Huang Yuliang, Wang Haiyang, Li Chenguang, Hu Qiaoqiao, Liu Hongjia, Deng Jun, Li Weibo, Wang Ruoxi, Wu Hao, Zhang Yibao
Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital and Institute, Beijing, China.
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, United States.
Front Oncol. 2020 Sep 29;10:574889. doi: 10.3389/fonc.2020.574889. eCollection 2020.
To evaluate the feasibility of dose-guided adaptive radiotherapy (ART) based on deformable image registration (DIR) using fractional megavoltage cone-beam CT (MVCBCT) images from Halcyon system that uses identical beams for treatment and imaging and to retrospectively investigate the influence of anatomic changes on target coverage and organ-at-risk (OAR) sparing across various tumor sites. Four hundred twenty-two MVCBCT images from 16 patients (three head and neck, seven thoracic, three abdominal, and three pelvic cases) treated in a phase II clinical trial for Halcyon were selected. DIR between the planning CT and daily MVCBCT image was implemented by Velocity software to create pseudo CT. To investigate the accuracy of dose calculation on pseudo CT, three evaluation patients with rescanned CT and adaptive plans were selected. Dose distribution of adaptive plans calculated on pseudo CT was compared with that calculated on the rescanned planning CT on the three evaluation patients. To investigate the impact of inter-fractional anatomic changes on target dose coverage and dose to OARs of the 16 patients, fractional dose was calculated and accumulated incrementally based on deformable registration between planning CT and daily MVCBCT images. Passing rates using 3 mm/3%/10% threshold local gamma analysis were 93.04, 96.00, and 91.68%, respectively, for the three evaluation patients between the reconstructed dose on pseudo CT (MVCBCT) and rescanned CT, where accumulated dose deviations of over 97% voxels were smaller than 0.5 Gy. Planning target volume (PTV) D95% and D90% (the minimum dose received by at least 95/90% of the volume) of the accumulated dose could be as low as 93.8 and 94.5% of the planned dose, respectively. OAR overdose of various degrees were observed in the 16 patients relative to the planned dose. In most cases, OARs' dose volume histogram (DVH) lines of accumulated and planned dose were very close to each other if not overlapping. Among cases with visible deviations, the differences were bilateral without apparent patterns specific to tumor sites or organs. As a confidence building measure, this simulation study suggested the possibility of ART for Halcyon based on DIR between planning CT and MVCBCT. Preliminary clinical data suggested the benefit of patient-specific dose reconstruction and ART to avoid unacceptable target underdosage and OAR overdosage.
为评估基于可变形图像配准（DIR）的剂量引导自适应放疗（ART）的可行性，该研究使用了Halcyon系统的分次兆伏级锥形束CT（MVCBCT）图像，该系统使用相同的射束进行治疗和成像，并回顾性研究解剖结构变化对不同肿瘤部位靶区覆盖和危及器官（OAR）保护的影响。选取了在Halcyon的II期临床试验中接受治疗的16例患者（3例头颈部、7例胸部、3例腹部和3例盆腔病例）的422幅MVCBCT图像。通过Velocity软件在计划CT和每日MVCBCT图像之间进行DIR，以创建伪CT。为研究伪CT上剂量计算的准确性，选取了3例重新扫描CT并制定了自适应计划的评估患者。将在伪CT上计算的自适应计划的剂量分布与在3例评估患者的重新扫描的计划CT上计算的剂量分布进行比较。为研究16例患者分次间解剖结构变化对靶区剂量覆盖和OAR剂量的影响，基于计划CT和每日MVCBCT图像之间的可变形配准，逐步计算并累积分次剂量。对于3例评估患者，在伪CT（MVCBCT）上重建的剂量与重新扫描的CT之间，使用3 mm/3%/10%阈值局部伽马分析的通过率分别为93.04%、96.00%和91.68%，其中超过97%体素的累积剂量偏差小于0.5 Gy。累积剂量的计划靶体积（PTV）D95%和D90%（至少95/90%体积所接受的最小剂量）分别可低至计划剂量的93.8%和94.5%。相对于计划剂量，在16例患者中观察到不同程度的OAR剂量过量。在大多数情况下，累积剂量和计划剂量的OAR剂量体积直方图（DVH）曲线即使不重叠也非常接近。在有明显偏差的病例中，差异是双侧的，没有特定于肿瘤部位或器官的明显模式。作为一项增强信心的措施，该模拟研究表明基于计划CT和MVCBCT之间的DIR对Halcyon进行ART的可能性。初步临床数据表明，针对患者的剂量重建和ART有助于避免不可接受的靶区剂量不足和OAR剂量过量。
