Background: A new type of microscope has been developed for acquiring cross-sectional images of living skin noninvasively. It takes advantage of the short temporal coherence of a broad-band light source to reject scattered light. Because this microscope is still in an early stage of development, its potential as a diagnostic tool in dermatology has not yet been determined. Objective: This study was designed to explore potential applications of optical coherence microscopy in dermatology. The aim was to investigate the structures in skin that can be seen without staining or using sophisticated image-processing methods. Methods: A prototype fiberoptic microscope was assembled that uses a 1,300-nm light-emitting diode as a light source. Scans were obtained from the skin on the index finger and forearm. Subsurface structures were identified based on knowledge of the anatomy of normal healthy skin. Results: Structures located as deep as 1 mm below the surface of the skin could be imaged with a resolution of about 10 μm in the axial and lateral dimensions. In optical slices taken perpendicular to the skin surface, the contours of the epidermal ridges and the boundary between the epidermis and dermis were readily observed. Conclusions: The results of this study suggest that an optical coherence microscope may have value as a diagnostic tool for cases in which visualization of subcellular details is not required. The resolution, contrast and scanning speed of the microscope need to be improved.

Three-dimensional (3D) endomicroscopy imaging of the human gastrointestinal tract is demonstrated in vivo using a swept source optical coherence tomography (OCT) system. 3D datasets of normal and pathologic regions of the colon, rectum, and anal verge were obtained from seven volunteers undergoing diagnostic or therapeutic colonoscopy. 3D-OCT enables high resolution endomicroscopy examination through visualization of tissue architectural morphology using virtual cross-sectional images with arbitrary orientations as well as en face projection images. Axial image resolutions of 6 μm in tissue are obtained over a ~180 mm 2 field with an imaging range of 1.6 mm. A Fourier domain mode locked (FDML) laser providing a tuning range of 180 nm at a sweep rate of 62 kHz is used as the system light source. This clinical pilot study demonstrates the potential of 3D-OCT for distinguishing normal from pathologic colorectal tissue, assessing endoscopic therapies and healing progression.

Miniature optical sensors that can detect blood vessels in front of advancing instruments will significantly benefit many interventional procedures. Towards this end, we developed a thin and flexible coherence-gated Doppler (CGD) fiber probe (O.D. = 0.125 mm) that can be integrated with minimally-invasive tools to provide real-time audio feedback of blood flow at precise locations in front of the probe. Coherence-gated Doppler (CGD) is a hybrid technology with features of laser Doppler flowmetry (LDF) and Doppler optical coherence tomography (DOCT). Because of its confocal optical design and coherence-gating capabilities, CGD provides higher spatial resolution than LDF. And compared to DOCT imaging systems, CGD is simpler and less costly to produce. In vivo studies of rat femoral vessels using CGD demonstrate its ability to distinguish between artery, vein and bulk movement of the surrounding soft tissue. Finally, by placing the CGD probe inside a 30-gauge needle and advancing it into the brain of an anesthetized sheep, we demonstrate that it is capable of detecting vessels in front of advancing probes during simulated stereotactic neurosurgical procedures. Using simultaneous ultrasound (US) monitoring from the surface of the brain we show that CGD can detect at-risk blood vessels up to 3 mm in front of the advancing probe. The improved spatial resolution afforded by coherence gating combined with the simplicity, minute size and robustness of the CGD probe suggest it may benefit many minimally invasive procedures and enable it to be embedded into a variety of surgical instruments.

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