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Direct DCT Encoding by Space Variant Excitation Disclosure Number: IPCOM000174451D
Publication Date: 2008-Sep-09
Document File: 2 page(s) / 44K

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Title Direct DCT Encoding by Space Variant Excitation

Inventors Holger Eggers

Ulrich Katscher

Peter Börnert


Commonly, the received signal in MRI is spatially resolved by Fourier encoding with B0 gradients. With the advent of transmit coil arrays, the alternative or supplementary use of B1 gradients has regained relevance [1]. Unlike B0 gradients, they permit a local manipulation of the signal's ampli- tude and phase, thus opening up an additional degree of freedom in the encoding process.

[1] Katscher U, et. al. B1 gradient-based MRI using a multi-element transmit system. Proc ISMRM 2007; 679.


Although non-Fourier encoding, including wavelet and singular value encoding, has been consider- ed and investigated to some extent, it has never been employed widely, mainly because of the inefficiencies and imperfections involved in its (indirect) realization with B0 gradients.


This manuscript proposes to exploit the ability of B1 gradients to simultaneously alter the signal's amplitude and phase as a function of spatial position to achieve a direct non-Fourier encoding. More specifically, it suggests employing them for an encoding based on discrete cosine transforms, which are well-known for allowing a particularly compact representation of signal distributions.


This primary application of the proposed technique is MRI with transmit coil arrays.

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The signal