Quantification of fluorophore concentration in tissue-simulating media by fluorescence measurements with a single optical fiber

Abstract

Quantifying fluorescent compounds in turbid media such as tissue is made difficult by the effects of multiple scattering and absorption of the excitation and emission light. The approach that we used was to measure fluorescence using a single 200-microm optical fiber as both the illumination source and the detector. Fluorescence of aluminum phthalocyanine tetrasulfonate (AlPcS4) was measured over a wide range of fluorophore concentrations and optical properties in tissue-simulating phantoms. A root-mean-square accuracy of 10.6% in AlPcS4 concentration was attainable when fluorescence was measured either interstitially or at the phantom surface. The individual effects of scattering, absorption, and the scattering phase function on the fluorescence signal were also studied by experiments and Monte Carlo simulations.

Intravascular near-infrared fluorescence catheter with ultrasound guidance and blood attenuation correction

“…Diffusion models of light propagation have demonstrated average RMSE between 5% and 25% when measuring fluorescence from tissue-mimicking phantoms, and a similar 1-D formulation demonstrated less than 10% RMSE when assessing fluorescence from epithelial and stromal tissues within the human cervix. 29,31,32,44 A limitation of these approaches is the reliance on a priori knowledge of the optical properties of the tissues being studied. The attenuation of whole blood can be measured prior to an imaging procedure, but the optical properties of the vessel wall cannot.…”

“…After calibration to known fluorophore concentrations in tissue-mimicking phantoms, estimated values of μ a;f;x · Φ can be used to determine the concentration of unknown fluorescent samples. 32 …”

A review of attenuation correction techniques for tissue fluorescence

“…The use of multiple optical-fibres ensured a good signal to noise ratio was obtained. Diamond et al (2003b) extended the work by establishing a calibration curve to allow fluorophore concentrations to be quantified. For wavelengths in the red to near infrared region, fluorophore concentrations were recovered from tissue phantoms with an r.m.s.…”

Prostate PDT dosimetry

“…Recent in vivo studies have shown large variation of photosensitizer concentration in different tissue types, thus suggesting determination of this quantity in vivo in the region of treatment directly [22,58]. To include the drug concentration in the evaluation of PDT dose, in situ fluorescence [59] or absorption [39,[60][61][62][63] measurements of photosensitizer can be made interstitially using optical fibers. Absorption spectroscopy has the advantage that, in addition to drug concentration, tissue hemodynamics can be monitored, which is important because tissue oxygenation is known to affect PDT efficacy in vitro [36,64].…”