Resonance Image Guided Radiation Therapy Research Articles

Dosimetric Comparison of Real-Time MRI-Guided Tri-Cobalt-60 Versus Linear Accelerator-Based Stereotactic Body Radiation Therapy Lung Cancer Plans.

Purpose:Magnetic resonance imaging–guided radiation therapy has entered clinical practice at several major treatment centers. Treatment of early-stage non-small cell lung cancer with stereotactic body radiation therapy is one potential application of this modality, as some form of respiratory motion management is important to address. We hypothesize that magnetic resonance imaging–guided tri-cobalt-60 radiation therapy can be used to generate clinically acceptable stereotactic body radiation therapy treatment plans. Here, we report on a dosimetric comparison between magnetic resonance imaging–guided radiation therapy plans and internal target volume–based plans utilizing volumetric-modulated arc therapy.Materials and Methods:Ten patients with early-stage non-small cell lung cancer who underwent radiation therapy planning and treatment were studied. Following 4-dimensional computed tomography, patient images were used to generate clinically deliverable plans. For volumetric-modulated arc therapy plans, the planning tumor volume was defined as an internal target volume + 0.5 cm. For magnetic resonance imaging–guided plans, a single mid-inspiratory cycle was used to define a gross tumor volume, then expanded 0.3 cm to the planning tumor volume. Treatment plan parameters were compared.Results:Planning tumor volumes trended larger for volumetric-modulated arc therapy–based plans, with a mean planning tumor volume of 47.4 mL versus 24.8 mL for magnetic resonance imaging–guided plans (P = .08). Clinically acceptable plans were achievable via both methods, with bilateral lung V20, 3.9% versus 4.8% (P = .62). The volume of chest wall receiving greater than 30 Gy was also similar, 22.1 versus 19.8 mL (P = .78), as were all other parameters commonly used for lung stereotactic body radiation therapy. The ratio of the 50% isodose volume to planning tumor volume was lower in volumetric-modulated arc therapy plans, 4.19 versus 10.0 (P < .001). Heterogeneity index was comparable between plans, 1.25 versus 1.25 (P = .98).Conclusion:Magnetic resonance imaging–guided tri-cobalt-60 radiation therapy is capable of delivering lung high-quality stereotactic body radiation therapy plans that are clinically acceptable as compared to volumetric-modulated arc therapy–based plans. Real-time magnetic resonance imaging provides the unique capacity to directly observe tumor motion during treatment for purposes of motion management.

Real-Time Magnetic Resonance Imaging Guided Radiation Therapy for Gastroesophageal Junction/Gastric Cancers

Real-Time Magnetic Resonance Imaging Guided Radiation Therapy for Gastroesophageal Junction/Gastric Cancers

Multiparametric Magnetic Resonance Imaging Guided Radiation Therapy for Prostate Cancer Using Learning-Based Magnetic Resonance Imaging–Computed Tomography Registration

Multiparametric Magnetic Resonance Imaging Guided Radiation Therapy for Prostate Cancer Using Learning-Based Magnetic Resonance Imaging–Computed Tomography Registration

Treatment of Gastric MALT Lymphoma Utilizing a Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) System: Evaluation of Interfractional Target Motion

Treatment of Gastric MALT Lymphoma Utilizing a Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) System: Evaluation of Interfractional Target Motion

Multi-Institutional Investigation of Relative Pancreatic Tumor to Duodenal Motion in Magnetic Resonance Imaging Guided Radiation Therapy for Potential Online Adaptive Radiation Therapy

Multi-Institutional Investigation of Relative Pancreatic Tumor to Duodenal Motion in Magnetic Resonance Imaging Guided Radiation Therapy for Potential Online Adaptive Radiation Therapy

First Ever Magnetic Resonance Image Guided Radiation Therapy for Accelerated Partial Breast Irradiation: Early Results of a Single Institution′s Prospective Experience

First Ever Magnetic Resonance Image Guided Radiation Therapy for Accelerated Partial Breast Irradiation: Early Results of a Single Institution′s Prospective Experience

Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) for the Treatment of Prostate Cancer: Initial Clinical Experience and Patient Selection

Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) for the Treatment of Prostate Cancer: Initial Clinical Experience and Patient Selection

Vector Analysis of Bladder Cancer Patient Setup Utilizing a Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) System

Vector Analysis of Bladder Cancer Patient Setup Utilizing a Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) System

Dosimetric Evaluation of Magnetic Resonance–Image Guided Radiation Therapy 3-Source Co-60 and Linear Accelerator–Based Intensity Modulated Radiation Therapy Plans for Pancreas Stereotactic Body Radiation Therapy

Dosimetric Evaluation of Magnetic Resonance–Image Guided Radiation Therapy 3-Source Co-60 and Linear Accelerator–Based Intensity Modulated Radiation Therapy Plans for Pancreas Stereotactic Body Radiation Therapy

The Physics of a Novel Compact Linear Accelerator–Based Magnetic Resonance Imaging–Guided Radiation Therapy System

The Physics of a Novel Compact Linear Accelerator–Based Magnetic Resonance Imaging–Guided Radiation Therapy System

The Design and Implementation of a Novel Compact Linear Accelerator–Based Magnetic Resonance Imaging–Guided Radiation Therapy (MR-IGRT) System

The Design and Implementation of a Novel Compact Linear Accelerator–Based Magnetic Resonance Imaging–Guided Radiation Therapy (MR-IGRT) System

Magnetic Resonance Image Guided Radiation Therapy for External Beam Accelerated Partial-Breast Irradiation: Evaluation of Delivered Dose and Intrafractional Cavity Motion

To use magnetic resonance image guided radiation therapy (MR-IGRT) for accelerated partial-breast irradiation (APBI) to (1) determine intrafractional motion of the breast surgical cavity; and (2) assess delivered dose versus planned dose. Thirty women with breast cancer (stages 0-I) who underwent breast-conserving surgery were enrolled in a prospective registry evaluating APBI using a 0.35-T MR-IGRT system. Clinical target volume was defined as the surgical cavity plus a 1-cm margin (excluding chest wall, pectoral muscles, and 5mm from skin). No additional margin was added for the planning target volume (PTV). A volumetric MR image was acquired before each fraction, and patients were set up to the surgical cavity as visualized on MR imaging. To determine the delivered dose for each fraction, the electron density map and contours from the computed tomography simulation were transferred to the pretreatment MR image via rigid registration. Intrafractional motion of the surgical cavity was determined by applying a tracking algorithm to the cavity contour as visualized on cine MR. Median PTV volume was reduced by 52% when using no PTV margin compared with a 1-cm PTV margin used conventionally. The mean (± standard deviation)difference between planned and delivered dose to the PTV (V95) was 0.6%±0.1%. The mean cavity displacement in the anterior-posterior and superior-inferior directions was 0.6±0.4mm and 0.6±0.3mm, respectively. The mean margin required for at least 90% of the cavity to be contained by the margin for 90% of the time was 0.7mm (5th-95th percentile: 0-2.7mm). Minimal intrafractional motion was observed, and the mean difference between planned and delivered dose was less than 1%. Assessment of efficacy and cosmesis of this MR-guided APBI approach is under way.

A comparative planning study for lung SABR between tri-Co-60 magnetic resonance image guided radiation therapy system and volumetric modulated arc therapy

Background and purposeTo compare the plan quality of tri-60Co magnetic-resonance image-guided radiation therapy (IGRT) to that of volumetric modulated arc therapy (VMAT) for lung stereotactic ablative radiotherapy (SABR). Materials and methodsA total of 22 patients with lung tumors located in the lower lobe were selected retrospectively. For each patient, VMAT plans with linac and intensity-modulated radiation therapy (IMRT) plans with the tri-60Co system were generated with prescription doses of 60Gy (daily dose=15Gy). For both plan types, identical CT image sets and structures were used, with the exception of planning target volumes (PTV). The PTV for VMAT was generated from the internal target volume (ITV) while the PTV for the tri-60Co system was generated from the gross tumor volume (GTV). Clinically relevant dose-volumetric parameters were calculated and analyzed. ResultsThe average PTV volumes of tri-60Co plans and VMAT plans were 10.5±12.3cc vs. 27.2±23.5cc, respectively (p<0.001). The maximum and mean doses to PTVs were 64.0±2.6Gy vs. 62.5±0.9Gy (p=0.005) and 61.4±1.7Gy vs. 60.0±0.5Gy (p<0.001), respectively. The conformity and homogeneity indices were 1.89±0.38 vs. 1.01±0.40 (p<0.001) and 0.06±0.02 vs. 0.04±0.00 (p<0.001), respectively. No considerable differences for organs at risk (OARs) were observed between tri-60Co plans and VMAT plans. In terms of target conformity, integral dose and lung mean dose, the plan quality of tri-60Co plans was inferior to that of VMAT plans when the PTV volumes of tri-60Co plans were less than 10cc. However, all treatment plans of tri-60Co system were clinically acceptable. ConclusionFor lung SABR, the quality of ITV-based VMAT plans was better than that of GTV-based tri-60Co plans especially when the PTV volumes of the tri-60Co plans were less than 10cc. If the breathing pattern of a patient is reproducible, VMAT is considered the optimal option for lung SABR, otherwise the tri-60Co IGRT should be considered due to the ability to monitor tumor motion during treatment.

Magnetic resonance image guided radiation therapy for primary splenic diffuse large B-cell lymphoma: A teaching case

Magnetic resonance image guided radiation therapy for primary splenic diffuse large B-cell lymphoma: A teaching case

TU‐AB‐BRA‐12: Quality Assurance of An Integrated Magnetic Resonance Image Guided Adaptive Radiotherapy Machine Using Cherenkov Imaging

Purpose:To investigate the viability of using Cherenkov imaging as a fast and robust method for quality assurance tests in the presence of a magnetic field, where other instruments can be limited.Methods:Water tank measurements were acquired from a clinically utilized adaptive magnetic resonance image guided radiation therapy (MR‐IGRT) machine with three multileaf‐collimator equipped 60Co sources. Cherenkov imaging used an intensified charge coupled device (ICCD) camera placed 3.5m from the treatment isocenter, looking down the bore of the 0.35T MRI into a water tank. Images were post‐processed to make quantitative comparison between Cherenkov light intensity with both film and treatment planning system predictions, in terms of percent depth dose curves as well as lateral beam profile measurements. A TG‐119 commissioning test plan (C4: C‐Shape) was imaged in real‐time at 6.33 frames per second to investigate the temporal and spatial resolution of the Cherenkov imaging technique.Results:A .33mm/pixel Cherenkov image resolution was achieved across 1024×1024 pixels in this setup. Analysis of the Cherenkov image of a 10.5×10.5cm treatment beam in the water tank successfully measured the beam width at the depth of maximum dose within 1.2% of the film measurement at the same point. The percent depth dose curve for the same beam was on average within 2% of ionization chamber measurements for corresponding depths between 3–100mm. Cherenkov video of the TG‐119 test plan provided qualitative agreement with the treatment planning system dose predictions, and a novel temporal verification of the treatment.Conclusions:Cherenkov imaging was successfully used to make QA measurements of percent depth dose curves and cross beam profiles of MRI‐IGRT radiotherapy machines after only several seconds of beam‐on time and data capture; both curves were extracted from the same data set. Video‐rate imaging of a dynamic treatment plan provided new information regarding temporal dose deposition.This study has been funded by NIH grants R21EB17559 and R01CA109558, as well as Norris Cotton Cancer Center Pilot funding.

Vector analysis of bladder cancer patient setup utilizing a magnetic resonance image-guided radiation therapy (MR-IGRT) system.

412 Background: Inter and intra-fraction anatomy changes in patients undergoing radiation therapy (RT) for bladder cancer (BC) are common but have thus far been studied with implanted fiducial markers, limited quality 2-D orthogonal films and computed tomography (CT). The adverse impact of daily set-up variation could be more significant than appreciated. Our goal was to employ the soft tissue imaging capabilities of an integrated magnetic resonance image-guided RT (MR-IGRT) system to analyze daily positioning. Methods: Fourteen patients with BC were treated on a MR-IGRT system. Patient setup was performed via volumetric MR imaging with a resolution of 0.15 x 0.15 cm. Alignment was performed according to skin marks then shifts assessed by comparing the treatment volume from the planning CT to the daily MR image. 240 pretreatment MR images were analyzed and 3 shifts were recorded for each image. A vector shift was calculated by combining the square root of the combined sum of the shifts squared. Number of times that the vector of combined shifts would have exceeded the planning tumor volume (PTV) was recorded. Results: Daily volumetric MR imaging allowed for accurate alignment and daily monitoring of bladder volume and normal tissue anatomy. Recorded shifts of the treated volume were 0.9±0.5 cm in the right/left direction, 0.7±0.3 cm in the anterior/posterior direction, and 0.7±0.4 cm in the cranio-caudal direction. In 66 (28%) of cases the vector shift was initially greater than the PTV margin. For 2 patients, pre-treatment MR imaging revealed the tumor reduced in size and dose to the bowel would have exceeded constraints, and treatment adaptation was performed to reduce normal tissue toxicity. Using CTCAE criteria, no grade 3 or higher toxicities have been reported. Conclusions: Accurate and reproducible treatment delivery is required to avoid marginal misses to the target volume as well as excess dose to normal tissue. MR-IGRT allows for excellent soft tissue visualization which enables for the avoidance of potential setups errors by allowing daily alignment changes to ensure the target is included in the PTV. It also allows the ability to make treatment changes based on anatomy variations.

Accelerated Partial-Breast Irradiation Utilizing an On-board Magnetic Resonance Image Guided Radiation Therapy System: Evaluation of Intrafraction Motion of the Lumpectomy Cavity

Accelerated Partial-Breast Irradiation Utilizing an On-board Magnetic Resonance Image Guided Radiation Therapy System: Evaluation of Intrafraction Motion of the Lumpectomy Cavity

Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system.

To characterize the performance of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy (MR-IGRT) system. The imaging performance characterization included four components: ACR (the American College of Radiology) phantom test, spatial integrity, coil signal to noise ratio (SNR) and uniformity, and magnetic field homogeneity. The ACR phantom test was performed in accordance with the ACR phantom test guidance. The spatial integrity test was evaluated using a 40.8 × 40.8 × 40.8 cm(3) spatial integrity phantom. MR and computed tomography (CT) images of the phantom were acquired and coregistered. Objects were identified around the surfaces of 20 and 35 cm diameters of spherical volume (DSVs) on both the MR and CT images. Geometric distortion was quantified using deviation in object location between the MR and CT images. The coil SNR test was performed according to the national electrical manufacturers association (NEMA) standards MS-1 and MS-9. The magnetic field homogeneity test was measured using field camera and spectral peak methods. For the ACR tests, the slice position error was less than 0.10 cm, the slice thickness error was less than 0.05 cm, the resolved high-contrast spatial resolution was 0.09 cm, the resolved low-contrast spokes were more than 25, the image intensity uniformity was above 93%, and the percentage ghosting was less than 0.22%. All were within the ACR recommended specifications. The maximum geometric distortions within the 20 and 35 cm DSVs were 0.10 and 0.18 cm for high spatial resolution three-dimensional images and 0.08 and 0.20 cm for high temporal resolution two dimensional cine images based on the distance-to-phantom-center method. The average SNR was 12.0 for the body coil, 42.9 for the combined torso coil, and 44.0 for the combined head and neck coil. Magnetic field homogeneities at gantry angles of 0°, 30°, 60°, 90°, and 120° were 23.55, 20.43, 18.76, 19.11, and 22.22 ppm, respectively, using the field camera method over the 45 cm DSV. The onboard imaging unit of the first commercial MR-IGRT system meets ACR, NEMA, and vendor specifications.

Benchmark and Performance Evaluation of a Clinical 60Co IMRT Treatment Planning System for Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT)

Benchmark and Performance Evaluation of a Clinical 60Co IMRT Treatment Planning System for Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT)

Validation of the First Clinical On-Board Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) System

Validation of the First Clinical On-Board Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) System