A gamma tracking detector for nuclear medicine

The concept of tracking the interactions of a gamma ray through a solid state detector is being pursued by several groups in the nuclear physics community. Here the ability to rid the detectors of the escape suppression shields and decrease the Doppler broadening of the spectroscopic lines will enable new physics measurements. Our group has embarked upon a project to apply this technology to medical imaging. We report on the progress in developing a planar germanium detector with gamma ray tracking ability, for positron emission tomography (PET). The prototype detector is a planar high purity germanium unit with X-Y readout electrodes. Using digital signal processing the timing and depth of individual interactions are recorded for each gamma ray. Compton scattering information for some of the events can be used to reconstruct the angle of the gamma ray to the first interaction point. In a similar technique to the Compton camera, this information can be used to reduce random coincidence rates in the PET system and provide the possibility for highly efficient use of events in the tomography reconstruction.