The value of late phase imaging with FDG-PET/CT in liver metastases of colorectal carcinoma

Abstract

Aim: Our aim was investigated the role of late phase imaging with F18-FDG-PET/CT in colorectal carcinoma patients with liver metastases. Method: Dual phase FDG-PET/CT scan was retrospectively evaluated in colorectal carcinoma patients with liver metastases. Late phase imaging was acquired 92-253 minutes (mean 158.53±35.7 minutes) after the FDG injection. Sixty-eight metastatic lesions were determined in 37 patients. Mean lesion SUVmax and lesion-to non-tumorous liver tissue ratio were calculated and results of routine FDG-PET imaging were compared with late phase imaging. Results: Metastatic lesion sizes were 9 to230 mm (mean 3.71±3.7 cm). SUVmax values of the metastasis and non-tumorous liver SUVmax for routine and late-phase imaging were as follows; 7.19±3.8, 10.3±5.4; 2.98±0.7, 2.41±0.6 respectively. Metastatic liver lesions, SUVmax values were increased (p 0.01) and non-tumorous liver SUV max values were decreased (p 0.01) in late phase imaging. Compared to routine imaging, in late phase lesion to non-tumorous liver tissue was increased (p 0.001). Lesion retention index was 45.74± 31.8% and the non-tumorous liver index was decreased 18.63 ± 10.4%. Conclusion: The results of this study indicates that normal liver FDG uptake decreases in time and late phase imaging improves the tumor to normal tissue ratio and enable differentiation of metastatic liver lesions from normal liver.