A transmit-receive array for brain imaging with a high-performance gradient insert

doi:10.1002/mrm.28261

A transmit-receive array for brain imaging with a high-performance gradient insert

2020-05-08

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DOI：10.1002/mrm.28261

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Purpose The aim of this work was to provide parallel imaging capability for the human head in a gradient insert of 33-cm inner diameter within the related constraints of space, encoding ambiguity, and eddy current immunity. Methods Eddy current behavior of the 8-channel transmit-receive array coil was investigated via heating and field deviation measurements. RF performance was evaluated using S-parameters, noise statistics, B-1 maps, and g-factor maps. In vivo images of a human head and knee were acquired with Cartesian readout and TE below 0.45 ms. Results Under intense gradient use, the shield was heated up to 55 degrees C and other coil structures to 40 degrees C. After standard preemphasis calibration, eddy current-related field distortions caused by the developed RF coil were smaller than for a commercial receive-only coil. In the ambiguous regions of the gradient, B1+ is 20 dB lower than in the center of the FOV. Coupling between elements is below -15 dB, and noise correlation is less than 0.31 when the coil is loaded with a head. Power efficiency was 0.52 +/- 0.02 mu T/root W, and the SD of the flip angle was below 10% in central slices of the brain. 2D, up to fourfold acceleration causes less than 30% noise amplification. The RF coil can be used during full gradient performance. Conclusion Based on the described features, the presented coil enables parallel imaging in the high-performance gradient insert.

Keywords:

Cartesian ultrashort echo time sequence

eddy currents

gradient-induced heating

local gradient coils

parallel imaging

RF array coil

A transmit-receive array for brain imaging with a high-performance gradient insert

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