Evaluation of Coronary Plaques and Stents with Conventional and Photon-counting CT: Benefits of High-Resolution Photon-counting CT

Purpose: To compare the performance of energy-integrating detector (EID) CT, photon-counting detector CT (PCCT), and high -resolution PCCT (HR-PCCT) for the visualization of coronary plaques and reduction of stent artifacts in a phantom model. Materials and Methods: An investigational scanner with EID and PCCT subsystems was used to image a coronary artery phantom con-taining cylindrical probes simulating different plaque compositions. The phantom was imaged with and without coronary stents using both subsystems. Images were reconstructed with a clinical cardiac kernel and an additional HR-PCCT kernel. Regions of interest were drawn around probes and evaluated for in-plane diameter and a qualitative comparison by expert readers. A linear mixed-effects model was used to compare the diameter results, and a Shrout-Fleiss intraclass correlation coefficient was used to assess consistency in the reader study. Results: Comparing in-plane diameter to the physical dimension for nonstented and stented phantoms, measurements of the HR-PCCT images were more accurate (nonstented: 4.4% +/- 1.1 [standard deviation], stented: -9.4% +/- 4.6) than EID (nonstented: 15.5% +/- 4.0, stented: -19.5% +/- 5.8) and PCCT (nonstented: 19.4% +/- 2.5, stented: -18.3% +/- 4.4). Our analysis of variance found diameter measurements to be different across image groups for both nonstented and stented cases (P < .001). HR-PCCT showed less change on average in percent stenosis due to the addition of a stent (-5.5%) than either EID (+90.5%) or PCCT (+313%). For both nonstented and stented phantoms, observers rated the HR-PCCT images as having higher plaque conspicuity and as being the image type that was least impacted by stent artifacts, with a high level of agreement (interclass correlation coefficient = 0.85). Conclusion: Despite increased noise, HR-PCCT images were able to better visualize coronary plaques and reduce stent artifacts com-pared with EID or PCCT reconstructions. (C) RSNA, 2021