Development of small-diameter endoscope capable of high-resolution visualization and laser therapy through a shared optical aperture

Abstract

Minimally invasive surgical (MIS) techniques have increased the efficacy and safety of many previously open surgical procedures, while reducing cost. An enabling tool for MIS procedures is the endoscope, which frequently hosts technologies to illuminate, visualize, and apply a phototherapy laser to a surgical scene. Unfortunately, some candidate MIS procedures are not presently possible due to the insufficiently small diameter of currently available endoscopes, which is the result of illumination, visualization, and phototherapy functions each requiring a unique, adjacent, optical aperture. Furthermore, some MIS procedures in common practice could realize better outcomes with smaller diameter endoscopes. Small-diameter visual sensors have been realized with Spectrally Encoded Endoscopy (SEE), which uses an optical chain with a diffraction grating at the distal end to spectrally encode the (broadband) optical illumination signal in a line across the surgical scene.

When the device is azimuthally rotated and the optical return signal processed, a high-quality 2-dimensional image can be reconstructed. With the objective of achieving very small endoscope diameter and therefore extending the reach of MIS, here a technology called Therapy Spectrally Encoded Endoscopy (TSEE), which adds the capability of laser therapy to SEE, is presented in three major variants. In the first variant, visualization, illumination, and the therapy laser are all transmitted through a common optical aperture. In the second and third variants, illumination and the therapy laser are transmitted through a common optical aperture, and external fiber optics are used to collect the image signal photons. The devices have respective diameters of 500 [mu]m and 1.4 mm, and are capable of transmitting a continuous-wave therapy laser with wavelength 532nm.

Benign Paroxysmal Positional Vertigo (BPPV) and Twin-to-twin Transfusion Syndrome (TTTS) are evaluated for application of the TSEE technology, and to drive design requirements.