Dual-Source Photon-Counting CT for Thoracic Arteries: Enhancing Image Quality and Diagnostic Assessability with Low-Energy Virtual Monoenergetic Imaging

Background/Objectives: This study aimed to investigate the impact of low-energy virtual monoenergetic imaging (VMI) on quantitative and qualitative image characteristics, as well as its effect on the diagnostic assessability of thoracic arteries in photon-counting computed tomography angiography (CTA). Methods: We retrospectively evaluated 125 patients who underwent dual-source photon-counting CTA scans of thoracic arteries. We reconstructed standard CT images at 120 kV and VMI series at 15 keV intervals, ranging from 40 to 100 keV, and conducted quantitative and qualitative image analyses. For quantitative analysis, we assessed vascular CT numbers and contrast-to-noise ratio (CNR). For qualitative evaluation, three board-certified radiologists independently rated image quality, vascular contrast, and diagnostic assessability of the thoracic arteries using a five-point scale. Results: Quantitative image analysis revealed that 40 keV VMI reconstructions exhibited the highest mean CT value (HU: 1205 ± 286) and CNR (29.22 ± 9.13), followed by the 55 keV series (HU: 679 ± 161, CNR: 22.54 ± 7.36), significantly improved compared to higher keV levels and the standard 120 kV CT series (p < 0.001). Qualitative analysis showed the highest rating scores for 55 keV reconstructions, significantly higher than those of VMI series at higher energy levels and the standard 120 kV series (p < 0.001). Conclusions: VMI reconstructions at low energy levels (40–55 keV) significantly enhance vascular CTvalue and CNR, offering superior image quality and diagnostic assessability for thoracic arteries compared to standard CT series in photon-counting CTA.