Photon-counting CT with tungsten as contrast medium: Experimental evidence of vessel lumen and plaque visualization

Background and aims: We aimed to investigate the potential of a preclinical photon-counting detector CT (PCT) scanner with an experimental tungsten-based contrast medium for carotid artery imaging. Methods: A carotid artery specimen was imaged on a PCT system using the multi-energy bin option (pixel size 0.5 x 0.5 mm(2); tube voltage 140 kVp, contrast media-dependent energy thresholds: iodine 20, 75 key; tungsten 20, 68 keV) at two radiation doses (CTDIvol of 100 mGy and 10 mGy) with iodine and tungsten as contrast media at equal mass-concentrations. Standard CT, virtual non-calcium (VNCa) and calcium-only images were reconstructed. Subjective image quality (4-point Likert scale) was rated using histology as reference. Noise and attenuation measurements were performed. Simulations were conducted to assess the material-decomposition efficiency for different object diameters. Results: Image quality on VNCa images was significantly higher for tungsten at lower dose (reader 1/reader 2: 2, [2,21/2, [2,2] vs 1.5, [2,11/1, [1,1.75], p < 0.05). Noise was significantly lower at both dose levels for tungsten VNCa images as compared to iodine images (higher dose: tungsten 24 vs iodine 31; lower dose: tungsten 60 vs iodine 82; both p < 0.01). Simulations indicated improved material-decomposition efficiency for tungsten than for iodine pronounced at smaller object diameters. Conclusions: PCT employing the multi-energy bin option in combination with tungsten as contrast media enables improved carotid artery imaging with respect to lumen and plaque visualization and image noise.