Hara Hikari, Shibayama Yusuke, Fukunaga Jun-Ichi, Hirose Taka-Aki, Matsumoto Ryoji, Komiya Isao, Kato Toyoyuki
Division of Radiology, Department of Medical Technology, Kyushu University Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2023 May 20;79(5):453-461. doi: 10.6009/jjrt.2023-1323. Epub 2023 Mar 14.
To investigate fundamental dosimetric properties of surface dose, exit dose, and beam profile of the brass mesh bolus for 4, 6, and 10 MV high-energy photon beams in radiation therapy.
Surface dose and exit dose in the water-equivalent phantom were measured, and percent depth doses (PDDs) were calculated with no bolus, one layer of brass mesh, two layers of brass mesh bolus, three layers of brass mesh bolus, and 0.5 cm tissue-equivalent (TE) bolus. Exit dose was measured at a phantom thickness of 10 cm. Beam profiles were measured at phantom depths of 0 cm and 10 cm. All dosimetry was performed for 4, 6, and 10 MV photon beams using a linear accelerator.
The surface dose at a phantom depth of 0 cm increased to 37.3%, 36.3%, and 31.0% for 4, 6, and 10 MV, respectively, with the brass mesh bolus compared to the case of no bolus. The surface dose decreased with one layer of brass mesh bolus compared to that with the 0.5 cm TE bolus. On the other hand, the exit dose increased to 22.0%, 23.1%, and 22.8% for 4, 6, and 10 MV, respectively, with the brass mesh bolus compared to the case of no bolus. The beam profile at the depth of 0 cm showed oscillations, and the difference between the maximum and minimum doses was up to 13.1% with one layer of brass mesh bolus.
It was suggested that the brass mesh bolus not only increases the surface dose but also has different properties from the conventional TE bolus.
研究用于放射治疗中4、6和10兆伏高能光子束的黄铜网填充物的表面剂量、出射剂量和射野轮廓的基本剂量学特性。
在水等效体模中测量表面剂量和出射剂量，并计算无填充物、一层黄铜网、两层黄铜网填充物、三层黄铜网填充物以及0.5厘米组织等效（TE）填充物时的百分深度剂量（PDD）。在体模厚度为10厘米时测量出射剂量。在体模深度为0厘米和10厘米处测量射野轮廓。使用直线加速器对4、6和10兆伏光子束进行所有剂量测定。
与无填充物的情况相比，对于4、6和10兆伏光子束，使用黄铜网填充物时，体模深度为0厘米处的表面剂量分别增加到37.3%、36.3%和31.0%。与0.5厘米TE填充物相比，一层黄铜网填充物时表面剂量降低。另一方面，与无填充物的情况相比，对于4、6和10兆伏光子束，使用黄铜网填充物时出射剂量分别增加到22.0%、23.1%和22.8%。0厘米深度处的射野轮廓显示出振荡，一层黄铜网填充物时最大剂量与最小剂量之间的差异高达13.1%。
结果表明，黄铜网填充物不仅增加表面剂量，而且具有与传统TE填充物不同的特性。
