Time‐varying view angle tilting with spiral readout gradients

Abstract

The conventional Fourier-transform-based spin-echo sequence with a view angle tilting gradient during data acquisition can correct the in-plane distortion induced by a chemical shift or B0 field inhomogeneity. However, when extended for 3D applications, alternate k-space sampling can be beneficial for reducing the lengthy scan time. As spiral trajectories have high k-space acquisition efficiency, we investigated the applicability of spiral trajectory on a spin-echo view angle tilting pulse sequence. Computer simulations and phantom and in vivo experiments were performed to validate the usage of spiral readout gradients in the presence of a view angle tilting gradient. The results show that as long as the readout time is comparable to Cartesian readout, the resulting images have similar quality.

Imaging near metal: The impact of extreme static local field gradients on frequency encoding processes

“…Adding spatial off-resonance effects using the relations defined in Eqs. [5][6][7][8][9] then leaves:…”

“…Optimized protocols taking these factors into account can improve diagnostic capabilities near some metal alloys (1)(2)(3). Applications of the view-angle-tilting technique (4) also show significant bulk-distortion reductions, but also highlight problems with remaining slice-selective distortions (5)(6)(7).…”

Fast quantitative three‐dimensional ultrashort echo time (UTE) Cones magnetic resonance imaging of major tissues in the knee joint using extended sprial sampling

“…However, more research is needed to investigate the effect of sampling window on quantification accuracy, especially considering the increased short T 2 * blurring at a higher field strength. 3D spiral trajectories are suitable for UTE acquisitions because they begin at the center of k‐space (minimizing TE), efficiently filling k‐space compared with radial trajectories, and are entirely frequency encoded without the need for phase encoding 30,31 . An extended sampling window has the advantage of more efficient k‐space sampling, which allows rapid scanning time, but with the disadvantage of greater sensitivity to T 2 * decay and increased susceptibility to flow effects and off‐resonance blurring 14 .…”

Accelerated MR whole brain imaging with sheared voxel imaging using aliasing separation gradients

“…14,15 A sinc demodulation can be applied to correct this blurring at the cost of noise amplification as in view angle tilting technique (VAT). 16,17 In this work, we extended the wideband approach to accelerating single slice 2D imaging and merged it with 3D imaging acceleration along both in-plane and through-plane phase encoding (PE) directions. In contrast to the previous studies, the proposed method does not require special RF pulses for multi-slice/slab excitation using cosine modulation.…”