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18 December 1995 Time-resolved transmittance imaging with a diffusion model
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Images of realistic tissue phantoms were obtained by means of time-resolved transmittance measurements interpreted with the diffusion theory. A system for time-correlated single photon counting was used to collect time-resolved transmittance curves with an instrument response less than 50 ps (FWHM). Tissue phantoms were agarose solutions containing appropriate amounts of ink (absorber) and intralipid (diffuser). The optical properties selected for the background ((mu) 's approximately equal to 8 cm -1 and (mu) a approximately equal to 0.1 cm-1) were typical for tissues at near infrared wavelengths and the thickness (4.3 cm) was comparable with the average values in x-ray mammography. The presence of a tumor mass was simulated through an embedded agarose cylinder (6 or 11 mm in diameter). The optical parameters of the inclusion were increased by a factor of 1.5 or 2 with respect to the values in the surrounding medium. Measurements were performed over a 4 cm by 4 cm area, with an acquisition point every 2 mm. With an incident power less than 1 mW, the typical acquisition time was 1 sec/point. The experimental data were fitted with the diffusion approximation to evaluate (mu) 's and (mu) a. Images were constructed by plotting the optical parameters as a function of position. For comparison, time-gated images were constructed from the same experimental curves as used for the fit. The technique proved more sensitive than time-gating to changes in scattering properties. On the contrary, it was not possible to obtain good quality images based on differences in the absorption coefficient.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Rinaldo Cubeddu, Antonio Pifferi, Paola Taroni, Alessandro Torricelli, and Gianluca Valentini "Time-resolved transmittance imaging with a diffusion model", Proc. SPIE 2626, Photon Propagation in Tissues, (18 December 1995);

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