Tissue Characterisation Using Acoustic Microscopy
It has been recognised for some time in clinical ultrasound that the speckle-like appearance of regions of relatively homogeneous tissue in B scans can provide significant diagnostic information - particularly in the case of diffuse disease. Improved understanding of the scattering and diffractive processes experienced by an acoustic wave propagating through such tissue regions can be expected to enhance the clinical assessment of the corresponding B scans.
The scanning acoustic microscope provides a suitable method for imaging variations in the acoustic properties of in vitro samples with a resolution comparable to the acoustic wavelength. We discuss here techniques for the derivation of quantitative values for velocity and impedance from acoustic microscope image data. In particular we demonstrate the validity of a paraxial theory of microscope operation and show that enhanced sensitivity can be achieved by careful selection of the microscope coupling liquid. Maps of acoustic velocity and impedance are derived for human liver.
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