Mojzeszek N, Klodowska M, Komenda W, Stolarczyk L, Kopec R, Olko P
Institute of Nuclear Physics PAN (IFJ PAN), Radzikowskiego 152, Kraków, Poland.
Radiat Prot Dosimetry. 2018 Aug 1;180(1-4):334-337. doi: 10.1093/rpd/ncx206.
For commissioning of a proton therapy unit depth dose distributions must be determined and introduced into the Treatment Planning System. In pencil beam scanning (PBS) technique, integral depth dose (IDD) acquisition should be performed with detector large enough to ensure entire beam laterally broadened by scattered and secondary contributions. The purpose of this article is to quantify, using measurements and Monte Carlo transport calculations, the ionization chamber's (IC) geometrical efficiency versus the chamber radius and proton beam energy. The geometrical efficiency of 0.99 was determined for energies up to 160 and 190 MeV for 4.08 and 6 cm radius IC. Much lower geometrical efficiency was obtained for the energy of 226.08 MeV and results in charge loss of 5.8 and 3.6%, respectively. Relative IDD differences between IC 4.08 and 6 cm in radius increase with proton energy and reach 2.4% at the mid-range depth for 226.08 MeV.
对于质子治疗装置的调试，必须确定深度剂量分布并将其引入治疗计划系统。在笔形束扫描（PBS）技术中，应使用足够大的探测器进行积分深度剂量（IDD）采集，以确保整个束流在横向因散射和二次贡献而展宽。本文的目的是通过测量和蒙特卡罗输运计算，量化电离室（IC）的几何效率与电离室半径和质子束能量的关系。对于半径为4.08和6 cm的电离室，在能量高达160和190 MeV时，确定几何效率为0.99。对于能量为226.08 MeV的情况，获得的几何效率要低得多，分别导致电荷损失5.8%和3.6%。半径为4.08和6 cm的电离室之间的相对IDD差异随质子能量增加，在226.08 MeV的中程深度处达到2.4%。
