And God said: “Let there be light”, and there was light. And God saw that the light was good. (Bible, Old Testament, Genesis 1:3–4)

Optical coherence tomography (OCT) is an imaging technique, based on near-infrared light, that allows cross-sectional imaging of biological systems. The technique is based on the measurement of optical reflections of biological tissues. An optical signal transmitted through, or reflected from, a biological tissue contains time-to-flight information, which in turn yields spatial information about tissue microstructure.1

Although first used in ophthalmology to assess non-invasively the human retina, it has been recently applied to cardiology to allow an invasive visualisation of the vessel wall of the coronary arteries from inside the lumen, through a dedicated wire (where the OCT probe is located) tracked in the vessel of interest. The images are comparable in shape to those of intravascular ultrasound (IVUS). However, in comparison with this well-established technique, OCT offers an at least 10 times higher spatial resolution (from around 150–200 μm for IVUS to 15–20 μm for OCT), owing to the different properties and wavelength of light versus ultrasound. This higher resolution translates in practice into the possibility of acquiring much more detailed images and of visualising details of anatomy and devices, not visible with IVUS.2 A second advantage of OCT over IVUS is the faster acquisition time, so that the pullback speed of the probe to obtain sequential tomographic images of the coronary artery and thus a volumetric reconstruction of the segment of interest can be quicker than the IVUS speed, which is usually 0.5–1 mm/s.3

On the other hand, the penetration power of OCT is lower than that of IVUS. In coronary arteries, with OCT it is possible to visualise around 2 mm thickness of the vessel wall starting from the lumen border, …