IN-VIVO MEASUREMENT OF DYE CONCENTRATION USING AN EVANESCENT-WAVE OPTICAL SENSOR

A miniaturised evanescent-wave optical sensor is proposed for in vivo measurement of dye concentrations. It enables a continuous monitoring to the optical-dye attenuation or fluorescence spectra between 380 and 650 nm. The sensor is constructed with polished fibres: the cladding of a single-mode fibre is removed by longitudinal polishing. The proxi mity of the core to the medium favours penetration of the evanescent p art of the modal field into the bio fluid. The dimensions of the probe permit several potential applications: for example, insertion into hy podermic needles for spectroscopic analysis of tissues and blood. In t he paper, a gastro-enterologic application of the sensor introduced in to a catheter is reported. In vivo tests demonstrate the feasibility o f quantitative measurement of dye clearance in the gastro-oesophageal tract.