Comparison of whole-body 18F-FDG SPECT and posttherapeutic 131I scintigraphy in the detection of metastatic thyroid cancer

Purpose The usefulness of fluorine 18 fluorodeoxyglucose (18F-FDG) imaging in differentiated thyroid cancer (DTC) has been demonstrated by investigators. The aim of this study is to compare the ability of fluorodeoxyglucose (FDG)-single photon emission computed tomography (SPECT) to detect metastatic DTC with posttherapeutic iodine131 (131I) scintigraphy. Methods 239 patients (78 men, 161 women; age range, 23–76 years, mean 45 years); All patients underwent FDG-SPECT and 131I whole-body scan. Results The sensitivity of 18F-FDG and 131I imaging in the patients with high hTg levels is 48.7% (114/234) and 50.4% (118/234) respectively. However, the combined sensitivity of both protocols is 89.7% (210/234). In the patients with 131I Imaging negative, the sensitivity of 18F-FDG is 79.3%,but in the patients with 131I imaging positive, the sensitivity of 18F-FDG is only 18.6%. Conclusion This study with 131I and 18F-FDG in FDG-SPECT further demonstrates the single study of 131I whole body scan or 18F-FDG imaging can not provide a high enough sensitivity for the detection of metastatic thyroid cancer. But, the combined protocols can get better results for the staging of thyroid carcinoma with the alternating uptake of 131I and 18F-FDG.