Development of an instrument for time–activity curve measurements during PET imaging of rodents

Molecular imaging using PET in small rodents requires commonly the knowledge of the input function of the tracer (quantitative and kinetic studies of the metabolism, development of new drugs or new tracers, etc.). In this paper, we report the status and the performances of the prototype of a counting system that is under development at DAPNIAa in collaboration with SHFJb. The detection device is made of silicon diodes of 0.3 mm thickness proper to measure the positrons emitted by the radiotracer contained in arterial blood flowing in a thin-wall microtube. Such diodes are poorly efficient for the 511 keV gammas from the rodent and thus require a rather light lead shielding and allow operating very close by to the animal. The detectors, the front-end electronics (for signal preamplification, shaping, and discrimination) and the acquisition circuits are mounted on a single card. The device is connected directly to a portable computer via an USB port. design provides a compact, rugged and portable device for working close to a small animal PET camera. Preliminary results show the performances of this counting system with 18F solution and a time–activity curve for FDG blood samples (with ∣∼30 μL/samples) from a rat.