Internal radiation dose measurements in live experimental animals. II.

Abstract

Silver phosphate glass dosimeter rods were implanted in various portions of the digestive tract and the radiation dose was measured after ingestion of a known amount of yttrium-90. It was found that a state of diarrhea reduced the average radiation dose by a factor of from 2 to 4. In the constipated animal the dose was increased by a factor of from 3 to 7. Investigation was made to determine the role of various processes governing the radiation dose delivered to gastrointestinal mucosa. The total dose to a particular site along the intestinal tract was obtained by determination of the time integral of the radioactive concentration. Serial sacrifices were made at specific times after administration of the radioactivity. Calculations in this manner agreed exceptionally well with the doses that were measured by the glass dosimeter method. It is estimated that 4 microc and 17 microc of yttrium-90 for the dog and goat, respectively, will deliver a 300-mrad dose to the critical organ, the lower large intestine. The twelvefold average difference in dose between the diarrhea and constipation groups of dogs emphasizes the importance of the physical state of bowel passages upon the dose delivered to the critical organ.