A pilot investigation on feasibility of clinical photon‑counting CT for in vivo study of atherosclerotic plaques in rabbit model: comparison with histopathology

Computed tomography (CT) angiography is the primary non-invasive imaging technique for coronary artery disease assessment. Photon-counting CT (PCCT) offers improved spatial resolution and spectral sensitivity over conventional CT, potentially enhancing the diagnosis of high-risk plaques in small vessels. Although phantom and post-mortem studies have demonstrated the superior performance of PCCT in plaque imaging, the feasibility of clinical PCCT for in-vivo atherosclerotic plaque characterization in small vessels using histopathologic results as the ground truth remains to be investigated. Therefore, we conducted a pilot study using the rabbit model of atherosclerosis. PCCT scans were performed on rabbit models before and after the injection of iodine contrast agents, followed by histopathological analysis of excised abdominal aortas. Using the acquired PCCT and corresponding histopathological data, we (1) qualitatively validated the reliability of our contrast agent injection protocol and setup, (2) assessed the feasibility of clinical PCCT for in vivo small animal imaging through ultra-high-resolution reconstruction and cinematic volume rendering processing, and (3) systematically compared CT numbers extracted from histopathologically-confirmed plaque region and vessel lumen across different perfusion phases, reconstruction parameters, and virtual monoenergetic energy levels. Our analysis yielded preliminary insights into how these factors influence plaque characterization. This study confirms the feasibility of clinical PCCT for in vivo characterization of atherosclerotic plaques in rabbit models, with histopathology serving as reference. Further validation with larger animal cohorts is ongoing to strengthen these findings, which may facilitate the comprehensive interpretation of the performance of clinical PCCT systems in coronary artery disease diagnostics.