Fine mapping of tissue properties on excised samples of melanoma and skin without the need for histological staining.

This paper develops a novel two-frequency approach for noninvasive evaluation of cancerous tissue with optimum depth and resolution. Frequencies of about 50 MHz are used in thickly sliced tissue to detect differences of the relative attenuation (C-scan mode scanning) with relatively limited resolution. Thus, suspect zones can be identified according to a quantitative criterion. These suspect zones are then selected for preparation of thin, transversal slices from within the original thick slices. Very-high-resolution (1-μm) visualization of cells is obtained at around 600 MHz on these transversal sections and adjacent sections are prepared for histological study in parallel. The technique's feasibility and potential are demonstrated on both normal and cancerous (melanoma) skin tissue. Isotropy of the specimens is experimentally verified to ensure that conditions were coherent for use of a 5-layer, angular spectrum model made to simulate longitudinal velocity, allowing estimation of longitudinal velocity from semiquantitative V(z) data.