Computational analysis of interfractional anisotropic shape variations of the rectum in prostate cancer radiation therapy

Haekal, Mohammad; Arimura, Hidetaka; Hirose, Taka aki; Shibayama, Yoshihiko; Ohga, Shouichi; Fukunaga, Junichi; Umezu, Yoshiyuki; Honda, Hiroshi; Sasaki, Takahiro

doi:10.1016/j.ejmp.2017.12.019

Cited by 11 publications

(8 citation statements)

References 56 publications

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“…Clinical results have proven this fear unfounded, and the practice has since been changed into cropping the rectum in such cases. 1 Systematic shape errors due to rectal deformation have previously been studied by Hoogeman et al 21 and Haekal et al 22 There, the treatment CTs were not registered to gold markers, and, contrary to our results, both studies found the largest systematic errors in the anterior region. As such, the current results are a testament to the success of fiducial markers.…”

Section: Discussioncontrasting

confidence: 85%

Reducing systematic errors due to deformation of organs at risk in radiotherapy

et al. 2021

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In radiotherapy (RT), the planning CT (pCT) is commonly used to plan the full RT-course. Due to organ deformation and motion, the organ shapes seen at the pCT will not be identical to their shapes during RT. Any difference between the pCT organ shape and the organ's mean shape during RT will cause systematic errors. We propose to use statistical shrinkage estimation to reduce this error using only the pCT and the population mean shape computed from training data. Methods: The method was evaluated for the rectum in a cohort of 37 prostate cancer patients that had a pCT and 7-10 treatment CTs with rectum delineations. Deformable registration was performed both within-patient and between patients, resulting in point-to-point correspondence between all rectum shapes, which enabled us to compute a population mean rectum. Shrinkage estimates were found by combining the pCTs linearly with the population mean. The method was trained and evaluated using leave-one-out cross validation. The shrinkage estimates and the patient mean shapes were compared geometrically using the Dice similarity index (DSI), Hausdorff distance (HD), and bidirectional local distance. Clinical dose/volume histograms, equivalent uniform dose (EUD) and minimum dose to the hottest 5% volume (D5%) were compared for the shrinkage estimate and the pCT. Results: The method resulted in moderate but statistically significant increase in similarity to the patient mean shape over the pCT. On average, the HD was reduced from 15.6 to 13.4 mm, while the DSI was increased from 0.74 to 0.78. Significant reduction in the bias of volume estimates was found in the DVHrange of 52.5-65 Gy, where the bias was reduced from −1.3 to −0.2 percentage points, but no significant improvement was found in EUD or D5%, Conclusions: The results suggest that shrinkage estimation can reduce systematic errors due to organ deformations in RT. The method has potential to increase the accuracy in RT of deformable organs and can improve motion modeling.

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Section: Discussioncontrasting

confidence: 85%

Reducing systematic errors due to deformation of organs at risk in radiotherapy

et al. 2021

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“…However, pretreatment QA cannot be used to detect interfractional variation, such as setup errors and anatomical changes, which can occur over the course of the treatment. In the case of treatment for prostate cancer (PC), many studies have reported that variation in inter‐ and intrafractional size and position of the prostate and surrounding tissues impacts the doses delivered to the target and the organs at risk (OARs) . In the case of head and neck cancer (HNC), many researchers have reported that tumor shrinkage and anatomical changes occur during the course of the treatment .…”

Section: Introductionmentioning

confidence: 99%

Analyses of integrated EPID images for on‐treatment quality assurance to account for interfractional variations in volumetric modulated arc therapy

Matsushita

Nakamura

Sasaki

et al. 2020

J Applied Clin Med Phys

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Purpose: To investigate the effects of interfractional variation, such as anatomical changes and setup errors, on dose delivery during treatment for prostate cancer (PC) and head and neck cancer (HNC) by courses of volumetric modulated arc therapy (VMAT) aided by on-treatment electronic portal imaging device (EPID) images.Methods: Seven patients with PC and 20 patients with HNC who had received VMAT participated in this study. After obtaining photon fluence at the position of the EPID for each treatment arc from on-treatment integrated EPID images, we calculated the differences between the fluence for the first fraction and each subsequent fraction for each arc. The passing rates were investigated based on a tolerance level of 3% of the maximum fluence during the treatment courses and the correlations between the passing rates and anatomical changes.Results: In PC, the median and lowest passing rates were 99.8% and 95.2%, respectively. No correlations between passing rates and interfractional variation were found. In HNC, the median passing rate of all fractions was 93.0%, and the lowest passing rate was 79.6% during the 35th fraction. Spearman's correlation coefficients between the passing rates and changes in weight or neck volume were − 0.77 and − 0.74, respectively.Conclusions: Analyses of the on-treatment EPID images facilitates estimates of the interfractional anatomical variation in HNC patients during VMAT and thus improves assessments of the need for re-planning or adaptive strategies and the timing thereof.

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“…This study aimed to verify the interfractional robustness of scanning CIRT for prostate cancer based on the dose distribution using a complete series of daily in-room CT image datasets. Prior studies analyzed the interfractional robustness of IMRT 16,17,22,27,28 and proton therapy 16,17,[20][21][22][29][30][31] using various types of CT images. In CIRT, the robustness of the dose distribution of passive CIRT was analyzed using daily in-room CT datasets.…”

Section: Discussionmentioning

confidence: 99%

Interfractional robustness of scanning carbon ion radiotherapy for prostate cancer: An analysis based on dose distribution from daily in‐room CT images

Tsuchida

Minohara

Kusano

et al. 2021

J Applied Clin Med Phys

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Purpose: We analyzed interfractional robustness of scanning carbon ion radiotherapy (CIRT) for prostate cancer based on the dose distribution using daily in-room computed tomography (CT) images. Materials and Methods:We analyzed 11 consecutive patients treated with scanning CIRT for localized prostate cancer in our hospital between December 2015 and January 2016. In-room CT images were taken under treatment conditions in every treatment session. The dose distribution on each in-room CT image was recalculated, while retaining the pencil beam arrangement of the initial treatment plan.Then, the dose-volume histogram (DVH) parameters including the percentage of the clinical target volume (CTV) with 95% and 90% of the prescribed dose area (V95% of CTV, V90% of CTV) and V80% of rectum were calculated. The acceptance criteria for the CTV and rectum were set at V95% of CTV ≥95%, V90% of CTV ≥98%, and V80% of rectum < 10 ml.Results: V95% of CTV, V90% of CTV, and V80% of rectum for the reproduced plans were 98.8 ± 3.49%, 99.5 ± 2.15%, and 4.39 ± 3.96 ml, respectively. Acceptance of V95% of CTV, V90% of CTV, and V80% of rectum was obtained in 123 (94%), 125 (95%) and 117 sessions (89%), respectively. Acceptance of the mean dose of V95% of CTV, V90% of CTV, and V80% of rectum for each patient was obtained in 10 (91%), 10 (91%), and 11 patients (100%), respectively. Conclusions:We demonstrated acceptable interfractional robustness based on the dose distribution in scanning CIRT for prostate cancer.

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Computational analysis of interfractional anisotropic shape variations of the rectum in prostate cancer radiation therapy

Abstract: The anisotropic shape variations of the rectum, especially in the ROP regions, should be considered when determining a planning risk volume (PRV) margins for the rectum associated with the acute toxicities.

Cited by 11 publications

References 56 publications

Reducing systematic errors due to deformation of organs at risk in radiotherapy

Reducing systematic errors due to deformation of organs at risk in radiotherapy

Analyses of integrated EPID images for on‐treatment quality assurance to account for interfractional variations in volumetric modulated arc therapy

Interfractional robustness of scanning carbon ion radiotherapy for prostate cancer: An analysis based on dose distribution from daily in‐room CT images

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