Fiber-optical and microscopic detection of malignant tissue by use of infrared spectrometry.

Several investigations were performed in order to develop an in vivo endoscopic method to differentiate between malignant and healthy tissue working on the assumption that each diseased state of biological tissue has its own characteristic infrared (IR) spectral pattern. The technical design of the laboratory setup is presented here together with the experimental details and the results. Two regions (1245-1195) and (1045-995) cm(-1) within the fingerprint (<1500 cm(-1)) region were selected for analysis. Lead salt diode lasers were used as excitation sources and IR radiation was transmitted via silver halide wave guides to the tissue to be investigated. The IR radiation is returned to a mercury-cadmium-telluride detector by another IR cable. The measurements were carried out in attenuated total reflectance and diffuse reflection/remission. Human colon carcinoma tissue, under humid conditions, was used as a target for experiments to simulate in vivo conditions. Specimens were mapped using a stepper, motor powered, x/y/z-translation stage with a spatial resolution of 1 microm. The results were compared with similar measurements from a Fourier transform IR (FTIR) interferometer/FTIR microscope setup in the wave number region of 4000-900 cm(-1).