A model for local accumulation of bone imaging radiopharmaceuticals.

A simple models, having phenomenological parameters as variables, is developed for predicting local radioactive tracer accumulation in bone. Blood delivering tracer to one gram of bone is treated as a compartment separate from the remainder of the circulation in order to observe the effects produced by variations in both bone flow and barrier permeability. Kinetic curves derived by analog computer were obtained for normal and perturbed values of the parameters for F-18 and Ca-47 in a segment of rabbit bone. Apparent confirmation of the predicted influence of decreased blood flow on F-18 deposition was obtained by measuring bone uptake following constriction of the right femoral artery in five rabbits. Such models may prove useful in explaining variations in uptake for different agents, in selecting imaging times, and in correlating uptake patterns with disease.