Characterization of TlBr Strip Detectors with Waveform Readouts

Single photon emission computed tomography (SPECT) is used to make a variety of clinical diagnoses. Recently there is an increased interest in SPECT systems with improved energy resolution to distinguish between multiple isotopes in alpha-emitting radio-nuclide therapy. Semiconductor detectors are ideal for this task as direct conversion of photon energy yields improved signal statistics. Both strip and pixel configurations can be optimized to meet spatial resolution requirements. Thallium bromide (TlBr) crystals have become of interest due to their high stopping power, large band-gap and ease of crystal purification. Since transport properties and stability has been improved it is timely to develop a complete understanding of TlBr and its best detector configurations. We have developed a time-dependent forward model for double-sided strip detectors. By sampling signal waveforms we have a tool for finding interaction depth and sub-pixel spatial resolution. Our work concludes by comparing simulation results to a TlBr 8x8 strip array developed by RMD. Our results show it may be possible to use "hit" strip waveforms to determine interaction depth. The waveform from the neighbor strips can contribute to sub-strip-pitch spatial resolution.