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Title: SU-F-T-397: Evaluating the Impact of Bladder Filling Status for the Organs at Risk Dose Distribution in Cervical Cancer Patients with Intensity Modulated Radiotherapy

Abstract

Purpose: To investigate the impact of bladder filling status of the organs at risk (OARs) on dose distribution during intensity modulated radiotherapy (IMRT) for cervical cancer patients. Methods: Twelve cervical cancer patients treated with IMRT were selected for this study. The prescription dose was 45Gy/25 fractions with the 6 MV photon beam. All patients performed two CT scans, one with an empty bladder, the other one with bladder filled. For the registration of two CT scans, the fusion was automatically carried out upon the bony anatomy. The OARs (bladder, rectum, pelvic bone and small intestine) were delineated to planning CT to evaluate the dose distributions. These dose distributions were compared between empty bladder and bladder filling. Results: The bladder volume with empty bladder and bladder filling was 403.2±124.13cc and 101.4±87.5cc, respectively. There were no statistical differences between empty bladder and bladder filling in the mean value of pelvic bone V10Gy, V20Gy, V40Gy; rectum V40Gy and V45Gy. The bladder V40Gy and V45Gy were lower in the bladder filling group than in the empty bladder group (63.7%±5.8% vs 87.5%±7.8%, 45.1%±9.5% vs 62.4%±11.8%, respectively). The V45Gy for small intestine in the bladder filling group was significantly less than the empty bladder group (146.7cc±95.3ccmore » vs 245.7cc±101.8cc). Conclusion: Our study finds that the bladder filling status did not have a significant impact on dose distribution in the rectum and pelvic bone. However, the changes of bladder filling have a large impact on bladder and small intestine doses. A full bladder is strongly recommended during treatment for cervical cancer patients.« less

Authors:
 [1];  [2]
  1. Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China)
  2. The First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong (China)
Publication Date:
OSTI Identifier:
22648994
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BLADDER; COMPUTERIZED TOMOGRAPHY; HAZARDS; NEOPLASMS; PATIENTS; PHOTON BEAMS; RADIATION DOSE DISTRIBUTIONS; RADIOTHERAPY; RECTUM; SKELETON

Citation Formats

Zhang, JY, and Hong, DL. SU-F-T-397: Evaluating the Impact of Bladder Filling Status for the Organs at Risk Dose Distribution in Cervical Cancer Patients with Intensity Modulated Radiotherapy. United States: N. p., 2016. Web. doi:10.1118/1.4956582.
Zhang, JY, & Hong, DL. SU-F-T-397: Evaluating the Impact of Bladder Filling Status for the Organs at Risk Dose Distribution in Cervical Cancer Patients with Intensity Modulated Radiotherapy. United States. doi:10.1118/1.4956582.
Zhang, JY, and Hong, DL. Wed . "SU-F-T-397: Evaluating the Impact of Bladder Filling Status for the Organs at Risk Dose Distribution in Cervical Cancer Patients with Intensity Modulated Radiotherapy". United States. doi:10.1118/1.4956582.
@article{osti_22648994,
title = {SU-F-T-397: Evaluating the Impact of Bladder Filling Status for the Organs at Risk Dose Distribution in Cervical Cancer Patients with Intensity Modulated Radiotherapy},
author = {Zhang, JY and Hong, DL},
abstractNote = {Purpose: To investigate the impact of bladder filling status of the organs at risk (OARs) on dose distribution during intensity modulated radiotherapy (IMRT) for cervical cancer patients. Methods: Twelve cervical cancer patients treated with IMRT were selected for this study. The prescription dose was 45Gy/25 fractions with the 6 MV photon beam. All patients performed two CT scans, one with an empty bladder, the other one with bladder filled. For the registration of two CT scans, the fusion was automatically carried out upon the bony anatomy. The OARs (bladder, rectum, pelvic bone and small intestine) were delineated to planning CT to evaluate the dose distributions. These dose distributions were compared between empty bladder and bladder filling. Results: The bladder volume with empty bladder and bladder filling was 403.2±124.13cc and 101.4±87.5cc, respectively. There were no statistical differences between empty bladder and bladder filling in the mean value of pelvic bone V10Gy, V20Gy, V40Gy; rectum V40Gy and V45Gy. The bladder V40Gy and V45Gy were lower in the bladder filling group than in the empty bladder group (63.7%±5.8% vs 87.5%±7.8%, 45.1%±9.5% vs 62.4%±11.8%, respectively). The V45Gy for small intestine in the bladder filling group was significantly less than the empty bladder group (146.7cc±95.3cc vs 245.7cc±101.8cc). Conclusion: Our study finds that the bladder filling status did not have a significant impact on dose distribution in the rectum and pelvic bone. However, the changes of bladder filling have a large impact on bladder and small intestine doses. A full bladder is strongly recommended during treatment for cervical cancer patients.},
doi = {10.1118/1.4956582},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}
  • Purpose: To design and evaluate individualized nonadaptive and online-adaptive strategies based on a pretreatment established motion model for the highly deformable target volume in cervical cancer patients. Methods and Materials: For 14 patients, nine to ten variable bladder filling computed tomography (CT) scans were acquired at pretreatment and after 40 Gy. Individualized model-based internal target volumes (mbITVs) accounting for the cervix and uterus motion due to bladder volume changes were generated by using a motion-model constructed from two pretreatment CT scans (full and empty bladder). Two individualized strategies were designed: a nonadaptive strategy, using an mbITV accounting for the full-rangemore » of bladder volume changes throughout the treatment; and an online-adaptive strategy, using mbITVs of bladder volume subranges to construct a library of plans. The latter adapts the treatment online by selecting the plan-of-the-day from the library based on the measured bladder volume. The individualized strategies were evaluated by the seven to eight CT scans not used for mbITVs construction, and compared with a population-based approach. Geometric uniform margins around planning cervix-uterus and mbITVs were determined to ensure adequate coverage. For each strategy, the percentage of the cervix-uterus, bladder, and rectum volumes inside the planning target volume (PTV), and the clinical target volume (CTV)-to-PTV volume (volume difference between PTV and CTV) were calculated. Results: The margin for the population-based approach was 38 mm and for the individualized strategies was 7 to 10 mm. Compared with the population-based approach, the individualized nonadaptive strategy decreased the CTV-to-PTV volume by 48% {+-} 6% and the percentage of bladder and rectum inside the PTV by 5% to 45% and 26% to 74% (p < 0.001), respectively. Replacing the individualized nonadaptive strategy by an online-adaptive, two-plan library further decreased the percentage of bladder and rectum inside the PTV (0% to 10% and -1% to 9%; p < 0.004) and the CTV-to-PTV volume (4-96 ml). Conclusions: Compared with population-based margins, an individualized PTV results in better organ-at-risk sparing. Online-adaptive radiotherapy further improves organ-at-risk sparing.« less
  • Purpose: Intensity-modulated radiotherapy (IMRT) treatment for lung cancer is difficult due to the heterogeneous dose distribution and excessive dose to the organs at risk (OARs). We introduce a simple method based on the base dose function (BDF) in Eclipse treatment planning system to overcome the difficulties. Methods: Thirteen patients suffered from stage III non-small cell lung cancer (NSCLC) were enrolled in the study. Three kinds of approaches were applied to obtain clinically acceptable treatment plans: 1) conventionally optimizing method with hot and cold spots re-optimization (CO); 2) target-divided optimizing method (TDO) in which the optimization objective in the lung densitymore » of planning target volume (PTV) was set to 2 to 4 Gy higher than in the soft tissue density; 3) base dose function (BDF) in which the treatment plan was produced based on the original plan for re-optimization. CO, TDO and BDF methods were then compared in terms of conformity index (CI), homogeneity index (HI), OARs sparing and monitor units (MUs). Additionally, delta4, portal dosimetry and IMSure were used to measure the dose delivering accuracy. Results: The BDF technique provided more superior CI and HI than the other two methods. Moreover, the new method also reduced the lung, esophagus, heart and spinal cord dose. However, the BDF plans needed extra 15% and 10% MUs than the CO and TDO methods. Dose verification results demonstrated good and comparable γ pass rates among the three methods. Conclusion: The proposed BDF method greatly improves the dose homogeneity and OARs sparing in the IMRT treatment for lung cancer.« less
  • Purpose: To examine how much lifetime attributable risk (LAR) as an in silico surrogate marker of radiation-induced secondary cancer would be lowered by using proton beam therapy (PBT) in place of intensity modulated x-ray therapy (IMXT) in pediatric patients. Methods: From 242 pediatric patients with cancers who were treated with PBT, 26 patients were selected by random sampling after stratification into four categories: a) brain, head, and neck, b) thoracic, c) abdominal, and d) whole craniospinal (WCNS) irradiation. IMXT was re-planned using the same computed tomography and region of interest. Using dose volume histogram (DVH) of PBT and IMXT, themore » LAR of Schneider et al. was calculated for the same patient. The published four dose-response models for carcinoma induction: i) full model, ii) bell-shaped model, iii) plateau model, and ix) linear model were tested for organs at risk. In the case that more than one dose-response model was available, the LAR for this patient was calculated by averaging LAR for each dose-response model. Results: Calculation of the LARs of PBT and IMXT based on DVH was feasible for all patients. The mean±standard deviation of the cumulative LAR difference between PBT and IMXT for the four categories was a) 0.77±0.44% (n=7, p=0.0037), b) 23.1±17.2%,(n=8, p=0.0067), c) 16.4±19.8% (n=8, p=0.0525), and d) 49.9±21.2% (n=3, p=0.0275, one tailed t-test), respectively. The LAR was significantly lower by PBT than IMXT for the the brain, head, and neck region, thoracic region, and whole craniospinal irradiation. Conclusion: In pediatric patients who had undergone PBT, the LAR of PBT was significantly lower than the LAR of IMXT estimated by in silico modeling. This method was suggested to be useful as an in silico surrogate marker of secondary cancer induced by different radiotherapy techniques. This research was supported by the Translational Research Network Program, JSPS KAKENHI Grant No. 15H04768 and the Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, founded by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.« less
  • Purpose: RapidPlan uses a library consisting of expert plans from different patients to create a model that can predict achievable dose-volume histograms (DVHs) for new patients. The goal of this study is to investigate the impacts of model library population (plan numbers) on the DVH prediction for rectal cancer patients treated with volumetric-modulated radiotherapy (VMAT) Methods: Ninety clinically accepted rectal cancer patients’ VMAT plans were selected to establish 3 models, named as Model30, Model60 and Model90, with 30,60, and 90 plans in the model training. All plans had sufficient target coverage and bladder and femora sparings. Additional 10 patients weremore » enrolled to test the DVH prediction differences with these 3 models. The predicted DVHs from these 3 models were compared and analyzed. Results: Predicted V40 (Vx, percent of volume that received x Gy for the organs at risk) and Dmean (mean dose, cGy) of the bladder were 39.84±13.38 and 2029.4±141.6 for the Model30,37.52±16.00 and 2012.5±152.2 for the Model60, and 36.33±18.35 and 2066.5±174.3 for the Model90. Predicted V30 and Dmean of the left femur were 23.33±9.96 and 1443.3±114.5 for the Model30, 21.83±5.75 and 1436.6±61.9 for the Model60, and 20.31±4.6 and 1415.0±52.4 for the Model90.There were no significant differences among the 3 models for the bladder and left femur predictions. Predicted V40 and Dmean of the right femur were 19.86±10.00 and 1403.6±115.6 (Model30),18.97±6.19 and 1401.9±68.78 (Model60), and 21.08±7.82 and 1424.0±85.3 (Model90). Although a slight lower DVH prediction of the right femur was found on the Model60, the mean differences for V30 and mean dose were less than 2% and 1%, respectively. Conclusion: There were no significant differences among Model30, Model60 and Model90 for predicting DVHs on rectal patients treated with VMAT. The impact of plan numbers for model library might be limited for cancers with similar target shape.« less
  • Purpose: The aim of this study was to evaluate the impact of variations in pelvic dimensions on the dose delivered to the target volumes and the organs at risk (OARs) in patients with high-risk prostate cancer (PCa) to be treated with whole pelvic radiation therapy (WPRT) in an attempt to define the hostile pelvis in terms of intensity modulated radiation therapy (IMRT). Methods and Materials: In 45 men with high-risk PCa to be treated with WPRT, the target volumes and the OARs were delineated, the dose constraints for the OARs were defined, and treatment plans were generated according to themore » Radiation Therapy Oncology Group 0924 protocol. Six dimensions to reflect the depth, width, and height of the bony pelvis were measured, and 2 indexes were calculated from the planning computed tomographic scans. The minimum dose (D{sub min}), maximum dose (D{sub max}), and mean dose (D{sub mean}) for the target volumes and OARs and the partial volumes of each of these structures receiving a specified dose (V{sub D}) were calculated from the dose-volume histograms (DVHs). The data from the DVHs were correlated with the pelvic dimensions and indexes. Results: According to an overall hostility score (OHS) calculation, 25 patients were grouped as having a hospitable pelvis and 20 as having a hostile pelvis. Regarding the OHS grouping, the DVHs for the bladder, bowel bag, left femoral head, and right femoral head differed in favor of the hospitable pelvis group, and the DVHs for the rectum differed for a range of lower doses in favor of the hospitable pelvis group. Conclusions: Pelvimetry might be used as a guide to define the challenging anatomy or the hostile pelvis in terms of treatment planning for IMRT in patients with high-risk PCa to be treated with WPRT.« less