Development of compact readout electronics and efficient maximum-likelihood position estimator for multi-anode-PMT scintillation cameras

In this study, a scintillation gamma camera applied to micro-SPECT is developed. The camera is composed of a NaI(Tl) scintillator, compact readout electronics and an efficient maximum-likelihood position estimator (MLPE) for a 64-anode PMT. The readout electronics consists of the symmetric charge division (SCD) circuits, the signal processing circuits and a multi-channel DAQ system to output 16 channel digital signals. Moreover, the MLPE is developed with the multivariate normal model and the truncated center-of-gravity combined with local directed search (TCOG-LDS) method to estimate the gamma-ray event position rapidly and accurately. To verify the feasibility of the proposed readout electronics and MLPE, simulation study and preliminary experiment for acquiring the mean detector response function (MDRF) of the gamma camera are performed. The simulated and preliminary experimental results show the TCOG-LDS method is faster than the exhaustive search by about 150 times and maintains the same position estimation accuracy. Furthermore, the integral uniformity (IU) of the proposed gamma camera is 43% and 26% in the useful field of view (UFOV) and the central field of view (CFOV) respectively in the simulation study. In the preliminary experiment, the IU of proposed gamma camera is 99.8% in both the UFOV and CFOV. Finally, probability matrices generated from the MDRF data are used to reassign counts in the flood image and in consequence improve the camera IU from 99.8% to 49.1%.