Dosimetry-guided 131I therapy for differentiated thyroid carcinoma with diffuse pulmonary metastases / 中华核医学杂志

ABSTRACT

Objective 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.