Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, Georgia, USA.
J Appl Clin Med Phys. 2023 Jun;24(6):e13925. doi: 10.1002/acm2.13925. Epub 2023 Feb 6.
Cardiac radioablation (CR) is a noninvasive treatment option for patients with refractory ventricular tachycardia (VT) during which high doses of radiation, typically 25 Gy, are delivered to myocardial scar. In this study, we investigate motion from cardiac cycle and evaluate the dosimetric impact in a cohort of patients treated with CR.
This retrospective study included eight patients treated at our institution who had respiratory-correlated and ECG-gated 4DCT scans acquired within 2 weeks of CR. Deformable image registration was applied between maximum systole (SYS) and diastole (DIAS) CTs to assess cardiac motion. The average respiratory-correlated CT (AVG ) was deformably registered to the average cardiac (AVG ), SYS, and DIAS CTs, and contours were propagated using the deformation vector fields (DVFs). Finally, the original treatment plan was recalculated on the deformed AVG CT for dosimetric assessment.
Motion magnitudes were measured as the mean (SD) value over the DVFs within each structure. Displacement during the cardiac cycle for all chambers was 1.4 (0.9) mm medially/laterally (ML), 1.6 (1.0) mm anteriorly/posteriorly (AP), and 3.0 (2.8) mm superiorly/inferiorly (SI). Displacement for the 12 distinct clinical target volumes (CTVs) was 1.7 (1.5) mm ML, 2.4 (1.1) mm AP, and 2.1 (1.5) SI. Displacements between the AVG and AVG scans were 4.2 (2.0) mm SI and 5.8 (1.4) mm total. Dose recalculations showed that cardiac motion may impact dosimetry, with dose to 95% of the CTV dropping from 27.0 (1.3) Gy on the AVG to 20.5 (7.1) Gy as estimated on the AVG .
Cardiac CTV motion in this patient cohort is on average below 3 mm, location-dependent, and when not accounted for in treatment planning may impact target coverage. Further study is needed to assess the impact of cardiac motion on clinical outcomes.
心脏放射消融术（CR）是一种非侵入性治疗方法，用于治疗难治性室性心动过速（VT）患者，在此过程中，心脏瘢痕组织会接受高达 25Gy 的高剂量辐射。在这项研究中，我们调查了心脏周期中的运动，并评估了在接受 CR 治疗的患者队列中的剂量学影响。
这项回顾性研究包括在我们机构接受治疗的 8 名患者，他们在 CR 治疗后 2 周内接受了呼吸相关和心电图门控的 4DCT 扫描。最大收缩期（SYS）和舒张期（DIAS）CT 之间应用可变形图像配准来评估心脏运动。平均呼吸相关 CT（AVG）通过变形向量场（DVFs）可变形配准到平均心脏（AVG）、SYS 和 DIAS CT 上，并对轮廓进行传播。最后，原始治疗计划在变形的 AVG CT 上重新计算以进行剂量评估。
通过每个结构内的 DVFs 测量运动幅度作为平均值（标准差）。心脏周期内所有腔室的位移为内侧/外侧（ML）方向 1.4（0.9）mm，前/后（AP）方向 1.6（1.0）mm，上/下（SI）方向 3.0（2.8）mm。12 个不同的临床靶体积（CTV）的位移为 ML 方向 1.7（1.5）mm，AP 方向 2.4（1.1）mm，SI 方向 2.1（1.5）mm。AVG 和 AVG 扫描之间的位移为 SI 方向 4.2（2.0）mm 和总方向 5.8（1.4）mm。剂量重新计算表明，心脏运动可能会影响剂量学，95%CTV 的剂量从 AVG 上的 27.0（1.3）Gy 降至 AVG 上估计的 20.5（7.1）Gy。
该患者队列的心脏 CTV 运动平均小于 3mm，位置依赖性，并且在治疗计划中未考虑到这些运动时，可能会影响靶区覆盖。需要进一步研究来评估心脏运动对临床结果的影响。
