Dosimetry of swallowed non absorbed 99mTc radiopharmaceuticals in pediatric patients.

A calculation is presented which derives the absorbed dose experienced by pediatric patients of different ages who swallow a non absorbable 99mTc compound. All previous models assume sudden movement of radionuclide from one compartment of the gastrointestinal tract to another. The present model is novel in considering continuous distal motion through the gut and so more closely approximates the physiologic situation. Published S values are used to derive absorbed doses. The resulting calculated absorbed doses are comparable to, or lower than, those previously published and these differences are most marked in the large gut, which remains the critical organ.