An investigation of a double-tracer technique for positron computerized tomography.

We describe a double-tracer technique for positron computed tomography (PCT) that utilizes the differences in physical decay rates to distinguish between two positron emitters. The technique is applied to PCT studies on phantoms (a) to separate two tracers with different half-lives, and (b) to measure simultaneously the attenuation coefficients and the tracer concentrations in a phantom. Results from these experiments are encouraging, but they also reveal a major limitation of the technique, namely, noise enhancement that is related to the relative half-lives of the two tracers and the time duration of the PCT scans, as well as to the relative concentrations of the two tracers. If these parameters are carefully selected, the double-tracer technique will have high potential for examining simultaneously two different biological processes with PCT and for measuring tracer concentrations and attenuation correction factors at the same time.