Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA 23298, USA.
Med Phys. 2012 Feb;39(2):1102-11. doi: 10.1118/1.3679856.
To develop a probabilistic treatment planning (PTP) method which is robust to systematic patient setup errors and to compare PTP plans with plans generated using a planning target volume (PTV) margin optimized to give the same target coverage probability as the PTP plan.
Plans adhering to the RTOG-0126 protocol are developed for 28 prostate patients using PTP and margin-based planning. For PTP, an objective function that simultaneously considers multiple possible patient positions is developed. PTP plans are optimized using clinical target volume (CTV) structures and organ at risk (OAR) structures. The desired CTV coverage probability is 95%. Plans that cannot achieve a 95% CTV coverage probability are re-optimized with a desired CTV coverage probability reduced by 5% until the desired CTV coverage probability is achieved. Margin-based plans are created which achieve the same CTV coverage probability as the PTP plans by iterative adjustment of the CTV-to-PTV margin. Postoptimization, probabilistic dose-volume coverage metrics are used to compare the plans.
For equivalent target coverage probability, PTP plans significantly reduce coverage probability for rectum objectives (-17% for D(35) < 65 Gy, p = 0.0010; -23% for D(25) < 70 Gy, p < 0.0001; and -27% for D(15) < 75 Gy, p < 0.0001). Physician assessment indicates PTP plans are entirely preferred 71% of the time while margin-based plans are entirely preferred 7% of the time.
For plans having the same target coverage probability, PTP has potential to reduce rectal doses while maintaining CTV coverage probability. In blind comparisons, physicians prefer PTP plans over optimized margin plans.
开发一种针对系统患者摆位误差具有稳健性的概率治疗计划（PTP）方法，并将 PTP 计划与通过优化计划靶区（PTV）边界以获得与 PTP 计划相同的靶区覆盖率概率的计划生成进行比较。
为 28 例前列腺患者使用 PTP 和基于边界的计划制定方案。对于 PTP，开发了一个同时考虑多个可能患者位置的目标函数。使用临床靶区（CTV）结构和器官危及器官（OAR）结构对 PTP 计划进行优化。期望 CTV 覆盖率概率为 95%。对于不能达到 95%CTV 覆盖率概率的计划，通过将期望 CTV 覆盖率概率降低 5%进行重新优化，直到达到期望 CTV 覆盖率概率。通过迭代调整 CTV 至 PTV 边界来创建基于边界的计划，以实现与 PTP 计划相同的 CTV 覆盖率概率。优化后，使用概率剂量-体积覆盖指标来比较计划。
对于等效的靶区覆盖率概率，PTP 计划显著降低了直肠目标的覆盖率概率（D（35）<65 Gy 时减少 17%，p=0.0010；D（25）<70 Gy 时减少 23%，p<0.0001；D（15）<75 Gy 时减少 27%，p<0.0001）。医生评估表明，71%的时间 PTP 计划完全优于 PTP 计划，而基于边界的计划完全优于 PTP 计划的时间为 7%。
对于具有相同靶区覆盖率概率的计划，PTP 有潜力在维持 CTV 覆盖率概率的同时降低直肠剂量。在盲法比较中，医生更喜欢 PTP 计划而不是优化边界计划。
