Katayama Hiroki, Kobata Takuya, Kitaoka Motonori, Takahashi Shigeo, Shibata Toru
Department of Clinical Radiology, Kagawa University Hospital, Kagawa, Japan.
Department of Radiation Oncology, Kagawa University Hospital, Kagawa, Japan.
Rep Pract Oncol Radiother. 2024 Dec 4;29(5):531-543. doi: 10.5603/rpor.102616. eCollection 2024.
Dynamic conformal arc therapy (DCAT) and volumetric modulated arc therapy (VMAT) can achieve near equal plan quality in single-isocenter multiple target stereotactic radiosurgery (SRS) for brain metastases. This study aimed to investigate the impact of multi-leaf collimator (MLC) errors during beam delivery on the dose distribution for each technique.
A 10-mm diameter delineation of the three targets was employed on the computed tomography images of a head phantom, and the reference plans were created using the DCAT and VMAT. We simulated the systematic opened and closed MLC errors. 10 MLC error plans with different magnitudes of errors were created in each technique. We investigated the relationship between the magnitude of MLC errors and the change in dose-volume histogram parameters of the targets and normal brain tissue.
The percentage change in the D (Gy) and D (Gy) of the target per millimeter of the MLC errors were 13.3% and 2.7% for the DCAT and 15.3% and 9.3% for the VMAT, respectively. The fluctuations of the maximum dose were very small for the DCAT compared to the VMAT. Changes in the V (cc) of the normal brain tissue were 47.1%/mm and 53.2%/mm for the DCAT and VMAT, respectively, which are comparable changes for both techniques.
Although the impact of MLC errors on the target coverage and the normal brain tissue is comparable for both techniques, the internal dose of the targets generated by the DCAT technique is robust to the MLC errors.
在脑转移瘤的单等中心多靶点立体定向放射外科治疗（SRS）中，动态适形弧形治疗（DCAT）和容积调强弧形治疗（VMAT）可实现近乎相同的计划质量。本研究旨在探讨射束传输过程中多叶准直器（MLC）误差对每种技术剂量分布的影响。
在头部体模的计算机断层扫描图像上对三个靶点进行直径10毫米的勾画，并使用DCAT和VMAT创建参考计划。我们模拟了MLC的系统性打开和关闭误差。在每种技术中创建了10个具有不同误差幅度的MLC误差计划。我们研究了MLC误差幅度与靶点及正常脑组织剂量体积直方图参数变化之间的关系。
对于DCAT，每毫米MLC误差导致的靶点D（Gy）和D（Gy）的百分比变化分别为13.3%和2.7%，对于VMAT分别为15.3%和9.3%。与VMAT相比，DCAT的最大剂量波动非常小。对于DCAT和VMAT，正常脑组织V（cc）的变化分别为47.1%/毫米和53.2%/毫米，两种技术的变化相当。
尽管两种技术中MLC误差对靶点覆盖和正常脑组织的影响相当，但DCAT技术产生的靶点内部剂量对MLC误差具有较强的耐受性。
