title: Range discrimination in ultrasonic vibrometry: theory and experiment.
abstract: A technique has been developed to demodulate periodic broadband ultrasonic interrogation signals that are returned from multiple scattering sites to simultaneously determine the low-frequency displacement time histories of each individual site. The technique employs a broadband periodic transmit signal. The motions of scattering sites are separately determined from the echoed receive signal by an algorithm involving comb filtering and pulse synthesis. This algorithm permits spatial resolution comparable to pulse-echo techniques and displacement sensitivities comparable to pure-tone techniques. A system based on this technique was used to image transient audio-frequency displacements on the order of 1-10 μm peak (≥ 50 nm/√Hz) that were produced by propagating shear waves in a tissue phantom. The system used concentric transmitting and receiving transducers and a carrier signal centered at 2.5 MHz with an 800 kHz bandwidth. The system was self-noise-limited and capable of detecting motions of strongly reflecting regions on the order of 1 nm/√Hz. System performance is limited by several factors including signal selection, component hardware, and ultrasonic propagation within the media of interest.
authors: School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA. james.martin@me.gatech.edu
authors: J S
authors: JS
authors: Martin
authors: P H
authors: PH
authors: Rogers
authors: M D
authors: MD
authors: Gray
mesh_terms: D000465:Algorithms; D004453:Echoencephalography / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D008962:Models, Theoretical; D009038:Motion; D019047:Phantoms, Imaging; D012542:Scattering, Radiation; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014159:Transducers; D014465:Ultrasonics / Q000295:instrumentation / Q000379:methods*; D014732:Vibration