Coronary plaque risk classification in images acquired with photon-counting-detector (PCD) CT was performed using a radiomics-based machine learning (ML) model. With IRB approval, 17 coronary CTA patients were scanned on a PCD-CT (NAEOTOM Alpha, Siemens Healthineers) with median CTDIvol of 4.56 mGy. Four types of images: 120-kV PCD-CT image, virtual monoenergetic images (VMIs) at 50-keV and 100-keV, and iodine maps were reconstructed using an iterative reconstruction algorithm, a vascular kernel (Bv40) and 0.6-mm/0.4-mm slice thickness/increment. Atherosclerotic plaques were segmented using semi-automatic software (Research Frontier, Siemens). Segmentation confirmation and risk stratification (low- vs high-risk) were performed by a board-certified cardiac radiologist. A total of 1674 radiomic features were extracted from each image using PyRadiomics (v2.2.0b1). For each feature, a t-test was performed between low- and high-risk plaques (p<0.05 considered significant). Feature reduction was performed with a clustering algorithm and 6 non-redundant features were input into a linear support vector machine (SVM). A leave-one-out cross-validation strategy was adopted and the area under the ROC curve (AUC) was computed. Twelve low-risk and 5 high-risk plaques were identified by the radiologist. A total of 80, 66, 183, and 48 out of 1674 features in 120-kV, 50-keV, 100-keV, and iodine map images were statistically significant. The SVM classified 16/17 plaques correctly in the 120-kV PCD-CT and 50-keV VMI images. The AUC was 0.967, 0.967, 0.917, and 0.833 in 120-kV, 50-keV, 100-keV, and iodine map images, respectively. A ML model using coronary PCD-CTA images at 120-kV and 50-keV best automatically differentiated low- and high-risk coronary plaques.
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