Detection of fluorescent and light-absorbing optical heterogeneity in tissue-mimicking phantoms using frequency-domain techniques
Both theory and experimental results show the capacity to locate the presence of a fluorescent volume incurred within a scattering medium from frequency-domain measurements of photon migration. Frequency-domain measurements consisted of monitoring the phase-shift and amplitude demodulation of fluorescent and excitation light reemitted from a tissue phantom in response to a sinusoidally modulated excitation source located 2.8 cm away from a detecting fiber positioned on the phantom periphery. Measurements of modulation phase- shift and amplitude were conducted as a 9 mm diameter cylindrical heterogeneity containing micromolar concentrations of IR-125 and DTTCI in 0.5%. Intralipid was moved within a 20 cm diameter vessel filled with 0.5 Intralipid. These measurements were investigated to evaluate the contrast offered by lifetime, fluorescent yield, and the fluorophore concentration difference between the heterogeneity and its surroundings. Our results show that the degree of contrast offered by fluorescence is always superior to that afforded by light absorption, enabling better detection of a diseased tissue with preferential fluorescent dye uptake. Contrast is also enhanced by the lifetime of the fluorescent dye, its uptake into simulated diseased volume, and the volume into which preferential uptake occurs relative to the surrounding tissues.
Advances in Fluorescence Sensing Technology III
- Pub Date:
- May 1997