Dual-time-point FDG-PET/CT for the detection of hepatic metastases

Purpose: To prove the sensitivity of dual-time-point imaging with 18F-flourodeoxyglucose-positron emission tomography (18F-FDG-PET) of the liver to evaluate possible changes in the tumor-to-background ratio considering an improved detection rate of liver lesions. Procedures: Image acquisition for the first whole-body scan started at a mean time point of 69 min (55-110 min). The mean time interval between the injection of 18F-FDG and the second delayed scan was 100 min (85-166 min). Results: Of 90 proven liver metastases in 34 patients, the first scan detected 53 (59%) liver lesions correctly, whereas in the second, delayed scan 81 (90%) lesions were diagnosed correctly (p < 0.001). The mean Standardized uptake values in the first and second delayed scan were 6.59 g/ml versus 8.09 g/ml, respectively (p < 0.001). Tumor-to-background ratio of the first and second delayed scan were 2.0 and 2.7, respectively (p = 0.04). Conclusions: Dual-time-point-imaging of the liver showed a significant increase of tumor-to-background ratio and hypermetabolic lesion diameter. Although, 30% of all verified liver lesions could only be detected in the second delayed scan 10% of all malignant liver lesions were missed with FDG-PET.