Photon-counting CT review

Flohr, Thomas; Petersilka, Martin; Henning, André; Ulzheimer, Stefan; Ferda, Jiří; Schmidt, Bernhard

doi:10.1016/j.ejmp.2020.10.030

Cited by 309 publications

(255 citation statements)

References 74 publications

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“…Post-processing with PCD-CT behaves differently compared EID-CT [ 11 ]. Due to the increased weighting of low energy x-ray photons in PCD-CT compared to EID-CT, T3D image reconstructions—providing an equivalent to conventional polychromatic 120 kV reconstructions—do not result in attenuation identical to 120 kV on EID-CT. With PCD-CT, the new standard for image post-processing is VMI.…”

Section: Discussionmentioning

confidence: 99%

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Coronary Calcium Scoring with First Generation Dual-Source Photon-Counting CT—First Evidence from Phantom and In-Vivo Scans

et al. 2021

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We evaluated the accuracy of coronary artery calcium (CAC) scoring on a dual-source photon-counting detector CT (PCD-CT). An anthropomorphic chest phantom underwent ECG-gated sequential scanning on a PCD-CT at 120 kV with four radiation dose levels (CTDIvol, 2.0–8.6 mGy). Polychromatic images at 120 kV (T3D) and virtual monoenergetic images (VMI), from 60 to 75 keV without quantum iterative reconstruction (no QIR) and QIR strength levels 1–4, were reconstructed. For reference, the same phantom was scanned on a conventional energy-integrating detector CT (120 kV; filtered back projection) at identical radiation doses. CAC scoring in 20 patients with PCD-CT (120 kV; no QIR and QIR 1–4) were included. In the phantom, there were no differences between CAC scores of different radiation doses (all, p > 0.05). Images with 70 keV, no QIR (CAC score, 649); 65 keV, QIR 3 (656); 65 keV; QIR4 (648) and T3D, QIR4 (656) showed a <1% deviation to the reference (653). CAC scores significantly decreased at increasing QIR levels (all, p < 0.001) and for each 5 keV-increase (all, p < 0.001). Patient data (median CAC score: 86 [inter-quartile range: 38–978] at 70 keV) confirmed relationships and differences between reconstructions from the phantom. First phantom and in-vivo experience with a clinical dual-source PCD-CT system shows accurate CAC scoring with VMI reconstructions at different radiation dose levels.

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Section: Discussionmentioning

confidence: 99%

“…Compared to EID-CT, photon-counting detector CT (PCD-CT) represents a fundamentally different approach for CT imaging [ 11 , 12 , 13 ]. Photon-counting detectors count the number of incoming photons and the electronic signal is proportional to the deposited energy of each photon [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Coronary Calcium Scoring with First Generation Dual-Source Photon-Counting CT—First Evidence from Phantom and In-Vivo Scans

et al. 2021

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“…This effect is called polarization and also can lead to ICC. 34,38 Polarization might cause noticeable ring artifacts in the reconstructed images at higher photon fluxes, 32 and also rapid decrease in signal pulses above a definite high flux rate. 39 In the correction algorithm, using the simulated detector response matrix the distorted spectrum is first corrected for the flux-independent effects, such as charge sharing, WP cross talk, X-ray fluorescence (escape peaks), Compton scattering and electronic noise.…”

Section: The Detector and Data Correction For Spectral Distortionmentioning

confidence: 99%

The significance of the spectral correction of photon counting detector response in material classification from spectral x-ray CT

Jumanazarov

Koo

Poulsen

et al. 2021

Quantum Optics and Photon Counting 2021

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Photon counting imaging detectors (PCD) has paved the way for the emergence of Spectral X-ray Computed Tomography (SCT), which simultaneously measures a material's linear attenuation coefficient (LAC) at multiple energies defined by the energy thresholds. In previous work SCT data was analysed with the SIMCAD method for material classifications. The method measures system-independent material properties such as electron density, ρ e and effective atomic number, Z eff to identify materials in security applications. The method employs a spectral correction algorithm that reduce the primary spectral distortions from the raw data that arise from the detector response: charge sharing and weighting potential cross-talk, fluorescence radiation, scattering radiation, pulse pile up and incomplete charge collection. In this work, using real experimental data we analyze the influence of the spectral correction on material classification performance in security applications. We use a vectorial total variation (L ∞ -VTV) as a convex regularizer for image reconstruction of the spectral sinogram. This reconstruction algorithm employs a L ∞ norm to penalize the violation of the inter energy bin dependency, resulting in strong coupling among energy bins. Due to the strong inter-bin correlation, L ∞ -VTV leads to noticeably better performance compared to bin-by-bin reconstructions including SIRT and total variation (TV) reconstruction algorithms. The image quality was evaluated with the correlation coefficient that is computed relative to ground-truth images. A positive weighting parameter defines the strength of the L ∞ -VTV regularization term and thus controls the trade-off between a good match to spectral sinogram data and a smooth reconstruction in both the spatial and spectral dimension. The classification accuracy both for raw and corrected data is analyzed over a set of weighting parameters. For material classification, we used 20 different materials for calibrating the SIMCAD method and 15 additional materials in the range of 6 ≤ Z eff ≤ 15 for evaluating the classification performance. We show that the correction algorithm accurately reconstructs the measured attenuation curve, and thus gives higher detection rates. We show that using the spectral correction leads to an accuracy increase of 1.6 and 3.8 times in estimating ρ e and Z eff , respectively.

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“…The separation layer (about 0.1 mm) needed in scintillator-based detectors design reduces the dose efficiency due to the layer's absorption. As the layer width cannot be reduced, decreasing the size of the scintillators will reduce the geometric efficiency, limiting the achievable spatial resolution of scintillator-based detectors [99]. Instead, the geometrical dose efficiency of a PCD is only reduced by the unavoidable anti-scatter collimator blades or grids.…”

Section: Direct Ct Detectorsmentioning

confidence: 99%

The Core of Medical Imaging: State of the Art and Perspectives on the Detectors

et al. 2021

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In this review, the roles of detectors in various medical imaging techniques were described. Ultrasound, optical (near-infrared spectroscopy and optical coherence tomography) and thermal imaging, magnetic resonance imaging, computed tomography, single-photon emission tomography, positron emission tomography were the imaging modalities considered. For each methodology, the state of the art of detectors mainly used in the systems was described, emphasizing new technologies applied.

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Photon-counting CT review

Cited by 309 publications

References 74 publications

Coronary Calcium Scoring with First Generation Dual-Source Photon-Counting CT—First Evidence from Phantom and In-Vivo Scans

Coronary Calcium Scoring with First Generation Dual-Source Photon-Counting CT—First Evidence from Phantom and In-Vivo Scans

The significance of the spectral correction of photon counting detector response in material classification from spectral x-ray CT

The Core of Medical Imaging: State of the Art and Perspectives on the Detectors

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