MATERIALS AND METhODS

low uptake of radiolabeled antibodies in tumors, single photon emission computed tomography (SPECT) has be come an appropriate tool in tumor imaging (9,10). A sufficiently high activity must be administered to the pa tient to obtain good image statistics. Consequently, several normal tissues, e.g., bone marrow, liver and kidneys, may receive an undesirable radiation exposure, thus limiting the administered activity. Accurate dosimetric investiga tions are of the utmost importance in order to fulfill radiation protection requirements and to minimize radia tion burden to the patient (11). This is of special impor tance if radiolabeled tumor- and nontumor-specific anti bodies are used for screening tests, in pediatric nuclear medicine or volunteers in research. In this paper, the long-term biokinetics and biodistri bution of ' ‘‘In-labeledanti-CEA-F(ab')2BW43 1/3 1 frag ment were studied in normal rats. The biokinetics and tissue distribution from the animal model were scaled to man utilizing absorbed dose fractions compiled by the MIRD committee. Absorbed doses to humans were esti mated for ‘‘‘Inand for radionucide impurity of ‘l4mIn. The biodistribution results in the animals were compared to published human data, i.e., scintigramsand tissue biop sies from patients who received the same F(ab')2 fragment