Smaller and more informative medical endoscopy

Abstract

Recent advances in medical endoscopes allow clinicians to perform surgical and diagnostic procedures less invasively, reducing patient discomfort and recovery times. While current state-of-the-art video endoscopes transmit high-quality images, their overall size is dictated by the dimensions of the sensors and electronics that deliver clinically useful images. Smaller and more flexible endoscopes that use optical fiber bundles have recently become available where each individual fiber is used to transmit one pixel in the image. However, maintaining acceptable image quality is challenging when only a limited number of fibers can be packed into an endoscope of a given diameter. Several research groups have attempted to rapidly scan light from an optical fiber to obtain an image.1–3 While high-quality images have been obtained using this technique, the size of the scanningmechanismmakes this method difficult to implement in the smallest medical endoscopes. We have recently introduced a new approach for single-fiber endoscopy—spectrally encoded endoscopy (SEE)—which could overcome the limitations of today’s fiber bundles. In the SEE system, broadband light emanating from a fiber is separated into different colors (or wavelengths) using a lens-grating pair at the distal end (tip) of the endoscopic probe (see Figure 1). This optical configuration focuses each color onto a different location on the tissue. The light reflected back from the tissue through the SEE probe is then decoded outside of the body using a fast spectrometer to form a single transverse line of the image. Twodimensional coverage is obtained by rotating the fiber using motors or galvanometric scanners at the proximal end of the probe, outside the patient. Since a high-speed scanning mechanism is not required at the distal end of the endoscope, the diameter of the SEE probe can be as narrow as the optical fiber itself, typically in the range of 80– 250μm. Furthermore, the number of pixels in an SEE image can Figure 1. Photograph of the SEE probe (top) next to a human hair (bottom) for size comparison. Visible light is coupled into the probe, illuminating a piece of paper below.