Effects of acoustic radiation force and shear waves for absorption and stiffness sensing in ultrasound modulated optical tomography

Ultrasound-modulated optical tomography (UOT) combines optical contrast with ultrasound spatial resolution and has great potential for soft tissue functional imaging. One current problem with this technique is the weak optical modulation signal, primarily due to strong optical scattering in diffuse...

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Bibliographic Details
Published in:Optics express 2011-04, Vol.19 (8), p.7299-7311
Main Authors: Li, Rui, Elson, Daniel S, Dunsby, Chris, Eckersley, Robert, Tang, Meng-Xing
Format: Article
Language:English
Subjects:
Acoustics - instrumentation
Contrast Media
Equipment Design
Image Enhancement - instrumentation
Image Enhancement - methods
Lasers
Materials Testing
Optics and Photonics
Phantoms, Imaging
Tomography, Optical - instrumentation
Tomography, Optical - methods
Ultrasonics
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Summary:Ultrasound-modulated optical tomography (UOT) combines optical contrast with ultrasound spatial resolution and has great potential for soft tissue functional imaging. One current problem with this technique is the weak optical modulation signal, primarily due to strong optical scattering in diffuse media and minimal acoustically induced modulation. The acoustic radiation force (ARF) can create large particle displacements in tissue and has been shown to be able to improve optical modulation signals. However, shear wave propagation induced by the ARF can be a significant source of nonlocal optical modulation which may reduce UOT spatial resolution and contrast. In this paper, the time evolution of shear waves was examined on tissue mimicking-phantoms exposed to 5 MHz ultrasound and 532 nm optical radiation and measured with a CCD camera. It has been demonstrated that by generating an ARF with an acoustic burst and adjusting both the timing and the exposure time of the CCD measurement, optical contrast and spatial resolution can be improved by ~110% and ~40% respectively when using the ARF rather than 5 MHz ultrasound alone. Furthermore, it has been demonstrated that this technique simultaneously detects both optical and mechanical contrast in the medium and the optical and mechanical contrast can be distinguished by adjusting the CCD exposure time.
ISSN:1094-4087
1094-4087
DOI:10.1364/OE.19.007299