Iwai Yoshio, Ozawa Shuichi, Ageishi Tatsuya, Pellegrini Roberto, Yoda Kiyoshi
Research Physics, Elekta KK, 3-9-1 Shibaura, Minato-ku, Tokyo 108-0023, Japan
Department of Radiation Oncology, Institute of Biomedical and Health Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
J Radiat Res. 2014 Sep;55(5):1015-20. doi: 10.1093/jrr/rru042. Epub 2014 Jun 18.
The feasibility of single isocenter, multi-arc non-coplanar volumetric modulated arc therapy (VMAT) for multiple brain tumors was studied using an Elekta Synergy linear accelerator with an Agility multileaf collimator and a Monaco treatment planning system. Two VMAT radiosurgery plans consisting of a full arc and three half arcs were created with a prescribed dose of 20 Gy in a single fraction. After dose delivery to a phantom, ionization chambers and radiochromic films were used for dose measurement. The first VMAT radiosurgery plan had nine targets inside the phantom, and the doses were measured by the chambers at two different points and by the films on three sagittal and three coronal planes. The differences between the calculated dose and the dose measured by a Farmer ionization chamber and a pinpoint ionization chamber were <1.00% and <2.30%, respectively, and the average pass rates of gamma indices among the six planes under each of 3%/3 mm and 2%/2 mm criteria were 98.6% and 92.6%, respectively. The second VMAT radiosurgery plan was based on a clinical 14 brain metastases. Differences between calculated and film-measured doses were evaluated on two sagittal planes. The average pass rates of the gamma indices on the planes under each of 3%/3 mm and 2%/2 mm criteria were 97.8% and 88.8%, respectively. It was confirmed that single-isocenter, non-coplanar multi-arc VMAT radiosurgery for multiple brain metastases was feasible using Elekta Synergy with Agility and Monaco treatment planning systems. It was further shown that film dosimetry was accurately performed for a dose of up to nearly 25 Gy.
使用配备敏捷多叶准直器的医科达Synergy直线加速器和Monaco治疗计划系统，研究了单等中心、多弧非共面容积调强弧形治疗（VMAT）用于多个脑肿瘤的可行性。创建了两个VMAT放射外科计划，一个由全弧组成，另一个由三个半弧组成，单次处方剂量为20 Gy。将剂量输送到模体后，使用电离室和放射变色胶片进行剂量测量。第一个VMAT放射外科计划在模体内有九个靶区，剂量由电离室在两个不同点以及胶片在三个矢状面和三个冠状面上进行测量。计算剂量与 Farmer电离室和针点电离室测量剂量之间的差异分别<1.00%和<2.30%，在3%/3 mm和2%/2 mm标准下六个平面的伽马指数平均通过率分别为98.6%和92.6%。第二个VMAT放射外科计划基于14例临床脑转移瘤。在两个矢状面上评估计算剂量与胶片测量剂量之间的差异。在3%/3 mm和2%/2 mm标准下各平面伽马指数的平均通过率分别为97.8%和88.8%。证实了使用医科达Synergy与敏捷和Monaco治疗计划系统，单等中心、非共面多弧VMAT放射外科用于多个脑转移瘤是可行的。进一步表明，对于高达近25 Gy的剂量，胶片剂量测定能够准确进行。
