Effects of serum glucose on SUL of normal liver, a dynamic glucose metabolism organ

Objectives Serum glucose is a direct competitor to FDG for uptake in tissues. However, liver, a frequently used background tissue reference, is responsible for glycogen synthesis and potentially may be affected by hyperglycemic states differently than tumor. We examined the effects of glucose level on normal liver SUV.

Methods We reviewed 890 consecutive adult(>18yo) FDG PET/CT studies performed with GE Discovery LS or RX scanner in 833 patients from 4/1/2010 through 7/31/2010. SUV mean corrected for lean body mass (SUL) was measured in a 3cm diameter spherical ROI drawn over the right liver lobe. Fasting blood glucose level (FBS) immediately prior to FDG injection was obtained.

Results There is a weak but significant positive correlation of liver SUL to glucose level (r=0.12, p<0.01). Patients with normal glucose level (FBS<100) have liver SUL of 1.47 SD±0.25, significantly lower than patients with glucose impairment (FBS≥100) with liver SUL of 1.54 SD±0.27 (p<0.01) and patients with provisional diagnosis of diabetes (FBS≥126) with liver SUL of 1.56 SD±0.31 (p<0.01). Additionally, patients with a provisional diagnosis of diabetes have significantly higher hepatic SUL than those without the diagnosis (FBS<126) with liver SUL of 1.50 SD±0.18 (p=0.03). The variance(var) of liver SUL in normal glucose patients (var=0.063) appear higher than patients with glucose impairment (var=0.074) and patients with provisional diagnosis of diabetes (var=0.096).

Conclusions There is a positive correlation of FBS to liver SUL with a significant difference in liver SUL and variance among patients with normal FBS, glucose impairment, and presumptive diagnosis of diabetes. The difference from euglycemic patient liver SUL may be due to high glucose level activation of liver glycogen synthesis, and thus increased FDG uptake

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