Feasibility of improving vascular imaging in the presence of metallic stents using spectral photon counting CT and K-edge imaging

Monica Sigovan,Daniel Bar-Ness,Philippe Douek,Julia Mitchell,Gilles Rioufol,Ira Blevis,Ewald Roessl,Philippe Coulon,Jean-Baptiste Langlois,Loic Boussel,Salim Si-Mohamed,Michal Rokni

doi:10.1038/s41598-019-56427-6

Abstract

Correct visualization of the vascular lumen is impaired in standard computed tomography (CT) because of blooming artifacts, increase of apparent size, induced by metallic stents and vascular calcifications. Recently, due to the introduction of photon-counting detectors in the X-ray imaging field, a new prototype spectral photon-counting CT (SPCCT) based on a modified clinical CT system has been tested in a feasibility study for improving vascular lumen delineation and visualization of coronary stent architecture. Coronary stents of different metal composition were deployed inside plastic tubes containing hydroxyapatite spheres to simulate vascular calcifications and in the abdominal aorta of one New Zealand White (NZW) rabbit. Imaging was performed with an SPCCT prototype, a dual-energy CT system, and a conventional 64-channel CT system (B64). We found the apparent widths of the stents significantly smaller on SPCCT than on the other two systems in vitro (p < 0.01), thus closer to the true size. Consequently, the intra-stent lumen was significantly larger on SPCCT (p < 0.01). In conclusion, owing to the increased spatial resolution of SPCCT, improved lumen visualization and delineation of stent metallic mesh is possible compared to dual-energy and conventional CT.

Highlights

Correct visualization of the vascular lumen is impaired in standard computed tomography (CT) because of blooming artifacts, increase of apparent size, induced by metallic stents and vascular calcifications
The higher spatial resolution of spectral photon-counting CT (SPCCT) resulted in a better visualization of the intra-stent lumen
The visual separation of the calcification from the stent was only possible on images acquired with the SPCCT (Fig. 2, arrows indicate the calcification). 3D Volume Rendering views of the platinum coated stent (Promus Premier) performed on conventional HU images allowed clear visualization of the metallic mesh on SPCCT images (Fig. 2)

Summary

Introduction

Correct visualization of the vascular lumen is impaired in standard computed tomography (CT) because of blooming artifacts, increase of apparent size, induced by metallic stents and vascular calcifications. Owing to the increased spatial resolution of SPCCT, improved lumen visualization and delineation of stent metallic mesh is possible compared to dual-energy and conventional CT. The recent development of a clinically based small field-of-view (FOV) spectral photon counting CT (SPCCT) prototype achieves higher spatial resolutions than standard CT at similar energies, owing to an important reduction in detector size[3]. Ultra-high resolution mode resulting in a 0.25 × 0.25 mm pixel size at iso-center was demonstrated recently for a photon-counting CT system[4] This increase in spatial resolution is expected to strongly reduce blooming artifacts, potentially improving restenosis detection and interpretation[5]. The objective of the study was to assess the capability of the SPCCT scanner to improve vascular lumen delineation and visualization of stent architecture, in vitro and in a single live rabbit, in comparison with dual-energy and standard CT

Objectives

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Conclusion