Time-resolved optical imaging of a solid tissue-equivalent phantom.

A solid plastic phantom has been developed with optical properties that closely match those of human breast tissue at near-IR wavelengths. The phantom is a 54-mm-thick slab containing four small cylinders of contrasting scatter and absorption. A detailed description of the phantom is followed by an account of an attempt to image the phantom by a time-resolved imaging technique. Images generated with transmitted light with the shortest flight times revealed the embedded cylinders with greater visibility than images obtained with continuous light transillumination. However, images corresponding to flight times of less than ~700 ps were severely degraded from a lack of detected photons. An attempt was made to overcome this degradation by extrapolating the measured temporal distributions with an analytic model of photon transport. Results suggest that subcentimeter resolution imaging of low-contrast tumors in the breast is scientifically possible. Our phantom is available to any other research groups wishing to evaluate their systems.