Department of Radiology, University of Washington School of Medicine, Seattle, Washington.
Department of Radiation Oncology, University of Washington School of Medicine, Seattle, Washington.
Neurosurgery. 2020 Nov 16;87(6):1157-1166. doi: 10.1093/neuros/nyaa202.
Spinal cord dose limits are critically important for the safe practice of spine stereotactic body radiotherapy (SBRT). However, the effect of inherent spinal cord motion on cord dose in SBRT is unknown.
To assess the effects of cord motion on spinal cord dose in SBRT.
Dynamic balanced fast field echo (BFFE) magnetic resonance imaging (MRI) was obtained in 21 spine metastasis patients treated with SBRT. Planning computed tomography (CT), conventional static T2-weighted MRI, BFFE MRI, and dose planning data were coregistered. Spinal cord from the dynamic BFFE images (corddyn) was compared with the T2-weighted MRI (cordstat) to analyze motion of corddyn beyond the cordstat (Dice coefficient, Jaccard index), and beyond cordstat with added planning organ at risk volume (PRV) margins. Cord dose was compared between cordstat, and corddyn (Wilcoxon signed-rank test).
Dice coefficient (0.70-0.95, median 0.87) and Jaccard index (0.54-0.90, median 0.77) demonstrated motion of corddyn beyond cordstat. In 62% of the patients (13/21), the dose to corddyn exceeded that of cordstat by 0.6% to 13.8% (median 4.3%). The corddyn spatially excursed outside the 1-mm PRV margin of cordstat in 9 patients (43%); among these dose to corddyn exceeded dose to cordstat >+ 1-mm PRV margin in 78% of the patients (7/9). Corddyn did not excurse outside the 1.5-mm or 2-mm PRV cord cordstat margin.
Spinal cord motion may contribute to increases in radiation dose to the cord from SBRT for spine metastasis. A PRV margin of at least 1.5 to 2 mm surrounding the cord should be strongly considered to account for inherent spinal cord motion.
脊髓剂量限制对于脊柱立体定向体放射治疗（SBRT）的安全实践至关重要。然而，SBRT 中脊髓固有运动对脊髓剂量的影响尚不清楚。
评估脊髓运动对 SBRT 中脊髓剂量的影响。
对 21 例接受 SBRT 治疗的脊柱转移瘤患者进行动态平衡快速场回波（BFFE）磁共振成像（MRI）检查。对计划 CT、常规静态 T2 加权 MRI、BFFE MRI 和剂量计划数据进行配准。将动态 BFFE 图像中的脊髓（corddyn）与 T2 加权 MRI（cordstat）进行比较，以分析 corddyn 超出 cordstat 的运动（Dice 系数、Jaccard 指数），以及超出 cordstat 并加入计划器官危及体积（PRV）边界的运动。比较 cordstat 和 corddyn 之间的脊髓剂量（Wilcoxon 符号秩检验）。
Dice 系数（0.70-0.95，中位数 0.87）和 Jaccard 指数（0.54-0.90，中位数 0.77）表明 corddyn 超出 cordstat 的运动。在 62%的患者（21 例中有 13 例）中，corddyn 的剂量超过 cordstat 的剂量 0.6%至 13.8%（中位数为 4.3%）。在 9 例患者（43%）中，corddyn 在空间上超出了 cordstat 的 1-mm PRV 边界；在这些患者中，78%（7/9）的患者的 corddyn 剂量超过 cordstat+1-mm PRV 边界。corddyn 未超出 cordstat 周围 1.5mm 或 2mm PRV 脊髓边界。
脊柱转移瘤 SBRT 中脊髓运动可能导致脊髓受照剂量增加。为了考虑固有脊髓运动，应强烈考虑在脊髓周围设置至少 1.5 至 2mm 的 PRV 边界。
