Optimize position readout circuits in positron emission tomography front-end electronics

Most of the front-end position readout circuits in PET detectors originate from the Anger logic design. to order to simplify the PMT readout circuits, many different schemes of combining multiple PMTs with simplified (X^-, X⁺, Y^-, Y⁺) outputs have been investigated. Crystal irradiation image produced from eight-bit digitized (X^-, X⁺, Y^-, Y⁺) often shows noticeable artifacts. These artifacts are mainly caused by truncation and round-off errors, which occur in the irradiation image processes. To examine these errors, we applied the root-sum-square (RSS) analysis and the uniform distribution analysis methods. In addition, we studied the correspondent function of the event energy with image regions. It is demonstrated that energy non-uniformity could be introduced if signal gains in the front-end analog circuits were not adjusted properly. We also discussed how to judge balanced gains in the position circuits. In general, we aim at optimizing the front-end position readout circuits.