TRA Based Ultrasound Focusing

Time Reversal Acoustics (TRA) is a novel concept introduced by Mathias Fink of the University of Paris for focusing and steering acoustic beams in complex heterogeneous media. Scattering, refractions and reflections in highly inhomogeneous media, which distort focusing in conventional acoustic focusing systems and are viewed as a significant technical hurdle, lead to improvement of the focusing ability of the TRA system. Thus, TRA takes advantage of these usually undesirable processes. Artann Laboratories has developed a family of TRA Electronic Systems for a variety of medical and industrial applications based on Time Reversal Acoustics principles. TRA electronic systems can receive, digitize, store, time reverse and transmit acoustic signals in a wide frequency range. The projects of Artann based on the use of the TRA principles conducted in the last few years include the NIH funded projects “Diagnostic Technologies Based on Acoustic Radiation Force” and ”MR Elastography Using Time Reversed Acoustics” (conducted in collaboration with the University of Michigan), “Land Mine Detection By Time Reversal Acousto-Seismic Method” project supported by the Department of Defense, NASA funded project “Time Reversal Acoustic Structural Health Monitoring Using Array Of Embedded Sensors", and “Vibration Based Structural Health Monitoring using Time Reversal Acoustics” funded by DoD/AirForce.

Applications of Time Reversal Acoustics

• Medical Diagnostics

• Land Mine Detection

• Structural Health Monitoring

• Nondestructive Evaluation of Composite Materials

Medical Diagnostics 

For the past four years, Artann has been exploring the possibility of using TRA based focusing of ultrasound in applications related to Elasticity Imaging, a recently emerged medical diagnostic technique aiming at visualization of tissue mechanical parameters and structure. Elasticity Imaging is an area of activity of Artann from its very inception. Artann pioneered development of a branch of Elasticity Imaging, Shear Wave Elasticity Imaging (SWEI). The core of SWEI is remote generation of shear wave in the tissue by radiation pressure of focused ultrasound and following detection and visualization of shear wave propagation. Tissue motion resulting from the shear wave can be detected either by ultrasound or by MRI. Artann is exploring both ultrasonic and MR approaches to detection and visualization of propagating shear waves. The use TRA focusing of ultrasound to generate highly localized shear stress has numerous advantages over alternative techniques.

Artann has completed two NIH-funded projects related to SWEI using TRA focusing. The first project, conducted in collaboration with the University of Paris, France, and Kharkiv National University, Ukraine, was based on remote detection of shear waves using ultrasound Doppler techniques. One of the key goals of this project was quantitative assessment of soft tissue viscosity, which appeared to be a highly informative structural parameter reflecting pathological changes in tissue. Several laboratory prototypes demonstrating feasibility of the technique were built and successfully tested.

The second project conducted in collaboration with the University of Michigan, Ann Arbor, was on Magnetic Resonance (MR) Elastography based on Shear Wave Elasticity Imaging (SWEI) using the TRA focusing of ultrasound. The goal of the project was to enhance diagnostic potential of MRI by adding to it additional tissue characterization abilities. MR compatible TRA based ultrasound focusing system is designed as an attachment to conventional MRI devices.

Land Mine Detection 

Artann in collaboration with Los Alamos National Laboratory developed a method of land mine detection based on the combination of TRA with nonlinear acoustic method. TRA is very effective at focusing seismic waves in time and space, significantly improving detection capabilities using both linear and nonlinear acoustic wave methods. The feasibility of the developed approach is being tested the laboratory and in small scale field experiments under the project funded by US Army.

Structural Health Monitoring 

In a project funded by NASA and conducted in collaboration with Los Alamos National Laboratories, Artann developed a new approach to in-situ nondestructive evaluation (NDE) for airspace, automotive, and other industries based on TRA principles of ultrasonic scanning using embedded sensors. TRA-based focusing of ultrasonic waves in combinations with embedded sensors and nonlinear acoustic methods has a potential of highly improving sensitivity of conventional acoustic NDE methods. The TRA focusing system provides high concentration of the ultrasound energy in the tested region, thus enhancing nonlinear acoustic effects (for example, higher harmonic generation). The analysis of TRA signal distortion and nonlinear acoustic effects in the different paths of propagation provides information necessary for tomographic mapping of damage and degradation.

Nondestructive Evaluation of Composite Materials 

In a project funded by the DOD/Air Force, Artann developed a prototype of a portable device based on the TRA principles for assessment of fiber composites and fiber hybrids, for quality control in the manufacturing, and the assessment of structural integrity of materials prior to assembly, immediately following assembly, and during operational life. Although immediate applications of the device are for detection of flaws, cracks, and progressive damage of composite material parts, the approaches and instrumentation developed in Artann is also applicable to a multitude parts, structures and samples featuring a variety of materials and shapes, including all composite materials, carbon and graphite fiber, metals, glass, sandstone, and concrete parts.

Presentations and Publications

1. Dos Santos S, Choi BK, Sutin A, Sarvazyan A: Nonlinear imaging based on time reversal acoustic focusing. Proc 8-th Congress of French Acoustics 2006; Tours, France:359-362.
2. Choi BK, Sutin A, Sarvazyan A. Time reversal acoustic focused field and its prediction based on impulse response. The 9th Western Pacific Acoustic Conference 2006 June; Seoul, Korea.
3. Sutin A, Libbey B, Kurtenoks V, Fenneman D, Sarvazyan A: Nonlinear detection of land mines using wide bandwidth time-reversal techniques. Proc SPIE 2006; 6217:398-409, Detection and Remediation Technologies for Mines and Minelike Targets XI; Thomas J Broach, Russell S Harmon, John H Holloway Jr; Eds.
4. Kharin N, Choi BK, Sutin A, Davis B, Sarvazyan A: Nonlinear acoustic assessment of the human calcaneus. XII Workshop Nonlinear Elasticity in Materials 2006 June; Sorrento, Italy.
5. Sutin A, Sinelnikov Y, Sarvazyan A: Time reversal acoustic focusing system based on the liquid-filled acoustic resonator. 150th Meeting of the Acoustical Society of America, 2006 June; Providence, RI.
6. Sinelnikov Y, Sutin A, Zou Y, Sarvazyan A: Time reversal acoustic focusing with liquid resonator for medical applications. Internat Symposium on Therapeutic Ultrasound 2006 Aug-Sep; Oxford University, UK.
7. Sutin A, Johnson P, TenCate J, Sarvazyan A: Time reversal acousto-seismic method for land mine detection. Proc SPIE 5794 2005; 706.
8. Ostrovsky L, Ilinskii Y, Sarvazyan A, Sutin A: Non-dissipative mechanisms of radiation force and shear wave generation. J Acoust Soc Am 2005; 118.
9. Sarvazyan A, Sutin A: Generation of ultrasound radiation force with the use of time reversal acoustics principles. J Acoust Soc Am 2005; 118.
10. Haworth K, Kripfgans O, Steele D, Swanson S, Sutin A, Sarvazyan A:\ Acoustically induced tissue displacement for shear wave elasticity imaging using MRI. J Acoust Soc Am 2005; 118:1942.
11. Sutin A, Sarvazyan A: Advantages of time reversal acoustic focusing system in biomedical applications. J Acoust Soc Am 2005; 118:1941.
12. Ostrovsky L, Sutin A, Sarvazyan A: Forces generated in biological tissue-like media due to second-order effects in the focal region of an ultrasonic beam. J Acoust Soc Am 2004; 116:2598.
13. Sutin A, Roides E, Sarvazyan A: Optimization of time-reversal acoustic focusing. J Acoust Soc Am 2004; 116:2568.
14. Sutin A, Roides E, Sarvazyan A: Damage detection in composites using the time-reversal acoustics method. J Acoust Soc Am 2004; 116:2567.
15. Sutin A, Sarvazyan A, Johnson P, TenCate J: Land mine detection by time reversal acousto-seismic method. J Acoust Soc Am 2005; 115(5):2384.
16. Sutin A, Sarvazyan A, Montaldo G, Palacio D, Bercoff J, Tanter M, Fink M: Broadband time reversed acoustic focusing and steering system. J Acoust Soc Am 2004; 115(5):2596.
17. Palacio D, Bercoff J, Montaldo G, Tanter M, Fink M, Sarvazyan A, Sutin A: 3D shear wave generation in soft tissues using the time reversal kaleidoscopes. J Acoust Soc Am 2004; 115:2595.
18. Sutin A, Sarvazyan A: Spatial and temporal concentrating of ultrasound energy in complex systems by single transmitter using time reversal principles. Proc of World Congress on Ultrasonics 2003 Sep; Paris, 863-6.
19. Sutin A, Sarvazyan A: Radiation force produced by time reversal acoustic focusing system. J Acoust Soc Am 2003; 114:2378.
20. Sutin A, Sarvazyan A: Focusing of ultrasound in composite medium using time reversal acoustics. 2003 IEEE International Symposium 2003 Oct; Hawaii, 416.