Measurement of residual radioactivity in postoperative inpatients with differentiated thyroid carcinoma after 131I treatment using robot / 中华核医学与分子影像杂志

ABSTRACT

Objective@#To evaluate the residual radioactivity after 131I treatment in postoperative inpatients with differentiated thyroid carcinoma (DTC) using service robot in nuclear medicine ward, and assess the time for patients to be released from isolation.@*Methods@#From September 2017 to June 2018, 297 patients (94 males, 203 females, age 19-80 years) with DTC who underwent 131I treatment after surgery were included. According to the purpose of treatment and the prescription dosage of 131I, patients were divided into 8 groups 4 groups accepted 131I remnant ablation therapy (RAT) with different dosages, which were 3 700 MBq (RAT1, n=34), 4 440 MBq (RAT2, n=122), 5 550 MBq (RAT3, n=81) and 7 400 MBq (RAT4, n=27), respectively; 4 groups had 131I treatment for recurrent/metastatic lesions (RMLT), and the dosages were 3 700 MBq (n=1), 4 440 MBq (n=2), 5 550 MBq (n=14) and 7 400 MBq (n=16). At 4, 24, 48 and 72 h after 131I administration, the dose equivalent rates at 2 cm away from the patient′s neck and at 1 m away from the body were measured by the robot designed for nuclear medicine ward. Kruskal-Wallis rank sum test and Mann-Whitney U test were used to analyze the data.@*Results@#Neck dose equivalent rates for patients with RAT at different time points (4, 24, 48 and 72 h) after 131I administration were significantly different among 4 groups (H values 20.889-46.410, all P<0.05), as well as the body dose equivalent rates (H values 27.181-35.497, all P<0.05). The neck dose equivalent rates at 24, 48 and 72 h after 131I administration were statistically different between group 3 and 4 for patients with RMLT (z values 2.328-3.076, all P<0.05; data in group 1 and 2 were too limited to be compared), while there was no statistical difference for the body dose equivalent rates (z values 0.333-1.621, all P>0.05). The radioactivity retention in patients decreased rapidly within 24 h, then slowed down gradually and became extremely low at 72 h. At 72 h after 131I administration, 96.6%(255/264) patients with RAT and 100%(33/33) patients with RMLT were lower than 23.3 μSv/h, which meant the patients could be discharged from hospitalization.@*Conclusions@#Nuclear medicine ward service robots may dynamically measure residual radioactivity in DTC patients who take 131I treatment, providing individualized isolation solutions.