RT Journal Article SR Electronic T1 Dual-Time-Point 18F-FDG PET for the Evaluation of Gallbladder Carcinoma JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 633 OP 638 VO 47 IS 4 A1 Yoshihiro Nishiyama A1 Yuka Yamamoto A1 Kotaro Fukunaga A1 Naruhide Kimura A1 Akihiro Miki A1 Yasuhiro Sasakawa A1 Hisao Wakabayashi A1 Katashi Satoh A1 Motoomi Ohkawa YR 2006 UL http://jnm.snmjournals.org/content/47/4/633.abstract AB Conventional imaging techniques such as ultrasonography, CT, and MRI are able to detect gallbladder abnormalities but are not always able to differentiate a malignancy from other disease processes such as cholecystitis. The purpose of the present study was to evaluate the efficacy of dual-time-point 18F-FDG PET for differentiating malignant from benign gallbladder disease. Methods: The study evaluated 32 patients who were suspected of having gallbladder tumors. 18F-FDG PET (whole body) was performed at 62 ± 8 min (early) after 18F-FDG injection and was repeated 146 ± 14 min (delayed) after injection only in the abdominal region. We evaluated the 18F-FDG uptake both visually and semiquantitatively. Semiquantitative analysis using the standardized uptake value (SUV) was performed for both early and delayed images (SUVearly and SUVdelayed, respectively). The retention index (RI) was calculated according to the equation (SUVdelayed − SUVearly) × 100/SUVearly. The tumor-to-liver ratio was also calculated. Results: The final diagnosis was gallbladder carcinoma in 23 patients and benign disease in 9 patients. For visual analysis of gallbladder carcinoma, delayed 18F-FDG PET images improved the specificity of diagnosis in 2 patients. When an SUVearly of 4.5, SUVdelayed of 2.9, and RI of −8 were chosen as arbitrary cutoffs for differentiating between malignant and benign conditions, sensitivity increased from 82.6% to 95.7% and 100% for delayed imaging and combined early and delayed imaging (i.e., RI), respectively. With the same criteria, specificity decreased from 55.6% to 44.4% for delayed imaging and combined early and delayed imaging, respectively. The specificity of 18F-FDG PET improved to 80% in the group with a normal level of C-reactive protein (CRP) and decreased to 0% in the group with an elevated CRP level. For gallbladder carcinoma, both SUV and tumor-to-liver ratios derived from delayed images were significantly higher than the ratios derived from early images (P < 0.0001). Conclusion: Delayed 18F-FDG PET is more helpful than early 18F-FDG PET for evaluating malignant lesions because of increased lesion uptake and increased lesion-to-background contrast. However, the diagnostic performance of 18F-FDG PET depends on CRP levels.