Radiation dose to the human body from intravenously administered 75Se-sodium selenite

The dose of radiation to the human body and some of its organs after intravenous administration of 75Se-sodium selenite for diagnostic purposes has been calculated on the basis of followup of 26 patients for as long as 517 days with measurements of: 1. The retention of 75Se in the whole body. 2. The retention of 75Se in the blood, liver, kidneys, ovaries, testicles, and hair. 3. The excretion of 75Se in urine and feces. Whole-body counting and profile scanning were done on the patients and samples of blood from different organs, urine, and feces were measured for radioactivity. The dose of radiation received was calculated for an average patient of 70 kg. These doses were found to be slightly higher than previously reported on a smaller number of patients and with a shorter follow-up. They were slightly lower than those from 75Se-methionine to the whole body but higher to the liver and kidneys. The margin of error in this investigation was estimated to be about 20% for the whole-body dose and probably higher for different organs, mostly due to the poorly known rate of retention of selenite in different organs.