Zhu Mingyao, Kaiser Adeel, Mishra Mark V, Kwok Young, Remick Jill, DeCesaris Cristina, Langen Katja M
Department of Radiation Oncology, Maryland Proton Treatment Center, University of Maryland School of Medicine, Baltimore, Maryland.
Department of Radiation Oncology, University of Maryland Medical Center, Baltimore, Maryland.
Adv Radiat Oncol. 2019 Dec 26;5(5):1022-1031. doi: 10.1016/j.adro.2019.12.003. eCollection 2020 Sep-Oct.
To propose a method of optimizing intensity modulated proton therapy (IMPT) plans robust against dosimetric degradation caused by random anatomic variations during treatment.
Fifteen patients with prostate cancer treated with IMPT to the pelvic targets were nonrandomly selected. On the repeated quality assurance computed tomography (QACTs) for some patients, bowel density changes were observed and caused dose degradation because the treated plans were not robustly optimized (non-RO). To mitigate this effect, we developed a robust planning method based on 3 CT images, including the native planning CT and its 2 copies, with the bowel structures being assigned to air and tissue, respectively. The RO settings included 5 mm setup uncertainty and 3.5% range uncertainty on 3 CTs. This method is called pseudomultiple-CT RO (pMCT-RO). Plans were also generated using RO on the native CT only, with the same setup and range uncertainties. This method is referred to as single-CT RO (SCT-RO). Doses on the QACTs and the nominal planning CT were compared for the 3 planning methods.
All 3 plan methods provided sufficient clinical target volumes D95% and V95% on the QACTs. For pMCT-RO plans, the normal tissue D on QACTs of all patients was at maximum 109.1%, compared with 144.4% and 116.9% for non-RO and SCT-RO plans, respectively. On the nominal plans, the rectum and bladder doses were similar among all 3 plans; however, the volume of normal tissue (excluding the rectum and bladder) receiving the prescription dose or higher is substantially reduced in either pMCT-RO plans or SCT-RO plans, compared with the non-RO plans.
We developed a robust optimization method to further mitigate undesired dose heterogeneity caused by random anatomic changes in pelvic IMPT treatment. This method does not require additional patient CT scans. The pMCT-RO planning method has been implemented clinically since 2017 in our center.
提出一种优化调强质子治疗（IMPT）计划的方法，使其能有效抵御治疗期间随机解剖变异导致的剂量学退化。
非随机选取15例接受盆腔靶区IMPT治疗的前列腺癌患者。在部分患者的重复质量保证计算机断层扫描（QACT）中，观察到肠道密度变化并导致剂量退化，原因是治疗计划未进行稳健优化（非稳健优化，non-RO）。为减轻这种影响，我们基于3幅CT图像开发了一种稳健规划方法，包括原始规划CT及其2个副本，其中肠道结构分别被指定为空气和组织。稳健优化（RO）设置包括在3幅CT上5mm的摆位不确定性和3.5%的射程不确定性。该方法称为伪多CT稳健优化（pMCT-RO）。还仅在原始CT上使用RO生成计划，具有相同的摆位和射程不确定性。该方法称为单CT稳健优化（SCT-RO）。比较了3种规划方法在QACT和标称规划CT上的剂量。
所有3种计划方法在QACT上均提供了足够的临床靶区体积D95%和V95%。对于pMCT-RO计划，所有患者QACT上的正常组织D最高为109.1%，而非RO计划和SCT-RO计划分别为144.4%和116.9%。在标称计划上，所有3种计划中直肠和膀胱剂量相似；然而，与非RO计划相比，接受处方剂量或更高剂量的正常组织（不包括直肠和膀胱）体积在pMCT-RO计划或SCT-RO计划中均显著减少。
我们开发了一种稳健优化方法，以进一步减轻盆腔IMPT治疗中随机解剖变化引起的不良剂量不均匀性。该方法不需要额外的患者CT扫描。自2017年以来，pMCT-RO规划方法已在我们中心临床应用。
