RESOLUTION OF TIME-RESOLVED BREAST TRANSILLUMINATION - IN-VITRO MEASUREMENTS COMPARED WITH THEORETICAL PREDICTIONS

The resolution of time-gated breast transillumination images has been investigated both theoretically and experimentally. The resolution lim it is quantified as the size of the smallest object visible on an imag e (the image quality index), which depends on such image parameters as the transfer function, the contrast, and the noise. The smallest diam eter of a detectable carcinoma located in the breast has been determin ed on the basis of Monte Carte simulation results as well as in vitro time-of-flight measurements on breast samples. The comparison of the M onte Carte simulation of light propagation within biological tissues w ith the experimental data has been able to confirm the validity of the simulation. The simulation results, compared with measurements, sugge st that the formation of time-resolved transillumination images of bio logical tissues can be adequately modeled in the near infrared. The en hancement of the transfer function by the introduction of time-gated d etection is verified, and the limiting contribution of the noise at sh ort integration times has been investigated. The estimated diameter of the smallest detectable sphere embedded on the front surface of a 20- mm-thick breast slab is around 3 mm. Extrapolated for a full-size brea st, the estimate is still better by a factor of 2 than the resolution of classical diaphanography, which is commonly taken to be worse than 20 mm.