Department of Radiation Oncology, Aichi Cancer Center Hospital, 1-1 Kanokoden, Chikusa-Ku, Nagoya, Aichi, 464-8681, Japan; Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences,323-1 Kamioki, Maebashi, Gunma, 371-0052, Japan.
Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences,323-1 Kamioki, Maebashi, Gunma, 371-0052, Japan.
Med Dosim. 2020;45(4):327-333. doi: 10.1016/j.meddos.2020.03.003. Epub 2020 Jun 7.
The epidural disease progression is the most common pattern of failure after spine stereotactic body radiotherapy. The aim of this study was to clarify the effect of the dose calculation grid size (CGS) during volumetric modulated arc therapy planning on the dose to the epidural space target.
In the planning, the volume obtained by subtracting the planning organ at risk volume (PRV) of the spinal cord and/or cauda equina from the planning target volume (PTV) was defined as the PTV. First, we compared the epidural space dose that overlapped with the PTV at dose CGSs of 1 mm and 2 mm. Next, we compared the dose that can be given, according to the isotropic distance from the PRV of the spinal cord and/ or cauda equina at dose CGSs of 1 mm and 2 mm.
The dose to the epidural space overlapping with the PTV was significantly larger at the dose CGS of 1 mm (60 to 80 cGy, 3% of the prescription dose) than at the dose CGS of 2 mm (p < 0.01). In addition, compared with the dose CGS of 2 mm, the dose CGS of 1 mm provided a larger dose to 95% of the volume in the regions where the PTV overlapped at isotropic distances of 0 to < 1, 1 to 2, 2 to 3, 3 to 4, and 4 to 5 mm from the PRV of the spinal cord and/or cauda equina.
During spine stereotactic body radiotherapy by volumetric modulated arc therapy, the dose CGS of 1 mm improved the dose calculation accuracy and increased the dose to the epidural space target compared with the dose CGS of 2 mm.
硬膜外疾病进展是脊柱立体定向体部放射治疗后最常见的失败模式。本研究旨在阐明容积调强弧形治疗计划中剂量计算网格大小（CGS）对硬膜外空间靶区剂量的影响。
在计划中，通过从计划靶区（PTV）中减去脊髓和/或马尾的计划器官受照体积（PRV）来定义 PTV。首先，我们比较了剂量 CGS 为 1mm 和 2mm 时与 PTV 重叠的硬膜外间隙剂量。其次，我们比较了剂量 CGS 为 1mm 和 2mm 时，根据脊髓和/或马尾 PRV 的各向同性距离，可以给予的剂量。
剂量 CGS 为 1mm 时与 PTV 重叠的硬膜外间隙剂量明显大于剂量 CGS 为 2mm 时（60 至 80cGy，为处方剂量的 3%）（p < 0.01）。此外，与剂量 CGS 为 2mm 相比，剂量 CGS 为 1mm 在各向同性距离为 0 至 <1、1 至 2、2 至 3、3 至 4 和 4 至 5mm 时，在与 PTV 重叠的区域为 95%体积提供了更大的剂量脊髓和/或马尾 PRV。
在使用容积调强弧形治疗进行脊柱立体定向体部放射治疗时，与剂量 CGS 为 2mm 相比，剂量 CGS 为 1mm 提高了剂量计算准确性，并增加了硬膜外空间靶区的剂量。
