A NEW SCALABLE MODULAR DATA-ACQUISITION SYSTEM FOR SPECT (PET)

We describe a modular decentralized data acquisition system that conti nuously samples shaped PMT pulses from a SPECT detector. The pulse wav eform data are used by signal processors to accurately reconstruct amp litude and time for each scintillation event. Data acquisition for a P MT channel is triggered in two alternative ways, either when its own s ignal exceeds a selected digital threshold, or when it receives a trig ger pulse from one of its neighboring PMTs. The triggered region is re stricted to seven, thirteen or nineteen neighboring PMT channels. Each acquisition module supports three PMT channels and connects to all ot her modules and a reconstruction computer via Firewire to cover the 72 channels in the Stockholm University/Karolinska Hospital cylindrical SPECT camera.