A study of the effects of strong magnetic fields on the image resolution of PET scanners

Very high resolution images can be achieved in small animal PET systems utilizing solid state silicon pad detectors. In such systems with sub-millimeter intrinsic resolutions, the range of the positron is becoming the dominant 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 ⁶⁸Ga and ^94mTc which are gaining importance in small animal studies, the width of the annihilation point distribution dominates the spatial resolution. This positron range effect can be reduced by embedding the field of view of the PET scanner in a strong magnetic field. In order to confirm this effect experimentally we have developed a high resolution PET instrument based on silicon pad detectors that can operate in a 7 T magnetic field. In this paper we present the preliminary results of a study of the effects of magnetic fields up to 7 T on PET image resolution for ²²Na and ⁶⁸Ga point sources.