Physiological distribution of ⁶⁸Ga-DOTA-TATE: an atlas of standardized uptake values

Objectives The purpose of this study was to analyze the biodistribution of ⁶⁸Ga-DOTA-TATE uptake in the normal tissues in the population of patients with known neuroendocrine tumor (NET) using semiquantitative SUV measurements.

Methods 38 patients (mean age±SD: 58.1±12.2) with confirmed diagnosis of NET underwent PET/CT 57±5.8 minutes following administration of 5.8±0.75 mCi ⁶⁸Ga-DOTA-TATE. SUV_mean and SUV_max were measured in 37 normal anatomical structures for each patient. We examined the range and average uptake for each structure and correlations between uptakes in different organs.

Results ⁶⁸Ga-DOTA-TATE uptake in 26 structures was significantly greater than left atrial blood pool (SUV_max=1±0.3) at the p<0.01 significance level. Table summarizes uptake in tissues with high physiologic uptake. Activity in the GI tract was variable and was higher in the stomach and jejunum than distal bowel. Salivary excretion of tracer and activity along the parotid gland duct was invariably observed. Significant biliary excretion was not present at one hour after injection. For structures with uptake greater than blood pool (with the exception of pituitary, gonads, gallbladder, and urinary tract), SUV_max correlated with reticuloendothelial uptake (SUV_mean) in spleen/bone marrow (r>0.5, p<0.01), suggesting that splenic and bone marrow uptakes can be potentially useful as internal references for image interpretation and quality assurance. There was overall weak correlation between the physiologic tissue SUV_max and blood pool (r=0.19±0.21) or urine SUV_mean (r=-0.06±0.16).

Conclusions Various tissues have different SUVs reflecting underlying physiologic variability in somatostatin receptor expression. These are important for accurate interpretation of the clinical ⁶⁸Ga-DOTA-TATE examinations.

Research Support Supported by department of radiology, Stanford University.