Adapting MRI acoustic radiation force imaging for in vivo human brain focused ultrasound applications

Kaye, Elena; Pauly, Kim Butts

doi:10.1002/mrm.24308

Cited by 35 publications

(55 citation statements)

References 31 publications

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“…Some investigators have directly included viscous effects 32,33 while others have used a more simplified model to account for the noninstantaneous tissue response. 28,36 In order to account for the noninstantaneous tissue response, we assumed that displacement due to the T III. MR-ARFI displacement results for all phantoms.…”

Section: Discussionmentioning

confidence: 99%

“…It has been found that the phase aberration correction obtained from using empirical MR-ARFI measurements results in a more intense and sharpened focal spot when compared with the correction computed using a segmented skull model obtained from computed tomography (CT) images. 21,[26][27][28][29] Finally, MR-ARFI can be used in the post-treatment phase to assess the change of mechanical properties of the treated tissue. Bitton et al 30 found that the MR-ARFI-measured peak displacement in previously ablated regions in human cadaver breasts decreased by approximately 55%.…”

Section: Introductionmentioning

confidence: 99%

“…29 An overdamped response model to relate the tissue motion due to the acoustic radiation force to the duration of the ultrasound pulse has also been presented. 28,36 This paper presents a new technique to model the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model mapped to a full 3D Cartesian grid. While several other theories have been presented, the model used in this work was developed specifically for use for MR-ARFI applications where the ultrasound pulse duration is typically on the order of several milliseconds.…”

Section: Introductionmentioning

confidence: 99%

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A simulation technique for 3D MR‐guided acoustic radiation force imaging

et al. 2015

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Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic radiation force imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the radiation force exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source force acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The radiation force field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green's function with the force field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green's function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30-and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028-0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison with experimentally obtained 3D displacement data in homogeneous gelatin phantoms using a 3D MR-ARFI sequence. The agreement of the experimentally measured and simulated results demonstrates the potential to use MR-ARFI displacement data in MRgFUS therapies. C 2015 American Association of Physicists in Medicine. [http://dx

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A simulation technique for 3D MR‐guided acoustic radiation force imaging

et al. 2015

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“…This MR technique shares an essentially similar principle with diffusion weighted imaging with respect to the use of a motion encoding gradient. Both gradient-recalled echo and spin echo MR-ARFI sequences have been implemented in combination with line scans or 2D Fourier transformation readouts [30,31]. Recently, an in vivo animal application of MR-ARFI under free breathing was reported to be feasible [32].…”

Section: Mr-acoustic Radiation Force Imagingmentioning

confidence: 99%

Advances in MR image-guided high-intensity focused ultrasound therapy

Kim

2014

International Journal of Hyperthermia

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The clinical role of magnetic resonance image-guided high-intensity focused ultrasound (MR-HIFU) is rapidly expanding due to its merit of non-invasiveness. MR thermometry based on a proton resonance frequency shift technique is able to accurately measure HIFU-induced temperature changes, which provides considerable advantages over ultrasonography-guided HIFU in terms of safety and therapeutic efficacy. Recent studies and the resulting technological advances in MR-HIFU such as MR thermometry for moving organs, MR-acoustic radiation force imaging, and a volumetric mild hyperthermia technique further will expand its clinical roles from mere ablation therapy to targeted drug delivery and chemo- or radio-sensitisation for cancer treatment. In this article, MR-HIFU therapy is comprehensively reviewed with an emphasis on the roles of MR imaging in HIFU therapy, techniques of MR monitoring, recent advances in clinical MR-HIFU systems, and potential future applications of MR-HIFU therapy. In addition, the pros and cons of MR-HIFU when compared with ultrasonography-guided HIFU are discussed.

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“…An experimental displacement image is derived by applying a small ultrasound pulse to the tissue and measuring the resulting tissue displacement phase due to the beam's radiation force using a 2D spin echo MR-ARFI pulse sequence [8].…”

Section: Experimental Displacement Pattern (F Exp )mentioning

confidence: 99%