Cheung J Y, Yu K N, Ho R T, Yu C P
Gamma Knife Centre (HK), Canossa Hospital, and Department of Physics and Materials Science, City University of Hong Kong, Kowloon.
Med Phys. 1999 Jul;26(7):1252-6. doi: 10.1118/1.598639.
The Monte Carlo technique and GafChromic films were employed to verify the accuracy of the dose planning system (Leksell GammaPlan) used in Gamma Knife (type B) radiosurgery when plugged collimator helmets were used. The EGS4 Monte Carlo code was used to calculate the dose distribution along the x, y, and z axes when a single shot was delivered at the center point (unit center point: x = 100, y = 100, z = 100) of a spherical polystyrene phantom, with gamma angle of 90 degrees. Two different sizes of the plugged collimator helmets, 4 and 18 mm, were studied. Two typical plugged patterns, 51 plugs and 99 plugs along the y direction, were examined. The results of our Monte Carlo trials showed good consistency with GammaPlan calculations and GafChromic film measurements. Furthermore, the Monte Carlo results showed that radiation leakage from the plugs was too small to affect the overall isodose curve distribution even when the heavily plugged pattern of up to 99 plugs was employed. The results of this project provide confidence to all Gamma Knife centers using the Leksell GammaPlan treatment planning system.
采用蒙特卡罗技术和 GafChromic 胶片来验证伽玛刀（B 型）放射外科手术中使用的剂量规划系统（Leksell GammaPlan）在使用堵塞式准直器头盔时的准确性。当在球形聚苯乙烯模体的中心点（单位中心点：x = 100，y = 100，z = 100）单次照射且伽马角为 90 度时，使用 EGS4 蒙特卡罗代码计算沿 x、y 和 z 轴的剂量分布。研究了两种不同尺寸的堵塞式准直器头盔，分别为 4 毫米和 18 毫米。检查了两种典型的堵塞模式，即沿 y 方向有 51 个堵塞物和 99 个堵塞物。我们的蒙特卡罗试验结果与 GammaPlan 计算结果和 GafChromic 胶片测量结果显示出良好的一致性。此外，蒙特卡罗结果表明，即使采用多达 99 个堵塞物的密集堵塞模式，堵塞物的辐射泄漏也小到不会影响整体等剂量曲线分布。该项目的结果为所有使用 Leksell GammaPlan 治疗计划系统的伽玛刀中心提供了信心。
