Professor of Electrical and Computer Engineering and
Professor of Radiology
Yates Professor of Electrical and Computer Engineering
Ph.D., Cornell, 1965
Key Words:
Biomedical Ultrasound, Ultrasonic Signal Processing, Scattering, Imaging
Research Interests:
Research Goals and Specific Projects
The general objective of our work is the development of ultrasonic techniques
that improve the utility of ultrasound as a diagnostic tool in medicine.
To accomplish this objective, two major projects are underway. The first
is the characterization of wavefront distortion and the development of
adaptive compensation techniques. The second is development of high-resolution
and quantitative imaging techniques. Other current technical goals are
the determination of power spectra of tissue variations from the measurements
of angular scattering and the correlation of the measured scattering data
with the structure of tissue.
Studies of Wavefront Distortion and Compensation
Studies of wavefront distortion will emphasize collection of wavefront
distortion data from abdominal specimens, chest wall specimens, and other
tissue normally found between the transducer and structures being imaged.
Measurements will be made in a pulse-echo configuration with various f-number
transmitters to examine the influence of effective scattering volume size
on the estimation of time delay from scattering by a random medium. Measurements
will also be made to determine the isoplanatic patch size, i.e., the size
of the region over which a single set of corrections can be used effectively.
Wavefront compensation techniques will be evaluated using measured data
with new algorithms based on space-time processing methods developed in
our laboratory as well as with new algorithms developed by others.
High-Resolution and Quantitative Imaging
Studies of focussing through aberrations will be accomplished using our
special ring transducer system. Investigations of focussing through aberrations
will also be accomplished using our special two-dimensional array transducer
and associated electronics. Our focus correction methods are uniquely
able to compensate for distortion in the shape of waveforms as well as
in their arrival times. This involves calculations of predistorted waveforms
that are then emitted by individual elements driven by programmable signal
generators. Additionally, studies of image reconstruction techniques that
do not employ the Born or Rytov approximation will be conducted. These
studies will include analysis of a novel method in which eigenfunctions
of the scattering operator are employed.
