Detection of malignant tissues by using infrared microscopy and fiberoptic spectroscopy

Optical fibers transparent in the mid-infrared (IR) make it possible to carry out absorption measurements in remote location. Such IR fibers can be used for measurements in the Attenuated Total Reflectance (ATR)-mode. If the IR-fiber is in contact with a sample that has characteristic absorption lines, the total transmission of the fiber and sample will decrease at these lines. This can be used to determine the absorption of a sample in a non-destructive manner. It has been known that normal tissues exhibit absorption spectra different from diseased tissues, and each diseased state of biological tissue has its own characteristic IR spectral pattern. In this work we report our effort to develop an infrared method to differentiate between malignant and healthy tissue in vivo. This paper will present the technical design of the laboratory set up and the results obtained in experiments carried out on melanoma tumors in the skin of male mice. Silver halide fibers were used to carry out ATR measurements on tumor sections. Further results were compared with detailed measurements carried out using an FTIR-microscope and thin tissue sections in the spectral range of 4000 - 900 cm^-1. The results indicate that IR spectroscopy would be a useful tool for biodiagnosis, in vivo and in real time. The fiberoptic method described here will easily lend itself to endoscopic applications.