MR imaging of shear waves generated by focused ultrasound

Wu, Tao; Felmlee, Joel P.; Greenleaf, James F.; Riederer, Stephen J.; Ehman, Richard L.

doi:10.1002/(sici)1522-2594(200001)43:1<111::aid-mrm13>3.0.co;2-d

Cited by 86 publications

(58 citation statements)

References 11 publications

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“…It also showed that the estimated displacements were proportional to the applied acoustic power as expected for linear, plane-wave ultrasound propagation 16,40 and that in some situations the transverse component of the displacement can be mapped. This technique has potential uses for elastography and for guiding and monitoring therapies based on pulsed ultrasound exposures, such as targeted drug delivery.…”

Section: Discussionmentioning

confidence: 99%

“…17 This work is not the first to use focused ultrasound as a source for MRI-based elastography. In addition to the studies discussed above, 16,17,27 Sinkus et al recently presented preliminary data using an approach similar in many ways to MR-ARFI to guide high-power focused ultrasound thermal ablation. 47 Also, in one of the first tests of MRI-based elastography, Sarvazyan et al used focused ultrasound as a local source for shear waves, which were detected using a line scan sequence similar to that used in this work.…”

Section: Discussionmentioning

confidence: 99%

“…A number of researchers have investigated alternative elastography approaches that employ one or more focused ultrasound beams to provide a local source of tissue displacement. [8][9][10][11][12][13][14][15][16][17] These methods take advantage of radiation force that produces a displacement at the focus on the order of a few microns. This local displacement in the longitudinal direction or the shear waves that propagate radially away from the focus as the tissue is pushed can then be mapped and related to mechanical tissue properties.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic resonance acoustic radiation force imaging

2008

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Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are "stiffness weighted" and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging ͑MR-ARFI͒ was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom ͑R 2 = 0.99͒. At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetic resonance acoustic radiation force imaging

2008

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“…7 An alternative way of generating tissue motion is by using acoustical radiation force ͑ARF͒ from focused ultrasound ͑FUS͒. [8][9][10][11][12][13][14][15][16] One advantage of this approach is potentially higher displacement amplitude at deep tissues. Furthermore, the motion is localized near the focus, therefore avoiding the complicated issues of wave reflection by bones or other structures commonly associated with surface drivers.…”

Section: Introductionmentioning

confidence: 99%

MR acoustic radiation force imaging: In vivo comparison to ultrasound motion tracking

et al. 2009

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MR acoustic radiation force ͑ARF͒ imaging was developed for measuring tissue elastic properties using focused ultrasound to deliver a localized tissue motion. In this study, an imaging ultrasound transducer was mounted on the focused ultrasound transducer and ultrasound motion tracking was performed simultaneously to MR ARF imaging to validate the measurement results. In vivo studies on rabbit thigh muscle were performed and results showed a general agreement between the two modalities ͑slope= 0.96 and R 2 = 0.67͒. The temporal information by the ultrasound measurement indicates that the parameters in MR ARF imaging should be optimized according to the tissue type, acoustic power, and envelope and frequency of the ARF modulation.

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“…[6,7,8] We refer to these techniques in general as Shear Wave Elasticity Imaging (SWEI). In linear, isotropic, elastic media, the shear wave propagation speed, SWS is directly related to the material's stiffness quantified by the Young's modulus E. We and others [9,10,11,12,13] have demonstrated that, although the complexity of cervical microstructure forbids the derivation of E from SWS estimates, the latter can be feasibly used to track changes in cervical stiffness in humans.…”

Section: Introductionmentioning

confidence: 99%