Identification of cholesterol gallstones using in vitro low-fluence laser-induced fluorescence spectroscopic analysis

Identifying the chemical composition of gallstones may be important in certain cases of calculus biliary disease when planning a dissolution therapy or a fragmentation of the calculi using pulsed lasers. The present study was conducted in vitro to evaluate the feasibility of distinguishing cholesterol gallstones from pigment stones. We propose an identification method in which the stone fluorescence spectrum, induced by a low fluence laser, is recorded using an optical multichannel analyser. Fluorescence spectra of twenty-two stones were recorded together with the fluorescence spectra of various pure compounds likely to compose the gallstones, using successively four different pump lasers (_p=308 nm, 337 nm, 423 nm, 469 nm). The fluorescence spectra of cholesterol gallstones are quite different from the pigment ones. Ratios of fluorescence intensities taken at three different wavelengths enable one to distinguish easily between cholesterol and pigment stones.