The value of dual time point ~(18)F-FDG PET imaging for the differentiation between malignant and benign lesions

Objective To assess the clinical value of dual-time point ~ 18 F- FDG PET imaging for differentiating malignant from benign lesions. Methods Twenty-eight patients with primary lung cancer, 18 patients with digestive system carcinoma, 13 patients with other kind of malignant tumors, and 37 patients with benign lesions underwent PET-CT at 2 time points: scan 1 at 45 min and scan 2 at 150-180 min after the intravenous injection of 185-370 MBq ~ 18 F- FDG. Reconstructed images were evaluated qualitatively and quantitatively. The maximum standardized uptake value (SUV_ max ) and average SUV (SUV_ mean ) within the lesions were calculated for both time points. By adopting a SUV change 10% between the first and second scans was as a criterion for increase and decrease. Results Twenty-four of 28 primary lung cancers had SUV2.5 at scan 1. Among them, 23 showed increase uptake and the other one showed no change of SUV in the delayed imaging (scan 2). The other 4 primary lung tumors had SUVs between 1.5 and 2.5 at scan 1 which showed suspected positive, three of whose SUVs increased at time point 2. Seventeen of 18 malignant lesions in digestive system showed SUV2.5, the other one showed negative at scan 1, and all showed increase in SUV at scan 2. Of 13 other kinds of tumors, all had SUV 2.5 at scan 1 and SUVs increased at time point 2. For the benign lesions, 12 showed positive at early and 4 positive in delayed images. The sensitivity, specificity, accuracy, positive and negative predicted value for the early and delayed imaging were 91.5%, 67.6%, 82.3%, 68.4% and 83.3% and 98.3%, 86.5%, 93.8%, 92.1% and 97.0%, respectively. Conclusion These data showed that dual time imaging appeared to be helpful for differentiating benign lesions from malignant lesions. Almost all malignant tumors had SUV2.5 at scan 1 and showed further increase at scan 2, but some benign lesions also had this kind of character.