Evaluation of dosimetric uncertainty caused by <scp>MR</scp> geometric distortion in <scp>MRI</scp>‐based liver <scp>SBRT</scp> treatment planning

Han, Silu; Yin, Fang‐Fang; Cai, Jing

doi:10.1002/acm2.12520

Cited by 7 publications

(7 citation statements)

References 21 publications

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“…Using population‐based HUs on five tissue segments resulted in a mean difference of 0.1% for target coverage according to our previous study . The dosimetric uncertainty caused by MRI geometric distortion only was ~0.5% when the distortion was 3 mm . Therefore, the combined uncertainty of distortion, segmentation accuracy, and population‐HU assignment is estimated to be ~0.6%.…”

Section: Discussionmentioning

confidence: 75%

“…19 The dosimetric uncertainty caused by MRI geometric distortion only was~0.5% when the distortion was 3 mm. 22 Therefore, the combined uncertainty of distortion, segmentation accuracy, and population-HU assignment is estimated to be~0.6%. This result indicates that the dosimetric accuracy is clinically acceptable and demonstrates the potential of using MRI alone for treatment planning in the abdomen.…”

Section: Discussionmentioning

confidence: 99%

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A technique to generate synthetic CT from MRI for abdominal radiotherapy

Hsu

DuPre

Peng

2020

J Applied Clin Med Phys

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Purpose To investigate a method to classify tissues types for synthetic CT generation using MRI for treatment planning in abdominal radiotherapy. Methods An institutional review board approved volunteer study was performed on a 3T MRI scanner. In‐phase, fat and water images were acquired for five volunteers with breath‐hold using an mDixon pulse sequence. A method to classify different tissue types for synthetic CT generation in the abdomen was developed. Three tissue clusters (fat, high‐density tissue, and spine/air/lungs) were generated using a fuzzy‐c means clustering algorithm. The third cluster was further segmented into three sub‐clusters that represented spine, air, and lungs. Therefore, five segments were automatically generated. To evaluate segmentation accuracy using the method, the five segments were manually contoured on MRI images as the ground truth, and the volume ratio, Dice coefficient, and Hausdorff distance metric were calculated. The dosimetric effect of segmentation accuracy was evaluated on simulated targets close to air, lungs, and spine using a two‐arc volumetric modulated arc therapy (VMAT) technique. Results The volume ratio of auto‐segmentation to manual segmentation was 0.88–2.1 for the air segment and 0.72–1.13 for the remaining segments. The range of the Dice coefficient was 0.24–0.83, 0.84–0.93, 0.94–0.98, 0.93–0.96, and 0.76–0.79 for air, fat, lungs, high‐density tissue, and spine, respectively. The range of the mean Hausdorff distance was 3–29.1 mm, 0.5–1.3 mm, 0.4–1 mm, 0.7–1.6 mm, and 1.2–1.4 mm for air, fat, lungs, high‐density tissue, and spine, respectively. Despite worse segmentation accuracy in air and spine, the dosimetric effect was 0.2% ± 0.2%, with a maximum difference of 0.8% for all target locations. Conclusion A method to generate synthetic CT in the abdomen was developed, and segmentation accuracy and its dosimetric effect were evaluated. Our results demonstrate the potential of using MRI alone for treatment planning in the abdomen.

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Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

A technique to generate synthetic CT from MRI for abdominal radiotherapy

Hsu

DuPre

Peng

2020

J Applied Clin Med Phys

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“…The dosimetric impact of MR geometric inaccuracy for stereotactic radiation therapy has been evaluated and reported in previous studies [34,35]. In these studies, the MR geometric inaccuracy was rep- These results suggested the importance to assess dosimetric impact of the MR geometric inaccuracies during motion especially for regions of interest lying within a relatively large FOV since the magnitude of system related geometric inaccuracies increases with growing radial distance from the scanner's isocenter.…”

Section: Discussionmentioning

confidence: 92%

“…The dosimetric impact of MRI system-related inaccuracies has been evaluated and reported in the literature [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. These evaluations were performed using either images issued from real patients or images issued from digital phantoms.…”

Section: Introductionmentioning

confidence: 99%

Digital phantoms for evaluating the dosimetric Impact of MRI Geometric inaccuracy in SBRT planning for liver cancer in the presence of motion

Torfeh¹

2022

IJCIMR

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MRI is increasingly being used in radiotherapy applications for tumor delineation and tracking in the presence of respiratory motion.The purpose of this work is to investigate the impact of systemrelated MR geometric inaccuracies on dose distributions for liver stereotactic-body radiation therapy (SBRT) using digital phantoms.A methodology of generating digital phantom was developed and presented in this study. Based on this methodology, two types of digital phantoms were generated. The first type is composed of 3D shapes with well-known geometry while the second type is extracted from CT patient images. These digital phantoms were then deformed based on a previously calculated distortion map. Highly conformal volumetric (VMAT) modulated arc therapy plans were then optimized on the distorted dataset and transferred to the original dataset and dose distribution was analyzed. Dosimetric evaluation on these digital phantoms showed that the dose received by the original set of images was higher than the dose received by the distorted images. Results also showed that the difference in the DVH is inversely proportional to the target size.The methodology used in this study, represents an important technique allowing the assessment of the dosimetric impact of organ deformation for different anatomic sites as well as treatment techniques.

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“…Han et al. ( 28 ) simulated a 2.77 mm average geometric distortion of the MRI with a phantom, and the average dose uncertainties for the target volumes and critical structures were small. The average distortion of the GE Discovery-sim 750 was 2.82 mm, which is close to Han’s result; thus, small distortions have minimal impact on the dosimetry for the MRI systems.…”

Section: Discussionmentioning

confidence: 99%

A Comparison of the Distortion in the Same Field MRI and MR-Linac System With a 3D Printed Phantom

Liu

Rong

et al. 2021

Front. Oncol.

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PurposeA 3D printed geometric phantom was developed that can be scanned with computed tomography (CT) and magnetic resonance imaging (MRI) to measure the geometric distortion and determine the relevant dose changes.Materials and MethodsA self-designed 3D printed photosensitive resin phantom was used, which adopts grid-like structures and has 822 1 cm2 squares. The scanning plan was delivered by three MRI scanners: the Elekta Unity MR-Linac 1.5T, GE Signa HDe 1.5T, and GE Discovery-sim 750 3.0T. The geometric distortion comparison was concentrated on two 1.5T MRI systems, whereas the 3.0T MRI was used as a supplemental experiment. The most central transverse images in each dataset were selected to demonstrate the plane distortion. Some mark points were selected to analyze the distortion in the 3D direction based on the plane geometric distortion. A treatment plan was created with the off-line Monaco system.ResultsThe distortion increases gradually from the center to the outside. The distortion range is 0.79 ± 0.40 mm for the Unity, 1.31 ± 0.56 mm for the GE Signa HDe, and 2.82 ± 1.48 mm for the GE Discovery-sim 750. Additionally, the geometric distortion slightly affects the actual planning dose of the radiotherapy.ConclusionGeometric distortion increases gradually from the center to the outside. The distortion values of the Unity were smaller than those of the GE Signa HDe, and the Unity has the smallest geometric distortion. Finally, the Unity’s dose variation best matched with the standard treatment plan.

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Evaluation of dosimetric uncertainty caused by MR geometric distortion in MRI‐based liver SBRT treatment planning

Cited by 7 publications

References 21 publications

A technique to generate synthetic CT from MRI for abdominal radiotherapy

A technique to generate synthetic CT from MRI for abdominal radiotherapy

Digital phantoms for evaluating the dosimetric Impact of MRI Geometric inaccuracy in SBRT planning for liver cancer in the presence of motion

A Comparison of the Distortion in the Same Field MRI and MR-Linac System With a 3D Printed Phantom

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