The goal of this project is to create images of shear stiffness in tissue with the aim
to develop a new medical diagnostic tool. The data comes from performing two experiments
simultaneously. One of these experiments is to impart a low frequency (50-100 Hz)
impulse to the boundary of the tissue with a two bar device. The impulse produces a propagating elastic
wave that has both a fast moving compression wave (1500 meters/sec) and a much
slower moving shear wave (3 meters/sec in normal tissue). The compression wave is
immediately seen everywhere in a piece of tissue; however, the shear wave propagates slow enough to have an observable propagating
front. In the second experiment a transducer array located
between the bars measures the displacement of the downward component of the elastic
wave which makes it possible to determine the arrival time of the shear wave front at
each point in the tissue.
We show that the arrival time function determines the shear wave speed and use a level
set method to develop an algorithm to recover that wave speed. Images are created
from laboratory data from the laboratory of Mathias Fink, ESPCI, Paris where the ultrafast
data acquisition system developed in his lab generates the displacement data.
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