The Clinical Value of Dual Time Point F-18 FDG PET/CT Imaging for the Differentiation of Colonic Focal Uptake Lesions

Kim, Jin Suk; Lim, Seok Tae; Jeong, Young Jin; Kim, Dong Wook; Jeong, Hwan Jeong; Sohn, Myung Hee

Abstract

PURPOSE: F-18 FDG can be accumulated in the liver, bowel, kidney, urinary tract, and muscles physiologically. The aim of this study was to evaluate the clinical value of dual time point 18F-FDG PET/CT imaging for the differentiation of the colonic focal uptake lesions.
MATERIALS AND METHODS
One hundred thirty two patients (M:F=77:55, Age 62.8 +/-11.6 years) underwent 18F-FDG PET/CT at two time points, prospectively: early image at 50-60 min and delayed image at 4-4.5 hours after the intravenous injection of 18F-FDG. Focally increased uptake lesions on early images but disappeared or shifted on delayed images defined a physiological uptake. For the differential evaluation of persistent focal uptake lesions on delayed images, colonoscopy and histopathologic examination were performed. SUVmax changes between early and delayed images were also compared.
RESULTS
Among the 132 patients, 153 lesions of focal colonic uptake were detected on early images of 18F-FDG PET/CT. Of these, 72 (47.1%) lesions were able to judge with physiological uptake because the focal increased uptake disappeared from delayed image. Among 81 lesions which was showed persistent increased uptake in delayed image, 61 (75.3%) lesions were confirmed as the malignant tumor and 14 (17.3%) lesions were confirmed as the benign lesions including adenoma and inflammatory disease. Remaining 6 (7.4%) lesions were confirmed as the physiological uptake because there was no particular lesion in the colonoscopy. In the malignant lesions, the calculated dual time point change for SUVmax (delta%SUVmax) was 20.8%+/-18.7%, indicating a significant increase in SUVmax between the two point (p<0.01). In contrast, the change in SUVmax for the non-malignant lesions including benign lesions and physiological uptake was -13.7%+/-24.2%. For the differentiation of the malignant and non-malignant focal colonic uptake lesions, delta%SUVmax was the most effective parameter, and the cut-off value using -5% provided the best sensitivity, specificity, and accuracy.
CONCLUSION
The dual time point 18F-FDG PET/CT imaging with SUVmax change evaluation could be an important noninvasive method for the differentiation of malignant and benign focal colonic uptake lesions including physiologic uptake.