Abstract
Purpose: Compton interactions amount to a significant fraction of the registered counts in a silicon detector. In a Compton interaction, only a part of the photon energy is deposited and a single incident photon can result in multiple counts unless tungsten shielding is used. Deep silicon has proved to be a competitive material for photon-counting CT detectors, but to improve the performance further, one possibility is to use coincidence techniques to identify Compton-scattered photons and reconstruct their incident energies. Approach: In a detector with no tungsten shielding, incident photons can interact through a series of interactions. Based on the position and energy of each interaction, probability-based methods can be used to estimate the incident photon energy. Here, we present a maximum likelihood estimation framework along with an alternative method to estimate the incident photon energy and position in a silicon detector. Results: Assuming one incident photon per time frame, we show that the incident photon energy can be estimated with a mean error of and an RMS error of for a realistic case in which we assume a detector with limited energy and spatial resolution. The interaction position was estimated with a mean error of in direction and in direction. Corresponding RMS errors of and were achieved in and , respectively. Conclusions: The presented results show the potential of using probability-based methods to improve the performance of silicon detectors for CT.
Highlights
Photon-counting spectral detectors are emerging and are predicted to replace scintillators in computed tomography (CT)
For applications in CT, one research focus has been on cadmium-based detectors: cadmium telluride (CdTe) or cadmium zinc telluride (CZT), whereas another research focus has been on silicon-based detectors, which are currently being evaluated in prototype systems in the clinic
We propose using a detector with similar spatial resolution to estimate the incident photon energy and position using a maximum likelihood approach based on Compton scattering
Summary
Photon-counting spectral detectors are emerging and are predicted to replace scintillators in computed tomography (CT). Contrary to conventional CT using energy-integrating detectors, photon-counting detectors (PCDs) are able to register the energy of each interacting photon. The energy information obtained with a PCD can be used for improved spectral imaging such as energy-weighting or material basis decomposition in which tissue-specific images can be created. Since PCDs are based on semiconductor materials, they are associated with a lower noise and a higher spatial resolution.[1,2,3]. For applications in CT, one research focus has been on cadmium-based detectors: cadmium telluride (CdTe) or cadmium zinc telluride (CZT), whereas another research focus has been on silicon-based detectors, which are currently being evaluated in prototype systems in the clinic. We will investigate possible further developments on deep silicon detectors
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