[Differentiation between Hepatic Focal Lesions and Heterogenous Physiological Accumulations by Early Delayed Scanning in 18 F-FDG PET/CT Examination].

PURPOSE: We examined whether early delayed scanning is useful for differentiation of liver lesion and heterogenous physiological accumulation in positron emission tomography (PET) examination.

METHODS: The subjects of the study were 33 patients with colorectal cancer who underwent PET examination and were added early delayed scanning to distinguish between liver lesions and heterogenous physiological accumulation to conventional early images. We placed same regions of interest (ROI) in the tumor and hepatic parenchyma for early delayed and conventional early images. Then, we measured SUVmax of the ROIs and calculated tumor to liver parenchyma uptake ratio (TLR). In addition, change rates between early and early delayed images were calculated for the SUVmax and TLR.

RESULTS: The receiver operating characterstic (ROC) analysis result of SUVmax showed the highest SUVmax change rate, and the ROC analysis result of TLR showed the highest early delayed scanning. The SUVmax of the lesions did not change between early scan and early delayed scanning (p=0.98), but it decreased significantly in the normal group (p<0.001). TLR of the lesion group was significantly increased (p<0.001) in early delayed images compared to early scan and TLR significantly decreased in the normal group (p<0.001). The AUC of the ROC curve showed the highest SUVmax change rate (0.99).

CONCLUSION: Early delayed scanning could distinguish between liver lesions and heterogenous physiological accumulation in colon cancer patients.