London Regional Cancer Program, London Health Sciences Centre, 790 Commissioners Road East, London, Ontario, Canada.
Clin Oncol (R Coll Radiol). 2011 Nov;23(9):625-31. doi: 10.1016/j.clon.2011.03.007. Epub 2011 Apr 11.
The success of delivering the prescribed radiation dose to the prostate while sparing adjacent sensitive tissues is largely dependent on the ability to accurately target the prostate during treatment. Kilovoltage cone beam computed tomography (CBCT) imaging can be used to monitor and compensate for inter-fraction prostate motion, but this procedure increases treatment session time and adds incidental radiation dose to the patient. We carried out a retrospective study of CBCT data to evaluate the systematic and random correction shifts of the prostate with respect to bones and external marks.
A total of 449 daily CBCT studies from 17 patients undergoing intensity-modulated radiotherapy (IMRT) for localised prostate cancer were analysed. The difference between patient set-up correction shifts applied by radiation therapists (via matching prostate position in CBCT and planning computed tomography) and shifts obtained by matching bony anatomy in the same studies was used as a measure of the daily inter-fraction internal prostate motion.
The average systematic and random shifts in prostate positions, calculated over all fractions versus only 10 fractions, were not found to be significantly different.
The measured prostate shifts with respect to bony anatomy and external marks after the first 10 imaging sessions were shown to provide adequate predictive power for defining patient-specific margins in future fractions without a need for ongoing computed tomography imaging. Different options for CBCT imaging schedule are proposed that will reduce the treatment session time and imaging dose to radiotherapy patients while ensuring appropriate prostate cover and normal tissue sparing.
将规定的辐射剂量成功递送至前列腺，同时保护相邻的敏感组织，在很大程度上取决于在治疗过程中准确瞄准前列腺的能力。千伏锥形束计算机断层扫描（CBCT）成像可用于监测和补偿分次间前列腺运动，但该程序会增加治疗时间，并给患者带来额外的偶然辐射剂量。我们对 CBCT 数据进行了回顾性研究，以评估前列腺相对于骨骼和外部标记的系统和随机校正移位。
分析了 17 名接受局部前列腺癌调强放疗（IMRT）的患者的 449 次每日 CBCT 研究。通过匹配 CBCT 和计划计算机断层扫描中的前列腺位置来应用的放射治疗师的患者设置校正移位与在相同研究中通过匹配骨骼解剖结构获得的移位之间的差异被用作每日分次内前列腺运动的度量。
发现所有分数与仅 10 个分数相比，前列腺位置的平均系统和随机移位没有显著差异。
在最初的 10 次成像后，测量的前列腺相对于骨骼解剖结构和外部标记的移位，在无需进行连续计算机断层扫描成像的情况下，为确定未来分次中特定患者的边界提供了足够的预测能力。提出了不同的 CBCT 成像方案选择，这些方案将减少治疗时间和成像剂量，同时确保适当的前列腺覆盖和正常组织保护，为放疗患者带来好处。
