Harmonic Vibro-Acoustography

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2007-07, Vol.54 (7), p.1346-1351
• Main Authors: Chen, Shigao, Kinnick, Randall R., Greenleaf, James F., Fatemi, Mostafa
• Format: Article
• Language: English
• Subjects: Acoustic beams; Acoustic emission; Acoustic imaging; Acoustic propagation; Acoustic signal detection; Acoustic transducers; Acoustics; Algorithms; Beams (radiation); Biological and medical sciences; Cardiovascular system; Exact sciences and technology; Frequency; Fundamental areas of phenomenology (including applications); General equipment and techniques; Harmonics; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Imaging; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Microorganisms; Nonlinearity; Object detection; Phantoms, Imaging; Physics; Reproducibility of Results; Sensitivity and Specificity; Transducers; Ultrasonic imaging; Ultrasonic investigative techniques; Ultrasonic transducers; Ultrasonics, quantum acoustics, and physical effects of sound; Ultrasonography - instrumentation; Ultrasonography - methods; Vibration
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2007.394

Vibro-acoustography is an imaging method that uses the radiation force of two interfering ultrasound beams of slightly different frequency to probe an object. An image is made using the acoustic emission resulted from the object vibration at the difference frequency. In this paper, the feasibility of imaging objects at twice the difference frequency (harmonic acoustic emission) is studied. Several possible origins of harmonic acoustic emission are explored. As an example, it is shown that microbubbles close to resonance can produce significant harmonic acoustic emission due to its high nonlinearity. Experiments demonstrate that, compared to the fundamental acoustic emission, harmonic acoustic emission greatly improves the contrast between microbubbles and other objects in vibro-acoustography (an improvement of 17-23 dB in these experiments). Applications of this technique include imaging the nonlinearity of the object and selective detection of microbubbles for perfusion imaging. The impact of microbubble destruction during the imaging process also is discussed.