The impact of an eccentric intravascular ImageWire during coronary optical coherence tomography imaging

Optical coherence tomography (OCT) provides high-resolution imaging which enables characterisation of atherosclerosis and vascular response to injury, but to ensure optimal analysis, one must realise potential sources of image distortion. We designed a series of analyses, using coronary stents as a model, to investigate the influence of wire position on OCT-derived vascular images.

The study evaluated intracoronary OCT images from the Cardialysis-Cleveland University Hospitals Cardiovascular Imaging Core Laboratories database. Intracoronary OCT images were acquired with the M2 system (LightLab Imaging Inc., Westford, MA, USA) and analysed using a customised software. Wire concentric index (WCI) was calculated as "wire-lumen distance/lumen radius". Lumen, stent, and strut contours were defined and 360 chords (1 degree increments) were placed radially between the lumen and stent contours. Strut length was defined by the number of chords spanned by each strut. Strut level thickness (SLT) was measured with each chord. SLT variability ([Max-Min SLT]/number of chords per strut) was calculated. Lumen measurements were performed with optimal calibration and repeated with ±1% changes from optimal Z-offset. The hemisphere containing an eccentric wire had shorter strut reflections (5.0±1.6° vs. 6.6±2.1°, p<0.001) compared to the opposite hemisphere. Eccentric wires depicted 84% of the struts as non-parallel to the luminal surface (>10% SLT variability). Changing Z-offset by 1% resulted in a non-uniform shrinkage or expansion of the luminal contour in images generated from eccentric wires, but not from concentric wires.

Eccentric intraluminal position of the OCT ImageWire occurs frequently and affects calibration and interpretation of images, including length, orientation and visibility of vessel wall structures.