Vibro-acoustography: An imaging modality based on ultrasound-stimulated acoustic emission

Abstract

We describe theoretical principles of an imaging modality that uses the acoustic response of an object to a highly localized dynamic radiation force of an ultrasound field. In this method, named ultrasound-stimulated vibro-acoustography (USVA), ultrasound is used to exert a low-frequency (in kHz range) force on the object. In response, a portion of the object vibrates sinusoidally in a pattern determined by its viscoelastic properties. The acoustic emission field resulting from object vibration is detected and used to form an image that represents both the ultrasonic and low-frequency (kHz range) mechanical characteristics of the object. We report the relation between the emitted acoustic field and the incident ultrasonic pressure field in terms of object parameters. Also, we present the point-spread function of the imaging system. The experimental images in this report have a resolution of about 700 m, high contrast, and high signal-to-noise ratio. USVA is sensitive enough to detect object motions on the order of nanometers. Possible applications include medical imaging and material evaluation.

In vitro comparative study of vibro-acoustography versus pulse-echo ultrasound in imaging permanent prostate brachytherapy seeds

“…In previous publications, VA was presented as a technique based on the modulated radiation pressure (MRP) of ultrasound waves [11,12]. Two intersecting ultrasound beams slightly shifted in frequency and focused at the same point in space produce a dynamic radiation force (or stress in 3D) on or inside an object.…”

“…The purpose of the present study is to examine seed imaging as a function of seed orientation using an innovative ultrasound-based imaging method known as vibro-acoustography (VA) [11][12][13], which is based on the dynamic radiation force of ultrasound [14]. In this method, two intersecting ultrasound beams driven at slightly different frequencies are focused on or inside the object to be imaged, producing a localized tapping radiation force oscillating at the difference frequency of the incident ultrasound beams.…”

Acoustic radiation force-based elasticity imaging methods

“…Fatemi & Greenleaf [64,65] proposed the use of interfering ultrasonic beams with slightly offset frequencies (differences ranging from approx. 100 Hz to 10 kHz) to generate oscillating radiation force excitations at the beat frequency in the region of overlap between the two beams.…”

Therapeutic ultrasound: Surgery and drug delivery

“…image contrast [28,29]. Diagnostic ultrasound is principally used in B-mode for lesion guidance and targeting [30], in Doppler-mode for hemostasis applications [31], and in the new elastography and vibro-acoustography modalities for lesion monitoring [32][33][34]. B-mode scans exploit the transient minimal bubble activity that is present before the onset of a thermal lesion and indicates the area where the energy is delivered as hyperechoic in the image.…”