STUDIES OF SKELETAL TRACER KINETICS .3. TC-99M(SN)METHYLENEDIPHOSPHONATE UPTAKE IN THE CANINE TIBIA AS A FUNCTION OF BLOOD-FLOW

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 20  (12) , 1257-1261
Abstract
Dogs [14] were used to study the effect of changes in bone blood flow on the tibial uptake of the skeletal tracer 99mTc(Sn)methylenediphosphonate (99mTc MDP). Aortic blood was diverted through a pulsatile-flow pump to monitor and control femoral arterial blood flow. Tibial nutrient perfusion, measured with labeled microspheres, paralleled the changes in arterial flow. Increments in bone blood flow up to 4 .times. normal produced only minimal augmentation of 99mTc MDP uptake (mean = 33%), a markedly nonproportional relationship. The data points clustered about a predicted curve produced by perturbing the rate constants of a 7-compartment model obtained in normal dogs. Apparently bone uptake of 99mTc MDP is diffusion-limited. Apparently, the method used for many years for estimating bone blood flow, the so-called skeletal tracer clearance technique, may not be valid. Nerve section, performed in 14 other dogs, augmented 99mTc MDP uptake by about 50% at supranormal flows, suggesting a parallel-flow model of the microcirculation in bone, under sympathetic control. Such a model satisfactorily explains many scintigraphic findings in disease states.