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Concurrent Visualization of Acoustic Radiation Force Displacement and Shear Wave Propagation with 7T MRI.

Liu Y, Fite BZ, Mahakian LM, Johnson SM, Larrat B, Dumont E, Ferrara KW - PLoS ONE (2015)

Bottom Line: In this study, an MRgFUS system combines high field (7T) MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm), as compared with current clinical systems.The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave.Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, University of California Davis, Davis, CA, 95616, United States of America.

ABSTRACT
Manual palpation is a common and very informative diagnostic tool based on estimation of changes in the stiffness of tissues that result from pathology. In the case of a small lesion or a lesion that is located deep within the body, it is difficult for changes in mechanical properties of tissue to be detected or evaluated via palpation. Furthermore, palpation is non-quantitative and cannot be used to localize the lesion. Magnetic Resonance-guided Focused Ultrasound (MRgFUS) can also be used to evaluate the properties of biological tissues non-invasively. In this study, an MRgFUS system combines high field (7T) MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm), as compared with current clinical systems. MR-Acoustic Radiation Force Imaging (MR-ARFI) provides a reliable and efficient method for beam localization by detecting micron-scale displacements induced by ultrasound mechanical forces. The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave. Our motivation in combining these two measurements is to develop a technique that can rapidly provide both ARFI and shear wave velocity estimation data, making it suitable for use in interventional radiology. Secondly, we validate this sequence in vivo by estimating the displacement before and after high intensity focused ultrasound (HIFU) ablation, and we validate the shear wave velocity in vitro using tissue-mimicking gelatin and tofu phantoms. Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable.

No MeSH data available.


Related in: MedlinePlus

Localization of the acoustic beam by MR-ARFI.(A) Seven coronal slices were acquired at -3, -2, -1, 0, 1, 2 and 3 mm away from the US focal plane along the depth axis with -3 dB contour lines. (B) The diameter of the area enclosed within a -3 dB contour line was calculated at different depths. (C) The peak displacement amplitude at each depth.
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pone.0139667.g003: Localization of the acoustic beam by MR-ARFI.(A) Seven coronal slices were acquired at -3, -2, -1, 0, 1, 2 and 3 mm away from the US focal plane along the depth axis with -3 dB contour lines. (B) The diameter of the area enclosed within a -3 dB contour line was calculated at different depths. (C) The peak displacement amplitude at each depth.

Mentions: The displacement produced by the ultrasound beam was assessed based on the ARFI images acquired while sonicating the 8% gelatin phantom. The diameter of the region enclosed within a -3 dB displacement contour was 2.74 ± 0.05, 2.50 ± 0.02, 1.64 ± 0.04, 1.00 ± 0.00, 1.00 ± 0.05, 1.53 ± 0.05 and 2.35 ± 0.08 mm2 at -3, -2, -1, 0, 1, 2, 3 mm from the ultrasound focus, respectively, as aligned with the MR coordinates (Fig 3Ai–Fig 3Avii), Fig 3B). The maximum displacement was 0.96 μm at a depth of -3 mm relative to the focus, increased to 2.65 μm at the focal center and then decreased to 1.42 μm at 3 mm from the focus (Fig 3C). As anticipated, with increasing depth the diameter of the effective displacement narrowed at the transducer focus, and widened again in the far field.


Concurrent Visualization of Acoustic Radiation Force Displacement and Shear Wave Propagation with 7T MRI.

Liu Y, Fite BZ, Mahakian LM, Johnson SM, Larrat B, Dumont E, Ferrara KW - PLoS ONE (2015)

Localization of the acoustic beam by MR-ARFI.(A) Seven coronal slices were acquired at -3, -2, -1, 0, 1, 2 and 3 mm away from the US focal plane along the depth axis with -3 dB contour lines. (B) The diameter of the area enclosed within a -3 dB contour line was calculated at different depths. (C) The peak displacement amplitude at each depth.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4594908&req=5

pone.0139667.g003: Localization of the acoustic beam by MR-ARFI.(A) Seven coronal slices were acquired at -3, -2, -1, 0, 1, 2 and 3 mm away from the US focal plane along the depth axis with -3 dB contour lines. (B) The diameter of the area enclosed within a -3 dB contour line was calculated at different depths. (C) The peak displacement amplitude at each depth.
Mentions: The displacement produced by the ultrasound beam was assessed based on the ARFI images acquired while sonicating the 8% gelatin phantom. The diameter of the region enclosed within a -3 dB displacement contour was 2.74 ± 0.05, 2.50 ± 0.02, 1.64 ± 0.04, 1.00 ± 0.00, 1.00 ± 0.05, 1.53 ± 0.05 and 2.35 ± 0.08 mm2 at -3, -2, -1, 0, 1, 2, 3 mm from the ultrasound focus, respectively, as aligned with the MR coordinates (Fig 3Ai–Fig 3Avii), Fig 3B). The maximum displacement was 0.96 μm at a depth of -3 mm relative to the focus, increased to 2.65 μm at the focal center and then decreased to 1.42 μm at 3 mm from the focus (Fig 3C). As anticipated, with increasing depth the diameter of the effective displacement narrowed at the transducer focus, and widened again in the far field.

Bottom Line: In this study, an MRgFUS system combines high field (7T) MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm), as compared with current clinical systems.The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave.Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, University of California Davis, Davis, CA, 95616, United States of America.

ABSTRACT
Manual palpation is a common and very informative diagnostic tool based on estimation of changes in the stiffness of tissues that result from pathology. In the case of a small lesion or a lesion that is located deep within the body, it is difficult for changes in mechanical properties of tissue to be detected or evaluated via palpation. Furthermore, palpation is non-quantitative and cannot be used to localize the lesion. Magnetic Resonance-guided Focused Ultrasound (MRgFUS) can also be used to evaluate the properties of biological tissues non-invasively. In this study, an MRgFUS system combines high field (7T) MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm), as compared with current clinical systems. MR-Acoustic Radiation Force Imaging (MR-ARFI) provides a reliable and efficient method for beam localization by detecting micron-scale displacements induced by ultrasound mechanical forces. The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave. Our motivation in combining these two measurements is to develop a technique that can rapidly provide both ARFI and shear wave velocity estimation data, making it suitable for use in interventional radiology. Secondly, we validate this sequence in vivo by estimating the displacement before and after high intensity focused ultrasound (HIFU) ablation, and we validate the shear wave velocity in vitro using tissue-mimicking gelatin and tofu phantoms. Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable.

No MeSH data available.


Related in: MedlinePlus