Extracellular Volume Quantification With Cardiac Late Enhancement Scanning Using Dual-Source Photon-Counting Detector CT

Abstract

Objectives: The aim of this study was to evaluate the feasibility and accuracy of cardiac late enhancement (LE) scanning for extracellular volume (ECV) quantification with dual-source photon-counting detector computed tomography (PCD-CT). Materials and Methods: In this institutional review board-approved study, 30 patients (mean age, 79 years; 12 women; mean body mass index, 28 kg/m 2 ) with severe aortic stenosis undergoing PCD-CT as part of their preprocedural workup for transcatheter aortic valve replacement were included. The scan protocol consisted of a nonenhanced calcium-scoring scan, coronary CT angiography (CTA) followed by CTA of the thoracoabdominal aorta, and a low-dose LE scan 5 minutes after the administration of 100 mL contrast media (all scans electrocardiogram-gated). Virtual monoenergetic (65 keV) and dual-energy (DE) iodine images were reconstructed from the LE scan. Extracellular volume was calculated using the iodine ratios of myocardium and blood-pool of the LE scan, and additionally based on single-energy (SE) subtraction of the nonenhanced scan from the LE scan. Three-dimensional analysis was performed automatically for the whole-heart myocardial volume by matching a heart model generated from the respective coronary CTA data. Bland-Altman and correlation analysis were used to compare the ECV values determined by both methods. Results: The median dose length product for the LE scan was 84 mGy•cm (interquartile range, 69; 125 mGy•cm). Extracellular volume quantification was feasible in all patients. The median ECV value was 30.5% (interquartile range, 28.4%-33.6%). Two focal ECV elevations matched known prior myocardial infarction. The DE-and SE-based ECV quantification correlated well (r = 0.87, P < 0.001). Bland-Altman analysis showed small mean errors between DE-and SE-based ECV quantification (0.9%; 95% confidence interval, 0.1%-1.6%) with narrow limits of agreement (−3.3% to 5.0%). Conclusions: Dual-source PCD-CT enables accurate ECV quantification using an LE cardiac DE scan at low radiation dose. Extracellular volume calculation from iodine ratios of the LE scan obviates the need for acquisition of a true nonenhanced scan and is not affected by potential misregistration between 2 separate scans.

Ultra-High-Resolution Coronary CT Angiography With Photon-Counting Detector CT

“…As detector cells are defined by the strong electric fields, there is no need for additional separation layers, thus optimizing geometric dose efficiency and allowing smaller detector sizes. 6,[8][9][10][11][12] With this scanner, an ultra-high-resolution mode is available with detector pixels of size 0.151 Â 0.176 mm 2 at the isocenter. 13 This translates to a maximum spatial in-plane image resolution of 0.11 mm and a maximum through-plane resolution of 0.16 mm.…”

“…Absorbed x-ray photons eventually induce electron-hole pairs in the semiconductor material, with the electrons immediately attracted to the pixelated anode by the strong voltage applied across the semiconductor. As detector cells are defined by the strong electric fields, there is no need for additional separation layers, thus optimizing geometric dose efficiency and allowing smaller detector sizes 6,8–12 . With this scanner, an ultra-high-resolution mode is available with detector pixels of size 0.151 × 0.176 mm 2 at the isocenter 13 .…”

Stability of spectral results in cardiac dual-source photon-counting CT

“…The copyright holder for this this version posted December 12, 2022. ; https://doi.org/10.1101/2022.12.07.22283222 doi: medRxiv preprint and PCCT illustrated good agreement with magnetic resonance imaging in terms of both visualization with VMI and iodine density maps and quantification of the extracellular volume important for evaluating myocardial fibrosis, edema, and viability in cardiomyopathy [23][24][25] . Virtual non contrast images, on the other hand, have exhibited improved preservation of stent and calcified structures compared to conventional CT for the surveillance post endovascular aneurysm repair 44 .…”

“…The copyright holder for this this version posted December 12, 2022. ; https://doi.org/10.1101/2022.12.07.22283222 doi: medRxiv preprint separate the iodine signal for the visualization of perfusion and vascular structures [23][24][25] and can also be analyzed quantitatively to characterize lesions, i.e. cysts vs. hepatocellular carcinoma 26,27 .…”

Photon-counting detector CT: early clinical experience review

“…The spectral capabilities of PCD-CT allow the user to reconstruct iodine maps, virtual non-contrast (VNC) and virtual monoenergetic images (VMIs) from every acquisition. The use of VMI for routine clinical PCD-CT imaging has exemplarily been shown for abdominal imaging, 28,66 cardiac CT [69][70][71] and coronary calcium quantification, 72 high-pitch CT angiography of the aorta, 67 lung 35,73 and brain imaging. 74 The benefits of low keV VMI include better visualization of small low-contrast structures and increased iodine signal.…”