A pilot study on the biodistribution pattern of 68Ga-DOTA-TATE in normal organs of adults

Objective To retrospectively study the biodistribution of 68Ga-DOTA-TATE as a SSTR imaging agent in human subjects. Methods A total of 106 patients with suspected disease were enrolled in this study. All patients were histologically proven for having either a single tumor <2 cm or without evidence of tumor during follow-up. Patients underwent PET/CT whole-body scan 17-100 min after intravenous injection of 55.2-220.0 MBq 68Ga-DOTA-TATE. ROI was drawn for measuring SUV of tracer-avid pathologies. One-way analysis of variance and two-sample t test were used for statistical analysis. Results High 68Ga-DOTA-TATE avidity was found in pituitary, with SUVmax of 4.00±1.21. Tracer was excreted mainly through urinary system resulting in highest uptake in the urinary tracts. The SUVmax of kidney cortex was 19.01±5.45. Mediastinal blood pool and liver SUVmax were 0.93±0.33 and 7.69±2.26, respectively. Mild uptake of 68Ga-DOTA-TATE was found in the brain, cerebellum, lung and muscle, all lower than that of mediastinal blood pool. Moderate accumulation of 68Ga-DOTA-TATE (close to or slightly higher than liver) was found in adrenal gland and spleen, with SUVmax 7.61±3.42 and 8.63±2.31, respectively. Other organs (pituitary, salivary gland, thyroid, pancreas, small intestine, colon, uterus, prostate and bone) showed tracer uptake in the range between those of mediastinal blood pool and liver. 68Ga-DOTA-TATE distribution in pancreas was not uniform. Nine patients had focal accumulation in the uncinate process of pancreas with highest SUVmax up to 8.48. However, the SUVmax and SUVmean in the rest of pancreas (head, neck, body and tail) showed insignificant difference (F values: 0.703, 0.563, both P>0.05). 68Ga-DOTA-TATE uptake in each organ reached equilibrium quickly after injection but with slight increase over time. The changes in SUV, however, showed insignificant difference among organs, including different parts of pancreas (t values: from -0.09 to 1.75, from -1.70 to -0.42, respectively, all P>0.05). Conclusions The biodistribution of 68Ga-DOTA-TATE reaches equilibrium shortly after intravenous administration and is stably maintained. The biodistribution activities are organ-specific, and characteristic to that of SSTR concentration. Key words: Octreotide; Gallium radioisotopes; Positron-emission tomography; Tomography, X-ray computed