Internal Dosimetry Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
J Radiol Prot. 2023 Nov 2;43(4). doi: 10.1088/1361-6498/ad04ef.
Age-specific dose coefficients are required to assess internal exposure to the general public. This study utilizes reference age-specific biokinetic models of iodine to estimate the total number of nuclear disintegrations ã(,τ) occurring in source regions () during the commitment time (τ). Age-specific S values are estimated for 35 target regions due toI present in 22using data from 10 paediatric reference computational phantoms (representing five ages for both sexes) published recently by the International Commission of Radiation Protection (ICRP). Monte Carlo transport simulations are performed in FLUKA code. The estimated ã(,τ) and S values are then used to compute the committed tissue equivalent dose H(τ) for 27 radiosensitive tissues and dose coefficients e(τ) for all five ages due to inhalation and ingestion ofI. The derived ã(,τ) values in the thyroid source are observed to increase with age due to the increased retention of iodine in the thyroid. S values are found to decrease with age, mainly due to an increase in target masses. Generally, H(τ) values are observed to decrease with age, indicating the predominant behaviour of S values over ã(,τ). On average, ingestion dose coefficients are 63% higher than for inhalation in all ages. The maximum contribution to dose coefficients is from the thyroid, accounting for 96% in the case of newborns and 98%-99% for all other ages. Furthermore, the estimated e(τ) values for the reference population are observed to be lower than previously published reference values from the ICRP. The estimated S, H(τ) and e(τ) values can be used to improve estimations of internal doses to organs/whole body for members of the public in cases ofI exposure. The estimated dose coefficients can also be interpolated for other ages to accurately evaluate the doses received by the general public duringI therapy or during a radiological emergency.
为了评估公众的内照射，需要特定年龄的剂量系数。本研究利用碘的参考特定年龄生物动力学模型来估算在承诺期（τ）内源区（）中发生的总核裂变次数（，τ）。由于 22 种放射性碘（I）存在于 35 个目标区域，因此使用最近由国际辐射防护委员会（ICRP）发布的 10 个儿科参考计算体模（代表两种性别各 5 个年龄）的数据，估算了 35 个目标区域的特定年龄 S 值。在 FLUKA 代码中进行蒙特卡罗传输模拟。然后，使用估算的（，τ）和 S 值来计算 27 个敏感组织的承诺组织等效剂量 H（τ）以及由于吸入和摄入 I 引起的所有五个年龄段的剂量系数 e（τ）。观察到甲状腺源中的（，τ）值随年龄增加而增加，这是由于甲状腺中碘的保留增加所致。发现 S 值随年龄减小，主要是由于靶质量的增加。通常，H（τ）值随年龄减小，表明 S 值相对于（，τ）的主导作用。平均而言，所有年龄段的摄入剂量系数均比吸入剂量系数高 63%。对剂量系数的最大贡献来自甲状腺，对于新生儿，其占 96%，对于所有其他年龄段，占 98%-99%。此外，与 ICRP 先前发布的参考值相比，参考人群的估计 e（τ）值较低。估计的 S、H（τ）和 e（τ）值可用于改善放射性碘暴露情况下公众器官/全身内照射剂量的估算。还可以对其他年龄的估计剂量系数进行插值，以准确评估公众在放射性碘治疗或放射性紧急情况下所接受的剂量。
