The relationship between standard uptake value (SUV) and Hounsfield Unit (HU) of oral contrast agent for FDG-PET/CT study

The aim of this study was to examine the relationship between CT density (Hounsfield Unit, HU) and the degree of fluoro-deoxyglucose (FDG) uptake, demonstrated as standard uptake value (SUV). Twenty contiguous patients (9 males, 11 females, age range of 29-79) were performed FDG-PET/CT scan with 750ml of 5% iodine-based oral contrast agent. A region of interest (ROI)was placed manually on oral contrast in the lumen of stomach, small bowel and ascending colon, avoiding contamination of other structures, and the average SUV and average HU were determined. R square and p value were applied to evaluate the correlation. The correlation between SUV and HU in each separate location is not significant. When all regions are combined, p value is significant (＜0.05), but R square is not significant. Oral contrast can be one factor that influences measured FDG, and it is possible it acts as an irritant that increases metabolism in the bowel wall, resulting in increased FDG uptake.