There are substantial technical problems attendant to the
removal of sessile polyps from the lumen of thin walled
gastrointestinal organs such as the colon. A laser system which
is capable of precise and circumscribed mucosal tissue vaporization
would be useful for this task. Because of technical shortcomings
of existing medical laser systems, we investigated the
possibilities of mid-infrared lasers which could take advantage of
large water absorption peaks in the 2 micron region to produce
precise vaporization while retaining fiberoptic transmissibility.
In addition to a high absorption wavelength, pulsed energy delivery
contributes to precise vaporizing capabilities. The laser system
that best fits our criteria is the 2.15 micron thulium-holmium-
chromium:YAG which produces 200 microsecond pulses of energies up
to 1 joule at firing rates up to 6 Hz. The laser output is
transmitted efficiently via low hydroxyl quartz fibers. Ablative
efficiency, defined here as the slope of the vaporization depth
versus energy, reveals that the THC:YAG produces approximately 3
times greater depth of vaporization per joule than the cw Nd:YAG.
On average, the Nd:YAG produced 1.5 times the amount of thermal
damage as the THC:YAG for a given depth of vaporization. The
THC:YAG laser should have an important clinical role since its use
could reduce the risk of perforation in endoscopic laser procedures
such as the removal of sessile polyps.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.