Radiation dose estimates for the carbon-14-labeled urea breath test

The use of the 14C-urea breath test for diagnosis of Helicobacter pylori infection in gastric mucosa has gained widespread acceptance and utilization. In order to obtain regulatory approval for this procedure, new dose estimates were required. Previous radiation dose equivalent estimates for males only were based upon data published in 1975 for bicarbonate metabolism. Since that time, calculational techniques for dose estimation have been significantly improved and the organ masses of Reference Man updated. We have calculated dose estimates for males and females who test positive (HP+) and negative (HP-) for gastric H. pylori infection. Our results indicate that the urinary bladder wall receives the highest absorbed dose in all four of the above subject populations (HP- males = 0.14 mGy/MBq; HP- females = 0.19 mGy/MBq; HP+ males = 0.10 mGy/MBq; HP+ females = 0.14 mGy/MBq). Gonadal absorbed doses were similar to those previously estimated (testes < 0.065 mGy/MBq and ovaries < 0.084 mGy/MBq, respectively).