Optical Coupling Method to Improve Laser Lithotripsy

Abstract

Four cystine stones immersed in water or aqueous solutions of carmine indigo (4% diluted 1:20) or methylene blue (1% diluted 1:20) with rifamycin (0.6% and 6%) and rifampicin (0.3% and 0.3%) were treated with 200 shots from a dye laser at 504 nm (energy 60 to 100 mJ). Another four stones were treated under the same conditions using an alexandrite laser at 755 nm (energy 40 to 80 mJ). The spectra of the substances, when previously analyzed with the spectrophotometer (optical path 1.0 mm) showed an absorption of almost 100% for rifamycin and rifampicin at a wave length of 504 nm. The most successful fragmentation occurred when the dye laser was used to treat stones immersed in rifamycin and rifampicin at the higher concentrations, whereas the dye laser was almost totally ineffective in fragmentating stones in carmine indigo and methylene blue solutions. The alexandrite laser failed to provoke fragmentation in stones immersed in any of the solutions. The quantity of fragmented material produced by treating a 10-cm³ cystine stone previously immersed in rifamycin and rifampicin, 0.3 and 0.1 cm³, respectively, confirmed previous results. The clinical use of rifamycin and rifampicin as mediators of lasertripsy is suggested, as they seem to increase the absorption of laser radiation by the stone.