Département de physique, Université de Montréal, Campus MIL, Montréal, Québec, Canada.
Centre de recherche du Centre hospitalier de l'Université de Montréal, Montréal, Québec, Canada.
J Appl Clin Med Phys. 2023 May;24(5):e13976. doi: 10.1002/acm2.13976. Epub 2023 Mar 30.
While IAEA's TRS-483 code of practice is adapted for the calibration of CyberKnife machines, AAPM's TG-51 is still the protocol recommended by the manufacturer for their calibration. The differences between both protocols could lead to differences in absorbed dose to water during the calibration process.
The aims of this work are to evaluate the difference resulting from the application of TG-51 (including the manufacturer's adaptations) and TRS-483 in terms of absorbed dose to water for a CyberKnife M6, and to evaluate the consistency of TRS-483.
Measurements are performed on a CyberKnife M6 unit under machine-specific reference conditions using a calibrated Exradin A12 ionization chamber. Monte Carlo (MC) simulations are performed to estimate and using a fully modeled detector and an optimized CyberKnife M6 beam model. The latter is also estimated experimentally. Differences between the adapted TG-51 and TRS-483 protocols are identified and their impact is quantified.
When using an in-house experimentally-evaluated volume averaging correction factor, a difference of 0.11% in terms of absorbed dose to water per monitor unit is observed when applying both protocols. This disparity is solely associated to the difference in beam quality correction factor. If a generic volume averaging correction factor is used during the application of TRS-483, the difference in calibration increases to 0.14%. In both cases, the disparity is not statistically significant according to TRS-483's reported uncertainties on their beam quality correction factor (i.e., 1%). MC results lead to and . Results illustrate that the generic beam quality correction factor provided in the TRS-483 might be overestimated by 0.36% compared to our specific model and that this overestimation could be due to the volume averaging component.
For clinical reference dosimetry of the CyberKnife M6, the application of TRS-483 is found to be consistent with TG-51.
国际原子能机构的 TRS-483 实践准则适用于 CyberKnife 机器的校准，而 AAPM 的 TG-51 仍然是制造商推荐用于其校准的协议。这两种协议之间的差异可能会导致校准过程中水吸收剂量的差异。
本工作的目的是评估在 CyberKnife M6 上应用 TG-51（包括制造商的改编）和 TRS-483 时在水吸收剂量方面的差异，并评估 TRS-483 的一致性。
使用校准的 Exradin A12 电离室，在特定于机器的参考条件下对 CyberKnife M6 单元进行测量。使用完全建模的探测器和优化的 CyberKnife M6 光束模型进行蒙特卡罗（MC）模拟，以估计 和 。后者也通过实验进行估计。确定改编的 TG-51 和 TRS-483 协议之间的差异，并量化其影响。
当使用内部实验评估的体积平均校正因子时，在应用两种协议时，水吸收剂量每监测单位的差异为 0.11%。这种差异仅与束质校正因子的差异有关。如果在应用 TRS-483 时使用通用体积平均校正因子，则校准的差异增加到 0.14%。在这两种情况下，根据 TRS-483 报告的束质校正因子的不确定度（即 1%），差异没有统计学意义。MC 结果导致 和 。结果表明，与我们的特定模型相比，TRS-483 中提供的通用束质校正因子可能高估了 0.36%，并且这种高估可能是由于体积平均成分所致。
对于 CyberKnife M6 的临床参考剂量测定，TRS-483 的应用被发现与 TG-51 一致。
