Systems, methods, and apparatus for providing a fluid and reduced-toxicity optical media with optical analysis and therapeutic energy delivery. An aspect of the invention provides an aqueous solution of increased-salinity of between about 1% and 35%. An increasing salinity in accordance with the invention provides improved transmissive efficiency at many wavelengths and less toxicity than many existing systems and methods. A catheter having integrated fibers for probing or treating internal lumens or other tissues can include a liquid-inflatable balloon or flushing mechanism using the solution for displacing blood or other obstructions in an optical path between the fiber and targeted tissue. Methods including spectroscopy can be employed with the solution for diagnosing medical conditions associated with diseased vessels or other tissues while reducing the risk of permanent damage resulting from the diagnosis. Additional applications include the deliver of therapeutic radiation externally and internally to tissues through h the solution media.
