TITLE:
Mid-Infrared Pulsed Laser Lithotripsy with a Tunable Laser Using Difference-Frequency Generation
AUTHORS:
Hisanao Hazama, Hiromu Kutsumi, Kunio Awazu
KEYWORDS:
Gallstone; Lithotripsy; Mid-Infrared Tunable Laser; Difference-Frequency Generation
JOURNAL NAME:
Optics and Photonics Journal,
Vol.3 No.4A,
August
9,
2013
ABSTRACT: A novel technique of lithotripsy was investigated with a
mid-infrared tunable pulsed laser using difference-frequency generation (DFG).
Human gallstone samples obtained from 24 patients were analyzed with their
infrared absorption spectra. It was found that the principal components of the
gallstones were different for the different patients and that the gallstone
samples used in this research could be classified into four groups, i.e., mixed stones, calcium bilirubinate
stones, cholesterol stones, and calcium carbonate stones. In addition, some
gallstone samples had different compositions within the single stone. The
mid-infrared laser tunable within a wavelength range of 5.5 - 10 μm was
irradiated to the cholesterol stones at two different wavelengths of 6.83 and
6.03 μm, where the cholesterol stones had relatively strong and weak absorption
peaks, respectively. As the result, the cholesterol stones were more
efficiently ablated at the wavelength of 6.83 μm with the strong absorption
peak. Therefore, it is suggested that the gallstones could be efficiently ablated
by tuning the wavelength of the laser to the strong absorption peak of the
gallstones. The higher efficiency of the ablation using the characteristic
absorption peaks should lead to the safer treatment without damage to the
surrounding normal tissues. In order to identify the composition of the
gallstones in the patients, endoscopic and spectroscopic diagnosis using the
DFG laser and an optical fiber probe made with two hollow optical fibers and a
diamond attenuation total reflection prism should be useful. The absorption
spectrum of the gallstones in the patients could be measured by measuring the
energy of the DFG laser transmitted through the optical fiber probe and by
scanning the wavelength of the DFG laser.