Monte Carlo simulation of an amorphous selenium-based multi-layer photon-counting detector for SPECT applications

Sahar Adnani; Abdollah Pil-Ali; Christopher C. Scott; Karim S. Karim

doi:10.1117/12.2582325

15 February 2021 Monte Carlo simulation of an amorphous selenium-based multi-layer photon-counting detector for SPECT applications

Sahar Adnani, Abdollah Pil-Ali, Christopher C. Scott, Karim S. Karim

Author Affiliations +

Proceedings Volume 11595, Medical Imaging 2021: Physics of Medical Imaging; 1159515 (2021) https://doi.org/10.1117/12.2582325
Event: SPIE Medical Imaging, 2021, Online Only

Abstract

In this work, we have used Geant4 Monte Carlo simulations to evaluate the spatial resolution and detection efficiency metrics of an amorphous selenium (a-Se) photon-counting detector for high energy gamma-ray detection with 1mm and 50µm pixel pitches and a varying number of detector layers. A noiseless monochromatic particle gun with an energy of 140 keV is used to resemble the typical energy of single-photon emission computed tomography (SPECT). At high energies like 140 keV, a-Se detection efficiency significantly drops due to its absorption coefficient. By using this novel multilayer a-Se detector, the drop in detection efficiency can be compensated. The point spread function (PSF) is obtained by illuminating the detector with 106 photons. The modulation transfer function (MTF) is calculated from the one-dimensional integral of the PSF, known as line spread function (LSF), and is compared to the ideal pixel MTF. Spatial resolution is considered as the spatial frequency at which the MTF is equal to 0.5. The simulation results indicate that by increasing the number of layers, the MTF was degraded slightly due to Compton scattering, however, it did not degrade spatial resolution for the 1mm pixel size. At the same time, by using more layers, the detection efficiency is increased to 80% for 10 layers. This detection efficiency includes the noise counts (error counts) caused by Compton scattering. Leveraging the photon-counting energy threshold enables partial compensation for noise counts. Using an energy threshold of 110 keV results in 52% efficiency for 10 layers and reduces the noise counts significantly. This increase in detection efficiency along with the high intrinsic spatial resolution makes a-Se a cost-effective candidate for large area SPECT applications.

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Sahar Adnani, Abdollah Pil-Ali, Christopher C. Scott, and Karim S. Karim "Monte Carlo simulation of an amorphous selenium-based multi-layer photon-counting detector for SPECT applications", Proc. SPIE 11595, Medical Imaging 2021: Physics of Medical Imaging, 1159515 (15 February 2021); https://doi.org/10.1117/12.2582325

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