比较使用带 MR-linac 的调强放疗和 VMAT 治疗肺部立体定向消融放疗的治疗计划。
Comparison of treatment plans between IMRT with MR-linac and VMAT for lung SABR.
机构信息
Department of Radiation Oncology, Seoul National University Hospital, Seoul, South Korea.
Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, South Korea.
出版信息
Radiat Oncol. 2019 Jun 13;14(1):105. doi: 10.1186/s13014-019-1314-0.
BACKGROUND
The aim of this study was to compare the plan quality of magnetic-resonance image-based intensity modulated radiation therapy (MRI-based-IMRT) with the MRIdian Linac system to that of volumetric modulated arc therapy (VMAT) with the TrueBeam STx system for lung stereotactic ablative radiotherapy (SABR).
METHODS
A total of 22 patients with tumors located in the lower lobe were retrospectively selected for the study. For each patient, both the MRI-based-IMRT and VMAT plans were generated using an identical CT image set and identical structures with the exception of the planning target volume (PTV). The PTVs of the MRI-based-IMRT were generated by adding an isotropic margin of 3 mm from the gross tumor volume, whereas those of VMAT were generated by adding an isotropic margin of 5 mm from the internal target volume. For both the MRI-based-IMRT and VMAT, the prescription doses to the PTVs were 60 Gy in four fractions.
RESULTS
The average PTV volume of the MRI-based-IMRT was approximately 4-times smaller than that of VMAT (p < 0.001). The maximum dose to the bronchi for the MRI-based-IMRT was smaller than that for the VMAT (20.4 Gy versus 24.2 Gy, p < 0.001). In addition, V of the rib for the MRI-based-IMRT was smaller than that for the VMAT (1.8 cm versus 7.7 cm, p = 0.008). However, the maximum doses to the skin and spinal cord for the MRI-based-IMRT (33.0 Gy and 14.5 Gy, respectively) were larger than those for the VMAT (27.8 Gy and 11.0 Gy, respectively) showing p values of less than 0.02. For the ipsilateral lung, the mean dose, V, V, and V for the MRI-based-IMRT were smaller than those for the VMAT (all with p < 0.05). For the contralateral lung, V, V, D, and D for the MRI-based-IMRT were larger than those for the VMAT (all with p < 0.05). The mean dose and V of the whole body for the MRI-based-IMRT were smaller than those for the VMAT (0.9 Gy versus 1.2 Gy, and 78.7 cm versus 103.5 cm, respectively, all at p < 0.001).
CONCLUSIONS
The MRI-based-IMRT using the MRIdian Linac system could reduce doses to bronchi, rib, ipsilateral lung, and whole body compared to VMAT for lung SABR when the tumor was located in the lower lobe.
背景
本研究旨在比较基于磁共振成像的调强放疗（MRI 引导调强放疗，MRI-based-IMRT）与基于容积旋转调强放疗（VMAT）的 TrueBeam STx 系统治疗肺癌立体定向消融放疗（SABR）的计划质量。
方法
回顾性选择 22 例肿瘤位于下叶的患者进行研究。对于每位患者，均使用相同的 CT 图像集和相同的结构（除了计划靶区（PTV）外）生成基于 MRI 的调强放疗和 VMAT 计划。基于 MRI 的调强放疗的 PTV 是从大体肿瘤体积外扩 3mm 生成的，而 VMAT 的 PTV 是从内部靶区外扩 5mm 生成的。对于基于 MRI 的调强放疗和 VMAT，PTV 的处方剂量均为 60Gy，分 4 次给予。
结果
基于 MRI 的调强放疗的平均 PTV 体积约为 VMAT 的 4 倍（p<0.001）。基于 MRI 的调强放疗的支气管最大剂量小于 VMAT（20.4Gy 比 24.2Gy，p<0.001）。此外，基于 MRI 的调强放疗的肋骨 V 小于 VMAT（1.8cm 比 7.7cm，p=0.008）。然而，基于 MRI 的调强放疗的皮肤和脊髓最大剂量（分别为 33.0Gy 和 14.5Gy）大于 VMAT（分别为 27.8Gy 和 11.0Gy），p 值小于 0.02。对于同侧肺，基于 MRI 的调强放疗的平均剂量、V、V 和 V 小于 VMAT（均 p<0.05）。对于对侧肺，基于 MRI 的调强放疗的 V、V、D 和 D 大于 VMAT（均 p<0.05）。基于 MRI 的调强放疗的全身体剂量和 V 小于 VMAT（0.9Gy 比 1.2Gy，78.7cm 比 103.5cm，均 p<0.001）。
结论
当肿瘤位于下叶时，基于磁共振成像的调强放疗（MRI 引导调强放疗，MRI-based-IMRT）与 TrueBeam STx 系统的容积旋转调强放疗（VMAT）相比，可降低支气管、肋骨、同侧肺和全身体剂量。
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