Estimation of the net influx rate Ki and the cerebral metabolic rate of glucose MRglc using a single static [18F]FDG PET scan in rats.

Since accurate quantification of 2-deoxy-2-18F-fluoro-D-glucose ([18F]FDG) positron emission tomography (PET) requires dynamic acquisition with arterial input function, more practical semi-quantitative (static) approaches are often preferred. However, static standardized uptake values (SUV) are typically biased due to large variations in body weight (BW) occurring over time in animal studies. This study aims to improve static [18F]FDG PET SUV quantification by better accounting for BW variations in rats. We performed dynamic [18F]FDG PET imaging with arterial blood sampling in rats (n = 27) with different BW (range 0.230-0.487 kg). By regressing the area under the curve of the input function divided by injected activity against BW (r2=0.697), we determined a conversion factor f(BW) to be multiplied with SUV and SUVglc to obtain ratSUV and ratSUVglc, providing an improved estimate of the net influx rate Ki (r = 0.758, p<0.0001) and cerebral metabolic rate of glucose MRglc (r = 0.906, p<0.0001), respectively. In conclusion, the proposed ratSUV and ratSUVglc provide a proxy for the Ki and MRglc based on a single static [18F]FDG PET SUV measurement improving clinical significance and translation of rodent studies. Given a defined strain, sex, age, diet, and weight range, this method is applicable for future experiments by converting SUV with the derived f(BW).