scholarly journals Polychromatic Iterative Statistical Material Image Reconstruction for Photon-Counting Computed Tomography

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Thomas Weidinger ◽  
Thorsten M. Buzug ◽  
Thomas Flohr ◽  
Steffen Kappler ◽  
Karl Stierstorfer
Keyword(s):  
Computed Tomography ◽  
Probability Function ◽  
Photon Counting ◽  
Charge Sharing ◽  
Material Decomposition ◽  
Beam Hardening ◽  
Pulse Pileup ◽  
Local Approximations ◽  
Photon Counting Detectors ◽  
Image Pixels

This work proposes a dedicated statistical algorithm to perform a direct reconstruction of material-decomposed images from data acquired with photon-counting detectors (PCDs) in computed tomography. It is based on local approximations (surrogates) of the negative logarithmic Poisson probability function. Exploiting the convexity of this function allows for parallel updates of all image pixels. Parallel updates can compensate for the rather slow convergence that is intrinsic to statistical algorithms. We investigate the accuracy of the algorithm for ideal photon-counting detectors. Complementarily, we apply the algorithm to simulation data of a realistic PCD with its spectral resolution limited by K-escape, charge sharing, and pulse-pileup. For data from both an ideal and realistic PCD, the proposed algorithm is able to correct beam-hardening artifacts and quantitatively determine the material fractions of the chosen basis materials. Via regularization we were able to achieve a reduction of image noise for the realistic PCD that is up to 90% lower compared to material images form a linear, image-based material decomposition using FBP images. Additionally, we find a dependence of the algorithms convergence speed on the threshold selection within the PCD.

Virtual monochromatic imaging reduces beam hardening artefacts in cardiac interior photon counting computed tomography: a phantom study with cadaveric specimens

2021 ◽  
Author(s):  
Satu Irene Inkinen ◽  
Mikael Asko Kaarlo Juntunen ◽  
Juuso Heikki Jalmari Ketola ◽  
Kristiina Korhonen ◽  
Pasi Sepponen ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Coronary Artery ◽  
Ex Vivo ◽  
Cardiac Computed Tomography ◽  
Photon Counting ◽  
High Energy ◽  
Ct Imaging ◽  
Material Decomposition ◽  
Beam Hardening ◽  
Selection Of

Abstract In interior cardiac computed tomography (CT) imaging, the x-ray beam is collimated to a limited field-of-view covering the heart volume, which decreases the radiation exposure to surrounding tissues. Spectral CT enables the creation of virtual monochromatic images (VMIs) through a computational material decomposition process. This study investigates the utility of VMIs for beam hardening (BH) reduction in interior cardiac CT, and further, the suitability of VMIs for coronary artery calcium (CAC) scoring and volume assessment is studied using spectral photon counting detector CT (PCD-CT). Ex vivo coronary artery samples (N=18) were inserted in an epoxy rod phantom. The rod was scanned in the conventional CT geometry, and subsequently, the rod was positioned in a torso phantom and re-measured in the interior PCD-CT geometry. The total energy (TE) 10-100 keV reconstructions from PCD-CT were used as a reference. The low energy 10-60 keV and high energy 60-100 keV data were used to perform projection domain material decomposition to polymethyl methacrylate and calcium hydroxylapatite basis. The truncated basis-material sinograms were extended using the adaptive detruncation method. VMIs from 30-180 keV range were computed from the detruncated virtual monochromatic sinograms using filtered back projection. Detrending was applied as a post-processing method prior to CAC scoring. The results showed that BH artefacts from the exterior structures can be suppressed with high (≥100 keV) VMIs. With appropriate selection of the monoenergy (46 keV), the underestimation trend of CAC scores and volumes shown in Bland-Altman (BA) plots for TE interior PCD-CT was mitigated, as the BA slope values were -0.02 for the 46 keV VMI compared to -0.21 the conventional TE image. To conclude, spectral PCD-CT imaging using VMIs could be applied to reduce BH artefacts interior CT geometry, and further, optimal selection of VMI may improve the accuracy of CAC scoring assessment in interior PCD-CT.

TU-E-217BCD-09: The Feasibility of the Dual-Dictionary Method for Breast Computed Tomography Based on Photon-Counting Detectors

2012 ◽  
Vol 39 (6Part24) ◽  
pp. 3915-3915 ◽  
Author(s):  
B Zhao ◽  
H Ding ◽  
Y Lu ◽  
G Wang ◽  
J Zhao ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Photon Counting ◽  
Photon Counting Detectors ◽  
Breast Computed Tomography

scholarly journals CdTe Based Energy Resolving, X-ray Photon Counting Detector Performance Assessment: The Effects of Charge Sharing Correction Algorithm Choice

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6093
Author(s):  
Oliver L. P. Pickford Scienti ◽  
Jeffrey C. Bamber ◽  
Dimitra G. Darambara
Keyword(s):  
Detection Efficiency ◽  
Photon Counting ◽  
Charge Sharing ◽  
Correction Algorithm ◽  
Detector Performance ◽  
Photon Counting Detector ◽  
Photon Counting Detectors ◽  
The Difference ◽  
Pixel Pitch ◽  
Made In

Most modern energy resolving, photon counting detectors employ small (sub 1 mm) pixels for high spatial resolution and low per pixel count rate requirements. These small pixels can suffer from a range of charge sharing effects (CSEs) that degrade both spectral analysis and imaging metrics. A range of charge sharing correction algorithms (CSCAs) have been proposed and validated by different groups to reduce CSEs, however their performance is often compared solely to the same system when no such corrections are made. In this paper, a combination of Monte Carlo and finite element methods are used to compare six different CSCAs with the case where no CSCA is employed, with respect to four different metrics: absolute detection efficiency, photopeak detection efficiency, relative coincidence counts, and binned spectral efficiency. The performance of the various CSCAs is explored when running on systems with pixel pitches ranging from 100 µm to 600µm, in 50 µm increments, and fluxes from 106 to 108 photons mm−2 s−1 are considered. Novel mechanistic explanations for the difference in performance of the various CSCAs are proposed and supported. This work represents a subset of a larger project in which pixel pitch, thickness, flux, and CSCA are all varied systematically.

Sign in / Sign up

Export Citation Format

Share Document