Assessment of the effect of hepatic steatosis on 18F-FDG uptake in PET-CT examinations and its relation with the body mass index (BMI)

Abstract Background Fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) is a key tool in the diagnosis, staging, and restaging of tumors. Currently, liver Standardized Uptake Value (SUV) has been adopted as a background tissue in a number of publications and guidelines, including the Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST criteria). Recently, hepatic steatosis has become the most prevalent chronic liver disease, often progressing to cirrhosis, with obesity and its related complications on the rise. Therefore, the current study aimed to assess the relationship between non-alcoholic fatty liver disease (NAFLD), obesity, and FDG uptake, as well as to evaluate the reliability of SUV measurements normalized to body weight versus those normalized to lean body mass, in relation to body mass index (BMI). Patients and methods Fifty cases were included in this study, which were first categorized into non-alcoholic fatty liver disease (NAFLD) with a mean liver Hounsfield Units (HU) of 33.5 ± 8.65 SD and non-fatty liver groups with a mean liver HU of 59.5 ± 8.81 SD. The cases were then further categorized according to body mass index into three groups: normal (18.5–24.9 kg/m 2 ), overweight (25–29.9 kg/m 2 ), and obese (≥ 30 kg/m 2 ). Standardized-uptake value (SUV) mean (SUV mean) and maximum (SUV max), SUV normalized to lean body mass (LBM) mean (SUL mean), and SUL maximum were measured. Results The measured SUV max and SUV mean normalized to body weight (BW) showed no significant difference between the NAFLD and non-fatty liver groups, with p -values of 0.666 and 0.122, respectively. Spleen attenuation showed a statistically significant difference ( p = 0.027), with the obese group having a lower mean spleen attenuation compared to the normal weight and overweight groups. Both SUV BW values demonstrated highly significant differences across BMI categories, with an increasing slope from the normal weight group to the obese group, where the p -value for SUV max was 0.016 and for SUV mean was 0.027. In contrast, SUL values showed no significant differences, with p -values of 0.313 and 0.550 for SUL max and SUL mean, respectively. Conclusion There was no association between hepatic fatty infiltration and FDG uptake in terms of SUV BW . On the basis of these data, it is acceptable to use the liver as a comparator for extrahepatic foci of increased FDG activity in patients with fatty liver disease. However, it is more reliable to use SUL values in obese patients.