[Determining the activities of 131I with dose-rate constraint method for the treatment of differentiated thyroid carcinoma with diffuse pulmonary metastases].
OBJECTIVE
To compare the dose-rate constraint method with empiric fixed activity method in determining the activities of 131I for the treatment differentiated thyroid carcinoma (DTC) with diffuse pulmonary metastases.


METHODS
The 80 mCi rule, a rule developed by the Medical Internal Radiation Dosimetry (MIRD) formalism, which states that the whole body retention of 131I at 48 h should not exceed 2.96 GBq (80 mCi), was applied to calculate the dose-rate constraint to lungs at 48 h in 131I therapy of DTC with diffuse pulmonary metastases. Ten consecutive DTC patients with diffuse pulmonary metastases were prospectively recruited. The whole body planar scintigrams were obtained after administration of 7.4 GBq 111I to the patients to acquire the kinetic parameters. According to the dose-rate constraint to lungs at 48 h, the activities of 131I were determined individually.


RESULTS
According to the 80 mCi rule and MIRD formalism, the absorbed dose-rate to lungs at 48 h should not exceed 46.4 mGy/h in 131I therapy of DTC with diffuse pulmonary metastases. The activities of nine patients determined by the dose-rate constraint method were larger than 7.4 GBq.


CONCLUSIONS
Dose-rate constraint method can reasonably adjust the activities of 131I determined by empiric fixed activity method for the treatment of DTC with diffuse pulmonary metastases.
Liu
Bin
B
Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu 610041, China.
Zeng
Yu
Y
Wang
Jian-Tao
JT
Zhao
Zhen
Z
Mu
Da
D
Kuang
An-Ren
AR
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008175:Lung Neoplasms / Q000532:radiotherapy* / Q000556:secondary*; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal; D013964:Thyroid Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D055815:Young Adult
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals