Background: In 131I therapies internal dosimetry is crucial for determining the mean absorbed dose to organs at risk, particularly the bone marrow, which has a dose constraint of 2 Gy. Traditionally, multicompartmental models have been used for bone marrow dosimetry, necessitating whole-body absorbed-dose assessments. However, noninvasive techniques, such as γ-camera scans or ceiling-mounted Geiger-Müller (GM) counters, can estimate the aforementioned. This study was aimed to evaluate the agreement between whole-body mean absorbed dose using γ-camera scans and ceiling-mounted GM in patients with thyroid carcinoma undergoing 131I therapy. Methods: This study included 31 patients with thyroid cancer who were treated with 131I. The whole-body time-integrated activity (TIA) and mean absorbed dose were estimated using the elimination curves obtained with γ-camera scans and ceiling-mounted GM. In addition, statistical analysis was performed on the data to determine the Coefficient Correlation Coefficient and the Bland-Altman limits of agreement for both parameters, as well as for the elimination curves' effective half-life. Results: The study revealed correlations of 0.562 and 0.586 between whole-body TIA and mean absorbed dose, respectively. The Bland-Altman limits of agreement were found to be below -3.75% and within 12.75% of the bone marrow dose constraint of 2 Gy. The nonparametric evaluation revealed that whole-body TIA and mean absorbed dose medians from GM were lower than those from γ-camera scans (p < 0.001). Effective half-life estimation mean was significantly lower in the GM than in the γ-camera of 13 and 23 h. Conclusions: Although GM calculates the whole-body absorbed dose with margins of error within clinical acceptance, underestimation of the effective half-life makes it an unacceptable substitute method for γ-cameras in clinical practice. Further research should be conducted to evaluate single-point GM measurement substitutions in time-activity curves.

中文翻译：

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使用安装在天花板上的 Geiger-Müller 探测器和 γ 相机扫描进行 131I 治疗时全身剂量测量的比较：一致性分析。

背景：在 131I 治疗中，内部剂量测定对于确定危险器官的平均吸收剂量至关重要，特别是骨髓，其剂量限制为 2 Gy。传统上，多室模型已用于骨髓剂量测定，需要进行全身吸收剂量评估。然而，非侵入性技术，例如 γ 相机扫描或安装在天花板上的盖革-穆勒 (GM) 计数器，可以估计上述内容。本研究旨在评估接受 131I 治疗的甲状腺癌患者使用 γ 相机扫描的全身平均吸收剂量与吊顶式 GM 之间的一致性。方法：本研究纳入了 31 名接受 131I 治疗的甲状腺癌患者。使用 γ 相机扫描和天花板安装 GM 获得的消除曲线估计全身时间积分活动 (TIA) 和平均吸收剂量。此外，对数据进行统计分析，以确定系数相关系数和两个参数的 Bland-Altman 一致性极限，以及消除曲线的有效半衰期。结果：研究显示全身 TIA 与平均吸收剂量之间的相关性分别为 0.562 和 0.586。发现 Bland-Altman 一致性限制低于 -3.75%，且在 2 Gy 骨髓剂量限制的 12.75% 以内。非参数评估显示，GM 的全身 TIA 和平均吸收剂量中位数低于 γ 相机扫描的结果 (p < 0.001)。GM 中的有效半衰期估计平均值显着低于 γ-相机中的 13 和 23 小时。结论：虽然GM计算的全身吸收剂量的误差范围在临床可接受范围内，但对有效半衰期的低估使其成为临床实践中不可接受的γ相机替代方法。应进行进一步的研究来评估时间-活动曲线中的单点 GM 测量替代。