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 SUV_max of 4.00 ± 1.21. Tracer was excreted mainly through urinary system resulting in highest uptake in the urinary tracts. The SUV_max of kidney cortex was 19.01 ± 5.45. Mediastinal blood pool and liver SUV_max 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 SUV_max 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 SUV_max up to 8.48. However, the SUV_max and SUV_mean 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. (authors)