AN OPTICAL PHANTOM WITH TISSUE-LIKE PROPERTIES IN THE VISIBLE FOR USEIN PDT AND FLUORESCENCE SPECTROSCOPY

The design and characterization of optical phantoms which have the sam e absorption and scattering characteristics as biological tissues in a broad spectral window (between 400 and 650 nm) are presented. These l ow-cost phantoms use agarose dissolved in water as the transparent mat rix. The latter is loaded with various amounts of silicon dioxide, Int ralipid, ink, blood, azide, penicillin, bovine serum and fluorochromes . The silicon dioxide and Intralipid particles are responsible for the light scattering whereas the ink and blood are the absorbers. The pen icillin and the azide are used to ensure the conservation of such phan toms when stored at 4 degrees C. The serum and fluorochromes, such as Coumarin 30, produce an autofluorescence similar to human tissues. Var ious fluorochromes or photosensitizers can be added to these phantoms to simulate a cancer photodetection procedure. The absorption and fluo rescence spectroscopy of the porphyrin-type fluorescent markers used c linically for such photodetection procedures is similar in these phant oms and in live tissues. The mechanical properties of these gelatinous phantoms are also of interest as they can easily be moulded and resha ped with a conventional cutter so that complex structures and shapes, with different optical properties, can be designed. The optical proper ties of these phantoms were determined between 400 and 650 nm by measu ring their effective attenuation coefficient (mu(eff)) and total refle ctance (R-d) The microscopic absorption and reduced scattering coeffic ients (mu(a), mu(s)') were deduced from mu(eff) and R-d using a Monte Carlo simulation.