Partially parallel imaging with localized sensitivities (PILS)

Griswold, Mark A.; Jakob, Peter M.; Nittka, Mathias; Goldfarb, James W.; Haase, Axel

doi:10.1002/1522-2594(200010)44:4<602::aid-mrm14>3.0.co;2-5

Cited by 285 publications

(238 citation statements)

References 10 publications

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“…Additionally, the mean gfactor values and their standard deviations are given for each 2D sampling scheme. (1) 6.36 Ϯ 3.80 1.41 1ϫ8 (2) 1.66 Ϯ 0.30 2.24 1ϫ8 (3) 1.53 Ϯ 0.21 2.83 1ϫ8 (4) 2.51 Ϯ 1.17 2 1ϫ8 (5) 1.54 Ϯ 0.21 2.83 1ϫ8 (6) 1.65 Ϯ 0.27 2.24 1ϫ8 (7) 6.02 Ϯ 3.58 1.41 2ϫ4 (0) 2.51 Ϯ 1.16 2 2ϫ4 (1) 1.87 Ϯ 0.51 2.24 2ϫ4 (2) 1.55 Ϯ 0.21 2.83 2ϫ4 (3) 1.86 Ϯ 0.46 2.24 4ϫ2 (0) 1.81 Ϯ 0.41 2 4ϫ2 (1) 1.80 Ϯ 0.40 2 8ϫ1 (0) 14.82 Ϯ 10.57 1…”

Section: Discussionmentioning

confidence: 99%

Controlled aliasing in volumetric parallel imaging (2D CAIPIRINHA)

Breuer

Blaimer

Mueller

et al. 2006

Magnetic Resonance in Med

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The CAIPIRINHA (Controlled Aliasing In Parallel Imaging Results IN Higher Acceleration) concept in parallel imaging has recently been introduced, which modifies the appearance of aliasing artifacts during data acquisition in order to improve the subsequent parallel imaging reconstruction procedure. This concept has been successfully applied to simultaneous multislice imaging (MS CAIPIRINHA). In this work, we demonstrate that the concept of CAIPIRINHA can also be transferred to 3D imaging, where data reduction can be performed in two spatial dimensions simultaneously. In MS CAIPIRINHA, aliasing is controlled by providing individual slices with different phase cycles by means of alternating multi-band radio frequency (RF) pulses. In contrast to MS CAIPIRINHA, 2D CAIPIRINHA does not require special RF pulses. Instead, aliasing in 2D parallel imaging can be controlled by modifying the phase encoding sampling strategy. This is done by shifting sampling positions from their normal positions in the undersampled 2D phase encoding scheme. Using this modified sampling strategy, coil sensitivity variations can be exploited more efficiently in multiple dimensions, resulting in a more robust parallel imaging reconstruction. Magn Reson Med 55:549 -556, 2006.

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Section: Discussionmentioning

confidence: 99%

Controlled aliasing in volumetric parallel imaging (2D CAIPIRINHA)

Breuer

Blaimer

Mueller

et al. 2006

Magnetic Resonance in Med

Self Cite

368

436

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“…To shorten acquisition time and reduce respiratory artifacts, PC-MRI may employ segmented k-space techniques at the expense of temporal resolution. Recently, several partial parallel acquisition strategies (5)(6)(7)(8)(9)(10)(11) have been introduced to accelerate imaging by undersampling the phase-encoding steps by a reduction factor R. The combination of partial parallel acquisition techniques with clinical imaging pulse sequences (such as PC-MRI in this work) can speed up the acquisition time and preserve the temporal and/or spatial resolution.…”

Section: Dynamic Phase Contrast (Pc) Mrimentioning

confidence: 99%

Optimized parallel imaging for dynamic PC‐MRI with multidirectional velocity encoding

Peng

Bauer

Huang

et al. 2010

Magnetic Resonance in Med

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Phase contrast MRI with multidirectional velocity encoding requires multiple acquisitions of the same k-space lines to encode the underlying velocities, which can considerably lengthen the total scan time. To reduce scan time, parallel imaging is often applied. In dynamic phase contrast MRI using standard generalized autocalibrating partially parallel acquisitions (GRAPPA), several central k-spaces for autocalibration of the reconstruction (autocalibrating signal lines (ACS)) are typically acquired, separately for each velocity direction and each cardiac timeframe, for calculating the reconstruction weights. To further accelerate data acquisition, we developed two methods, which calculated weights with a substantially reduced number of ACSl lines. The effects on image quality and flow quantification were compared to fully sampled data, standard GRAPPA, and time-interleaved sampling scheme in combination with generalized autocalibrating partially parallel acquisitions (TGRAPPA). The results show that the two proposed methods can clearly improve scan efficiency while maintaining image quality and accuracy of measured flow or myocardial tissue velocities. Compared to TGRAPPA, the proposed methods were more accurate in evaluating flow velocity. In conclusion, the proposed reconstruction strategies are promising for dynamic multidirectionally encoded acquisitions and can easily be implemented using the standard GRAPPA reconstruction algorithm. Magn Reson Med 64:472-480,

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“…In high resolution imaging, the fully encoded sub-images from each array element were processed into 2D wave images via phase subtraction. Following a procedure similar to PILS (22), a rectangular window was applied to the phase subtraction image of each coil and these sub-images were stacked in a matrix covering the entire FOV of the array. For a sinusoidal motion sensitizing gradient of amplitude G 0 and N periods, each of duration T, the magnitude of the phase accrued by each voxel, ϕ 0 , due to cyclic motion of each isochromat with peak displacement ξ 0 is given by [1] ( )…”

Section: Methodsmentioning

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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Partially parallel imaging with localized sensitivities (PILS)

Cited by 285 publications

References 10 publications

Controlled aliasing in volumetric parallel imaging (2D CAIPIRINHA)

Controlled aliasing in volumetric parallel imaging (2D CAIPIRINHA)

Optimized parallel imaging for dynamic PC‐MRI with multidirectional velocity encoding

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

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