Bilirubin calculi crushing by laser irradiation at a molecular oscillatingregion wavelength eased on infrared absorption spectrum analysis using a free-electron laser: An experimental study

We investigated a new laser technique of crushing bilirubin calculi, our ai m being to crush calculi in isolation using a minimally invasive procedure. Infrared absorption spectrum analysis of the bilirubin calculi was conduct ed, revealing maximum absorption spectrum at a wavelength of the C=O stretc hing vibration of ester binding that exists within the molecular structure of bilirubin calcium. As an experiment to crush calculi using the free-elec tron laser, we set the laser at the effective irradiation wavelength of est er binding, and conducted noncontact irradiation of the bilirubin calculi. The calculi began to slowly ablate until the irradiated site had been compl etely obliterated after 20s of irradiation. Moreover, absorption spectrum a nalysis of the irradiated site, from a comparison of absorption peak ratios , revealed that absorption peak intensities decreased over time at the abso rption wavelength of ester binding. These findings suggest that irradiation of molecular oscillating region wavelengths peculiar to calculi based on i nfrared absorption spectrum analysis results in the gradual crushing of cal culi in isolation by breaking down their molecular structure.