OCT: technology and current status.
In vivo imaging of body tissues at the cellular level, and in a clinical setting, is challenging since the widely used imaging modalities such as X-ray, CT, MRI, nuclear medicine and ultrasound cannot achieve the necessary spatial resolution, at least under reasonable conditions.
Early experimental techniques such as Photo Acoustic Tomography (PAT) gave the first indications that it might be possible to show cellular details of body tissue in vivo using harmless optical techniques. Since then, in vivo imaging of the skin and the epithelium using such optical techniques has developed considerably. There are now several commercially available systems using various imaging technologies which cover a range of resolution from 1 µm to 20µm and higher. [Figure 1]. Of the methods shown in Figure 1, Reflectance Confocal Microscopy (RCM) and Optical Coherence Tomography (OCT) are becoming increasingly popular in dermatology. Using the so-called “blood-water” window in the Near Infrared (NIR) region of the spectrum these techniques overcome the inherent resistance of the skin to the penetration of many kinds of radiation. RCM has a resolution of 1 µm (thus coming close to that of standard light microscopy).
The penetration depth of RCM is 200 µm, which is deep enough to visualize the epidermis and papillary dermis, but not for the reticular dermis. Read More