123I-2-Iodo-Tyrosine (123I-2IT) is an amino acid analogue that is currently used in tumour imaging. Its accumulation in tumours is mediated mainly by increased expression of the L-amino acid transport system 1 (LAT 1). The aim of this study was to evaluate the human biodistribution and radiation dosimetry of this new tracer. Methods: Radioiodination of 2IT was performed by Cu1+-assisted nucleophilic exchange in acidic and reducing conditions at 100°C during 60 min, yielding >98% 123I-2IT. We studied six healthy male volunteers who received 60-95MBq 123I-2IT each. Whole-body scans and blood samples were obtained at respectively five and nine time points up to 24 h after injection. Time-activity curves were generated for nine organs by fitting the organ activities in % of injected dose, obtained from regions of interest, as a function of the time after injection. The absorbed radiation dose for various organs was calculated using OLINDA 1.0 (Stabin, 2005) and the voiding bladder model with an interval of 4.8h. Results: 123I-2IT was cleared rapidly from the blood by renal excretion, and no major organs showed significant accumulation. The organs that received the highest absorbed doses were found to be the bladder wall (0.12mGy/MBq) and the small intestine (0.03mGy/MBq). The average effective dose and effective dose equivalent of 123I-2IT was estimated to be respectively 0.020 and 0.016 mSv/MBq. Conclusion: 123I-2IT has a favourable biodistribution for a tumour imaging agent. An average effective dose of 0.02mSv/MBq leads to a radiation dose that is comparable to other diagnostic nuclear medicine procedures.
- tumour imaging agent