Quantitative endoscopy by FOLCI-based distance sensor

In medical endoscopy, quantifying anatomical dimensions would be of great help, but the appropriate tools are not yet available. We present a novel method for the calibration and size measurement of endoscopic images. We realized an optical sensor, based on Fiber Optic Low Coherence Interferometry (FOLCI), capable of measuring the absolute distance between the tip of an endoscopic probe and an anatomical object under inspection. We showed that this sensor provides very sensitive and accurate (error lower than 0.1 mm) measurements of biological samples. The sensing fiber of the sensor was introduced in the operative channel of an Olympus rhinoscope. After calibrating the endoscope magnification system as a function of the distance, our system was capable of providing the size of any object included in the field of view of the endoscope. Tests performed on planar targets and pig trachea showed the accuracy of the system to be adequate for allowing quantitative dimensional information.