Abstract
Selective excitation or selective dissociation of molecules is possible using various characteristic absorption
lines caused by molecular vibrations in the mid-infrared (MIR) wavelength region. Therefore, less
invasive diagnosis and treatment are possible using MIR lasers. We successfully demonstrated the selective
removal of atherosclerotic lesion with a MIR tunable laser at a wavelength of 5.75 μm, which corresponds
to the characteristic absorption of the ester bond in the cholesterol esters in atherosclerotic lesions.
We developed a probe for endoscopic diagnosis with an attenuated total reflection (ATR) prism
and two hollow optical fibers for the diagnosis of gallstones. Cholesterol’s absorption spectrum was
measured with an ATR probe by scanning the wavelength of the MIR tunable laser, and the spectrum
was in good agreement with that measured by a commercial Fourier transform infrared spectrometer.
Safe treatment of early gastric cancer using endoscopic submucosal dissection with a CO2 laser was also
successfully demonstrated.
