^(131)I治疗分化型甲状腺癌肺转移吸收剂量学评价肺安全性

Lungs Absorbed Dose in Radioiodine Therapy of Differentiated Thyroid Carcinoma with Diffuse Pulmonary Metastases

估算131I治疗分化型甲状腺癌(DTC)弥散性肺转移,肺组织的吸收剂量。10例DTC弥散性肺转移患者服用7.4 GBq131I后采用连续显像法计算各时间点肺及全身的放射性计数,将放射性计数转化为百分摄碘率,拟合肺及全身的时间-放射性活度曲线,计算曲线下面积。假设沉积于肺的131I衰变释放出的β射线均被肺内弥散性DTC转移灶吸收,沉积于肺及剩余组织的131I衰变释放出的γ射线对肺组织造成照射损伤,由此按照美国核医学学会医用内照射剂量学委员会提出的内照射吸收剂量的计算方法,计算肺组织的吸收剂量。10例患者肺组织的吸收剂量中位值0.33 Gy(0.22~8.21 Gy)。按照经验性固定活度法治疗DTC弥散性肺转移,肺组织的吸收剂量较低。

The objective of this work was to estimate the absorbed dose of 131I to lungs in 131I therapy of differentiated thyroid carcinoma（DTC） with diffuse pulmonary metastases.Ten DTC patients with diffuse pulmonary metastases were recruited prospectively.Whole body planar scintigrams were acquired serially after administration of 7.4GBq 131I to patients.The counts from the regions of interest of lungs and total body were obtained and converted to the percent of administered activity.The time-activity curves of lungs and total body were fit,and the areas under the curves were calculated.It was assumed that β-eletron emissions from 131I deposited in lungs were completely absorbed by the diffuse DTC metastatic lesions,and that γ-photon emissions from 131I deposited in the lungs and the remainder of body were irradiating the lungs.The absorbed dose to lungs was calculated according to Medical Internal Radiation Dosimetry（MIRD） formula.The median lungs absorbed dose was 0.33Gy（range,0.22-8.21Gy）.Based on the empiric fixed activity therapy of DTC with diffuse pulmonary metastases,the absorbed dose to lungs is low.