Role of ultrahigh-spatial-resolution photon-counting CT in assessment of coronary artery disease

I had posted about photon counting CT which  converts X-rays directly to electronic signals unlike conventional CT which converts X-rays first to light and then to electronic signals. Direct  conversion allows low energy photons to be differentiated from electronic noise. When data is acquired directly from photons of different energy levels, better contrast-to-noise ratio can be realized. Photon-counting-detector CT also improves spatial resolution. A study published in Radiology, the flagship journal of the  Radiological Society of North America evaluated both in vivo and in vitro coronary stenosis using ultrahigh-spatial-resolution photon counting detector CT reconstructions [1]. This led to lower percentages of diameter stenosis compared with standard resolution and clinically relevant rates of reclassification in calcified stenoses.

In-vitro studies were carried out prospectively in a vessel phantom containing two stenoses of 25% and 50%. In-vivo study was retrospective, with reconstruction in patients who underwent ultrahigh-spatial-resolution cardiac photon counting detector CT. Reconstructions were at standard resolution of 0.6 mm section thickness, high spatial resolution with section thickness of 0.4 mm, and ultrahigh spatial resolution with section thickness of 0.2 mm. Section increments were 0.4 mm, 0.2 mm and 0.1 mm respectively. In in-vivo results, there was decreasing median percentage diameter stenosis with increasing spatial resolution for calcified stenoses. There was no significant difference for noncalcified and mixed plaques, though they were much smaller in number. Ultrahigh-spatial-resolution reconstructions led to reclassification to lower category in 54.4% patients than that was assigned using standard resolution.

Reference

1. Halfmann MC, Bockius S, Emrich T, Hell M, Schoepf UJ, Laux GS, Kavermann L, Graafen D, Gori T, Yang Y, Klöckner R, Maurovich-Horvat P, Ricke J, Müller L, Varga-Szemes A, Fink N. Ultrahigh-Spatial-Resolution Photon-counting Detector CT Angiography of Coronary Artery Disease for Stenosis Assessment. Radiology. 2024 Feb;310(2):e231956. doi: 10.1148/radiol.231956. PMID: 38376407.