Radiation Oncology Department, Calvary Mater Newcastle, Australia.
Radiother Oncol. 2011 Feb;98(2):162-8. doi: 10.1016/j.radonc.2011.01.006. Epub 2011 Feb 3.
To assess the accuracy of the initial CT plan dose-volume histograms (DVH's) for prostate, rectum and bladder by comparison to delivered doses determined from cone beam CT (CBCT) scans acquired during image-guided treatment.
Twelve prostate patients were treated using daily implanted fiducial guidance and following local protocol for bladder and rectal preparation. CBCT scans were acquired twice weekly and contoured for prostate, rectum and bladder. The planned beams were applied to all CBCT scans to determine the delivered doses. Prostate dose coverage was assessed by the proportion of the CTV fully encompassed by the 95% and 98% isodose lines. Rectal and bladder volumes receiving 40 Gy, 60 Gy and 70 Gy at treatment were compared to the initial plan, with significance determined using the one-sample t-test.
Four patients showed marginally compromised CTV coverage by the 95% isodose at all CBCT plans. For nine patients the initial plan rectal DVH was significantly outside the range of the treatment DVH's.
Dose coverage of the prostate was not achieved for all patients. Observed rectal and bladder doses were higher than predicted. The initial treatment plan cannot be assumed to represent accurate normal tissue doses.
通过与图像引导治疗过程中采集的锥形束 CT（CBCT）扫描所确定的实际剂量进行比较，评估初始 CT 计划剂量体积直方图（DVH）在前列腺、直肠和膀胱中的准确性。
12 例前列腺患者采用每日植入的基准点进行引导，并根据膀胱和直肠准备的局部方案进行治疗。每周采集 2 次 CBCT 扫描，并对前列腺、直肠和膀胱进行轮廓勾画。将计划的射束应用于所有 CBCT 扫描以确定实际剂量。通过 CTV 完全被 95%和 98%等剂量线覆盖的比例来评估前列腺的剂量覆盖情况。比较初始计划中直肠和膀胱接受 40 Gy、60 Gy 和 70 Gy 的体积，使用单样本 t 检验确定统计学意义。
在所有 CBCT 计划中，有 4 例患者的 CTV 受 95%等剂量线覆盖的程度略有不足。对于 9 例患者，初始计划的直肠 DVH 明显超出了治疗 DVH 的范围。
并非所有患者的前列腺均能达到剂量覆盖。观察到的直肠和膀胱剂量高于预测值。初始治疗计划不能被认为能准确代表正常组织的剂量。
