Beam Delivery Systems

Mechanisms that deliver the OCT imaging beam to the tissue of interest vary considerably depending on the application. Although the delivery may seem straight forward, the engineering of scanning mechanisms to translate or displace a focused beam through a specimen represents a challenge. A simple, reliable, and compact displacement mechanism is necessary for the instruments to be integrated into the surgical suite. The following will describe various beam delivery instruments.

Research Microscope The advantage of integrating OCT with a microscope is to allow the precise positioning of the imaging beam on the specimen or sample, particularly when the specimen is on the microscopic scale. High magnifications imply short confocal parameters or depths-of-field for the microscope objectives. The reserach microscope can be implemented using a fiber-optic collimator and single-lens microscope objectives with low numerical apertures.

Surgical Microscope OCT can be integrated with existing surgical or dissecting microscopes to permit simultaneous OCT imaging at an arbitrarily oriented tomographic plane with en face visualization. Dissecting or stereo microscopes are typically binocular microscopes with long working distances and large confocal parameters. These microscopes are utilized in microsurgical techniques to enable the surgeon to visualize small structures. The integration of OCT into the surgical microscope would allow for sub-surface, cross-sectional imaging of small structures, which would offer an improved degree of visualization and information. Below is a proposed illustration of an OCT surical microscope.

The OCT imaging beam is aligned with the viewing
axis of the surgical microscope and scanned in
arbitrary patterns with a pair of orthogonal galvanometers.

OCT Probes In order to image tissue deep within the body cavity, it is possible to insert a rigid imaging needle into the tissue. For imaging tortuous lumens, such as those of the vascular system or gastrointestinal tract, it's necessary to use a more flexible scanning catheter. The endothelium that lines the majority of lumens in the body is a region of active cell division and often a site of neoplastic change. Therefore, imaging these areas at high-resolution would be useful for directing surgical therapy.

Modified OCT catheter and optical coupling.
A) Modified catheter designed with short working distances for radial imaging of
small vessels and lumens. B) Free-space optical coupling permits catheter rotation
without optical backreflections from coupler.