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Steady-state and time-resolved fluorescence spectra for detection of colonic cancer

The steady-state and time-resolved autofluorescence spectroscopic differences between normal and carcinomatous colonic tissues and the optimal excitation wavelengths were studied. The fluorescence excitation wavelengths varying form 260 to 540 nm were used to induce tissue autofluorescence, and the corresponding emission spectra were measured in the range from 280 to 800 nm. These spectra then can be assembled into an excitation-emission matrix (EEM). Significant changes in fluorescence intensity of excitation-emission matrices were observed between normal and tumor colonic tissues. Low NAD(P)H and FAD, and high protoporphyrin IX fluorescence characterize high-grade malignant tissue when compared with normal colonic tissue, and the most marked difference being at the excitation wavelengths of 340, 380, 460 and 540 nm. Furthermore, the average lifetimes for the normal and carcinomatous colonic tissues were about 4.12 and 18.8 ns, respectively. The promising applications of laser-induced autofluorescence for colonic tissue diagnosis are indicated.