Incidental thyroid uptake on F-18 FDG PET/CT: correlation with ultrasonography and pathology.
OBJECTIVE
To evaluate the usefulness of maximum standard uptake value (max SUV) calculated from F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) examination and findings from ultrasonographic (US) examination on incidentally detected thyroid FDG uptake on FDG PET/CT.


METHODS
We collected and reviewed FDG PET/CT images performed at our institution from March 2005 to March 2008. This study included 190 subjects with increased FDG uptake of thyroid gland who later underwent thyroid US and histological examinations. Of these subjects, the uptake pattern on FDG PET/CT was classified as either diffuse or focal. The FDG uptake pattern, max SUV, and US findings were evaluated and correlated with the histological results.


RESULTS
In the focal FDG uptake pattern cases (n = 148), the mean max SUV of malignant cases was higher than that of benign cases (5.93 +/- 5.35 vs. 3.47 +/- 2.89). Of the diffuse FDG uptake cases (n = 42), nodules were detected in 25 subjects (59.5%) by US examination. Thyroid nodules were well characterized on US studies, and combined findings of suspicious US features or high max SUV of focal FDG uptake lesion increased sensitivity, PPV, NPV, and accuracy.


CONCLUSIONS
Focal uptake pattern and high max SUV may be helpful in differentiating benign and malignant nodules on FDG PET/CT. However, US examination provides further information, and for lesions with increased FDG uptake of thyroid, US examination should be recommended.
Kang
Bong Joo
BJ
Department of Radiology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, Kyoungi-do, 442-723, South Korea.
O
Joo Hyun
JH
Baik
Jun Hyun
JH
Jung
So Lyung
SL
Park
Young Ha
YH
Chung
Soo Kyo
SK
D000328:Adult; D001692:Biological Transport; D003937:Diagnosis, Differential; D004194:Disease; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000378:metabolism*; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography
D019788:Fluorodeoxyglucose F18