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Simultaneously driven linear and nonlinear spatial encoding fields in MRI

Gallichan, Daniel ORCID:, Cocosco, Chris. A., Dewdney, Andrew, Schultz, Gerrit, Welz, Anna, Hennig, Jürgen and Zaitsev, Maxim 2011. Simultaneously driven linear and nonlinear spatial encoding fields in MRI. Magnetic Resonance in Medicine 65 (3) , pp. 702-714. 10.1002/mrm.22672

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Spatial encoding in MRI is conventionally achieved by the application of switchable linear encoding fields. The general concept of the recently introduced PatLoc (Parallel Imaging Technique using Localized Gradients) encoding is to use nonlinear fields to achieve spatial encoding. Relaxing the requirement that the encoding fields must be linear may lead to improved gradient performance or reduced peripheral nerve stimulation. In this work, a custom-built insert coil capable of generating two independent quadratic encoding fields was driven with high-performance amplifiers within a clinical MR system. In combination with the three linear encoding fields, the combined hardware is capable of independently manipulating five spatial encoding fields. With the linear z-gradient used for slice-selection, there remain four separate channels to encode a 2D-image. To compare trajectories of such multidimensional encoding, the concept of a local k-space is developed. Through simulations, reconstructions using six gradient-encoding strategies were compared, including Cartesian encoding separately or simultaneously on both PatLoc and linear gradients as well as two versions of a radial-based in/out trajectory. Corresponding experiments confirmed that such multidimensional encoding is practically achievable and demonstrated that the new radial-based trajectory offers the PatLoc property of variable spatial resolution while maintaining finite resolution across the entire field-of-view.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Cardiff University Brain Research Imaging Centre (CUBRIC)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Uncontrolled Keywords: nonlinear spatial encoding; quadratic fields; PatLoc; Non-Fourier encoding
Publisher: John Wiley & Sons
ISSN: 0740-3194
Date of Acceptance: 14 October 2010
Last Modified: 02 Nov 2022 10:21

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