Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts, United States of America.
ETH Zürich, Zürich, Switzerland.
Phys Med Biol. 2021 Feb 25;66(5). doi: 10.1088/1361-6560/abe050.
The high conformality of intensity-modulated proton therapy (IMPT) dose distributions causes treatment plans to be sensitive to geometrical changes during the course of a fractionated treatment. This can be addressed using adaptive proton therapy (APT). One important question in APT is the frequency of adaptations performed during a fractionated treatment, which is related to the question whether plan adaptation has to be done online or offline. The purpose of this work is to investigate the impact of weekly and daily online IMPT plan adaptation on the treatment quality for head and neck patients. A cohort of ten head and neck patients with daily acquired cone-beam CT (CBCT) images was evaluated retrospectively. Dose tracking of the IMPT treatment was performed for three scenarios: base plan with no adaptation (BP), weekly online adaptation (OA), and daily online adaptation (OA). Both adaptation schemes used an in-house developed online APT workflow, performing Monte Carlo dose calculations on scatter-corrected CBCTs. IMPT plan adaptation was achieved by only tuning the weights of a subset of beamlets, based on deformable image registration from the planning CT to each CBCT. Although OAmitigated random delivery errors more effectively than OAon a fraction per fraction basis, both OAand OAachieved the clinical goals for all ten patients, while BP failed for six cases. In the high-risk CTV, accumulated values ofranged between 97.15% and 99.73% of the prescription dose for OA, with a median of 98.07%. For OA, values between 95.02% and 99.26% were obtained, with a median of 97.61% of the prescription dose. Otherwise, the dose to most organs at risk was similar for all three scenarios. Globally, our results suggest that OAcould be used as an alternative approach to OAfor most patients in order to reduce the clinical workload.
调强质子治疗（IMPT）剂量分布的高适形性导致治疗计划在分次治疗过程中对几何形状变化敏感。这可以通过自适应质子治疗（APT）来解决。APT 中的一个重要问题是在分次治疗过程中进行适应的频率，这与计划适应是否需要在线或离线进行有关。本工作旨在研究每周和每日在线 IMPT 计划适应对头颈部患者治疗质量的影响。回顾性评估了十名具有每日获得的锥形束 CT（CBCT）图像的头颈部患者队列。对三种情况进行了 IMPT 治疗的剂量跟踪：无适应的基础计划（BP）、每周在线适应（OA）和每日在线适应（OA）。两种适应方案均使用内部开发的在线 APT 工作流程，在散射校正 CBCT 上进行蒙特卡罗剂量计算。IMPT 计划适应仅通过基于从计划 CT 到每个 CBCT 的变形图像配准来调整子集的射束权重来实现。尽管 OA 在每分次的基础上比 OA 更有效地缓解了随机传递误差，但 OA 和 OA 都为所有十名患者实现了临床目标，而 BP 则在六例中失败。在高危 CTV 中，r 的累积值在 OA 为处方剂量的 97.15%至 99.73%之间，中位数为 98.07%。对于 OA，获得的值在 95.02%至 99.26%之间，中位数为处方剂量的 97.61%。否则，对于所有三个场景，大多数危及器官的剂量相似。总体而言，我们的结果表明，对于大多数患者，OA 可以作为 OA 的替代方法，以减少临床工作量。
