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Title: SU-F-P-26: Study of Radiation Dose Evaluation for Organs at Risk Using MRI in Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma

Abstract

Purpose: To study the contour and dosimetric feature of organs at risk (OARs) applying magnetic resonance imaging (MRI) images in intensity modulated radiation therapy (IMRT) of nasopharyngeal carcinoma (NPC) compared to computed tomography (CT) images. Methods: 35 NPC patients was selected into this trail. CT simulation with non-contrast and contrast enhanced scan, MRI simulation with non-contrast and contrast enhanced T1, T2 and diffusion weighted imaging were achieved sequentially. And the OARs were contoured on the CT and MRI images after rigid registration respectively. 9 beams IMRT plan with equal division angle were designed for every patients, and the prescription dose for tumor target was set as 72Gy (2.4Gy/ fration). The boundary display, volume and dose-volume indices of each organ were compared between on MRI and CT images. Results: Compared to CT, MRI showed clearer boundary of brainstem, spinal cord, the deep lobe of Parotid gland and the optical nerve in canal. MRI images increase the volume of lens, optical nerve, while reducing the volume of eye slightly, and the maximum dose of lens, the mean dose of eyes and optical raised in different percentage, while there was no statistical differences were found. The left and right parotid volume on MRImore » increased by 7.07%, 8.13%, and the mean dose raised by 14.95% (4.01Gy), 18.76% (4.95Gy) with statistical significant difference (p<0.05). The brainstem volume reduced by 9.33% (p<0.05), and the dose of 0.1cm3 volume (D0.1cm3) reduced by mean 8.46% (4.32Gy), and D0.1cm3 of spinal cord increased by 1.5Gy on MRI. Conclusion: It is credible to evaluate the radiation dose of lens, eye and the spinal cord, while it should be necessary to evaluate the dose of brainstem, parotid and the optical nerve applying MRI images sometime, it will be more meaningful for these organs with high risk of radiation injury.« less

Authors:
; ;  [1]
  1. Shandong Cancer Hospital and Institute, Jinan, Shandong (China)
Publication Date:
OSTI Identifier:
22624465
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; BIOMEDICAL RADIOGRAPHY; CARCINOMAS; COMPUTERIZED TOMOGRAPHY; EYES; GLANDS; HAZARDS; IMAGES; NERVES; NMR IMAGING; PATIENTS; RADIATION DOSES; RADIATION INJURIES; RADIOTHERAPY; SIMULATION; SPINAL CORD

Citation Formats

Gong, G, Guo, Y, and Yin, Y. SU-F-P-26: Study of Radiation Dose Evaluation for Organs at Risk Using MRI in Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma. United States: N. p., 2016. Web. doi:10.1118/1.4955733.
Gong, G, Guo, Y, & Yin, Y. SU-F-P-26: Study of Radiation Dose Evaluation for Organs at Risk Using MRI in Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma. United States. doi:10.1118/1.4955733.
Gong, G, Guo, Y, and Yin, Y. Wed . "SU-F-P-26: Study of Radiation Dose Evaluation for Organs at Risk Using MRI in Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma". United States. doi:10.1118/1.4955733.
@article{osti_22624465,
title = {SU-F-P-26: Study of Radiation Dose Evaluation for Organs at Risk Using MRI in Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma},
author = {Gong, G and Guo, Y and Yin, Y},
abstractNote = {Purpose: To study the contour and dosimetric feature of organs at risk (OARs) applying magnetic resonance imaging (MRI) images in intensity modulated radiation therapy (IMRT) of nasopharyngeal carcinoma (NPC) compared to computed tomography (CT) images. Methods: 35 NPC patients was selected into this trail. CT simulation with non-contrast and contrast enhanced scan, MRI simulation with non-contrast and contrast enhanced T1, T2 and diffusion weighted imaging were achieved sequentially. And the OARs were contoured on the CT and MRI images after rigid registration respectively. 9 beams IMRT plan with equal division angle were designed for every patients, and the prescription dose for tumor target was set as 72Gy (2.4Gy/ fration). The boundary display, volume and dose-volume indices of each organ were compared between on MRI and CT images. Results: Compared to CT, MRI showed clearer boundary of brainstem, spinal cord, the deep lobe of Parotid gland and the optical nerve in canal. MRI images increase the volume of lens, optical nerve, while reducing the volume of eye slightly, and the maximum dose of lens, the mean dose of eyes and optical raised in different percentage, while there was no statistical differences were found. The left and right parotid volume on MRI increased by 7.07%, 8.13%, and the mean dose raised by 14.95% (4.01Gy), 18.76% (4.95Gy) with statistical significant difference (p<0.05). The brainstem volume reduced by 9.33% (p<0.05), and the dose of 0.1cm3 volume (D0.1cm3) reduced by mean 8.46% (4.32Gy), and D0.1cm3 of spinal cord increased by 1.5Gy on MRI. Conclusion: It is credible to evaluate the radiation dose of lens, eye and the spinal cord, while it should be necessary to evaluate the dose of brainstem, parotid and the optical nerve applying MRI images sometime, it will be more meaningful for these organs with high risk of radiation injury.},
doi = {10.1118/1.4955733},
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 explore dosimetric effects of brainstem (BS) caused by weight loss during the course of intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods: Seventy-seven patients who were diagnosed with NPC by pathology biopsy have been enrolled. Every patients should receive weight measurement weekly and three times of computed tomography (CT) scans and replanning, at the 15th and 25th fraction during the treatment, respectively. The vertical diameter at the level of odontoid process (d1) and cervical vertebra 3 (d2) be measured from CT images (Supporting document Figure 1). All IMRT plans were designed by inverse planning with commercial treatmentmore » planning systems (Corvus 6.2 version, NOMOS Corporation). The dose differences between plan and actual delivery were generated to compare. Results: The weight loss was more in week 4–5 (3.21±2.19kg) than in week 1–3 (1.79±1.83kg) (Supporting document Figure 2). The d1 and d2 decreased was more significantly in week 4–5 than week 1–3, 2.83±1.75mm vs. 0.55±0.75mm and 2.98±2.96mm vs. 1.23±2.09mm, respectively. The maximum dose to the brainstem (BS Dmax) and the percentage of brainstem volume receiving ≥50Gy (BS V50) increased more significantly in week 4–5 than week 1–3, −3.02±5.49Gy vs. −1.85 ±4.88Gy and −1.85±4.88% vs. −0.77±3.32%, respectively. The changes of d1 and d2 and the BS-V50 and BS-Dmax were closely related to weight loss (p≤0.001)(Supporting document Table 1). Conclusion: The study results indicate that weight loss leads to the vertical diameter reduction, which results has a close relationship with dose of the brainstem during IMRT of NPC. This study was supported by Zhejiang Provincial Medicine and Health Foundation (2013KYB290) and Research Foundation of Science and Technology Department of Zhejiang Province 2015C33257.« 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
  • This study aimed to quantify dosimetric effects of weight loss for nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiation therapy (IMRT). Overall, 25 patients with NPC treated with IMRT were enrolled. We simulated weight loss during IMRT on the computer. Weight loss model was based on the planning computed tomography (CT) images. The original external contour of head and neck was labeled plan 0, and its volume was regarded as pretreatment normal weight. We shrank the external contour with different margins (2, 3, and 5 mm) and generated new external contours of head and neck. The volumes of reconstructed external contoursmore » were regarded as weight during radiotherapy. After recontouring outlines, the initial treatment plan was mapped to the redefined CT scans with the same beam configurations, yielding new plans. The computer model represented a theoretical proportional weight loss of 3.4% to 13.7% during the course of IMRT. The dose delivered to the planning target volume (PTV) of primary gross tumor volume and clinical target volume significantly increased by 1.9% to 2.9% and 1.8% to 2.9% because of weight loss, respectively. The dose to the PTV of gross tumor volume of lymph nodes fluctuated from −2.0% to 1.0%. The dose to the brain stem and the spinal cord was increased (p < 0.001), whereas the dose to the parotid gland was decreased (p < 0.001). Weight loss may lead to significant dosimetric change during IMRT. Repeated scanning and replanning for patients with NPC with an obvious weight loss may be necessary.« less
  • Purpose: This article evaluates [{sup 18}F] fluorodeoxyglucose positron emission tomography ({sup 18}F-FDG-PET) findings as a predictor for local responders (R) vs. nonresponders (NR) in nasopharyngeal carcinoma (NPC) patients with Stage T4 lesions, before and at 3 months after completion of concurrent chemotherapy and radiation therapy (CCRT). Methods and Materials: From January 2002 to November 2003, 39 T4 NPC patients were enrolled. All had magnetic resonance imaging and {sup 18}F-FDG-PET, both before and 3 months after CCRT. Any residual/recurrent lesions were confirmed histopathologically. Results: Of the 39 eligible patients, after a follow-up of 24.2 {+-} 9.5 months, 35 became disease-free andmore » 4 had residual or recurrent disease. Marginal differences in standard uptake values (SUV) were observed (10.9 {+-} 5.3 vs. 15.6 {+-} 3.4, p = 0.058) between R and NR before treatment, and value changes of SUV before and after CCRT were not significantly different. However, highly significantly lower values of SUV were noted for R than for NR 3 months after completion of CCRT (2.1 {+-} 0.8 vs. 5.5 {+-} 3.2, p 0.001). One hundred percent positive and negative predictive values were observed for SUV values of 4.0, set 3 months after completion of CCRT. Conclusions: Neither the pretreatment SUV nor the changes of SUV between pretreatment and posttreatment were significant predictors for local response. SUV at 3 months after completion of CCRT was a significant determinator for local response. The cutoff of 4.0 for SUV at 3 months after completion of CCRT was useful to be offered as a diagnostic reference for recurrent or residual tumor for NPC treatment.« less
  • Purpose: To compare the dosimetric characteristics of volumetric-modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for left-sided breast cancer patients with modified radical mastectomy. Methods: Twenty-four left-sided breast cancer patients treated with modified radical mastectomy were selected in this study. The planning target volume (PTV) was generated by using 7-mm uniform expansion of the clinical target volume (CTV) in all direction except the skin surface. The organs at risk (OARs) included heart, left lung, right lung, and right breast. Dose volume histograms (DVHs) were utilized to evaluate the dose distribution in PTV and OARs. Results: Bothmore » VMAT and IMRT plans met the requirement of PTV coverage. VMAT was superior to IMRT in terms of conformity, with a statistically significant difference (p=0.024). Mean doses, V5 and V10 of heart and both lungs in VMAT plans were significantly decreased compared to IMRT plans (P<0.05), but in terms of heart volume irradiated by high doses (V30 and V45), no significant differences were observed (P>0.05). For right breast, VMAT showed the reduction of V5 in comparison with IMRT (P<0.05). Additionally, the mean number of monitor units (MU) and treatment time in VMAT (357.21, 3.62 min) were significantly less than those in IMRT (1132.85, 8.74 min). Conclusion: VMAT showed similar PTV coverage and significant advantage in OARs sparing compared with IMRT, especially in terms of decreased volumes irradiated by low doses, while significantly reducing the treatment time and MU number.« less