Cross-sectional images of internal structures are generated by scanning the transverse position of the incident optical beam. Precision measurements of structures are performed by shining a beam of light onto the object and measuring the echo time delay of light, which is reflected or backscattered from different internal structures. Because the velocity of light is extremely high, it isn't possible to measure directly the echo time delay of reflections electronically. This provides a precise measurement of the echo time delay of the back-reflected light. The operation of the interferometer is analogous to heterodyne optical detection.
Cancer is the second leading cause of mortality in the industrialized world.
The middle figure is an image of a normal bowel, which shows columnar epithelium that is distinct from the esophagus. The bottom image shows a carcinoma, where the regular columnar formation in the bowel is severely disrupted. This loss of normal tissue structure is often a signature of neoplastic change. OCT images have already achieved resolutions ranging from 10 to 15 microns. While this is sufficient for imaging in many applications, it is still not enough to achieve cellular resolution.