Since carbon dioxide laser is
excellent for incision, hemostasis, coagulation, and vaporization of soft
tissues, it has been widely applied in clinical treatments as the laser knife.
In these days, flexible thin hollow optical fibers transmitting mid-infrared
light have been developed, and the application of carbon dioxide laser to
endoscopic therapy has become possible. However, it is expected that the
irradiation effect is influenced by the change in the laser power at the tip of
the hollow optical fiber due to the change in the transmittance by the bending
loss. The purpose of this research is to quantitatively evaluate the change in
the output power and therapeutic effect by bending the hollow optical fiber in
a gastrointestinal endoscope. The change in the transmittance of the hollow
optical fiber due to the insertion of the fiber into the endoscope and bending
of the head of the endoscope was measured. Then, the relationship between the
irradiated laser power and the incision depth for a porcine stomach was
investigated. As the results, the most significant decrease in the
transmittance of the hollow optical fiber was caused by the insertion of the
fiber into the instrument channel of the endoscope, and
bending of the head of the endoscope with the angle of 90° decreased the output
laser power and incision depth by 10% and 25%, respectively. Therefore, it was
confirmed that the bending loss of the hollow optical fiber due to the bending
of the head of the endoscope had no significant influence on the endoscopic
therapy using the carbon dioxide laser.
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