Photon-counting Detector CT Spectral Reconstructions for Radiomics-based Liver Lesion Classification

Objectives: Accurate noninvasive classification of hepatic lesions remains a diagnostic challenge, particularly on conventional CT. Photon Counting Detector CT (PCD-CT) offers spectral imaging capabilities that may enhance tissue characterization. This study aimed to evaluate the performance of radiomics-based machine learning for differentiating benign and malignant liver lesions using multispectral virtual monochromatic and material decomposition images derived from contrast-enhanced PCD-CT. Materials and Methods: This multicenter study included patients with focal hepatic lesions, scanned on PCD-CT at 2 separate institutions. Lesions were automatically segmented by a nnU-Net model and confirmed by an abdominal radiologist. Volumetric segmentations were used to extract radiomic features from 9 spectral datasets: 40, 50, 70, 90, 110, 140, and 180 keV, virtual non-contrast (VNC), and iodine density maps (IDM). A patient-based classification analysis was conducted by training multiple machine-learning models, with lesion-level predictions aggregated per patient. A Random Forest model further evaluated classification performancef across all train-test reconstruction combinations. Results: The cohort comprised 378 patients (median age: 62; 59.5% female) from 2 centers, including 190 benign (n=227 lesions) and 188 with malignant (n=2681 lesions) hepatic findings. Random forest model trained on VNC achieved highest performance [AUC: 0.899; 95% CI (0.840-0.951); Accuracy 83.5%). In the cross-domain analysis, all training reconstructions achieved similar mean AUCs (0.75 to 0.83). Evaluation performance varied across test levels. Models tested on 110, 140, and 180 keV, and VNC showed the highest stability (median AUC ≥ 0.83), while 40 keV, 50 keV, and IDM resulted in lower and more variable AUCs (median AUC ≤ 0.71). Conclusion: Radiomics-based machine learning enables reliable differentiation between malignant and benign hepatic lesions on PCD-CT. The choice of test reconstruction influenced performance: higher energy levels and VNC images yielded more stable results. Incorporating high-energy reconstructions and VNC images into radiomic workflows for liver lesion risk stratification may enable noninvasive triage and reduce the need for invasive diagnostics.