Thanks to advances in technology, office-based laser treatment is now possible for many patients with benign or premalignant laryngeal lesions. However, some have anatomically challenging lesions that can’t be accessed as easily in the office. This is because most laser fibers emit light only forward, in the line of sight toward the target. Lesions located off the longitudinal axis are less accessible.
In two high-definition larynx models, Chan and colleagues recently demonstrated that side-firing laser fibers could theoretically increase endoscopic access to difficult lesions.
Now, researchers at Brigham and Women’s Hospital have built on that work, corroborating the results in additional, more varied anatomic models. Elliana Kirsh DeVore, MD, a resident physician in the Department of Otolaryngology–Head and Neck Surgery, Thomas L. Carroll, MD, assistant professor in the department and director of the Brigham’s Voice Program, and colleagues report the details in The Laryngoscope.
The team compared four types of laser fiber models: a traditional forward-facing fiber (0° of angulation) and three side-firing fibers that emitted light at an angle of 45°, 70° or 90°. These were used under computer-generated simulated conditions:
- A simulation of the Pentax VNL-1570STK, a nasal flexible laryngoscope, carrying an optical fiber was deployed into seven different three-dimensional models of the larynx
- The models were created from micro-computed tomography scans of human cadaveric larynx specimens
- The laser fibers could be rotated independently of the endoscope
Even if a portion of tissue was reached by the simulated laser beam, it was considered inaccessible if the tissue surface was too distant from the laser fiber tip (arbitrarily defined as >3 mm) or the tissue was not directly visible from the endoscope’s camera.
The side-firing fibers granted more access to larynx tissue than the traditional forward-facing fiber, presumably because of the wider field:
- 45° vs. 0°—50% mean increase in tissue coverage
- 70° vs. 0°—74%
- 90° vs. 0°—84%
In addition, side-firing fibers provided access to areas of the larynx currently considered difficult to address, including the infraglottis, laryngeal ventricle, and areas of the right vocal fold.
Continued Scrutiny Needed
Although the angled fibers provided more potential tissue coverage, the undersurface of the false folds and true vocal folds weren’t visible to the endoscope in this simulation and might not be amenable to clinical intervention.
In addition, it must be considered that this simulation couldn’t assess the technical feasibility of achieving sufficient accuracy for laser treatment, especially considering that under real-life conditions in an awake patient, there would inevitably be movement of the larynx.