Dosimetric measurements of 68Ga-High Affinity DOTATATE

Summary Purpose: 68Ga-labelled compounds are increasingly used for somatostatin-receptor scintigraphy because of their favourable biokinetic properties, a higher tumour-to- background contrast and higher diagnostic accuracy compared to the gamma-emitting tracer 111In-DTPA-octreotide. Recently, we have introduced the new tracer 68Ga-DOTA- 3-iodo-Tyr3-Thr8-octreotide (68Ga-HA-DOTA- TATE). The present study demonstrates the biodistribution and radiation dosimetry of this tracer in humans. Patients, methods: Seven men were enrolled in this analysis. Every patient underwent a 20 min dynamic PET scan after intravenous injection of about 114 ± 9 MBq of 68Ga-HA-DOTATATE. This was followed by two whole-body scans at 30 min p. i. and 120 min p. i. Blood radioactivity concentration was determined non-invasively from a ROI drawn over the aorta. Urine was collected until the time of the last scan. Liver, spleen, kidneys and urinary bladder wall were included in the dosimetric estimation that was carried out with the software package OLINDA 1.0. Results: Physiological 68Ga- HA-DOTATATE uptake was observed in the pituitary gland, thyroid, salivary glands, liver, spleen, kidneys, urinary bladder, adrenals and intestine. Organs with the highest absorbed dose were spleen (0.26 ± 0.11 mSv/MBq), kidneys (0.14 ± 0.03 mSv/MBq) and liver (0.12 ± 0.02 mSv/MBq).The estimated effective dose was 0.024 ± 0.001 mSv/MBq. Conclusion: Our study demonstrates biokinetics and radiation exposure of the 68Ga-labelled tracer HA-DOTATATE to be comparable to other 68Ga-labelled SSR analogues in clinical use.