Light intensity distribution in images from rigid endoscopes used in minimal access sinus surgery

Abstract

Objectives/Hypothesis: To investigate the pattern of intensity levels in images generated by the two most commonly used rigid endoscopes angulations in sinus surgery: 0 and 30 .Methods: An enclosed light box containing an optical square grid, under endoscope illumination set just below saturation level, was used for measuring light distribution levels across test images. Endoscopes with 0 and 30 angulations were tested at 10 mm from the grid, typical for sinus surgery. The grid was set perpendicular to the axis of the shaft of the endoscope. The grayscale light intensity (GLI) levels (0 = black, 255 = white) in each of the grid squares were quantified from the digitized images.Results: Light intensity was highly non-uniform for both endoscopes. The brightest area of the field of view was at the center for the 0 endoscope and at about 20% of the image diameter proximally from the center for the 30 endoscope. For the 0 endoscope with a maximum value of about 230 GLI (90% of white saturation) at the center the minimum value was about 100 GLI at the periphery. The 30 endoscope with a similar maximum GLI value of 226 had a minimum of under 50 GLI at the most distant periphery, too dark for clear grid line definition. Conclusion:There are wide variations in light intensity across the image circle and much reduced illumination of the field edge. Surgeons should be aware of this fact so that accommodation can be made when surgical manipulation is performed away from the center of the endoscope field. This is especially relevant in angled cavities such as the frontal sinus recess, where the degree of angulation necessitates "edge of field" surgery.

A Novel Rigid Telescope Holder for Endoscopic Surgery in Otolaryngology

“…Since its inception over 50 years ago, rigid endoscopic telescopes (RET) have become a common imaging tool for minimal access surgery across various disciplines within otolaryngology. 1,2 Despite the recent nascence of flexible operative endoscopy in endonasal procedures, rigid endoscopy using RET remains the standard of care for endoscopic sinus surgery. 3 Within the realm of laryngology, microlaryngoscopy using RET permits both a high quality, ultra-close proximity examination of the larynx and the trachea (including the use of angled telescopes, which can have advantages over the straight line-of-site of a surgical microscope) and a panoramic view not easily equaled by the surgical microscope.…”