Interest in computing ultrasonic images from scattering data taken over many views has been stimulated by the clinical utility of systems that employ x-rays to produce tomograms from a number of projections. However, analogous ultrasonic methods based on simplifying assumptions that usually neglect multiple scattering effects have not yielded satisfactory quantitative images. Success, nevertheless, appears now possible because limitations of available imaging methods are better understood, new ultrasonic instrumentation has been developed, progress in the theory of inverse scattering has been made, and computing expertise as well as suitable hardware facilities are available for the solution of relevant large scale optimization and computing problems. This research utilizes data measured using a unique ring transducer system. The system permits transmit waveforms to be individually programmed, synthesis of arbitrary transmit and receive apertures, and alteration of transmit beams as well as receive focussing for iterative reconstruction. A new method of image reconstruction that uses eigenfunctions of the scattering operator has been developed. The method expresses the solution of the full nonlinear problem as an expansion in products of retransmitted fields defined in terms of the eigenfunctions. Progress has included compensation of transducer aberrations, high-resolution compound b-scan imaging, adaptive adjustment of gain, design of prescribed pulse wavefronts, development of an efficient solver for forward problems, and experience with measurements as well as computations for simple test objects. Overall, a strategy using eigenfunction analysis and optimization is being pursued to reconstruct images from measurements of scattering. Further studies will involve additional development of the current forward problem solver, measurements of scattering produced by larger and more complicated test objects, and continued development of the present image reconstruction method using eigenfunctions. Success in this research would significantly extend ultrasonic capabilities particularly in the area of breast imaging.
| Chiang, Chi-Tung; Shores, Kevin S; Freindorf, Marek et al. (2008) Size-restricted proton transfer within toluene-methanol cluster ions. J Phys Chem A 112:11559-65 |
| Kazmierkiewicz, Rajmund; Liwo, Adam; Scheraga, Harold A (2003) Addition of side chains to a known backbone with defined side-chain centroids. Biophys Chem 100:261-80 |
| Kazmierkiewicz, Rajmund; Liwo, Adam; Scheraga, Harold A (2002) Energy-based reconstruction of a protein backbone from its alpha-carbon trace by a Monte-Carlo method. J Comput Chem 23:715-23 |
| Liwo, Adam; Arlukowicz, Piotr; Czaplewski, Cezary et al. (2002) A method for optimizing potential-energy functions by a hierarchical design of the potential-energy landscape: application to the UNRES force field. Proc Natl Acad Sci U S A 99:1937-42 |
| Scheraga, Harold A; Pillardy, Jaroslaw; Liwo, Adam et al. (2002) Evolution of physics-based methodology for exploring the conformational energy landscape of proteins. J Comput Chem 23:28-34 |
| Scheraga, Harold A; Vila, Jorge A; Ripoll, Daniel R (2002) Helix-coil transitions re-visited. Biophys Chem 101-102:255-65 |
| Pillardy, J; Arnautova, Y A; Czaplewski, C et al. (2001) Conformation-family Monte Carlo: a new method for crystal structure prediction. Proc Natl Acad Sci U S A 98:12351-6 |
| Vila, J A; Ripoll, D R; Scheraga, H A (2001) Influence of lysine content and pH on the stability of alanine-based copolypeptides. Biopolymers 58:235-46 |
| Pillardy, J; Czaplewski, C; Liwo, A et al. (2001) Recent improvements in prediction of protein structure by global optimization of a potential energy function. Proc Natl Acad Sci U S A 98:2329-33 |
| Czaplewski, C; Rodziewicz-Motowidlo, S; Liwo, A et al. (2000) Molecular simulation study of cooperativity in hydrophobic association. Protein Sci 9:1235-45 |
Showing the most recent 10 out of 20 publications
