BACKGROUND AND PURPOSE To investigate deformable image registration (DIR) and multi-fractional dose accumulation accuracy of a clinical MR-guided online adaptive radiotherapy (MRgoART) program, utilizing clinically-based magnitudes of abdominal deformation vector fields (DVFs). MATERIALS AND METHODS A heterogeneous anthropomorphic multi-modality abdominal deformable phantom was comprised of MR and CT anatomically-relevant materials. Thermoluminescent dosimeters (TLDs) were affixed within regions of interest (ROIs). CT and MR simulation scans were acquired. CT was deformed to MR for dose calculations. MRgoART was executed on a MR-linac (MRIdian) for 5 Gy/5 fractions. Before each fraction, a deformation was applied. Ground truth was known for ROI volume, TLD position, and TLD dose measured by an accredited dosimetry calibration laboratory. To validate the range of applied deformations, phantom DVFs were compared to DVFs of clinical abdominal MRgoART fractions. MR-MR deformation accuracy was quantified through dice similarity coefficient (DSC), Hausdorff distance (HD), mean distance-to-agreement (MDA), and as mean-absolute-error (MAE) for CT-MR-MR deformation. Arithmetic-summation of calculated dose at respective TLD positions and deform-accumulated dose (MIM) was compared to TLD measured dose, respectively. MR-MR deformation statistics were quantified for MRIdian and MIM. RESULTS Mean phantom DVFs were 5.0 ± 2.9 mm compared to mean DVF of clinical abdominal patients at 5.2 ± 3.0 mm. Respective mean DSC, HD, MDA was 0.93 ± 0.03, 0.74 ± 0.80 cm, 0.08 ± 0.03 cm for MRIdian and 0.93 ± 0.03, 0.54 ± 0.27 cm, 0.08 ± 0.03 cm for MIM (N = 80 ROIs). Mean MAE was 20.5 HU. Respective mean and median dose differences were 0.3%, -0.3% for arithmetic-summation and 4.1%, 0.6% for deformed-accumulation. Maximum differences were 0.21 Gy (arithmetic-summation), 0.31 Gy (deformed-accumulation). CONCLUSIONS MRgoART deformation and dosimetric accuracy has been benchmarked for mean fractional DVFs of 5 mm in a multiple-rigid-body deformable phantom. Deformation accuracy was within TG132 criteria and clinically acceptable end-to-end MRgoART dosimetric agreement was observed for this phantom. Further efforts are needed in validation of deform-accumulated dose.

中文翻译：

---

MR 引导的在线自适应放射治疗 (MRgoART) 程序的验证：异质、可变形、拟人化体模的变形精度

背景和目的 利用基于临床的腹部变形矢量场 (DVF) 幅度，研究临床 MR 引导的在线自适应放射治疗 (MRgoART) 程序的可变形图像配准 (DIR) 和多分数剂量累积准确性。材料和方法异质拟人化多模态腹部可变形体模由 MR 和 CT 解剖相关材料组成。热释光剂量计 (TLD) 贴在感兴趣区域 (ROI) 内。获得了 CT 和 MR 模拟扫描。CT 变形为 MR 以进行剂量计算。MRgoART 在 MR-linac (MRIdian) 上执行，剂量为 5 Gy/5。在每个分数之前，应用变形。Ground Truth 以 ROI 体积、TLD 位置和由经认可的剂量学校准实验室测量的 TLD 剂量而闻名。为了验证应用变形的范围，将幻像 DVF 与临床腹部 MRgoART 分数的 DVF 进行了比较。MR-MR 变形精度通过骰子相似系数 (DSC)、Hausdorff 距离 (HD)、平均一致性距离 (MDA) 以及 CT-MR-MR 变形的平均绝对误差 (MAE) 进行量化。将各个 TLD 位置处的计算剂量和变形累积剂量 (MIM) 的算术总和分别与 TLD 测量剂量进行比较。对 MRIdian 和 MIM 量化了 MR-MR 变形统计。结果 与临床腹部患者的平均 DVF 为 5.2 ± 3.0 mm 相比，平均幻像 DVF 为 5.0 ± 2.9 mm。分别平均 DSC、HD、MDA 为 0.93 ± 0.03、0.74 ± 0.80 cm、0.08 ± 0.03 cm（MRIdian）和 0.93 ± 0.03、0.54 ± 0.27 cm、0.08 ± 0.03 cm（80 ROI）。平均 MAE 为 20.5 HU。各自的平均和中值剂量差异对于算术求和分别为 0.3%、-0.3% 和对于变形累积为 4.1%、0.6%。最大差异为 0.21 Gy（算术求和）、0.31 Gy（变形累积）。结论 MRgoART 变形和剂量测量精度已在多刚体可变形体模中以 5 毫米的平均分数 DVF 为基准。变形精度在 TG132 标准内，并且观察到该体模符合临床可接受的端到端 MRgoART 剂量学一致性。变形累积剂量的验证需要进一步的努力。结论 MRgoART 变形和剂量测量精度已在多刚体可变形体模中以 5 毫米的平均分数 DVF 为基准。变形精度在 TG132 标准内，并且观察到该体模符合临床可接受的端到端 MRgoART 剂量学一致性。变形累积剂量的验证需要进一步努力。结论 MRgoART 变形和剂量测量精度已在多刚体可变形体模中以 5 毫米的平均分数 DVF 为基准。变形精度在 TG132 标准内，并且观察到该体模符合临床可接受的端到端 MRgoART 剂量学一致性。变形累积剂量的验证需要进一步努力。