Progress in Visualizing Turbulent Flow using Single-Echo Acquisition Imaging

Wright, Steven M.; McDougall, Mary P.; Bosshard, John C.

doi:10.1109/iembs.2006.260797

Cited by 6 publications

(3 citation statements)

References 19 publications

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“…In an image acquired immediately after the tagging, the grid appears undistorted. A conventional non-refocused gradient echo pulse sequence was used in [9], and was modified to include spin-tagging [13][14] and a phase compensation gradient pulse rather than a phase encoding table. Spin-tagging was performed using DANTE RF pulse trains [15] where the pulse-width [rather than power levels] was modified.…”

Section: A Mri Spin Taggingmentioning

confidence: 99%

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Velocity extraction from spin-tagging MRI images using a weighted least-squares optical flow method

Stoitsis

Bastouni

Karampinos

et al. 2007

2007 IEEE International Workshop on Imaging Systems and Techniques

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Magnetic Resonance Imaging (MRI) can provide truly non-invasive measurements of internalflowfields. The extraction of velocityfrom spin-tagging images requires the quantitative tracking of grid nodes. A weighted least-squares optical flow method was used in this work to estimate the displacements ofthe grid nodes and tags from synthetic and real spin-tagging MRI images. To investigate the accuracy of the proposed method, synthetic spintagging images were generated using the Poiseuille law analytical profile. Three synthetic sequences with different levels ofnoise were generated and the average and maximum absolute errors were estimatedfor points corresponding to grid nodes and tags. Diferent sizes and shapes of region of interest (ROI) were investigated to determine the optimal size and shape for reliable extraction of velocity both for synthetic and real spin-tagging MRI images. The optimal ROI size was found to be 13x13 pixels2. The average and maximum absolute error for the velocity in vertical direction for synthetic data using the optimal ROI size rangedfrom 5.46% to 14.42% andfrom 6.39% to 31.96% respectively.

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Section: A Mri Spin Taggingmentioning

confidence: 99%

“…Wright et al [9] have used SEA-MRI to perform flow spin tagging (which involves placing a "texture" on the spins and then tracking it) and to image very fast flow in a channel with an obstruction. Although the distorted texture reveals all the qualitative aspects of the flow, there were no local velocities reported.…”

Section: Introductionmentioning

confidence: 99%

Velocity extraction from spin-tagging MRI images using a weighted least-squares optical flow method

Stoitsis

Bastouni

Karampinos

et al. 2007

2007 IEEE International Workshop on Imaging Systems and Techniques

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“…This has enabled single echo acquisition (SEA) imaging (15), in which each MR image is acquired in one echo, as well as highly accelerated MR microscopy over an extended field of view (FOV) (16). Applications such as turbulent flow (17) and microscopy of excised brain slices have been investigated. The system was further extended to facilitate imaging of thicker volumes using a biplanar receive array and an insertable x-, y-gradient coil to compensate for the phase gradient due to the RF coil elements (18).…”

Section: Introductionmentioning

confidence: 99%

Exploration of highly accelerated magnetic resonance elastography using high-density array coils

Bosshard

Yallapragada

McDougall

et al. 2017

Quant. Imaging Med. Surg.

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Background: Magnetic resonance elastography (MRE) measures tissue mechanical properties by applying a shear wave and capturing its propagation using magnetic resonance imaging (MRI). By using high density array coils, MRE images are acquired using single echo acquisition (SEA) and at high resolutions with significantly reduced scan times.Methods: Sixty-four channel uniplanar and 32×32 channel biplanar receive arrays are used to acquire MRE wave image sets from agar samples containing regions of varying stiffness. A mechanical actuator triggered by a stepped delay time introduces vibrations into the sample while a motion sensitizing gradient encodes micrometer displacements into the phase. SEA imaging is used to acquire each temporal offset in a single echo, while multiple echoes from the same array are employed for highly accelerated imaging at high resolutions. Additionally, stiffness variations as a function of temperature are studied by using a localized heat source above the sample. A custom insertable gradient coil is employed for phase compensation of SEA imaging with the biplanar array to allow imaging of multiple slices.Results: SEA MRE images show a mechanical shear wave propagating into and across agar samples. A set of 720 images was obtained in 720 echoes, plus a single reference scan for both harmonic and transient MRE.A set of 2,950 wave image frames was acquired from pairs of SEA images captured during heating, showing the change in mechanical wavelength with the change in agar properties. A set of 240 frames was acquired from two slices simultaneously using the biplanar array, with phase images processed into displacement maps. Combining the narrow sensitivity patterns and SNR advantage of the SEA array coil geometry allowed acquisition of a data set with a resolution of 156 µm × 125 µm × 1,000 µm in only 64 echoes, demonstrating high resolution and high acceleration factors.Conclusions: MRE using high-density arrays offers the unique ability to acquire a single frame of a propagating mechanical vibration with each echo, which may be helpful in non-repeatable or destructive testing. Highly accelerated, high resolution MRE may be enabled by the use of large arrays of coils such as used for SEA, but at lower acceleration rates supporting the higher resolution than provided by SEA imaging.

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An improved element design for 64‐channel planar imaging

Chang

Moody

McDougall

2011

Concepts Magn Reson

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Investigation of highly accelerated MRI has developed into a lively corner in the hardware and methodology arena in recent years. At the extreme of (one-dimensional) acceleration, our group introduced Single Echo Acquisition (SEA) imaging, in which the need to phase encode a 64×Nreadout image is eliminated and replaced with the well-localized spatial information obtained from an array of 64 very narrow, long, parallel coils. The narrow coil width (2mm) that facilitates this is accompanied by a concomitant constraint on the useful imaging depth. This note describes a 64-element planar array, constructed within the same 8×13cm total footprint as the original SEA array, still enabling full acceleration in one dimension, but with an element design modified to increase the imaging depth. This was accomplished by lowering the outer conducting legs of the planar pair with respect to the center conductor and adding a geometric decoupling configuration away from the imaging field of view. The element has been called a dual-plane pair in that the current carrying rungs in the imaging FOV function exactly as the planar pair, but are simply placed in two separate planes (sides of PCB in this case).

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Progress in Visualizing Turbulent Flow using Single-Echo Acquisition Imaging

Cited by 6 publications

References 19 publications

Velocity extraction from spin-tagging MRI images using a weighted least-squares optical flow method

Velocity extraction from spin-tagging MRI images using a weighted least-squares optical flow method

Exploration of highly accelerated magnetic resonance elastography using high-density array coils

An improved element design for 64‐channel planar imaging

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