QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Japan.
Association for Nuclear Technology in Medicine, Japan.
Phys Med. 2021 Aug;88:91-97. doi: 10.1016/j.ejmp.2021.06.010. Epub 2021 Jun 29.
We experimentally determined the radiophotoluminescent glass dosimeter (RPLD) dose responses for TomoTherapy, CyberKnife, and flattening-filter-free (FFF) linear accelerator (linac) outputs for dosimetry audits in Japan.
A custom-made solid phantom with a narrow central-axis spacing of three RPLD elements was used for output measurement to minimise the dose-gradient effect of the non-flattening filter beams. For RPLD dose estimation, we used the ISO 22127 formalism. Additional unit-specific correction factors were introduced and determined via the measured data. For TomoTherapy (7 units) and CyberKnife (4 units), the doses were measured under machine-specific reference fields. For FFF linac (5 units), in addition to the reference condition, we obtained the field-size effects for the range from 5×5 cm to 25×25 cm.
The correction factors were estimated as 1.008 and 0.999 for TomoTherapy and CyberKnife, respectively. For FFF linac, they ranged from 1.011 to 0.988 for 6 MV and from 1.011 to 0.997 for 10 MV as a function of the side length of the square field from 5 to 25 cm. The estimated uncertainties of the absorbed dose to water measured by RPLD for the units were 1.32%, 1.35%, and 1.30% for TomoTherapy, CyberKnife, and FFF linac, respectively. A summary of the dosimetry audits of these treatment units using the obtained correction factors is also presented. The average percentage differences between the measured and hospital-stated doses were <1% under all conditions.
RPLD can be successfully used as a dosimetry audit tool for modern treatment units.
我们通过实验确定了放射光致发光玻璃剂量计（RPLD）在日本剂量审计中的 TomoTherapy、CyberKnife 和无均整滤过（FFF）直线加速器（linac）输出的剂量响应。
使用带有三个 RPLD 元件的窄中心轴间距的定制固体体模进行输出测量，以最小化非均整滤过束的剂量梯度效应。对于 RPLD 剂量估计，我们使用了 ISO 22127 形式。通过测量数据引入并确定了额外的单位特定校正因子。对于 TomoTherapy（7 个单位）和 CyberKnife（4 个单位），在机器特定参考场下测量剂量。对于 FFF linac（5 个单位），除了参考条件外，我们还获得了 5×5 cm 至 25×25 cm 范围内的射野尺寸效应。
校正因子分别估计为 TomoTherapy 和 CyberKnife 的 1.008 和 0.999。对于 FFF linac，6 MV 的校正因子范围为 1.011 至 0.988，10 MV 的校正因子范围为 1.011 至 0.997，作为正方形射野边长从 5 至 25 cm 的函数。用 RPLD 测量的水吸收剂量的不确定度分别为 TomoTherapy、CyberKnife 和 FFF linac 的 1.32%、1.35%和 1.30%。还介绍了使用获得的校正因子对这些治疗单元进行剂量审计的总结。在所有条件下，测量剂量与医院报告剂量的平均百分比差异均<1%。
RPLD 可以成功用作现代治疗单元的剂量审计工具。
