The 2-hour delayed SUV and retention index calculated with dual-phase F-18 FDG PET distinguishes between benign and malignant thyroid carcinoma

Objectives We prospectively investigated whether the dual-phase FDG-PET was useful for the differentiating between benign and malignant thyroid carcinoma.

Methods 46 consecutive patients (male 17, femle 29, age 54.63 ± 4.22) with primary thyroid carcinoma underwent dual-phased FDG-PET. Maximum SUV at 1 hour (SUV1) and 2 hour (SUV 2) following the injection of FDG were determined, and the retention index (RI) was calculated by dividing the difference between SUV2 and SUV1 by SUV1(RI=(SUV2-SUV1)/SUV X 100%).

Results A diagnosis of thyroid carcinoma was histologically confirmed in 24 patients (52.17%) (17 papillary carcinoma, 4 Follicular carcinoma,1 Poorly differentiated carcinoma, 2 Undifferentiated (anaplastic) carcinoma). The SUV2 and RI of thyroid cancer were significantly higher than those of benign thyroid nodule. (SUV 2hr, Spearman's rho=0.49, P<0,05; RI, spearman's rho= 0.87, P<0.0001). However, the SUV 1hr was not significantly different between two groups.

Conclusions These data showed that 2 hour delayed F-18 FDG uptake and retention index can be used to evaluate thyroid malignancy. 2 hour delayed F-18 FDG PET and retention index can be a useful method for evaluating thyroid malignancy