Vijai Simha1, Firuza Darius Patel2, Suresh Chander Sharma2, Bhavana Rai2, Arun Singh Oinam2, Rahul krishnatry3, Bhaswanth Dhanireddy2. 1. Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. Electronic address: vijaiaditya1985@gmail.com. 2. Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. 3. Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India.
Abstract
PURPOSE/ INTRODUCTION: To assess the variation in the doses received by the organs at risk (OARs) that can occur during treatment planning of cervical cancer by image-based brachytherapy. METHODS AND MATERIALS: After intracavitary application, two sets of images-CT and MRI-were obtained. The two sets of images were fused together with respect to the applicator. Contouring was done separately on CT and MR images. Dose received by the OARs on CT images with respect to the plans made on the MR images was estimated and compared with those on the MR images. RESULTS: Although there was always a difference between the dose received by the OARs based on the CT and MRI contours, it was not significant for the bladder and rectum; 2 cc doses differed by 0.49 Gy (±0.44) p = 0.28 for the bladder and 0.30 Gy (±0.29) p = 0.16 for the rectum. The 1 cc and 0.1 cc differences were also not significant. However for the sigmoid colon, there was significant intrafraction variation in the 2 cc doses 0.61 (±0.6) p = 0.001, 1 cc doses 0.73 (±0.67) Gy p = 0.00, and 0.1 cc dose 0.97 (±0.93) Gy p = 0.009. CONCLUSIONS: The variation in the doses to the OARs must be considered while weighing target coverage against overdose to the OARs. Although not significant for the bladder and rectum, it was significant for the sigmoid colon. Estimated doses to OARs on the planning system may not be the same dose delivered at the time of treatment.
PURPOSE/ INTRODUCTION: To assess the variation in the doses received by the organs at risk (OARs) that can occur during treatment planning of cervical cancer by image-based brachytherapy. METHODS AND MATERIALS: After intracavitary application, two sets of images-CT and MRI-were obtained. The two sets of images were fused together with respect to the applicator. Contouring was done separately on CT and MR images. Dose received by the OARs on CT images with respect to the plans made on the MR images was estimated and compared with those on the MR images. RESULTS: Although there was always a difference between the dose received by the OARs based on the CT and MRI contours, it was not significant for the bladder and rectum; 2 cc doses differed by 0.49 Gy (±0.44) p = 0.28 for the bladder and 0.30 Gy (±0.29) p = 0.16 for the rectum. The 1 cc and 0.1 cc differences were also not significant. However for the sigmoid colon, there was significant intrafraction variation in the 2 cc doses 0.61 (±0.6) p = 0.001, 1 cc doses 0.73 (±0.67) Gy p = 0.00, and 0.1 cc dose 0.97 (±0.93) Gy p = 0.009. CONCLUSIONS: The variation in the doses to the OARs must be considered while weighing target coverage against overdose to the OARs. Although not significant for the bladder and rectum, it was significant for the sigmoid colon. Estimated doses to OARs on the planning system may not be the same dose delivered at the time of treatment.
Authors: Andre Karius; Vratislav Strnad; Michael Lotter; Stephan Kreppner; Christoph Bert Journal: Strahlenther Onkol Date: 2022-03-12 Impact factor: 4.033