摘要目的 从内照射剂量学角度探讨如何确定治疗分化型甲状腺癌弥散性肺转移(DTC-DPM)的131I活度.方法 依据美国核医学会医用内照射剂量学委员会提出的内照射剂量计算方法(MIRD体系),将131I治疗DTC-DPM服131I后48 h时滞留于患者体内的131I不超过2.96 GBq的限定(2.96 GBq法则)转变为服131I后48 h时肺组织剂量率限定(DRCLU·48h).假设眼131I后48 h时沉积于肺的131I与滞留于全身的131I活度比(F48h)在0.6～0.9间,131I在肺及剩余组织的有效半衰期(TLL、TRB)分别为20～120 h和10～20 h,参照OLINDA(Organ Level Internal Dose Assessment)软件中不同参考人体数据,计算不同DTC-DPM患者的131Ⅰ最大安全治疗活度(Amax).结果 依据MIRD体系和2.96 GBq法则,131I治疗DTC-DPM,DRCLU·48h应不超过46.4 mGy/h.按照不同的F48h、TLU及TRB,成年男性、成年女性、15岁和10岁DTC-DPM患者的Amax分别在6.77～81.36 GBq、5.29～56.20 GBq、5.08～55.19 GBq和3.87～40.52 GBq间.结论 内照射剂量学指导131I治疗DTC-DPM充分地考虑了131I在不同患者体内的代谢动力学差异,可在避免发生放射性肺炎、肺纤维化的前提下,调节131I用量.

abstractsObjective To determine the activities of 131I for treating differentiated thyroid carcinoma with diffuse pulmonary metastases ( DTC-DPM ) from the perspective of internal radiation dosimetry.Methods According to Medical Internal Radiation Dosimetry (MIRD) schema, the activity constraint,from which the whole bdy retention at 48 h should not exceed 2.96 GBq (2.96 GBq rule), was converted to dose-rate constraint(DRC) to lungs at 48 h ( DRCLU ·48 h ) in 131I therapy for DTC-DPM. Based on the assumption of DRCLU·48 h at 48 h in lung, the fractions of whole body activities ( F48 ), the effective half times of 131I in lungs ( TLL ) and the remainder of body ( TRB ) were 0.6-0.9, 20- 120 h, and 10- 20 h, respectively. The maximum safe activities of 131I for different human phantoms from the Organ Level Internal Dose Assessment (OLINDA) software were calculated. Results According to MIRD schema and 2.96 GBq rule, DRCLU ·48 h should not exceed 46.4 mGy/h in 131I therapy for DTC-DPM. Depending on varying F48 h,TLL and TRB, the maximum safe activities of 131I were 6.77-81.36, 5.29-56.20, 5.08-55.19 and 3.87-40. 52 GBq for the male adult, female adult, 15-year-old, and 10-year-old patients with DTC-DPM, respec tively. Conclusion Dosimetry-guided 131I therapy for DTC-DPM considers adequately the differences of 131I kinetics in individual patients and can adjust administered activities of 131I on the precondition of avoiding radiological pneumonitis and pulmonary fibrosis.