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Karger CP, Elter A, Dorsch S, Mann P, Pappas E, Oldham M. Validation of complex radiotherapy techniques using polymer gel dosimetry. Phys Med Biol 2024; 69:06TR01. [PMID: 38330494 DOI: 10.1088/1361-6560/ad278f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 02/08/2024] [Indexed: 02/10/2024]
Abstract
Modern radiotherapy delivers highly conformal dose distributions to irregularly shaped target volumes while sparing the surrounding normal tissue. Due to the complex planning and delivery techniques, dose verification and validation of the whole treatment workflow by end-to-end tests became much more important and polymer gel dosimeters are one of the few possibilities to capture the delivered dose distribution in 3D. The basic principles and formulations of gel dosimetry and its evaluation methods are described and the available studies validating device-specific geometrical parameters as well as the dose delivery by advanced radiotherapy techniques, such as 3D-CRT/IMRT and stereotactic radiosurgery treatments, the treatment of moving targets, online-adaptive magnetic resonance-guided radiotherapy as well as proton and ion beam treatments, are reviewed. The present status and limitations as well as future challenges of polymer gel dosimetry for the validation of complex radiotherapy techniques are discussed.
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Affiliation(s)
- Christian P Karger
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Alina Elter
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
- Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, D-69120 Heidelberg, Germany
| | - Stefan Dorsch
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Philipp Mann
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Evangelos Pappas
- Radiology & Radiotherapy Sector, Department of Biomedical Sciences, University of West Attica, Athens, Greece
| | - Mark Oldham
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, United States of America
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Castelluccia A, Marchesano D, Grimaldi G, Annessi I, Bianciardi F, Borrazzo C, Dipalma A, El Gawhary R, Masi M, Rago M, Valentino M, Verna L, Portaluri M, Gentile P. Stereotactic MR-guided adaptive radiotherapy (SMART) for primary rectal cancer: evaluation of early toxicity and pathological response. Rep Pract Oncol Radiother 2023; 28:437-444. [PMID: 37795221 PMCID: PMC10547417 DOI: 10.5603/rpor.a2023.0051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 07/17/2023] [Indexed: 10/06/2023] Open
Abstract
Background The purpose of this study is to measure the effects of stereotactic MR-guided adaptive radiotherapy (SMART) for rectal cancer patients in terms of early toxicity and pathological response. Materials and methods For this prospective pilot study, patients diagnosed with locally advanced rectal cancer (LARC) with positive lymph node clinical staging underwent SMART on rectal lesion and mesorectum using hybrid MR-Linac (MRIdian ViewRay). Dose prescription at 80% isodose for the rectal lesion and mesorectum was 40 Gy (8 Gy/fr) and 25 Gy (5 Gy/fr), respectively, delivered on 5 days (3 fr/week). Response assessment by MRI was performed 3 weeks after SMART, then patients fit for surgery underwent total mesorectal excision. Primary endpoint was evaluation of adverse effect of radiotherapy. Secondary endpoint was pathological complete response rate. Early toxicity was graded according to the Common Terminology Criteria for Adverse Events (CTCAE v5.0). Results From October 2020 to January 2022, twenty patients underwent rectal SMART. No grade 3-5 toxicity was recorded. Twelve patients were eligible for total mesorectal excision (TME). Mean interval between the completion of SMART and surgery was 4 weeks. Pathological downstaging occurred in all patients; rate of pathological complete response (pCR) was 17%. pCR occurred with a prolonged time to surgery (> 7 weeks). Conclusion To our knowledge, this is the first study to use stereotactic radiotherapy for primary rectal cancer. SMART for rectal cancer is well tolerated and effective in terms of tumor regression, especially if followed by delayed surgery.
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Affiliation(s)
| | - Domenico Marchesano
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Gianmarco Grimaldi
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Ivan Annessi
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Federico Bianciardi
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
- Radiation Oncology, UPMC Hillman Cancer Center San Pietro FBF, Rome, Italy
| | - Cristian Borrazzo
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Annamaria Dipalma
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Randa El Gawhary
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Marica Masi
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Maria Rago
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Maria Valentino
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | - Laura Verna
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
| | | | - PierCarlo Gentile
- Radiation Oncology, Provincia Religiosa di San Pietro Fatebenefratelli, Roma, Italy
- Radiation Oncology, UPMC Hillman Cancer Center San Pietro FBF, Rome, Italy
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Hall WA, Small C, Paulson E, Koay EJ, Crane C, Intven M, Daamen LA, Meijer GJ, Heerkens HD, Bassetti M, Rosenberg SA, Aitken K, Myrehaug S, Dawson LA, Lee P, Gani C, Chuong MD, Parikh PJ, Erickson BA. Magnetic Resonance Guided Radiation Therapy for Pancreatic Adenocarcinoma, Advantages, Challenges, Current Approaches, and Future Directions. Front Oncol 2021; 11:628155. [PMID: 34046339 PMCID: PMC8144850 DOI: 10.3389/fonc.2021.628155] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 03/03/2021] [Indexed: 12/15/2022] Open
Abstract
Introduction Pancreatic adenocarcinoma (PAC) has some of the worst treatment outcomes for any solid tumor. PAC creates substantial difficulty for effective treatment with traditional RT delivery strategies primarily secondary to its location and limited visualization using CT. Several of these challenges are uniquely addressed with MR-guided RT. We sought to summarize and place into context the currently available literature on MR-guided RT specifically for PAC. Methods A literature search was conducted to identify manuscript publications since September 2014 that specifically used MR-guided RT for the treatment of PAC. Clinical outcomes of these series are summarized, discussed, and placed into the context of the existing pancreatic literature. Multiple international experts were involved to optimally contextualize these publications. Results Over 300 manuscripts were reviewed. A total of 6 clinical outcomes publications were identified that have treated patients with PAC using MR guidance. Successes, challenges, and future directions for this technology are evident in these publications. MR-guided RT holds theoretical promise for the treatment of patients with PAC. As with any new technology, immediate or dramatic clinical improvements associated with its use will take time and experience. There remain no prospective trials, currently publications are limited to small retrospective experiences. The current level of evidence for MR guidance in PAC is low and requires significant expansion. Future directions and ongoing studies that are currently open and accruing are identified and reviewed. Conclusions The potential promise of MR-guided RT for PAC is highlighted, the challenges associated with this novel therapeutic intervention are also reviewed. Outcomes are very early, and will require continued and long term follow up. MR-guided RT should not be viewed in the same fashion as a novel chemotherapeutic agent for which dosing, administration, and toxicity has been established in earlier phase studies. Instead, it should be viewed as a novel procedural intervention which must be robustly tested, refined and practiced before definitive conclusions on the potential benefits or detriments can be determined. The future of MR-guided RT for PAC is highly promising and the potential implications on PAC are substantial.
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Affiliation(s)
- William A Hall
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Christina Small
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Eric Paulson
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Eugene J Koay
- Division of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Christopher Crane
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, United States
| | - Martijn Intven
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Lois A Daamen
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Gert J Meijer
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Hanne D Heerkens
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Michael Bassetti
- Department of Radiation Oncology, University of Wisconsin-Madison, Madison, WI, United States
| | - Stephen A Rosenberg
- Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, United States
| | - Katharine Aitken
- Department of Radiation Oncology, Royal Marsden NHS Foundation Trust, London, United Kingdom
| | - Sten Myrehaug
- Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada
| | - Laura A Dawson
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Percy Lee
- Division of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Cihan Gani
- Department of Radiation Oncology, Faculty of Medicine, University of Tübingen, Tübingen, Germany
| | | | - Parag J Parikh
- Henry Ford Medical Center, Henry Ford Health System, Detroit, MI, United States
| | - Beth A Erickson
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, United States
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Hales RB, Rodgers J, Whiteside L, McDaid L, Berresford J, Budgell G, Choudhury A, Eccles CL. Therapeutic Radiographers at the Helm: Moving Towards Radiographer-Led MR-Guided Radiotherapy. J Med Imaging Radiat Sci 2020; 51:364-372. [PMID: 32600981 DOI: 10.1016/j.jmir.2020.05.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 05/07/2020] [Accepted: 05/08/2020] [Indexed: 12/14/2022]
Abstract
INTRODUCTION Magnetic resonance-guided adaptive radiotherapy (MRgART) has the potential to improve treatment processes and outcomes for a variety of tumour sites; however, it requires significant clinical resources. Magnetic resonance linear accelerator (MR-linac) treatments require a daily multidisciplinary presence for delivery. To facilitate sustainable MRgART models, agreed protocols facilitating therapeutic radiographer (RTT)-led delivery must be developed to establish a service similar to conventional image-guided radiotherapy (IGRT). This work provides a clinical perspective on the implementation of a protocol-driven 'clinician-lite' MRgART workflow at one institution. METHODS To identify knowledge, skills, and competence required at each step in the MRgART workflow, an interdisciplinary informal survey and needs assessment were undertaken to identify additional or enhanced skills required for MRgART, over and above those required for conventional cone-beam computed tomography-based IGRT. The MRgART pathway was critically evaluated by relevant professionals to encourage multidisciplinary input and discussion, allowing an iterative development of the RTT-led workflow. Starting with the simplest online adaptation strategy, consisting of a virtual couch shift and online replanning, clear guidelines were established for the delivery of radical prostate radiotherapy with a reduction in staff numbers present. RESULTS The MRgART-specific skills identified included MRI safety and screening, MR image acquisition, MRI-based anatomy, multimodality image interpretation and registration, and treatment plan evaluation. These skills were developed in RTTs via tutorials, workshops, focussed self-directed reading, teaching of colleagues, and end-to-end workflow testing. After initial treatments and discussions, roles and responsibilities of the three professional groups (clinicians, RTTs, and physicists) have evolved to achieve a 'clinician-lite' workflow for simple radical prostate treatments. DISCUSSION Through applying a definitive framework and establishing agreed threshold and action levels for action within anticipated treatment scenarios similar to those in cone-beam computed tomography-based IGRT, we have implemented a 'clinician-lite' workflow for simple adaptive treatments on the MR-linac. The responsibility for online plan evaluation and approval now rests with physicists and RTTs to streamline MRgART. Early evaluation of the framework after treatment of 10 patients has required minimal online clinician input (1.5% of 200 fractions delivered). CONCLUSION A 'clinician-lite' prostate treatment workflow has been successfully introduced on the MR-linac at our institution and will serve as a model for other tumour sites, using more complex adaptive strategies. Early indications are that this framework has the potential to improve patient throughput and efficiency. Further identification and validation of roles and responsibilities such as online contouring, and more interactive online planning, will facilitate RTTs to fully lead in the online workflow as adaptive radiotherapy becomes ever more complex.
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Affiliation(s)
- Rosie B Hales
- Radiotherapy, The Christie NHS Foundation Trust, Manchester, UK
| | - John Rodgers
- Radiotherapy, The Christie NHS Foundation Trust, Manchester, UK
| | - Lee Whiteside
- Radiotherapy, The Christie NHS Foundation Trust, Manchester, UK
| | - Lisa McDaid
- Radiotherapy, The Christie NHS Foundation Trust, Manchester, UK
| | - Joseph Berresford
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK
| | - Geoff Budgell
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK
| | - Ananya Choudhury
- Division of Cancer Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, UK; Department of Clinical Oncology, The Christie NHS Foundation Trust, Manchester, UK
| | - Cynthia L Eccles
- Radiotherapy, The Christie NHS Foundation Trust, Manchester, UK; Division of Cancer Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, UK.
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Chen X, Paulson ES, Ahunbay E, Sanli A, Klawikowski S, Li XA. Measurement validation of treatment planning for a MR-Linac. J Appl Clin Med Phys 2019; 20:28-38. [PMID: 31254376 PMCID: PMC6612768 DOI: 10.1002/acm2.12651] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 03/11/2019] [Accepted: 05/02/2019] [Indexed: 11/20/2022] Open
Abstract
Purpose The magnetic field can cause a nonnegligible dosimetric effect in an MR‐Linac system. This effect should be accurately accounted for by the beam models in treatment planning systems (TPS). The purpose of the study was to verify the beam model and the entire treatment planning and delivery process for a 1.5 T MR‐Linac based on comprehensive dosimetric measurements and end‐to‐end tests. Material and methods Dosimetry measurements and end‐to‐end tests were performed on a preclinical MR‐Linac (Elekta AB) using a multitude of detectors and were compared to the corresponding beam model calculations from the TPS for the MR‐Linac. Measurement devices included ion chambers (IC), diamond detector, radiochromic film, and MR‐compatible ion chamber array and diode array. The dose in inhomogeneous phantom was also verified. The end‐to‐end tests include the generation, delivery, and comparison of 3D and IMRT plan with measurement. Results For the depth dose measurements with Farmer IC, micro IC and diamond detector, the absolute difference between most measurement points and beam model calculation beyond the buildup region were <1%, at most 2% for a few measurement points. For the beam profile measurements, the absolute differences were no more than 1% outside the penumbra region and no more than 2.5% inside the penumbra region. Results of end‐to‐end tests demonstrated that three 3D static plans with single 5 × 10 cm2 fields (at gantry angle 0°, 90° and 270°) and two IMRT plans successfully passed gamma analysis with clinical criteria. The dose difference in the inhomogeneous phantom between the calculation and measurement was within 1.0%. Conclusions Both relative and absolute dosimetry measurements agreed well with the TPS calculation, indicating that the beam model for MR‐Linac properly accounts for the magnetic field effect. The end‐to‐end tests verified the entire treatment planning process.
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Affiliation(s)
- Xinfeng Chen
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Eric S Paulson
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Ergun Ahunbay
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Aydin Sanli
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Slade Klawikowski
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - X Allen Li
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
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Pathmanathan AU, Schmidt MA, Brand DH, Kousi E, van As NJ, Tree AC. Improving fiducial and prostate capsule visualization for radiotherapy planning using MRI. J Appl Clin Med Phys 2019; 20:27-36. [PMID: 30756456 PMCID: PMC6414142 DOI: 10.1002/acm2.12529] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 11/06/2018] [Accepted: 12/10/2018] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Intraprostatic fiducial markers (FM) improve the accuracy of radiotherapy (RT) delivery. Here we assess geometric integrity and contouring consistency using a T2*-weighted (T2*W) sequence alone, which allows visualization of the FM. MATERIAL AND METHODS Ten patients scanned within the Prostate Advances in Comparative Evidence (PACE) trial (NCT01584258) had prostate images acquired with computed tomography (CT) and Magnetic Resonance (MR) Imaging: T2-weighted (T2W) and T2*W sequences. The prostate was contoured independently on each imaging dataset by three clinicians. Interobserver variability was assessed using comparison indices with Monaco ADMIRE (research version 2.0, Elekta AB) and examined for statistical differences between imaging sets. CT and MR images of two test objects were acquired to assess geometric distortion and accuracy of marker positioning. The first was a linear test object comprising straight tubes in three orthogonal directions, the second was a smaller test object with markers suspended in gel. RESULTS Interobserver variability for prostate contouring was lower for both T2W and T2*W compared to CT, this was statistically significant when comparing CT and T2*W images. All markers are visible in T2*W images with 29/30 correctly identified, only 3/30 are visible in T2W images. Assessment of geometric distortion revealed in-plane displacements were under 0.375 mm in MRI, and through plane displacements could not be detected. The signal loss in the MR images is symmetric in relation to the true marker position shown in CT images. CONCLUSION Prostate T2*W images are geometrically accurate, and yield consistent prostate contours. This single sequence can be used to identify FM and for prostate delineation in a mixed MR-CT workflow.
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Affiliation(s)
- Angela U Pathmanathan
- The Royal Marsden Hospital NHS Foundation Trust, London, UK.,The Institute of Cancer Research, London, UK
| | - Maria A Schmidt
- The Royal Marsden Hospital NHS Foundation Trust, London, UK.,The Institute of Cancer Research, London, UK
| | - Douglas H Brand
- The Royal Marsden Hospital NHS Foundation Trust, London, UK.,The Institute of Cancer Research, London, UK
| | - Evanthia Kousi
- The Royal Marsden Hospital NHS Foundation Trust, London, UK.,The Institute of Cancer Research, London, UK
| | - Nicholas J van As
- The Royal Marsden Hospital NHS Foundation Trust, London, UK.,The Institute of Cancer Research, London, UK
| | - Alison C Tree
- The Royal Marsden Hospital NHS Foundation Trust, London, UK.,The Institute of Cancer Research, London, UK
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