Program in Biomedical Radiation Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, Korea.
Department of Applied Bioengineering, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, Korea.
Health Phys. 2023 Nov 1;125(5):352-361. doi: 10.1097/HP.0000000000001727. Epub 2023 Aug 10.
We aim to develop a dose assessment method compensating for quality factors (Q factor) observed during in vivo EPR tooth dosimetry. A pseudo-in-vivo phantom made of tissue-equivalent material was equipped with one each of four extracted human central incisors. A range of Q factors was measured at tooth-depths of -2, 0, and 2 mm in the pseudo-in-vivo phantom. In addition, in vivo Q factors were measured from nine human volunteers. For the dose-response data, the above four sample teeth were irradiated at 0, 1, 2, 5, and 10 Gy, and the radiation-induced signals were measured at the same tooth-depths using an in vivo EPR tooth dosimetry system. To validate the method, the signals of two post-radiotherapy patients and three unirradiated volunteers were measured using the same system. The interquartile range of the Q factors measured in the pseudo-in-vivo phantom covered that observed from the human volunteers, which implied that the phantom represented the Q factor distribution of in vivo conditions. The dosimetric sensitivities and background signals were decreased as increasing the tooth-depth in the phantom due to the decrease in Q factors. By compensating for Q factors, the diverged dose-response data due to various Q factors were converged to improve the dosimetric accuracy in terms of the standard error of inverse prediction (SEIP). The Q factors of patient 1 and patient 2 were 98 and 64, respectively, while the three volunteers were 100, 92, and 99. The assessed doses of patient 1 and patient 2 were 2.73 and 12.53 Gy, respectively, while expecting 4.43 and 13.29 Gy, respectively. The assessed doses of the unirradiated volunteers were 0.53, 0.50, and - 0.22 Gy. We demonstrated that the suggested Q factor compensation could mitigate the uncertainty induced by the variation of Q factors.
我们旨在开发一种补偿体内 EPR 牙剂量测定中观察到的质量因子（Q 因子）的剂量评估方法。一个由组织等效材料制成的伪活体模型配备了四颗提取的人中切牙。在伪活体模型中，在牙深度为-2、0 和 2 毫米处测量了一系列 Q 因子。此外，还从九名志愿者体内测量了 Q 因子。对于剂量响应数据，上述四颗样本牙在 0、1、2、5 和 10 Gy 下进行照射，并使用体内 EPR 牙剂量测定系统在相同的牙深度处测量辐射诱导的信号。为了验证该方法，使用相同的系统测量了两名放疗后患者和三名未照射志愿者的信号。在伪活体模型中测量的 Q 因子的四分位距涵盖了从志愿者中观察到的 Q 因子，这意味着该模型代表了体内条件下的 Q 因子分布。由于 Q 因子的降低，在模型中牙深度增加导致剂量计灵敏度和背景信号降低。通过补偿 Q 因子，可以收敛由于各种 Q 因子引起的发散剂量响应数据，从而提高标准误差反预测（SEIP）方面的剂量计准确性。患者 1 和患者 2 的 Q 因子分别为 98 和 64，而三名志愿者的 Q 因子分别为 100、92 和 99。患者 1 和患者 2 的评估剂量分别为 2.73 和 12.53 Gy，而预期剂量分别为 4.43 和 13.29 Gy。未照射志愿者的评估剂量分别为 0.53、0.50 和-0.22 Gy。我们证明了所提出的 Q 因子补偿可以减轻 Q 因子变化引起的不确定性。
