TRACER FLOWS AND DIFFICULT ORGANS

This paper describes a method for measuring tracer kinetics in organs which are larger than the field of view of a gamma camera, by performi ng initial dynamic studies on part of that organ, followed by a later study to determine the tracer content of the entire organ. Information is transferred from the measured data to 'absolute values' by means o f a calculated intermediate number which is called the 'MTBE' (mean ti me in blood, equivalent). Initial testing of the technique with methyl ene diphosphonate (MDP) bone studies produced tracer flow rates of 0.0 00366 s(-1) into bone and 0.001525 s(-1) into interstitial fluid in pa tients with no known bone disease. Patients with active Paget's diseas e of bone had higher bone inflow rates, and showed some improvement fo llowing therapy with either editronate or pamidronate. The method has the potential to be applied to other situations, particularly SPET, us ing SPET to calculate tracer content and converting the result to flow rates using the formula: Inflow rate = Content/MTBE.