Very High Resolution Small Animal PET in Strong Magnetic Fields

Very high resolution images can be achieved in small animal PET systems utilizing solid state silicon detectors (Compton PET). In such systems with sub-millimeter intrinsic resolutions, the range of the positron is the largest contribution to image blur. The size of the positron range effect depends on the initial positron energy and hence the radioactive tracer used. For higher energy positron emitters, such as I-124 and Tc-94m which are gaining importance in small animal studies, the variation of the annihilation point dominates the spatial resolution. It has been suggested that this positron range effect can be reduced by embedding the PET field of view in a strong magnetic field. Conventional PET systems using scintillators and photomultiplier tubes require extensive modifications to operate in magnet fields; however, our silicon detector based system can operate in magnetic fields with minimal modifications. In this paper we present a progress report of embedding our small animal PET test-bench in magnetic fields up to 7 Tesla.