Division of Medical Physics, EuroMediTech Co., Ltd, 2-20-4 Higashi-Gotanda, Shinagawa, Tokyo 141-0022, Japan.
Department of Health Sciences, Komazawa University, 1-23-1 Komazawa, Setagaya, Tokyo 154-8525, Japan.
J Radiat Res. 2024 Sep 24;65(5):619-627. doi: 10.1093/jrr/rrae054.
This study aimed to clarify the dosimetric impact of calibration beam quality for calibration coefficients of the absorbed dose to water for an ionization chamber in an on-site dosimetry audit. Institution-measured doses of 200 photon and 184 electron beams were compared with the measured dose using one year data before and after the calibration of the ionization chamber used. For photon and electron reference dosimetry, the agreements of the institution-measured dose against two measured doses in this audit were evaluated using the calibration coefficients determined using 60Co (${N}{D,\mathrm{w},{}^{60}\mathrm{Co}}$) and linear accelerator (linac) (${N}{D,\mathrm{w},Q}$) beams. For electron reference dosimetry, the agreement of two institution-measured doses against the measured dose was evaluated using${N}{D,\mathrm{w},Q}$. Institution-measured doses were evaluated using direct- and cross-calibration coefficients. For photon reference dosimetry, the mean differences and standard deviation (SD) of institution-measured dose against the measured dose using ${N}{D,\mathrm{w},{}^{60}\mathrm{Co}}$ and ${N}{D,\mathrm{w},Q}$ were -0.1% ± 0.4% and -0.3% ± 0.4%, respectively. For electron reference dosimetry, the mean differences and SD of institution-measured dose using the direct-calibration coefficient against the measured dose using ${N}{D,\mathrm{w},{}^{60}\mathrm{Co}}$ and ${N}{D,\mathrm{w},Q}$ were 1.3% ± 0.8% and 0.8% ± 0.8%, respectively. Further, the mean differences and SD of institution-measured dose using the cross-calibration coefficient against the measured dose using ${N}{D,\mathrm{w},Q}$ were -0.1% ± 0.6%. For photon beams, the dosimetric impact of introducing calibration coefficients determined using linac beams was small. For electron beams, it was larger, and the measured dose using ${N}_{D,\mathrm{w},Q}$ was most consistent with the institution-measured dose, which was evaluated using a cross-calibration coefficient.
本研究旨在阐明在现场剂量审计中，为电离室校准吸收剂量的校准系数，对校准束质的剂量学影响。比较了 200 光子和 184 电子束的机构测量剂量与电离室校准前后一年的测量剂量。对于光子和电子参考剂量学，使用 60Co（${N}{D,\mathrm{w},{}^{60}\mathrm{Co}}$）和直线加速器（linac）（${N}{D,\mathrm{w},Q}$）束确定的校准系数，评估了该审计中机构测量剂量与两个测量剂量的一致性。对于电子参考剂量学，使用${N}{D,\mathrm{w},Q}$评估了两个机构测量剂量与测量剂量的一致性。机构测量剂量使用直接和交叉校准系数进行评估。对于光子参考剂量学，机构测量剂量与使用${N}{D,\mathrm{w},{}^{60}\mathrm{Co}}$和${N}{D,\mathrm{w},Q}$的测量剂量的平均值差异和标准偏差（SD）分别为-0.1%±0.4%和-0.3%±0.4%。对于电子参考剂量学，直接校准系数机构测量剂量与使用${N}{D,\mathrm{w},{}^{60}\mathrm{Co}}$和${N}{D,\mathrm{w},Q}$的测量剂量的平均值差异和 SD 分别为 1.3%±0.8%和 0.8%±0.8%。此外，使用交叉校准系数的机构测量剂量与使用${N}{D,\mathrm{w},Q}$的测量剂量的平均值差异和 SD 分别为-0.1%±0.6%。对于光子束，引入使用直线加速器束确定的校准系数的剂量学影响较小。对于电子束，影响较大，使用${N}_{D,\mathrm{w},Q}$的测量剂量与使用交叉校准系数评估的机构测量剂量最一致。
