Jamema Swamidas V, Saju Sherly, Mahantshetty Umesh, Pallad S, Deshpande D D, Shrivastava S K, Dinshaw K A
Department of Medical Physics, Tata Memorial Hospital, Mumbai, India.
J Med Phys. 2008 Jan;33(1):3-8. doi: 10.4103/0971-6203.39417.
The purpose is to compare CT-based dosimetry with International Commission on Radiation Units and Measurements (ICRU 38) bladder and rectum reference points in patients of carcinoma of uterine cervix treated with intracavitary brachytherapy (ICA). Twenty-two consecutive patients were evaluated. Orthogonal radiographs and CT images were acquired and transferred to PLATO planning system. Bladder and rectal reference points were identified according to ICRU 38 recommendations. Dosimetry was carried out based on Manchester system. Patient treatment was done using (192)Iridium high dose rate (HDR) remote after-loading machine based on the conventional radiograph-based dosimetry. ICRU rectal and bladder point doses from the radiograph plans were compared with D(2), dose received by 2 cm(3) of the organ receiving maximum dose from CT plan. V(2), volume of organ receiving dose more than the ICRU reference point, was evaluated. The mean (+/-standard deviation) volume of rectum and bladder was 60 (+/-28) cm(3) and 138 (+/-41) cm(3) respectively. The mean reference volume in radiograph and CT plan was 105 (+/-7) cm(3) and 107 (+/-7) cm(3) respectively. It was found that 6 (+/-4) cm(3) of rectum and 16 (+/-10) cm(3) of bladder received dose more than the prescription dose. V(2) of rectum and bladder was 7 (+/-1.7) cm(3) and 20.8 (+/-6) cm(3) respectively. Mean D(2) of rectum and bladder was found to be 1.11 (+/-0.2) and 1.56 (+/-0.6) times the mean ICRU reference points respectively. This dosimteric study suggests that comparison of orthogonal X-ray-based and CT-based HDR ICA planning is feasible. ICRU rectal point dose correlates well with maximum rectal dose, while ICRU bladder point underestimates the maximum bladder dose.
目的是比较腔内近距离放射治疗（ICA）宫颈癌患者中基于CT的剂量测定与国际辐射单位与测量委员会（ICRU 38）膀胱和直肠参考点的情况。对22例连续患者进行了评估。采集正交X线片和CT图像并传输至PLATO计划系统。根据ICRU 38建议确定膀胱和直肠参考点。基于曼彻斯特系统进行剂量测定。患者治疗采用基于传统X线片剂量测定的（192）铱高剂量率（HDR）远程后装治疗机。将X线片计划中的ICRU直肠和膀胱点剂量与CT计划中接受最大剂量的2 cm³器官所接受的D(2)剂量进行比较。评估接受剂量超过ICRU参考点的器官体积V(2)。直肠和膀胱的平均（±标准差）体积分别为60（±28）cm³和138（±41）cm³。X线片和CT计划中的平均参考体积分别为105（±7）cm³和107（±7）cm³。发现6（±4）cm³的直肠和16（±10）cm³的膀胱接受的剂量超过处方剂量。直肠和膀胱的V(2)分别为7（±1.7）cm³和20.8（±6）cm³。发现直肠和膀胱的平均D(2)分别为平均ICRU参考点的1.11（±0.2）倍和1.56（±0.6）倍。这项剂量测定研究表明，基于正交X射线和基于CT的HDR ICA计划的比较是可行的。ICRU直肠点剂量与直肠最大剂量相关性良好，而ICRU膀胱点低估了膀胱最大剂量。
