Measurement of coincidence timing resolution with CdTe detectors

The coincidence timing resolution is a critical performance parameter to determine if direct gamma-ray detection by semiconductor detector materials such as CdTe or CdZnTe may be suitable for use in positron emission tomography (PET) systems. We report experimental results of the coincidence timing resolution measured with a pair of 2×2×10 mm³ CdTe detectors irradiated by 511 keV gamma rays under conditions that allow good timing resolution and good energy resolution to be obtained simultaneously. The measured coincidence time resolutions ranged from 14 ns (350 keV lower energy threshold) to 24 ns (100 keV lower energy threshold). We also found that the coincidence timing resolution was proportional to the signal rise time, and that both of these were proportional to the electron transit time.