Characterization of a high-purity germanium detector for small-animal SPECT

Abstract

We present an initial evaluation of a mechanically-cooled, high-purity germanium double-sided strip detector as a potential gamma camera for small-animal SPECT. It is 90 mm in diameter and 10 mm thick with two sets of 16 orthogonal strips that have a 4.5 mm width with a 5 mm pitch. We found an energy resolution of 0.96% at 140 keV, an intrinsic efficiency of 43.3% at 122 keV and a FWHM spatial resolution of approximately 1.5 mm. We demonstrated depth-of-interaction estimation capability through comparison of pinhole acquisitions with a point source on and off axis. Finally, a flood-corrected-flood image exhibited a strip-level uniformity of less than 1%. This high-purity germanium offers many desirable properties for small-animal SPECT.

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

“…This study investigates our system's performance on several detector properties relevant to biomedical imaging. The excellent energy resolution of our system is on par with other similar HPGe systems, including our previously characterized system in [7], which had 0.96% compared to this system's 0.92% at 140 keV. The demonstrated depth-of-interaction estimation capabilities will mitigate blurring from parallax when pinhole collimation is utilized.…”

“…This specially-designed DSSD was fabricated from a germanium crystal 90 mm in diameter and 10 mm thick and consists of orthogonal sets of 16 strips on each side that are 4.75-mm wide with a 5-mm strip pitch and has a total active area of 55.1 cm 2 • The system is similar to that in [7] except for three main changes: the gap between strips has been reduced from 0.5 mm to 0.25 mm to help increase detection efficiency, the mechanical cooler and signal processing electronics have been reconfigured and relocated to facilitate easier mounting of the system on a rotating gantry, and the face of the detector has been moved to be only 6 mm away from the entrance window (as opposed to 2.9 cm) to allow for additional magnification options when a pinhole is utilized. Fig.…”

“…We currently are investigating the potential to use HPGe systems for small-animal single-photon emission computed tomography (SPECT), and have previously published characterization results of a similar system [7] that was not specifically designed for small-animal imaging. This paper aims to characterize the properties of a new, specially designed detector that are relevant to small-animal SPECT imaging including: energy resolution at relevant energies, detection efficiency, intrinsic spatial resolution, depth-of interaction estimation capabilities, scatter rejection and uniformity.…”

Inter-electrode charge collection in high-purity germanium detectors with amorphous semiconductor contacts

“…The Nuclear Compton Telescope (NCT) [3], Gamma-ray Imager/Polarimeter for Solar Flares (GRIPS) [4], and SmartPET [5] systems are examples of HPGe detectors utilizing position sensitivity for Compton imaging. Other applications in nuclear safeguards [6], medical imaging [7], and basic science [8,9] also take advantage of the simultaneous high energy resolution and imaging properties of segmented HPGe detectors.…”

“…Amorphous semiconductor contacts have been used to create position-sensitive detectors for x-ray and gamma-ray imaging [16,[19][20][21][22], applied to Li-drifted Si detectors [23,24], shown to be appropriate for thin entrance window applications [16,25], used to create very fine contact segmentation [9], and enabled unique detector configurations such as field shaping [21,22] and proximity electrode signal readout [26,27]. HPGe detectors with amorphous semiconductor contacts have been successfully used or are being developed for a wide variety of application areas including space science [3,[28][29][30][31][32]4], material science [9], nuclear and particle physics [8,33,34] medical imaging [7,35], nuclear nonproliferation and homeland security [6,[36][37][38], and environmental remediation [39].…”