(18)F-FDG PET/CT for the Preoperative Diagnosis of Papillary Thyroid Microcarcinoma: The Value of Dual Time Point Imaging / 핵의학분자영상

ABSTRACT

PURPOSE: We studied the patterns of FDG uptake of primary papillary thyroid microcarcinoma (PTMCa) lesions and benign thyroid nodules in dual time point (18)F-FDG PET/CT imaging. MATERIALS AND METHODS: Consecutive 134 patients (154 lesions) with PTMCa and 49 patients (61 nodules) with benign thyroid nodules equal to or less than 1.0 cm who underwent dual time point (18)F-FDG PET/CT study before surgery were enrolled. We calculated the maximum standardized uptake value of PTMCa and benign nodules in both time points, and percent change of SUVmax (delta%SUVmax) and lesion to background ratio of SUVmax (delta%LB ratio) between both time points. The mean time interval between scans was 23.4+/-4.4 minutes (thyroid to thyroid interval 10.7+/-4.4 minutes). RESULTS: The mean of SUVmax of PTMCa was increased from 4.9+/-4.3 to 5.3+/-4.7 (p<0.001) and delta%SUVmax was 12.3+/-23.6%. But, the mean of SUVmax of benign nodules was no definite change (2.1+/-1.0 to 2.1+/-1.3, p=0.686) and delta%SUVmax was -0.3+/-20.5%. Of the 154 PTMCa, 100 nodules (64.9%) showed an increase in SUVmax over time, while 19 (31.1%) of the 61 benign thyroid nodules showed an increase (p<0.001). The dual time point (18)F-FDG PET/CT found more PTMCa in visual assessment (62.3% vs. 76.6%, p=0.006), even in smaller than 0.5 cm (38.6% vs. 60.0%, p=0.011). CONCLUSION: Dual time time (18)F-FDG PET/CT imaging was more useful than single time point (18)F-FDG PET/CT imaging for distinction between PTMCa and benign nodule, especially when nodule showed equivocal or negative findings in single time point (18)F-FDG PET/CT imaging or was smaller than 0.5 cm.