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https://www.readbyqxmd.com/read/29876156/combined-inter-and-intrafractional-plan-adaptation-using-fraction-partitioning-in-magnetic-resonance-guided-radiotherapy-delivery
#1
Frank Lagerwaard, Omar Bohoudi, Shyama Tetar, Marjan A Admiraal, Tezontl S Rosario, Anna Bruynzeel
Magnetic resonance-guided radiation therapy (MRgRT) not only allows for superior soft-tissue setup and online MR-guidance during delivery but also for inter-fractional plan re-optimization or adaptation. This plan adaptation involves repeat MR imaging, organs at risk (OARs) re-contouring, plan prediction (i.e., recalculating the baseline plan on the anatomy of that moment), plan re-optimization, and plan quality assurance. In contrast, intrafractional plan adaptation cannot be simply performed by pausing delivery at any given moment, adjusting contours, and re-optimization because of the complex and composite nature of deformable dose accumulation...
April 5, 2018: Curēus
https://www.readbyqxmd.com/read/29850380/analysis-of-magnetic-resonance-image-signal-fluctuations-acquired-during-mr-guided-radiotherapy
#2
Adrian L Breto, Kyle R Padgett, John C Ford, Deukwoo Kwon, Channing Chang, Martin Fuss, Radka Stoyanova, Eric A Mellon
Magnetic resonance-guided radiotherapy (MRgRT) is a new and evolving treatment modality that allows unprecedented visualization of the tumor and surrounding anatomy. MRgRT includes daily 3D magnetic resonance imaging (MRI) for setup and rapidly repeated near real-time MRI scans during treatment for target tracking. One of the more exciting potential benefits of MRgRT is the ability to analyze serial MRIs to monitor treatment response or predict outcomes. A typical radiation treatment (RT) over the span of 10-15 minutes on the MRIdian system (ViewRay, Cleveland, OH) yields thousands of "cine" images, each acquired in 250 ms...
March 28, 2018: Curēus
https://www.readbyqxmd.com/read/29796358/daily-tracking-of-glioblastoma-resection-cavity-cerebral-edema-and-tumor-volume-with-mri-guided-radiation-therapy
#3
Shahil Mehta, Shefali R Gajjar, Kyle R Padgett, David Asher, Radka Stoyanova, John C Ford, Eric A Mellon
Radiation therapy (RT) plays a critical role in the treatment of glioblastoma. Studies of brain imaging during RT for glioblastoma have demonstrated changes in the brain during RT. However, frequent or daily utilization of standalone magnetic resonance imaging (MRI) scans during RT have limited feasibility. The recent release of the tri-cobalt-60 MRI-guided RT (MR-IGRT) device (ViewRay MRIdian, Cleveland, OH) allows for daily brain MRI for the RT setup. Daily MRI of three postoperative patients undergoing RT and temozolomide for glioblastoma over a six-week course allowed for the identification of changes to the cavity, edema, and visible tumor on a daily basis...
March 19, 2018: Curēus
https://www.readbyqxmd.com/read/29773331/novel-use-of-viewray-mri-guidance-for-high-dose-rate-brachytherapy-in-the-treatment-of-cervical-cancer
#4
Huaising C Ko, Jessie Y Huang, Jessica R Miller, Rupak K Das, Charles R Wallace, Anna-Maria A De Costa, David M Francis, Margaret R Straub, Bethany M Anderson, Kristin A Bradley
PURPOSE: To characterize image quality and feasibility of using ViewRay MRI (VR)-guided brachytherapy planning for cervical cancer. METHODS AND MATERIALS: Cervical cancer patients receiving intracavitary brachytherapy with tandem and ovoids, planned using 0.35T VR MRI at our institution, were included in this series. The high-risk clinical target volume (HR-CTV), visible gross tumor volume, bladder, sigmoid, bowel, and rectum contours for each fraction of brachytherapy were evaluated for dosimetric parameters...
May 14, 2018: Brachytherapy
https://www.readbyqxmd.com/read/29762130/ionization-chamber-correction-factors-for-mr-linacs
#5
Stefan Pojtinger, Oliver Steffen Dohm, Ralf-Peter Kapsch, Daniela Thorwarth

 Previously, readings of air-filled ionization chambers have been described as being influenced by magnetic fields. To use these chambers for dosimetry in magnetic resonance guided radiotherapy (MRgRT), this effect must be taken into account by introducing a correction factor kB.
 The purpose of this study is to systematically investigate kB for a typical reference setup for commercially available ionization chambers with different magnetic field strengths.
 
 Material and Methods:
 The Monte Carlo simulation tool EGSnrc was used to simulate eight commercially available ionization chambers in magnetic fields whose magnetic flux density was in the range of 0 to 2...
May 15, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29663429/remote-cherenkov-imaging-based-quality-assurance-of-a-magnetic-resonance-image-guided-radiotherapy-system
#6
Jacqueline M Andreozzi, Karen E Mooney, Petr Brůža, Austen Curcuru, David J Gladstone, Brian W Pogue, Olga Green
PURPOSE: Tools to perform regular quality assurance of magnetic resonance image-guided radiotherapy (MRIgRT) systems should ideally be independent of interference from the magnetic fields. Remotely acquired optical Cherenkov imaging-based dosimetry measurements in water were investigated for this purpose, comparing measures of dose accuracy, temporal dynamics, and overall integrated IMRT delivery. METHODS: A 40 × 30.5 × 37.5 cm3 water tank doped with 1 g/L of quinine sulfate was imaged using an intensified charge-coupled device (ICCD) to capture the Cherenkov emission while being irradiated by a commercial MRIgRT system (ViewRay™)...
April 16, 2018: Medical Physics
https://www.readbyqxmd.com/read/29573744/optimization-of-treatment-planning-workflow-and-tumor-coverage-during-daily-adaptive-magnetic-resonance-image-guided-radiation-therapy-mr-igrt-of-pancreatic-cancer
#7
Sven Olberg, Olga Green, Bin Cai, Deshan Yang, Vivian Rodriguez, Hao Zhang, Jin Sung Kim, Parag J Parikh, Sasa Mutic, Justin C Park
BACKGROUND: To simplify the adaptive treatment planning workflow while achieving the optimal tumor-dose coverage in pancreatic cancer patients undergoing daily adaptive magnetic resonance image guided radiation therapy (MR-IGRT). METHODS: In daily adaptive MR-IGRT, the plan objective function constructed during simulation is used for plan re-optimization throughout the course of treatment. In this study, we have constructed the initial objective functions using two methods for 16 pancreatic cancer patients treated with the ViewRay™ MR-IGRT system: 1) the conventional method that handles the stomach, duodenum, small bowel, and large bowel as separate organs at risk (OARs) and 2) the OAR grouping method...
March 24, 2018: Radiation Oncology
https://www.readbyqxmd.com/read/29166129/initial-clinical-observations-of-intra-and-interfractional-motion-variation-in-mr-guided-lung-sbrt
#8
David H Thomas, Anand Santhanam, Amar U Kishan, Minsong Cao, James Lamb, Yugang Min, Dylan O'Connell, Yingli Yang, Nzhde Agazaryan, Percy Lee, Daniel Low
OBJECTIVE: To evaluate variations in intra- and interfractional tumour motion, and the effect on internal target volume (ITV) contour accuracy, using deformable image registration of real-time two-dimensional-sagittal cine-mode MRI acquired during lung stereotactic body radiation therapy (SBRT) treatments. METHODS: Five lung tumour patients underwent free-breathing SBRT treatments on the ViewRay system, with dose prescribed to a planning target volume (defined as a 3-6 mm expansion of the 4DCT-ITV)...
February 2018: British Journal of Radiology
https://www.readbyqxmd.com/read/28916952/air-electron-stream-interactions-during-magnetic-resonance-igrt-skin-irradiation-outside-the-treatment-field-during-accelerated-partial-breast-irradiation
#9
Jong Min Park, Kyung Hwan Shin, Jung-In Kim, So-Yeon Park, Seung Hyuck Jeon, Noorie Choi, Jin Ho Kim, Hong-Gyun Wu
PURPOSE: To investigate and to prevent irradiation outside the treatment field caused by an electron stream in the air generated by the magnetic field during magnetic resonance image-guided accelerated partial breast irradiation (APBI). MATERIALS AND METHODS: In all, 20 patients who received APBI with a magnetic resonance image-guided radiation therapy (MR-IGRT) system were prospectively studied. The prescription dose was 38.5 Gy in 10 fractions of 3.85 Gy and delivered with a tri-cobalt system (the ViewRay system)...
January 2018: Strahlentherapie und Onkologie: Organ der Deutschen Röntgengesellschaft ... [et Al]
https://www.readbyqxmd.com/read/28887825/performance-of-a-multi-leaf-collimator-system-for-mr-guided-radiation-therapy
#10
Bin Cai, Harold Li, Deshan Yang, Vivian Rodriguez, Austen Curcuru, Yuhe Wang, Jie Wen, Rojano Kashani, Sasa Mutic, Olga Green
PURPOSE: The purpose of this study was to investigate and characterize the performance of a Multi Leaf Collimator (MLC) designed for Cobalt-60 based MR-guided radiation therapy system in a 0.35 T magnetic field. METHODS: The MLC design and unique assembly features in the ViewRay MRIdian system were first reviewed. The RF cage shielding of MLC motor and cables were evaluated using ACR phantoms with real-time imaging and quantified by signal-to-noise ratio. The dosimetric characterizations, including the leaf transmission, leaf penumbra, tongue-and-groove effect, were investigated using radiosensitive films...
December 2017: Medical Physics
https://www.readbyqxmd.com/read/28877344/development-of-a-3d-remote-dosimetry-protocol-compatible-with-mrgimrt
#11
Stewart Mein, Leith Rankine, John Adamovics, Harold Li, Mark Oldham
PURPOSE: To develop a novel remote 3D dosimetry protocol to verify Magnetic Resonance-guided Radiation Therapy (MRgRT) treatments. The protocol was applied to investigate the accuracy of TG-119 IMRT irradiations delivered by the MRIdian(®) system (ViewRay(®) , Oakwood Village, OH, USA) allowing for a 48-hour delay between irradiation at a field institution and subsequent readout at a base institution. METHODS: The 3D dosimetry protocol utilizes a novel formulation of PRESAGE(®) radiochromic dosimeters developed for high postirradiation stability and compatibility with optical-CT readout...
September 6, 2017: Medical Physics
https://www.readbyqxmd.com/read/28811038/fast-and-robust-online-adaptive-planning-in-stereotactic-mr-guided-adaptive-radiation-therapy-smart-for-pancreatic-cancer
#12
O Bohoudi, A M E Bruynzeel, S Senan, J P Cuijpers, B J Slotman, F J Lagerwaard, M A Palacios
BACKGROUND AND PURPOSE: To implement a robust and fast stereotactic MR-guided adaptive radiation therapy (SMART) online strategy in locally advanced pancreatic cancer (LAPC). MATERIAL AND METHODS: SMART strategy for plan adaptation was implemented with the MRIdian system (ViewRay Inc.). At each fraction, OAR (re-)contouring is done within a distance of 3cm from the PTV surface. Online plan re-optimization is based on robust prediction of OAR dose and optimization objectives, obtained by building an artificial neural network (ANN)...
December 2017: Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology
https://www.readbyqxmd.com/read/28760506/a-comparison-of-treatment-plan-quality-between-tri-co-60-intensity-modulated-radiation-therapy-and-volumetric-modulated-arc-therapy-for-cervical-cancer
#13
COMPARATIVE STUDY
Jong Min Park, So-Yeon Park, Jung-In Kim, Hyun-Cheol Kang, Chang Heon Choi
PURPOSE: To investigate the plan quality of tri-Co-60 intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for cervical cancer. METHODS: A total of 20 patients who received postoperative radiotherapy for cervical cancer were selected. For each patient, a tri-Co-60 IMRT plan for which the target volume was the planning target volume (PTV) generated by adding 1mm isotropic margins from the clinical target volume (CTV) and a VMAT plan for which the target volume was the PTV generated by adding 7mm and 10mm margins from the CTV were generated...
August 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28740928/magnetic-resonance-imaging-guided-reirradiation-of-recurrent-and-second-primary-head-and-neck-cancer
#14
Allen M Chen, Minsong Cao, Sophia Hsu, James Lamb, Argin Mikaeilian, Yingli Yang, Nzhde Agazaryan, Daniel A Low, Michael L Steinberg
PURPOSE: To report a single-institutional experience using magnetic resonance imaging (MRI) guided radiation therapy for the reirradiation of recurrent and second cancers of the head and neck. METHODS AND MATERIALS: Between October 2014 and August 2016, 13 consecutive patients with recurrent or new primary cancers of the head and neck that occurred in a previously irradiated field were prospectively enrolled in an institutional registry trial to investigate the feasibility and efficacy of MRI guided radiation therapy using a 0...
April 2017: Advances in Radiation Oncology
https://www.readbyqxmd.com/read/28692129/distortion-free-diffusion-mri-using-an-mri-guided-tri-cobalt-60-radiotherapy-system-sequence-verification-and-preliminary-clinical-experience
#15
Yu Gao, Fei Han, Ziwu Zhou, Minsong Cao, Tania Kaprealian, Mitchell Kamrava, Chenyang Wang, John Neylon, Daniel A Low, Yingli Yang, Peng Hu
PURPOSE: Monitoring tumor response during the course of treatment and adaptively modifying treatment plan based on tumor biological feedback may represent a new paradigm for radiotherapy. Diffusion MRI has shown great promises in assessing and predicting tumor response to radiotherapy. However, the conventional diffusion-weighted single-shot echo-planar-imaging (DW-ssEPI) technique suffers from limited resolution, severe distortion, and possibly inaccurate ADC at low field strength. The purpose of this work was to develop a reliable, accurate and distortion-free diffusion MRI technique that is practicable for longitudinal tumor response evaluation and adaptive radiotherapy on a 0...
October 2017: Medical Physics
https://www.readbyqxmd.com/read/28681448/an-analysis-of-the-arccheck-mr-diode-array-s-performance-for-viewray-quality-assurance
#16
Steven T Ellefson, Wesley S Culberson, Bryan P Bednarz, Larry A DeWerd, John E Bayouth
The ArcCHECK-MR diode array utilizes a correction system with a virtual inclinometer to correct the angular response dependencies of the diodes. However, this correction system cannot be applied to measurements on the ViewRay MR-IGRT system due to the virtual inclinometer's incompatibility with the ViewRay's multiple simultaneous beams. Additionally, the ArcCHECK's current correction factors were determined without magnetic field effects taken into account. In the course of performing ViewRay IMRT quality assurance with the ArcCHECK, measurements were observed to be consistently higher than the ViewRay TPS predictions...
July 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28675492/development-of-patient-controlled-respiratory-gating-system-based-on-visual-guidance-for-magnetic-resonance-image-guided-radiation-therapy
#17
Jung-In Kim, Hanyoung Lee, Hong-Gyun Wu, Eui Kyu Chie, Hyun-Cheol Kang, Jong Min Park
PURPOSE: The aim of this study is to develop a visual guidance patient-controlled (VG-PC) respiratory gating system for respiratory-gated magnetic-resonance image-guided radiation therapy (MR-IGRT) and to evaluate the performance of the developed system. METHODS: The near-real-time cine planar MR image of a patient acquired during treatment was transmitted to a beam projector in the treatment room through an optical fiber cable. The beam projector projected the cine MR images inside the bore of the ViewRay system in order to be visible to a patient during treatment...
July 4, 2017: Medical Physics
https://www.readbyqxmd.com/read/28048823/mo-fg-brb-04-debater
#18
J Seibert
Building on the energy and excitement of Washington DC in a presidential election year, AAPM will host its own Presidential Debate to better understand the views of the AAPM membership! Past presidents of the AAPM, Drs. Bayouth, Hazle, Herman, and Seibert, will debate hot topics in medical physics including issues facing education, professional practice, and the advancement of science. The moderators, Drs. Brock and Stern, will also draw in topics from Point-Counterpoint articles from the Medical Physics Journals...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048743/mo-fg-brb-00-aapm-presidential-debate
#19
Kristy Brock, Robin Stern
Building on the energy and excitement of Washington DC in a presidential election year, AAPM will host its own Presidential Debate to better understand the views of the AAPM membership! Past presidents of the AAPM, Drs. Bayouth, Hazle, Herman, and Seibert, will debate hot topics in medical physics including issues facing education, professional practice, and the advancement of science. The moderators, Drs. Brock and Stern, will also draw in topics from Point-Counterpoint articles from the Medical Physics Journals...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048700/tu-d-bra-00-treatment-planning-system-commissioning-and-qa
#20
Greg Salomons
INTRODUCTION: Treatment planning systems (TPS) are a cornerstone of modern radiation therapy. Errors in their commissioning or use can have a devastating impact on many patients. To support safe and high quality care, medical physicists must conduct efficient and proper commissioning, good clinical integration, and ongoing quality assurance (QA) of the TPS. AAPM Task Group 53 and related publications have served as seminal benchmarks for TPS commissioning and QA over the past two decades...
June 2016: Medical Physics
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