Abstract
The purpose of this study was to compare the correlation and agreement between AS derived from either an energy-integrating detector CT (EID-CT) or a photon-counting detector CT (PCD-CT). Reproducibility was also compared. In total, 26 calcified coronary lesions (from five cadaveric hearts) were identified for inclusion. The hearts were positioned in a chest phantom and scanned in both an EID-CT and a prototype PCD-CT. The EID-CT and PCD-CT acquisition and reconstruction parameters were matched. To evaluate the reproducibility, the phantom was manually repositioned, and an additional scan was performed using both methods. The EID-CT reconstructions were performed using the dedicated calcium score kernel Sa36. The PCD-CT reconstructions were performed with a vendor-recommended kernel (Qr36). Several monoenergetic energy levels (50–150 keV) were evaluated to find the closest match with the EID-CT scans. A semi-automatic evaluation of calcium score was performed on a post-processing multimodality workplace. The best match with Sa36 was PCD-CT Qr36 images, at a monoenergetic level of 72 keV. Statistical analyses showed excellent correlation and agreement. The correlation and agreement with regards to the Agatston score (AS) between the two methods, for each position as well as between the two positions for each method, were assessed with the Spearman´s rank correlation. The correlation coefficient, rho, was 0.98 and 0.97 respectively 0.99 and 0.98. The corresponding agreements were investigated by means of Bland–Altman plots. High correlation and agreement was observed between the AS derived from the EID-CT and a PCD-CT. Both methods also demonstrated excellent reproducibility.
Highlights
Energy-integrating detector computed tomography (EIDCT) is used for detection of atherosclerotic disease [1,2,3]
Continuous data are presented as mean ± standard deviation (SD) if normally distributed, or as median and interquartile rang (IQR) if non-normally distributed
The average image noise in the energy-integrating detector CT (EID-CT) Sa36 and the Photon counting detector CT (PCD-CT) Qr36 monoenergetic (72 keV) was 12.2 (± 2.1) and 14 (± 2.1) Hounsfield units (HU), respectively. In this ex vivo study of cadaveric hearts, there was an excellent correlation and agreement between the Agatston score (AS) derived from an EID-CT and a PCD-CT both methods demonstrated an excellent reproducibility
Summary
Energy-integrating detector computed tomography (EIDCT) is used for detection of atherosclerotic disease [1,2,3]. While EID-CTs convert incoming photons into electric currents using scintillator and photodiode layers indirectly, PCD-CTs directly convert X-ray photons into proportional electric signals using semiconductor materials. These technical characteristics of PCDs offer various advantages over conventional EID technology. With the PCD technology, low-weighting of low-energy photons leads to better image contrast This new technology, along with techniques for rendering energy-resolved data, reduces electronic noise resulting in higher dose efficiency, especially in low dose examinations. More energy thresholds can be applied, making advanced material decomposition possible [4] This is a feature expected to have large clinical benefits in coronary CT angiography imaging and characterization of atherosclerotic plaques [12, 13]
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