Cardiac Virtual Noncontrast Images for Calcium Quantification with Photon-counting Detector CT

Area of Science:

• Cardiovascular Imaging
• Medical Physics
• Radiology

Background:

• Photon-counting detector CT (PCD-CT) offers advanced imaging capabilities.
• Virtual noncontrast (VNC) imaging aims to reduce radiation dose by reconstructing noncontrast images from contrast-enhanced scans.
• Accurate quantification of cardiac calcifications is crucial for cardiovascular risk assessment.

Purpose of the Study:

• To evaluate the accuracy of VNC images from PCD-CT for quantifying aortic valve calcium (AVC), mitral annular calcium (MAC), and coronary artery calcium (CAC).
• To assess the effectiveness of VNC imaging in cardiovascular risk stratification compared to true noncontrast (TNC) images.
• To determine optimal VNC reconstruction parameters (keV, QIR strength) for accurate calcification quantification.

Main Methods:

• Retrospective analysis of 90 patients undergoing cardiac PCD-CT.
• Reconstruction of VNC images from late enhancement scans at various keV and quantum iterative reconstruction (QIR) strengths.
• Quantification of AVC, MAC, and CAC on both VNC and TNC images.
• Statistical comparison using Bland-Altman analysis, ICC, regression, and weighted kappa statistics.

Main Results:

• VNC images demonstrated high accuracy for AVC and MAC quantification at 80 keV (ICC > 0.99) and for CAC at 70 keV (ICC > 0.99), with minimal differences compared to TNC images.
• Optimal VNC parameters were 80 keV with QIR 4 for AVC/MAC and 70 keV with QIR 4 for CAC.
• Excellent agreement was observed between calcification categories derived from VNC and TNC images (κ > 0.96).

Conclusions:

• VNC imaging from cardiac PCD-CT provides accurate quantification of AVC, MAC, and CAC.
• VNC imaging facilitates reliable cardiovascular risk stratification.
• This technique offers a potential method to assess cardiac calcifications without a separate noncontrast scan, potentially reducing radiation exposure.