Biodistribution and estimation of radiation-absorbed doses in humans for 13N-ammonia PET

Objective To evaluate the biodistribution of radiation-absorbed doses of 13 N-ammonia in healthy people. Methods Five healthy human subjects underwent whole-body PET and CT scans after injection of 555–740 MBq of 13 N-ammonia. Five serial dynamic emission scans in each healthy volunteer were acquired. Regions of interest were drawn on the CT image and transferred to the corresponding transverse PET slice. Estimates of the radiation-absorbed doses were calculated using the medical internal radiation dosimetry method. Results The highest concentrations of 13 N-ammonia were found in the heart and liver, followed by pancreas, brain, spleen and stomach. The highest absorbed organ doses were to the heart wall (7.14E−03 ± 3.63E−03 mGy/MBq) and kidneys (6.02E−03 ± 3.53E−03 mGy/MBq). The effective dose (ED) was 6.58E−03 ± 1.23E−03 mSv/MBq. Conclusions With these new estimates for 13 N-ammonia dosimetry, the results for Chinese people were not appreciably different from those of the previous study performed with old devices. As one of the most important myocardial perfusion PET tracers, the whole-body 13 N-ammonia PET appears to be safe for humans, yielding a relatively modest radiation burden that would allow multiple PET studies on the same subject per year.