<title>Optical measurement of photosensitizer concentration using a probe with a small source-detector fiber separation</title>

Abstract

We present a novel minimally invasive method to measure the concentration of photodynamic thearapy drugs in real time. The method is based on measurements of backscattered and fluorescence light using a steady state fluorescence spectrometer. The ratio of the fluorescence to scattered light is found to be linearly proportional to the absorption coefficient of the photosensitizer. The fiber-optic probe used for the measurements has a small source-detector separation, therefore the measurements could be performed through the working channel of an endoscope.

Detecting cervical cancer progression through extracted intrinsic fluorescence and principal component analysis

“…Various techniques have been used to correct for the attenuation due to scatterers and absorbers from the measured fluorescence of the tissue samples. Schemes developed with judicious combinations of measurements like an intensity ratio of the fluorescence to scattered light, 12 ratios of diffuse reflectance, 13,14 and ratios of autofluorescence 15,16 at different wavelengths are used to extract intrinsic fluorescence. However, their accuracy in correcting for the attenuation is limited since the wavelength dependence of optical parameters is not taken into account.…”

A review of attenuation correction techniques for tissue fluorescence

“…Measurements made at a particular distance selectively record photons which have travelled, on average, a particular path length through the tissue. Canpolat & Mourant (2000) proposed that the concentration of an exogenous fluorophore could be recovered by determining the fluorescence-reflectance ratio at a specific distance. According to Beer's law, the ratio should vary proportionally with fluorophore concentration provided the product of fluorophore absorption coefficient and path length is less than 1, and the background absorption remains constant.…”