ABSTRACT
In 1881, working to measure the speed of light, physicist AA Michelson constructed an interferometer that divided a light source into a reference beam and a sample beam, and then recombined them to measure the interference between the two beams1. In 1991, Huang et al. published a manuscript describing optical coherence tomography (OCT), a novel digital imaging technique, that utilizes a Michelson interferometer to measure the depth of reflections from a tissue sample by the interference patterns with a reference beam2. Analysis of the interference pattern yields a cross-sectional image that is the optical analog of pulse-echo ultrasonography. Food and Drug Administration (FDA)-approved for scanning surface and subsurface retinal structures (microvasculature and nerves), OCT is available in flexible guidewire probes (similar to current microguide-wires used for intracranial endovascular neurosurgical procedures) which are being evaluated for use in the coronary circulation3-9. OCT produces images with a resolution of 1-20 µm. This compares favorably to intravascular ultrasound, which has a resolution of approximately 100 µm and confocal microscopy, which has a resolution of approximately 1 µm. OCT images have near-biopsy resolution and may be used as a nondestructive alternative to biopsy or as a screening step to reduce biopsy-sampling error. Cerebral applications are being described by several authors in the cerebrovascular as well as neuro-oncological arenas. For example, Satomura et al. have recently used in vivo OCT to image small animal microvessels10, and Boppart et al. have reported OCT to discriminate between normal cerebral cortex and melanoma metastasis11.
