Hofstra Northwell School of Medicine of Hofstra University, Manhasset and New Hyde Park, New York
Division of Nuclear Medicine and Molecular Imaging, Northwell Health, Manhasset and New Hyde Park, New York; and.
J Nucl Med. 2017 Oct;58(10):1588-1595. doi: 10.2967/jnumed.117.192278. Epub 2017 Apr 13.
To protect bone marrow from overirradiation, the maximum permissible activity (MPA) of I to treat thyroid cancer is that which limits the absorbed dose to blood (as a surrogate of marrow) to less than 200 cGy. The conventional approach (method 1) requires repeated γ-camera whole-body measurements along with blood samples. We sought to determine whether reliable MPA values can be obtained by simplified procedures. Data acquired over multiple time points were examined retrospectively for 65 thyroid cancer patients, referred to determine I uptake and MPA for initial treatment after thyroidectomy ( = 39), including 17 patients with compromised renal function and 22 patients with known ( = 16) or suspected ( = 6) metastases. The total absorbed dose to blood (D) was the sum of mean whole-body γ-ray dose component (D) from uncollimated γ-camera measurements and dose due to β emissions (D) from blood samples. Method 2 estimated D from D alone, method 3 estimated D from D alone, and method 4 estimated D from a single 48-h γ-camera measurement. MPA was computed as 200 cGy/D for each D estimate. Method 2 had the strongest correlation with conventional method 1 ( = 0.98) and values similar to method 1 (21.0 ± 13.7 cGy/GBq vs. 21.0 ± 14.1 cGy/GBq, = 0.11), whereas method 3 had a weaker ( = 0.001) correlation ( = 0.94) and method 4 had the weakest ( < 0.0001) correlation ( = 0.69) and lower dose (16.3 ± 14.8 cGy/GBq, < 0.0001). Consequently, correlation with method 1 MPA was strongest for method 2 MPA ( = 0.99) and weakest for method 4 ( = 0. 75). Method 2 and method 1 values agreed equally well regardless of whether patients had been treated with I previously or had abnormal renal function. Because MPA based on blood measurements alone is comparable to MPA obtained with combined body counting and blood sampling, blood measurements alone are sufficient for determining MPA.
为了保护骨髓免受过度辐射，用于治疗甲状腺癌的 I 的最大允许活度 (MPA) 应限制血液（作为骨髓的替代物）的吸收剂量小于 200 cGy。传统方法（方法 1）需要重复γ相机全身测量和血液样本。我们试图确定是否可以通过简化程序获得可靠的 MPA 值。对 65 名甲状腺癌患者进行回顾性分析，这些患者在甲状腺切除术后接受 I 摄取和 MPA 初始治疗（n = 39），包括 17 名肾功能受损患者和 22 名已知（n = 16）或疑似（n = 6）转移患者。血液总吸收剂量（D）是未经准直γ相机测量的全身γ射线剂量分量（D）和血液样本β发射剂量（D）的总和。方法 2 仅从 D 估算 D，方法 3 仅从 D 估算 D，方法 4 仅从 48 小时γ相机单次测量估算 D。对于每个 D 估计，MPA 计算为 200 cGy/D。方法 2 与传统方法 1 相关性最强（ = 0.98），值与方法 1 相似（21.0 ± 13.7 cGy/GBq 比 21.0 ± 14.1 cGy/GBq， = 0.11），而方法 3 的相关性较弱（ < 0.0001）（ = 0.94），方法 4 的相关性最弱（ < 0.0001）（ = 0.69）且剂量较低（16.3 ± 14.8 cGy/GBq， < 0.0001）。因此，方法 2 MPA 与方法 1 MPA 的相关性最强（ = 0.99），与方法 4 MPA 的相关性最弱（ = 0.75）。方法 2 和方法 1 的值无论患者是否接受过 I 治疗或肾功能异常，结果都一致。因为仅基于血液测量的 MPA 与结合全身计数和血液采样获得的 MPA 相当，因此仅进行血液测量就足以确定 MPA。
