Count statistics of nonparalyzable photon‐counting detectors with nonzero pulse length

Grönberg, Fredrik; Danielsson, Mats; Sjölin, Martin

doi:10.1002/mp.13063

Cited by 10 publications

(9 citation statements)

References 24 publications

(45 reference statements)

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“…where λ is the input count rate and τ is the dead time. The mean value and the variance of the output count rate for a non-paralyzable detector with non-zero pulse length, the so-called semi-nonparalyzable (SNP) model (Xu et al 2011), have been derived analytically (Grönberg et al 2018) and are given by…”

Section: Statistical Degradationmentioning

confidence: 99%

Photon-counting x-ray detectors for CT

2021

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The introduction of photon-counting detectors is expected to be the next major breakthrough in clinical x-ray computed tomography (CT). During the last decade, there has been considerable research activity in the field of photon-counting CT, in terms of both hardware development and theoretical understanding of the factors affecting image quality. In this article, we review the recent progress in this field with the intent of highlighting the relationship between detector design considerations and the resulting image quality. We discuss detector design choices such as converter material, pixel size, and readout electronics design, and then elucidate their impact on detector performance in terms of dose efficiency, spatial resolution, and energy resolution. Furthermore, we give an overview of data processing, reconstruction methods and metrics of imaging performance; outline clinical applications; and discuss potential future developments.

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Section: Statistical Degradationmentioning

confidence: 99%

Photon-counting x-ray detectors for CT

2021

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“…These models can be seen as extreme cases of real counting systems, and present the advantage of disposing of exact analytical formulas describing the mean of the measured counts C out and their variance as a function of the input flux, as long as the input events are Poisson distributed. Other more elaborate models have been studied in the literature [4,5] but with no exact analytical expressions for their variance, and therefore have not been used in the study.…”

Section: Deadtime and Pile-up Modelsmentioning

confidence: 99%

Degradation of signal-to-noise ratio in counting detectors due to pile-up effects

Magalhães

Fajardo

2023

J. Inst.

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This work proposes a methodology to quantify how the non-linearity of counting detectors due to pulse pile-up effects impacts detrimentally the signal-to-noise ratio of measurements and the resulting DQE. The method is presented from a conceptual point of view, justified and validated by both analytical and Monte Carlo methods applied to the ideal theoretical pile-up models usually discussed in the literature. Although the motivation of this work is the application to photon counting X-ray detectors, the study may be relevant for other type of particle or radiation detection systems operating at high count rate regimes, when pile-up is not negligible. The high count rates can be managed in actual experiments by implementing pile-up compensation methods in the detector readout chain, by applying correction algorithms to the measured data or by a combination of both. What has been less discussed in literature is the impact of those pile-up compensation techniques on the final statistical properties of the resulting data, and the proposed method can be potentially used for that purpose. The application of the method to more realistic systems is illustrated with an example of a simulated 2D X-ray photon counting detector that includes all the primary physical effects and the full readout chain.

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“…However, since the problem of having too many incident photons during the same time window requires a very fast detector, we expect problems with pileup to be smaller compared to in current detectors. Regardless of this, pulse pileup can be included in the likelihood functions by incorporating a pileup model, see e.g., Grönberg et al 17 This will mainly result in using fluxdependent spectral response functions that relate the deposited energy to the incident photon energy to include spectral distortion. Further, the assumed count statistics will also be affected since pulse pileup results in non-Poissonian count statistics at high incident fluxes.…”

Section: Interaction Chainmentioning

confidence: 99%

Compton coincidence in silicon photon-counting CT detectors

2022

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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 −0.07 AE 0.03 keV and an RMS error of 3.36 AE 0.02 keV 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 −2 AE 11 μm in x direction and 7 AE 11 μm in y direction. Corresponding RMS errors of 1.09 AE 0.01 and 1.10 AE 0.01 mm were achieved in x and y, respectively. Conclusions:The presented results show the potential of using probability-based methods to improve the performance of silicon detectors for CT.

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Count statistics of nonparalyzable photon‐counting detectors with nonzero pulse length

Cited by 10 publications

References 24 publications

Photon-counting x-ray detectors for CT

Photon-counting x-ray detectors for CT

Degradation of signal-to-noise ratio in counting detectors due to pile-up effects

Compton coincidence in silicon photon-counting CT detectors

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