Assessment of Flatness of Assumed Planar Surfaces for Ultrasound Investigation of Elastic Surfaces

AbstractThis study investigate the planarity of an assumed planar surface made of an elasomer fixed on its perimeter by a square acrylic frame. The central part of this surface is insonified with two different linear array transducers (types 8811 and 8670, BK Medical), yielding 11 images forming two 3D data sets. The change in flatness of the surface was determined by cross-correlation of the matrix of received signals. The cross-correlation was calculated between signals from the same image and as well as between signals that belonged to different images. The maximal change over the entire surface investigated is found to be in the order of a wavelength at about 12MHz (λ=120μm). Specifically, the surface showed weak concave bending for the two different transducers. The data was validated using the cross-correlation coefficient function. This yielded values of 0.99± 0.01 (mean± std) when the algorithm was applied to scan-lines in the same image plane and 0.93± 0.05 when it was applied to scanlines in different image planes