Medical Physics Seminar – Monday, October 21, 2013
Ultrasonic Motion Tracking for Large Deformations
Matthew Bayer (student of Dr. Tim Hall)
Research Assistant, Department of Medical Physics, UW-School of Medicine & Public Health, Madison, WI - USA -
Ultrasound elastography is a term for a variety of methods that use tracking
of tissue motion, either physiological or induced, in order to extract
information about tissue elastic properties. One property of interest is
the elastic nonlinearity, which measures the stiffening of tissue as it is
deformed. This nonlinearity may be able to help distinguish benign from
malignant breast tumors. Estimating nonlinearity requires large deformations
that are tracked over many steps through sequences of images, and this
multi-step tracking process contains temporal information that can be used
to improve tracking performance.
Our research has investigated the error properties for these sequences of
displacements, revealing unexpected covariances between displacement steps
that can guide the choice of tracking parameters. New tracking algorithms
have also been devised that take advantage of temporal continuity of
displacements to reduce errors. These findings and innovations promise to
improve tracking for the estimation of elastic nonlinearities as well as
other elastography methods.