A prototype high‐purity germanium detector system with fast photon‐counting circuitry for medical imaging

Abstract

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.

Performance characterization of a high-purity germanium detector for small-animal SPECT

“…These early efforts were impeded by limited computing power, cumbersome electronics and difficulties with detector fabrication. Additionally, bulky liquid nitrogen dewars were required to achieve the required operating temperatures [2]. High-purity germanium (HPGe) counting detectors are best known for their excellent energy resolution; however, double-sided strip detectors (DSSD) are also capable of providing good spatial resolution.…”

Dual-Modality Imaging: Combining Anatomy and Function

“…Their pioneering device used a single detector of high-purity germanium to acquire both CT and SPECT data (19)(20)(21). The difficulty of achieving an acceptable level of performance for both modalities led the group to explore a different design in which a clinical CT scanner was positioned in front of a SPECT camera (1).…”

Combining anatomy and function: the path to true image fusion

“…Early work by Hasegawa et al [6] and Lang et al [7] combined anatomical (CT) and functional imaging (SPECT) by using a single material, high-purity germanium, as the detector for both modalities. The X-ray CT images were, in addition, used to provide attenuation factors for correction of the SPECT data [8].…”