A SYSTEM TO OBTAIN RADIOTRACER UPTAKE DATA SIMULTANEOUSLY WITH NMR-SPECTRA IN A HIGH-FIELD MAGNET

Radiotracer techniques and nuclear magnetic resonance (NMR) spectrosco py are two complementary methods that are widely used to investigate c ardiac metabolism. We have now developed a novel gamma photon detector system that will operate within a nide-bore, 9.4 T magnet. With this detector in position it is possible to acquire radiotracer uptake data while simultaneously collecting NMR spectra. The advantages of this n ew system are firstly that it enables correlations between radiotracer and NMR data to be made on individual rat hearts, and secondly that i t allows the number of experiments required to obtain results of stati stical significance to be greatly decreased. The extension of our syst em, to one in which positron emission tomography (PET) and magnetic re sonance imaging (MRI) data are acquired simultaneously, clearly has en ormous clinical potential. The detector consists of a NaI(Tl) scintill ation crystal coupled to a magnetic field-insensitive photomultiplier tube by a 72.5 cm long, acrylic light pipe. This detector configuratio n satisfies the two, conflicting requirements of the crystal being nea r the sample, and thus in a high magnetic field, and the PMT being in a low magnetic field and thus far from the sample. The performance of the detector is not significantly altered by either the magnetic field or the collection of NMR data and, conversely, the performance of the NMR system is not affected by the presence of the detector. As expect ed, the light pipe causes a decrease in the amount of scintillation li ght reaching the photomultiplier tube; however, this does not constitu te a significant problem for the sensitivity of the complete detector system. In this paper we present the technical specifications of our n ew system together with what we believe are the first examples of simu ltaneously acquired NMR spectra and F-18-fluorodeoxyglucose ((18)FDG) uptake data, obtained from isolated, perfused rat hearts.