Image Characteristics of Virtual Non-Contrast Series Derived from Photon-Counting Detector Coronary CT Angiography-Prerequisites for and Feasibility of Calcium Quantification

Franziska M Braun; Franka Risch; Josua A Decker; Piotr Woźnicki; Stefanie Bette; Judith Becker; Katharina Rippel; Christian Scheurig-Münkler; Thomas J Kröncke; Florian Schwarz

doi:10.3390/diagnostics13223402

Image Characteristics of Virtual Non-Contrast Series Derived from Photon-Counting Detector Coronary CT Angiography-Prerequisites for and Feasibility of Calcium Quantification

Diagnostics (Basel). 2023 Nov 8;13(22):3402. doi: 10.3390/diagnostics13223402.

Authors

Affiliations

¹ Clinic for Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Augsburg, Stenglinstr. 2, 86156 Augsburg, Germany.
² Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Oberdürrbacher Straße 6, 97080 Würzburg, Germany.
³ DONAUISAR Clinic Deggendorf, Perlasberger Str. 41, 94469 Deggendorf, Germany.
⁴ Medical Faculty, Ludwig Maximilian University of Munich, Geschwister-Scholl-Platz 1, 80539 Munich, Germany.

Abstract

In photon-counting detector CT (PCD-CT), coronary artery calcium scoring (CACS) can be performed using virtual non-contrast (VNC) series derived from coronary CT angiography (CCTA) datasets. Our study analyzed image characteristics of VNC series in terms of the efficacy of virtual iodine "removal" and image noise to determine whether the prerequisites for calcium quantification were satisfied. We analyzed 38 patients who had undergone non-enhanced CT followed by CCTA on a PCD-CT. VNC reconstructions were performed at different settings and algorithms (conventional VNC_Conv; PureCalcium VNC_PC). Virtual iodine "removal" was investigated by comparing histograms of heart volumes. Noise was assessed within the left ventricular cavity. Calcium was quantified on the true non-contrast (TNC) and all VNC series. The histograms were comparable for TNC and all VNC. Image noise between TNC and all VNC differed slightly but significantly. VNC_Conv CACS showed a significant underestimation regardless of the reconstruction setting, while VNC_PC CACS were comparable to TNC. Correlations between TNC and VNC were excellent, with a higher predictive accuracy for VNC_PC. In conclusion, the iodine contrast can be effectively subtracted from CCTA datasets. The remaining VNC series satisfy the requirements for CACS, yielding results with excellent correlation compared to TNC-based CACS and high predicting accuracy.

Keywords: cardiac imaging; coronary artery calcium quantification; photon-counting detector CT; virtual non-contrast imaging.

Grants and funding

J.A.D. is partially funded via a physician–scientist grant from the medical faculty of the University of Augsburg. Otherwise, this research received no external funding.