Description of a multicompartmental model of the biodistribution of 111In-DTPA-D-Phe-1-octreotide in human.

ABSTRACT

The aim of this study was to use compartmental analysis as a theoretical tool to provide quantitative and unitary data for a more precise determination of 111In-OCT concentrations in a tumour site and various body organs. Five subjects (3 male and 2 female) with neoplasias were studied. Structural and parametric identification of the model was based on the plasma, urine, total body and ROI (soft tissue, spleen, kidney and tumour) activity values. The model was of the mammillary type with 5 compartments (blood, soft tissue, spleen, kidneys and urine) for the 4 patients with a negative scintiscan and 6 (blood, soft tissue, spleen, kidneys, urine and tumour) for the adenocarcinoma patient. Numerical constants were determined by running a best-fit procedure with the MINUIT minimisation program (CERN library) using a microVAX 3800 computer. The reliability of the models was also tested. 111In-OCT accumulates in the kidneys and spleen, from which it is slowly released into the blood. Elimination is via the urine at first rapidly, then more slowly. The maximum concentration in the tumour compartment is reached at 12-14 hours and remains almost constant.