Hasegawa B H, Stebler B, Rutt B K, Martinez A, Gingold E L, Barker C S, Faulkner K G, Cann C E, Boyd D P
University of California San Francisco, Department of Radiology, UCSF Physics Research Laboratory 94080.
Med Phys. 1991 Sep-Oct;18(5):900-9. doi: 10.1118/1.596606.
A data-acquisition system designed for x-ray medical imaging utilizes a segmented high-purity germanium (HPGe) detector array with 2-mm wide and 6-mm thick elements. The detectors are contained within a liquid-nitrogen cryostat designed to minimize heat losses. The 50-ns pulse-shaping time of the preamplifier electronics is selected as the shortest time constant compatible with the 50-ns charge collection time of the detector. This provides the detection system with the fastest count-rate capabilities and immunity from microphonics, with moderate energy resolution performance. A theoretical analysis of the preamplifier electronics shows that its noise performance is limited primarily by its input capacitance, and is independent of detector leakage current up to approximately 100 nA. The system experimentally demonstrates count rates exceeding 1 million counts per second per element with an energy resolution of 7 keV for the 60-keV gamma ray photon from 241Am. The results demonstrate the performance of a data acquisition system utilizing HPGe detector systems which would be suitable for dual-energy imaging as well as systems offering simultaneous x-ray transmission and radionuclide emission imaging.
一种为X射线医学成像设计的数据采集系统，采用了由宽2毫米、厚6毫米的元件组成的分段式高纯度锗（HPGe）探测器阵列。探测器置于一个旨在尽量减少热损失的液氮低温恒温器内。前置放大器电子设备的50纳秒脉冲整形时间被选为与探测器50纳秒电荷收集时间兼容的最短时间常数。这为检测系统提供了最快的计数率能力和抗颤噪性能，同时具备适度的能量分辨率性能。对前置放大器电子设备的理论分析表明，其噪声性能主要受其输入电容限制，并且在探测器漏电流高达约100纳安时与漏电流无关。该系统通过实验证明，对于来自241Am的60千电子伏特伽马射线光子，每个元件的计数率超过每秒100万次，能量分辨率为7千电子伏特。结果展示了利用HPGe探测器系统的数据采集系统的性能，该系统适用于双能成像以及提供同步X射线透射和放射性核素发射成像的系统。
