本研究中，我們提出一應用在微型單光子電腦斷層掃描系統之閃爍晶石式伽瑪相機，此相機由NaI(Tl)閃爍晶石、多陽極光電倍增管讀出電路加上最大可能性位置估算法組成。 讀出電路部分包括陽極通道縮減電路、訊號處理電路和資料擷取系統輸出16通道的數位訊號給電腦做後續處理。此外，最大可能性位置估算法由多變數常態分佈模型建立，且利用截尾重心法加上局域方向導引式尋找法(T-COG+LDS)快速而準確的估算每筆伽瑪射線發生位置。在平均響應函數實驗中，我們使用TTL雷射模組並將雷射擴束成直徑18mm圓形光束去模擬伽瑪射線經過NaI(Tl)閃爍晶石後的光源分佈。 實驗結果T-COG+LDS方法比窮舉尋找法計算速度快了近150倍，並保有相同位置估算準確率，最後利用機率矩陣重新分配計數值使相機整體均勻度從99.8%下降至49.1%。 In this study, a scintillation gamma camera applied to micro-SPECT is constructed. The camera is composed of a NaI(Tl) scintillator, compact readout electronics for a multi-anode PMT and a maximum-likelihood position estimator (ML-PE). The readout electronics is consisted of the anodes channel reduction circuits, the signal processing circuits and a multi-channel DAQ system to output 16 channel digital signals to computer. Moreover, the MLPE is developed with the multivariate normal model and the truncated center-of-gravity combined with local directed search (T-COG+LDS) method to estimate the gamma-ray event position rapidly and accurately. In the MDRF (mean detector response function) experiment, we used a TTL controlled laser with an expended beam of 18 mm diameter to mimic the light distribution at the PMT entrance face after a gamma ray hits the NaI(Tl) scintillator. The experimental results showed that the T-COG+LDS method was faster than the exhaustive search by 150 times and maintained the same position estimation accuracy. Finally, we used the probability matrices to reassign counts and in consequence improved the camera integral uniformity from 99.8% down to 49.1%.
