Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America. Author to whom any correspondence should be addressed.
Phys Med Biol. 2019 Oct 21;64(20):205021. doi: 10.1088/1361-6560/ab41bd.
The GammaPod breast treatment device has been introduced to provide stereotactic radiation therapy to the breast to patients in the prone position. The GammaPod, using a stereotactic coordinate system, dynamically delivers dose to the target by rotating 25 non-overlapping Co-60 beams while the patient's breast is translated continuously in three axes on the couch during delivery. From simulation to treatment, the patient's breast is immobilized using mild negative pressure (150 mm Hg below atmospheric pressure) through a device-specific dual-cup system with stereotactic fiducials. This technology can be used for boost, multi-fraction partial-breast steterotactic body radiotherapy (SBRT), or single-fraction stereotactic radiosurgery (SRS). This paper reports the commissioning of the system for clinical use. The GammaPod device has four major subsystems: mechanical, dosimetric, radiation safety, and safety interlocks. Detailed methods for testing each subsystem have been identified and quantified. Mechanical systems include couch motion and accuracy along with couch sag. Dosimetric tests include absolute dose calibration, dose profiles, timer error, and plan verifications. Radiation safety includes room and wall surveys, along with device leakage measurements. Safety interlocks deal with power systems, immobilization, and treatment interrupts. The absolute dose rate of the 25 mm collimator was determined using TG-21 dosimetry protocol. The relative output factor for the 15 mm collimator was 0.94. The difference of the full-width-at-half-maximum of the single shot of the 25 mm collimator between the treatment planning system and the measurement was 0.2 mm. All interlocks were found to perform correctly, and the shield was within state and Nuclear Regulatory Commission limits. The items and techniques for commissioning the GammaPod have been developed and tested using the methods reported here.
伽玛刀乳房治疗设备的引入是为了向俯卧位患者提供乳房的立体定向放射治疗。伽玛刀使用立体定向坐标系，通过在患者乳房在治疗过程中连续在三个轴上在治疗床上平移的同时旋转 25 个不重叠的 Co-60 射线束，动态地向目标输送剂量。从模拟到治疗，患者的乳房通过特定于设备的双杯系统用轻度负压（低于大气压 150 毫米汞柱）固定，该系统带有立体定向基准。该技术可用于助推、多分次部分乳房立体定向体部放射治疗（SBRT）或单次立体定向放射外科手术（SRS）。本文报告了该系统用于临床使用的调试情况。伽玛刀设备有四个主要子系统：机械、剂量学、辐射安全和安全互锁。已经确定并量化了测试每个子系统的详细方法。机械系统包括治疗床运动和准确性以及治疗床下垂。剂量学测试包括绝对剂量校准、剂量分布、定时器误差和计划验证。辐射安全包括房间和墙壁测量以及设备泄漏测量。安全互锁涉及电源系统、固定和治疗中断。使用 TG-21 剂量学协议确定了 25mm 准直器的绝对剂量率。15mm 准直器的相对输出因子为 0.94。治疗计划系统和测量之间的 25mm 准直器单次全宽半最大值的差异为 0.2mm。所有互锁都被发现运行正确，屏蔽符合国家核管理委员会的状态和限制。伽玛刀的调试项目和技术已经使用这里报告的方法进行了开发和测试。
