, 3008 AE Rotterdam, the Netherlands
| | - Barbara Knäusl
- Department of Radiation Oncology, Division of Medical Radiation Physics, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Vienna, Austria
| | - Oxana Actis
- Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland
| | - Christoph Bert
- Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
| | - Aleksandra K Biegun
- KVI-Center for Advanced Radiation Technology, University of Groningen, Groningen, the Netherlands
| | - Till T Boehlen
- Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland
| | - Hugo Furtado
- Department of Radiation Oncology, Division of Medical Radiation Physics, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Vienna, Austria
| | - Jamie McClelland
- Centre for Medical Image Computing, Dept. Medical Physics and Biomedical, University College London, London, UK
| | - Shinichiro Mori
- National Institute of Radiological Sciences for Charged Particle Therapy, Chiba, Japan
| | - Ilaria Rinaldi
- Lyon 1 University and CNRS/IN2P3, UMR 5822, 69622 Villeurbanne, France; MAASTRO Clinic, P.O. Box 3035, 6202 NA Maastricht, the Netherlands
| | | | - Antje C Knopf
- University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, the Netherlands.
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13
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Büther F, Ernst I, Frohwein LJ, Pouw J, Schäfers KP, Stegger L. Data-driven gating in PET: Influence of respiratory signal noise on motion resolution. Med Phys 2018; 45:3205-3213. [PMID: 29782653 DOI: 10.1002/mp.12987] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 05/09/2018] [Accepted: 05/09/2018] [Indexed: 12/14/2022] Open
Abstract
PURPOSE Data-driven gating (DDG) approaches for positron emission tomography (PET) are interesting alternatives to conventional hardware-based gating methods. In DDG, the measured PET data themselves are utilized to calculate a respiratory signal, that is, subsequently used for gating purposes. The success of gating is then highly dependent on the statistical quality of the PET data. In this study, we investigate how this quality determines signal noise and thus motion resolution in clinical PET scans using a center-of-mass-based (COM) DDG approach, specifically with regard to motion management of target structures in future radiotherapy planning applications. METHODS PET list mode datasets acquired in one bed position of 19 different radiotherapy patients undergoing pretreatment [18 F]FDG PET/CT or [18 F]FDG PET/MRI were included into this retrospective study. All scans were performed over a region with organs (myocardium, kidneys) or tumor lesions of high tracer uptake and under free breathing. Aside from the original list mode data, datasets with progressively decreasing PET statistics were generated. From these, COM DDG signals were derived for subsequent amplitude-based gating of the original list mode file. The apparent respiratory shift d from end-expiration to end-inspiration was determined from the gated images and expressed as a function of signal-to-noise ratio SNR of the determined gating signals. This relation was tested against additional 25 [18 F]FDG PET/MRI list mode datasets where high-precision MR navigator-like respiratory signals were available as reference signal for respiratory gating of PET data, and data from a dedicated thorax phantom scan. RESULTS All original 19 high-quality list mode datasets demonstrated the same behavior in terms of motion resolution when reducing the amount of list mode events for DDG signal generation. Ratios and directions of respiratory shifts between end-respiratory gates and the respective nongated image were constant over all statistic levels. Motion resolution d/dmax could be modeled as d/dmax=1-e-1.52(SNR-1)0.52, with dmax as the actual respiratory shift. Determining dmax from d and SNR in the 25 test datasets and the phantom scan demonstrated no significant differences to the MR navigator-derived shift values and the predefined shift, respectively. CONCLUSIONS The SNR can serve as a general metric to assess the success of COM-based DDG, even in different scanners and patients. The derived formula for motion resolution can be used to estimate the actual motion extent reasonably well in cases of limited PET raw data statistics. This may be of interest for individualized radiotherapy treatment planning procedures of target structures subjected to respiratory motion.
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Affiliation(s)
- Florian Büther
- Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Münster, 48149, Germany
| | - Iris Ernst
- German CyberKnife Centre, Senator-Schwartz-Ring 8, Soest, 59494, Germany
| | - Lynn Johann Frohwein
- European Institute for Molecular Imaging, University of Münster, Waldeyerstr. 15, Münster, 48149, Germany
| | - Joost Pouw
- Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Münster, 48149, Germany.,Magnetic Detection and Imaging Group, University of Twente, Drienerlolaan 5, Enschede, 7522 NB, The Netherlands
| | - Klaus Peter Schäfers
- European Institute for Molecular Imaging, University of Münster, Waldeyerstr. 15, Münster, 48149, Germany
| | - Lars Stegger
- Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Münster, 48149, Germany
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