Study of fiber-optic probes for in vivo medical Raman spectroscopy

Recent reports indicate that useful diagnostic information can be obtained from ex vivo tissue by using near-infrared Raman spectroscopy. A fiber-optic-based Raman system has been constructed that can obtain spectra in vivo from tissue, typically in less than 30 s. The spectral details are limited by the fluorescence and Raman signal generated in the silica delivery and collection fibers. In this study, fiber-optic probes that are designed to suppress these confounding signals have been characterized and compared with a probe constructed of unfiltered silica fiber. These suppressing probes used a novel design with "in-the-tip" filters, which also had optimized light collection efficiency. The spatial point response functions of the fibers were measured in air, water, and a tissue-simulating, optically turbid medium. Spectra from rabbit tissues were also collected with these probes to demonstrate their performance.