Dosimetry of leukocytes labeled with 99Tcm-albumin colloid

Biodistribution, kinetics and dosimetry of 9Tcm-albumin colloid labeled leukocytes (TAC-WBC) is described. A practical method of planar image data acquisition and processing is discussed. This method was used to obtain biodistribution data in 11 patients, two of whom were children. Dosimetry was calculated for fetuses, children and adults. The spleen is the critical organ, receiving 2.5 rad per 5 mCi procedure in adults and 3.6 rad per 2.15 mCi procedure in a 5-year-old child. These absorbed doses are about one-sixth of that absorbed from 111In-leukocytes procedures utilizing one-tenth the administered activity of TAC-WBC. The liver and red marrow are approximately equivalent secondary target organs, each receiving about 20% of the spleen dose. Fetal doses at any stage of gestation are similar, averaging about 14 mrad per mCi of TAC-WBC administered to the mother. The dosimetry of TAC-WBC is favorable enough to permit its use in children, adults and during pregnancy.