The use of iodine-131 S values based on reference computational phantoms with fixed thyroid model may lead to significant dosimetric errors in patients who may have different thyroid location from the reference phantoms. In the present study, we investigated individual thyroid location variation by examining the computed tomography image sets of 40 adult male and female patients. Subsequently, the thyroid location of the adult male and female mesh-type reference phantoms of the International Commission on Radiological Protection (ICRP) was adjusted to match each the highest, mean and the lowest locations of the thyroid observed in this dataset. The thyroid-adjusted phantoms were implemented into the Geant4 Monte Carlo code to calculate thyroid location-dependent iodine-131 S values (rT ← thyroid) for a total of 30 target regions. The maximum variation among the observed thyroid locations was 39 mm and 36 mm for male and female patients, respectively. The mean thyroid locations of both male and female patients showed a good agreement with the ICRP reference phantoms. The thyroid location-dependent Iodine-131 S values were significantly different from the reference phantoms for most target regions by up to a factor of 3. The use of thyroid location-dependent S values in dose reconstructions should help quantify the dosimetric uncertainty in epidemiologic investigations of patients receiving iodine-131 therapy for hyperthyroidism and thyroid cancer.

中文翻译：

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甲状腺位置对碘 131 S 值影响的研究。

使用基于具有固定甲状腺模型的参考计算模型的 iodine-131 S 值可能会导致甲状腺位置与参考模型不同的患者出现显着的剂量学误差。在本研究中，我们通过检查 40 名成年男性和女性患者的计算机断层扫描图像集来研究个体甲状腺位置的变化。随后，调整了国际放射防护委员会 (ICRP) 的成年男性和女性网状参考模型的甲状腺位置，以匹配该数据集中观察到的甲状腺的最高、平均和最低位置。将甲状腺调整体模实施到 Geant4 Monte Carlo 代码中，以计算总共 30 个目标区域的甲状腺位置相关碘 131 S 值（rT ← 甲状腺）。男性和女性患者观察到的甲状腺位置之间的最大差异分别为 39 毫米和 36 毫米。男性和女性患者的平均甲状腺位置与 ICRP 参考模型非常吻合。甲状腺位置依赖性碘 131 S 值与大多数目标区域的参考模型显着不同，最多可达 3 倍。在剂量重建中使用甲状腺位置依赖性 S 值应有助于量化流行病学调查中的剂量学不确定性接受碘 131 治疗甲状腺机能亢进和甲状腺癌的患者。