Introduction

Two intracoronary imaging techniques are routinely available to complement angiography in the management of coronary artery disease, namely intravascular ultrasound (IVUS) and optical coherence tomography (OCT). The former has been in clinical use for >25 years and has directly informed the fundamentals of atherosclerotic plaque composition and arterial remodelling, as well as contemporary optimal stent implantation technique.1 ,2 The latter, introduced 10 years ago, has only been more widely adopted with the development of the frequency domain (FD)-OCT imaging, which enables complete image acquisition over a 6–10 cm segment during a 3–5 s pullback period obtaining blood clearance with the pressure injection of iodinated contrast or other crystalloids. Although OCT may be limited when visualising the full thickness of atherosclerotic plaques as a result of low penetration power, it however allows for measurements on a micron scale due to the high resolution of light.3 ,4 IVUS has greater penetration and, with the exception of dense calcific plaques, is able to display the media-to-media diameter, an important measurement to evaluate remodelling and guide vessel expansion during angioplasty.5 Both IVUS and OCT are superior to angiography for quantification of vessel dimension and thus critically helpful in guiding coronary angioplasty (percutaneous coronary intervention (PCI)) and stent implantation.6–11 Greyscale IVUS can be augmented by implementation of virtual histology (VH), which offers qualitative information on …