Optical Coherence Tomography and Its Relevance to Neurosurgical Practice

light interference-based imaging technique that provides real-time, in situ, cross-sectional images of human tissues or biological materials with excellent resolution. It is based on differential reflection or backscattering of light waves with corresponding time delays and variable magnitudes used to generate depth-resolved images—in a sense, analogous to B-mode ultrasonography—except it uses light instead of sound. The image resolution with OCT is not as precise as that seen with confocal or fluorescence microscopy but it is far superior to the resolution obtained with ultrasonography. Ophthalmology was the first field to adopt this technology—the anatomic components of the eye transmit light with minimal optical attenuation and scattering providing high-resolution images of the retina with OCT. In fact, structural damage to the entire optic pathway can be assessed and response to therapy tracked with OCT. OCT also has the ability to penetrate nontransparent tissues extending its applications further. The roots of OCT lie in femtosecond optics—the concept of using echoes of light to see inside biological tissues. Its origins trace back to basic science and physics laboratories—in fact, its application as a clinical modality represents one of the best paradigms of innovative thinking, translational research, and multidisciplinary collaboration, along with industry and governmental support. In 1991, Huang first demonstrated its utility in imaging living tissues providing the first in vitro cross-sectional images of the retina. Shortly thereafter, in 1993, Swanson et al at the Massachusetts Institute of Technology provided the first in vivo human retinal images depicting the retinal nerve fiber layer