Absorbed doses of radiation after an intravenous injection of N-13 ammonia in man: concise communication.

Using body distribution data with the MIRD tables and equations, the radiation dose delivered by an i.v. injection of N-13 ammonia has been calculated for several human organs. The liver and the urinary bladder wall receive 0.017 and 0.051 rad/mCi injected respectively; the latter can be reduced by early post-injection voiding. The brain-to-brain absorbed dose is 0.016 rad/mCi injected. The absorbed doses for the whole body, the red marrow, the ovaries, and the testes are, respectively, 0.0055, 0.0054, 0.0098, and 0.0010 rad/mCi injected. Severe liver disease is associated with a reduction in the fraction of the injected N-13 that is excreted in the urine, and thus causes a reduction in the absorbed dose to the urinary bladder wall from the bladder contents. Hepatomegaly increases the fraction of the N-13 ammonia trapped by the liver, and complicates calculation of the absorbed dose of radiation. These data should facilitate the evaluation of the risk from radiation absorption following i.v. injections of N-13 ammonia in humans.