Effect of temperature on the stability and performance of an LSO-APD PET scanner

PET scanners with a large number of individual detectors require an equivalent number of electronics that will collect the detector signals and further process them. In the front end part, the detector is usually placed as close as possible to the preamplifier in order to avoid attenuation of the signal or unwanted stray capacitance. However, the power consumption of the preamplifier can cause heat transfer and consequently, gain drift to temperature sensitive photodetectors. Temperature measurements on the front end electronics of the MADPET-II small animal positron emission tomograph, when the power supply is turned on, have shown an increase of approximately 30degC in the area around the preamplifier and 10degC in the area around the APD-LSO detector with respect to room temperature. At the same time, energy spectra have been acquired for different count rates from which a significant drift of the photopeak (3.4% per degC) and a small increase of the mean energy resolution (3%) with increasing temperature has been observed. Thus, appropriate cooling of the system is required in order to achieve optimum and reproducible performance of the scanner