The (greatly simplified) fundamentals of Advanced OCT are shown in the diagram. Similar to a traditional laser, the swept-source laser produces light of only one ‘color’ at any instant in time. However, unlike a traditional laser, the swept-source changes the color of its output light very rapidly in time.
The output light is split in two: one beam stays internal to the console, while the second is transmitted through the catheter and focused into the tissue. Some of the light is reflected back from physiological structures within the tissue, and this reflected light is collected by the catheter and returned to the console.
Inside the console, the reflected and internal beams are combined and interfere with each other. After some processing, the interference signal yields an axial line (‘A-line’) that records the intensity of reflections at each depth in the tissue. Combining many consecutive A-lines into an image provides a cross-sectional look at all the reflecting structures in the tissue.