Optimizing image quality for endoscopy requires broad-spectrum lighting, red spectrum resolution, proper exposure, endoscope tip cleanliness, and lens viability. Different light sources produce different spectra of radio frequency energy, and light that appears “white” to the naked eye is of highly variable character. This can lead to poor display of certain colors, most commonly in the red spectrum, which is the most important for endoscopic imaging as the sinuses and their contents fall almost entirely in this range. It is critical that lighting supplied for endoscopy has a wide spectrum with significant broadband components in the reds, and that the camera chip and display monitor all be tuned to achieve the highest degree of red resolution. With regard to lighting, light intensity falls via the “inverse square rule”; thus, structures closer to the endoscope tip are exponentially brighter than those farther away. The autoexposure feature on most medical-grade imaging systems does not handle this well, resulting in blown highlights on closer structures and more distant objects being masked in shadow. Trial-and-error manipulation of image settings can sometimes improve exposure.

The endoscope tip must be fastidiously cleaned throughout the procedure. Meticulous hemostasis is paramount. Heat from the light is transmitted asymmetrically to the tip of the endoscope. Blood tends to cake on to the light transmitting fibers before the receptor fibers are affected. Thus, the light carrying capacity of the endoscope deteriorates first, and then the image becomes blurry. A moist cotton cloth and/or micro instrument wipe can be used to aggressively clean off debris throughout a procedure. A gentle surfactant or mucus can be subsequently applied to limit fogging of the lens once placed into the nasal cavity, and scope warmers also limit fogging. While devices such as the Medtronic Endoscrub can flush gross blood from the tip of the endoscope during surgery, small amounts of blood accumulate between the lens and device, so the Endoscrub must be removed and cleaned prior to producing production quality images.

For rigid endoscopes, the quality of the lens elements is important for eventual image quality. Most endoscopes contain three friction fitted lenses within the shaft. Light refraction will accommodate for minor problems within any one of the lenses; however, image resolution deteriorates markedly across the image with any lens defect. A special inspection tool is available from company representatives to check lens quality.

12.2
Image Series

There is no consensus on the standard static views of the paranasal sinuses. Useful views of the paranasal sinuses must show relevant anatomic landmarks, be oriented properly with respect to the vertical, and allow resolution of critical pathology. The critical presurgical landmarks include the inferior turbinate, axilla of the middle turbinate, superior turbinate, and choanae. In postsurgical patients, the following landmarks are also used: the planum sphenoidale, choanae, nasal floor, frontal process of maxilla, orbit, and fovea ethmoidalis. For many of the views that follow, only some of the borders are critical, and the remaining borders are allowed to follow based on the field of view of the endoscope. Analogous techniques can be also used for views of extended endoscopic procedures of the anterior skull base.

12.2.1 Anterior Nasal Cavity, Left and Right

The inferior border is the nasal floor; the superior border is at or just above the head of the inferior turbinate. Laterally, the insertion of the inferior turbinate is visible, and medially, the cartilaginous septum and maxillary crest are included. In the background, portions of the middle turbinate are visible.

This view is the same as “Anterior Nasal Cavity, Left and Right,” except angled upward so that the superior limit is the internal nasal valve. The entire scroll area should be visible. Focus on the articulation between the septum and upper lateral cartilage.

12.2.3 Sphenoethmoidal Recess, Left and Right

This view captures the posterior drainage pathway that drains the posterior ethmoids and sphenoid sinus. The inferolateral border is the root of the inferior turbinate, and the septum is the medial border. The superior turbinate occupies most of the image superolaterally. Ideally, the sphenoid ostium is captured in the image for perspective, but may not be visible in some patients based on their superior turbinate configuration.

12.2.4 Choana, Left and Right

The inferior border is the soft palate; the superior border is the superior aspect of the choana mucosa. Laterally, the view should include the entire torus tubarius, and medially, the posterior aspect of the septum should be visible. The inferior and middle turbinate may block views of the choana; thus, maximal decongestion of the nasal turbinates is required.

12.2.5 Middle Meatus, Left and Right

Use a 30-degree rigid scope angled laterally or a flexible chip-tip scope. The inferior border is the uppermost portion of the inferior concha and the superior limit is just above the axilla of the middle turbinate. Laterally, the view should include the entire frontal process of the maxilla from the inferior turbinate to the axilla. The medial border is the septum.

12.2.6 Nasopharynx

Inferiorly, the soft palate is just visible; superiorly, the adenoid remnant or nasopharyngeal roof is evident. Ideally, both Eustachian tube orifices are visible, although this may not be possible in patients who have not had a posterior septectomy; in that case, left and right views may be obtained.