Paper
6 March 2015 Amplitude-modulated ultrasound radiation force combined with phase-sensitive optical coherence tomography for shear wave elastography
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Abstract
Tissue stiffness can be measured from the propagation speed of shear waves. Acoustic radiation force (ARF) can generate shear waves by focusing ultrasound in tissue for ~100 μs. Safety considerations and electronics abilities limit ultrasound pressures. We previously presented shear wave elastography combining ARF and phase-sensitive optical coherence tomography (PhS-OCT) [1]. Here, we use amplitude-modulated ARF to enhance shear wave signal-to-noise ratio (SNR) at low pressures. Experiments were performed on tissue-mimicking phantoms. ARF was applied using a single-element transducer, driven by a 7.5 MHz, 3-ms, sine wave modulated in amplitude by a linear-swept frequency (1 to 7 kHz). Pressures between 1 to 3 MPa were tested. Displacements were tracked using PhS-OCT and numerically compressed using pulse compression methods detailed in previous work [2]. SNR was compared to that of 200-μs bursts. Stiffness maps were reconstructed using time-of-flight computations. 200-μs bursts give barely detectable displacements at 1 MPa (3.7 dB SNR). Pulse compression gives 36.2 dB at 1.5 MPa. In all cases with detectable displacements, shear wave speeds were determined in 5%-gelatin and 10%-gelatin phantoms and compared to literature values. Applicability to ocular tissues (cornea, intraocular lens) is under investigation.
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Thu-Mai Nguyen, Shaozhen Song, Bastien Arnal, Emily Y. Wong, Tueng T. Shen, Ruikang K. Wang, and Matthew O'Donnell "Amplitude-modulated ultrasound radiation force combined with phase-sensitive optical coherence tomography for shear wave elastography", Proc. SPIE 9327, Optical Elastography and Tissue Biomechanics II, 932705 (6 March 2015); https://doi.org/10.1117/12.2084609
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KEYWORDS
Ultrasonography

Signal to noise ratio

Tissues

Elastography

Optical coherence tomography

Wave propagation

Reconstruction algorithms

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