Study of Diagnosis Criteria for Pathological Tissues by Laser-Induced Fluorescence

Abstract

It has been confirmed that the differences in fluorescence spectra of normal and pathological biotissues can be used as a sensitive and nondestructive diagnostic probe. However, experiments show that not only are the fluorescence spectral features of different tissues very different but the features of the same tissue under different detection conditions are different too. Therefore, the diagnosis criteria of pathological tissues must be changed in accordance with different spectral features. In this paper, several diagnosis methods using native fluorescence characteristics of biotissues given in existing reports are analyzed. With the fourth harmonic at 266 nm of a Q-switched YAG laser as an excitation source, laser-induced fluorescence (LIF) spectra of native human normal and pathological breast and blood vessel tissues in vitro were measured and studied. According to their spectral characteristics, two diagnosis criteria are suggested: by the fluorescence intensity ratios at several specific wavelengths, cancerous (with p < 0.001) and benign tumor (p < 0.005) can be distinguished from the normal tissue; by the fluorescence intensity ratios of the two main peaks, atherosclerotic plague and thrombus (both with p < 0.005) can be distinguished from normal blood vessel. In order to make comparisons with the results from human cancerous breast tissues, spectra of a model mouse were also observed.