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.

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.

scholarly journals Appropriate utilization of cardiac computed tomography for the assessment of stable coronary artery disease

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Michael Hammer ◽  
Muhtashim Mian ◽  
Levi Elhadad ◽  
Mary Li ◽  
Idan Roifman
Keyword(s):  
Computed Tomography ◽  
Coronary Artery Disease ◽  
Coronary Artery ◽  
Cardiac Imaging ◽  
Cardiac Computed Tomography ◽  
The United States ◽  
Appropriate Use ◽  
Potential Cost ◽  
Cardiac Computed Tomography Angiography ◽  
Artery Disease

Abstract Background Appropriate use criteria (AUC) have been developed in response to growth in cardiac imaging utilization and concern regarding associated costs. Cardiac computed tomography angiography (CCTA) has emerged as an important modality in the evaluation of coronary artery disease, however its appropriate utilization in actual practice is uncertain. Our objective was to determine the appropriate utilization of CCTA in a large quaternary care institution and to compare appropriate utilization pre and post publication of the 2013 AUC guidelines. We hypothesized that the proportion of appropriate CCTA utilization will be similar to those of other comparable cardiac imaging modalities and that there would be a significant increase in appropriate use post AUC publication. Methods We employed a retrospective cohort study design of 2577 consecutive patients undergoing CCTA between January 1, 2012 and December 30, 2016. An appropriateness category was assigned for each CCTA. Appropriateness classifications were compared pre- and post- AUC publication via the chi-square test. Results Overall, 83.5% of CCTAs were deemed to be appropriate based on the AUC. Before the AUC publication, 75.0% of CCTAs were classified as appropriate whereas after the AUC publication, 88.0% were classified as appropriate (p < 0.001). The increase in appropriate utilization, when extrapolated to the Medicare population of the United States, was associated with potential cost savings of approximately $57 million per year. Conclusions We report a high rate of appropriate use of CCTA and a significant increase in the proportion of CCTAs classified as appropriate after the AUC publication.

Abstract 11726: Novel Non-Invasive Method to Estimate Myocardial Mass at Risk Calculated From Cardiac Computed Tomography Data: Validation Study Using Angiographic Myocardial Jeopardy Scores in Patients With Single Vessel Disease

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Seiko IDE ◽  
Satoru Sumitsuji ◽  
Kensuke Yokoi ◽  
Masatoki Yoshida ◽  
Isamu Mizote ◽  
...  
Keyword(s):  
Computed Tomography ◽  
At Risk ◽  
Heart Disease ◽  
Coronary Artery ◽  
Cardiac Computed Tomography ◽  
Myocardial Mass ◽  
Non Invasive ◽  
Vessel Disease ◽  
Single Vessel ◽  
Single Vessel Disease

Background: The myocardial mass at risk (MMAR), representing volume of myocardium distal to culprit lesion, is one of important factors for predicting adverse cardiac event in ischemic heart disease. However, current non-invasive cardiac imaging fails to quantify MMAR in patients with stable coronary artery disease. We have developed a new software calculating MMAR of any designated coronary artery by reconstructing the 3-dimensional-volume-data of cardiac computed tomography (CCT). The novel index, ratio of MMAR to whole left ventricular volume (%LV-MMAR), calculated with this software would be appealing to obtain MMAR objectively. This study aims to compare the %LV-MMAR with Bypass Angioplasty Revascularization Investigation (BARI) and modified Albert Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) scores, both of which are invasive angiographic methods widely used to estimate MMAR, in patients with single-vessel disease. Methods: Between April 2008 and March 2014, patients suspected of effort angina pectoris without history of previous myocardial infarction were assessed with CCT and invasive coronary angiography. Of those, 48 patients who were revealed single-vessel disease (left anterior descending artery (LAD): n=22, left circumflex artery (LCX): n=11 and right coronary artery (RCA): n=15) were included in this study. %LV-MMAR was calculated on the software. BARI and modified APPROACH score were calculated and compared with %LV-MMAR. Results: Mean %LV-MMAR was 27.6 [18.2-37.1] %. BARI and APPROACH scores showed a significant correlation (r=0.92, p<0.0001). Also, a significant correlation was observed between %LV-MMAR versus BARI and %LV-MMAR versus APPROACH (r=0.95, p<0.0001 and r=0.9, p<0.0001, respectively). %LV-MMAR showed significant correlation with BARI and APPROACH scores in all vessels; LAD (r=0.95, p<0.0001 and r=0.91, p<0.0001, respectively), LCX (r=0.91, p=0.0001 and r=0.83, p=0.0002, respectively) and RCA (r=0.92, p<0.0001 and r=0.85, p<0.0001, respectively). Conclusions: This study revealed %LV-MMAR, calculated from CCT data on novel software, to be a promising index for estimating perfusion territory noninvasively in good agreement with BARI and modified APPROACH score.

Multi-contrast CT imaging using a high energy resolution CdTe detector and a CZT photon-counting detector

2022 ◽  
Vol 17 (01) ◽  
pp. P01004
Author(s):  
N. Clements ◽  
D. Richtsmeier ◽  
A. Hart ◽  
M. Bazalova-Carter
Keyword(s):  
Contrast Agent ◽  
Energy Resolution ◽  
Photon Counting ◽  
High Energy ◽  
Ct Imaging ◽  
High Energy Resolution ◽  
Great Promise ◽  
Contrast Imaging ◽  
Low Contrast ◽  
Reconstruction Methods

Abstract Computed tomography (CT) imaging with high energy resolution detectors shows great promise in material decomposition and multi-contrast imaging. Multi-contrast imaging was studied by imaging a phantom with iodine (I), gadolinium (Gd), and gold (Au) solutions, and mixtures of the three using a cadmium telluride (CdTe) spectrometer with an energy resolution of 1% as well as with a cadmium zinc telluride (CZT) detector with an energy resolution of 13%. The phantom was imaged at 120 kVp and 1.1 mA with 7 mm of aluminum filtration. For the CdTe data collection, the phantom was imaged using a 0.2 mm diameter x-ray beam with 96 ten-second data acquisitions across the phantom at 45 rotation angles. For the CZT detector, we had 720 projections using a cone beam, and the six detector energy thresholds were set to 23, 33, 50, 64, 81, and 120 keV so that three thresholds corresponded to the K-edges of the contrast agents. Contrast agent isolation methods were then examined. K-edge subtraction and novel spectrometric algebraic image reconstruction (SAIR) were used for the CdTe data. K-edge subtraction alone was used for the CZT data. Linearity plots produced similar R 2 values and slopes for all three reconstruction methods. Comparing CdTe methods, SAIR offered less noise than CdTe K-edge subtraction and better geometric accuracy at low contrast concentrations. CdTe contrast agent images of I, Gd, and Au offered less noise and greater contrast than the CZT images, highlighting the benefits of high energy resolution CdTe detectors for possible use in pre-clinical or clinical CT imaging.

Technology of cardiac computed tomography

ESC CardioMed ◽  
2018 ◽  
pp. 537-541
Author(s):  
Stephan Achenbach
Keyword(s):  
Computed Tomography ◽  
Heart Rate ◽  
Coronary Arteries ◽  
Cardiac Computed Tomography ◽  
Ct Imaging ◽  
Breath Hold ◽  
Coronary Angiogram ◽  
Data Set ◽  
Careful Patient ◽  
Patient Preparation

Cardiac imaging by computed tomography (CT) has the unique advantage of providing a fully isotropic data set with high spatial resolution. However, the rapid motion of the heart poses substantial challenges to CT imaging. For this reason, specific techniques have been developed to increase the temporal resolution of CT imaging and to permit either image acquisition or data reconstruction in synchronization with the patient’s electrocardiogram. Next to the use of advanced scanner technology, careful patient preparation is important to avoid artefacts. This includes careful coaching and practising of the breath-hold sequence to lower the heart rate, especially when CT is used to visualize the coronary arteries. With modern scanners, radiation exposure is reasonably low and falls approximately in the range of an invasive coronary angiogram.

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