Performance 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 4.75 mm width with a 5 mm pitch. A sub-strip interpolation method is used to bin the data at a pixel size of 0.53mm x 0.53mm, while it is also possible to estimate the depth of interaction based on CFD time differences between the anode and cathode. The system has an energy resolution of 0.92% at 140 keY and an intrinsic efficiency of 55.40% at 122 keY.Simulations suggest that increases in the efficiency should be possible by altering signal processing to include Compton events in which charge is collected on more than one strip. Integral uniformity in the central field of view for strips was found to be less than 1 % in a flood-corrected flood while pixel-level uniformity was 2.98%. Due to the excellent energy resolution, the presence of a scattering medium did not greatly alter the FWHM or FWTM of a pinhole projection when compared to an acquisition without a scattering medium. This high-purity germanium system offers many desirable properties for small animal SPECT.

Molecular Breast Imaging Using Synthetic Projections From High-Purity Germanium Detectors: A Simulation Study

“…1.2 × 10 6 total detector voxels comprise each HPGe detector. A fixed ER of 1.0% FWHM at 140 keV and a lateral detector resolution of 1.5 mm FWHM were modeled based on measurements with our benchtop detector [20]. HPGe has an attenuation coefficient of 0.72 cm −1 at 140 keV, corresponding to an absorption efficiency of 51% in 10-mm thick HPGe cameras.…”

“…Recent technological advances have given rise to compact, mechanically-cooled HPGe gamma cameras that do not require bulky liquid nitrogen dewars. We have worked with an HPGe detector with a 8-cm diameter and of 10-mm thickness that offers ~1% ER at 140 keV and ~1.5 mm intrinsic spatial resolution in all three dimensions [20]. While this particular detector does not have a sufficiently large active area for MBI, herein, we investigate whether an HPGe detector of this type might offer some benefits for breast imaging.…”

Development of a Germanium Small-Animal SPECT System

“…Pixel size when using the interpolation method is 0.53 mm × 0.53 mm. This system also provides an estimate of the depth of interaction based on the difference between the measured rise times of the signals collected on the anode and cathode [17, 19]. A summary of the detector properties determined in [17] is shown in Table I.…”

“…This system also provides an estimate of the depth of interaction based on the difference between the measured rise times of the signals collected on the anode and cathode [17, 19]. A summary of the detector properties determined in [17] is shown in Table I. The detector uniformity was determined according to the NEMA standards [20] as described in [17].…”

Simulation of the effects of multiplexing in multi-pinhole SPECT using stacked Si-HPGe detectors

“…are currently developing for single photon emission computed tomography (SPECT) imaging [3], but due to the limited size of the HPGe detector, in order to achieve reasonable magnification with multiple pinholes, projections on the HPGe are likely to have some amount of multiplexing. This project examines, in simulation, whether the addition of a silicon detector with low-multiplexed projections stacked with an HPGe detector with highly-multiplexed projections will improve image quality.…”