Abuqbeitah Mohammad, Sağer Sait, Demir Mustafa, Yeyin Nami, Akovalı Burak, Sönmezoğlu Kerim
Nuclear Medicine Department, Istanbul University-Cerrahpasa, Cerrahpasa Medical School, Istanbul, Fatih, 0090, Turkey.
Med Phys. 2020 Nov;47(11):5810-5816. doi: 10.1002/mp.14478. Epub 2020 Oct 8.
The goal of the current study was to investigate the impact of different computational models on I dosimetry prior to hyperthyroidism therapy. It was also aimed to highlight an accurate and cost-effective method for routine dosimetry of graves and toxic adenoma patients.
A cohort of 45 patients was recruited in the current study with Graves (n = 30) and Toxic Adenoma (n = 15) diseases. The eligibility criterion was determined using the patients' blood test, Tc- pertechnetate scintigraphy, and ultrasound scan. A properly calibrated thyroid probe equipped with sodium iodide crystal [NaI(Tl)] was used to obtain the uptake measurements at 2, 24, 48, 72, and 96 h following administration of 0.27-0.73 MBq I tracer. The absorbed radiation dose of the thyroid gland/nodule was calculated by three different methods. The calculation models were based on the time-integrated activity (recommended by MIRD), effective half-life (recommended by EANM), and ellipsoidal-shape assumption.
The mean effective half-life was 138 ± 41 h and 110 ± 48 h in Graves and Toxic Adenoma patients, respectively. The mean residence time was 125 ± 5 h in Graves patients, while it was 93 ± 55 h in Toxic Adenoma. The amount of I activity required to deliver 200 Gy to the thyroid gland in Graves patients was calculated as 436 ± 381 MBq, 426 ± 370 MBq, and 488 ± 455 MBq according to MIRD, EANM, and ellipsoidal-shape model, respectively. However, the activity required to impart 300 Gy in the toxic nodules was computed as 622 ± 332 MBq by MIRD, 907 ± 588 MBq by EANM, and 1060 ± 639 MBq by the ellipsoidal-shape model. Overall, no significant difference was found between the MIRD and both of the EANM and ellipsoidal-shape models in the Graves patients (R = 0.99, P > 0.05). In contrast, less agreement (R = 0.86) was shown between EANM and MIRD in Toxic Adenoma patients with no statistically significant difference (P > 0.05), while the difference was significant (P < 0.05) between the MIRD and the ellipsoidal-shape model with moderate association (R = 0.66).
It was deduced that the effective half-life-based model (EANM model) is a successful and affordable method for performing dosimetry in Graves patients. While, unit density sphere model sounds the most appropriate approach to be used in Toxic Adenoma dosimetry. However, using the ellipsoidal-shape assumption in the thyroid gland/or nodule dose calculation leads to redundantly larger activity administration.
本研究的目的是调查不同计算模型对甲状腺功能亢进症治疗前剂量测定的影响。同时旨在突出一种针对格雷夫斯病和毒性腺瘤患者进行常规剂量测定的准确且经济高效的方法。
本研究招募了45例患有格雷夫斯病（n = 30）和毒性腺瘤（n = 15）的患者。使用患者的血液检查、高锝酸盐闪烁扫描和超声扫描来确定纳入标准。使用配备碘化钠晶体[NaI（Tl）]且经过适当校准的甲状腺探头，在给予0.27 - 0.73 MBq碘示踪剂后的2、24、48、72和96小时获取摄取测量值。通过三种不同方法计算甲状腺/结节的吸收辐射剂量。计算模型基于时间积分活度（由MIRD推荐）、有效半衰期（由EANM推荐）和椭球体假设。
格雷夫斯病和毒性腺瘤患者的平均有效半衰期分别为138 ± 41小时和110 ± 48小时。格雷夫斯病患者的平均停留时间为125 ± 5小时，而毒性腺瘤患者为93 ± 55小时。根据MIRD、EANM和椭球体模型，格雷夫斯病患者甲状腺给予200 Gy所需的碘活度分别计算为436 ± 381 MBq、426 ± 370 MBq和488 ± 455 MBq。然而，毒性结节给予300 Gy所需的活度，MIRD计算为622 ± 332 MBq，EANM计算为907 ± 588 MBq，椭球体模型计算为1060 ± 639 MBq。总体而言，格雷夫斯病患者中MIRD与EANM和椭球体模型之间均未发现显著差异（R = 0.99，P > 0.05）。相比之下，毒性腺瘤患者中EANM与MIRD之间的一致性较低（R = 0.86），差异无统计学意义（P > 0.05），而MIRD与椭球体模型之间差异显著（P < 0.05），相关性中等（R = 0.66）。
推断基于有效半衰期的模型（EANM模型）是对格雷夫斯病患者进行剂量测定的一种成功且经济实惠的方法。而单位密度球体模型似乎是毒性腺瘤剂量测定中最合适的方法。然而，在甲状腺/结节剂量计算中使用椭球体假设会导致给予的活度过大。
