Nakazawa Hisato, Uchiyama Yukio
Nagoya Radiosurgery Center, Nagoya Kyoritsu Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2015 Mar;71(3):177-85. doi: 10.6009/jjrt.2015_JSRT_71.3.177.
We assessed the impact of source positional discrepancy on dose and dose distributions in Gamma Knife (GK) Perfexion (PFX) stereotactic radiosurgery. A spherical phantom dedicated in GK machine was used and irradiated by 2 Gy in each position moved at an interval of 0.1 mm from its original position using three types of collimators (4, 8, 16 mm) to evaluate the changes of dose. In addition, to obtain the dose distributions, radiochromic film was inserted in the phantom and irradiated by 6 Gy in each position moved at an interval of 1 mm from its original position using three types of collimators. A distance-to-agreement analysis (DTA) was performed to compare isodose lines from 10% to 90% of dose distributions between the original and deviated position. As a result, when the source moved toward the discrepancy from the center of the collimator, the dose and dose distributions discrepancies increased according to the degree of discrepancy. Especially in 4-mm collimator, 0.5 mm discrepancy caused dose reduction of 5%. On the other hand, 0.5 mm discrepancy showed merely dose differences less than 0.5% in 8 mm and 16 mm collimators. Regarding dose distributions, 1 mm discrepancy in all collimators showed little changes in DTA within 1 mm on average.
我们评估了伽玛刀（GK）Perfexion（PFX）立体定向放射外科中源位置差异对剂量和剂量分布的影响。使用了一台专门用于GK机器的球形模体，并使用三种类型的准直器（4、8、16毫米），在从其原始位置以0.1毫米的间隔移动的每个位置处以2戈瑞进行照射，以评估剂量的变化。此外，为了获得剂量分布，将放射变色胶片插入模体中，并使用三种类型的准直器，在从其原始位置以1毫米的间隔移动的每个位置处以6戈瑞进行照射。进行了距离一致性分析（DTA），以比较原始位置和偏离位置之间剂量分布从10%到90%的等剂量线。结果，当源从准直器中心向差异方向移动时，剂量和剂量分布差异根据差异程度而增加。特别是在4毫米准直器中，0.5毫米的差异导致剂量降低了5%。另一方面，在8毫米和16毫米准直器中，0.5毫米的差异仅显示剂量差异小于0.5%。关于剂量分布，所有准直器中1毫米的差异在DTA中平均在1毫米内显示出微小变化。
