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Method for designing RF excitation pulses in magnetic resonance tomography

A technology of magnetic resonance and magnetic resonance data, which is used in magnetic resonance measurement, material analysis and diagnosis through resonance, etc.

Inactive Publication Date: 2008-08-06
SIEMENS AG +2
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Problems solved by technology

In turn, each set of waveforms results in a unique excitation pattern and thus different excitation artifacts

Method used

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  • Method for designing RF excitation pulses in magnetic resonance tomography
  • Method for designing RF excitation pulses in magnetic resonance tomography
  • Method for designing RF excitation pulses in magnetic resonance tomography

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Embodiment Construction

[0027] First, parallel excitation RF waveform design is discussed, followed by three algorithms for (approximately) solving the linear system of equations.

[0028] The equations describing the interaction between the RF waveform played along each coil array and the resulting excitation pattern are nonlinear and complex. Therefore, it is desirable to somehow reduce the system of equations to simplify the overall RF design process.

[0029] Grissom et al. simplified the RF design of parallel systems by first applying a parallel approximation of small tip cone angles to the original system of equations and then discretizing the results in space and time dimensions [3]. The use of a small tip cone angle approximation is very advantageous because it reduces the RF design problem from a set of nonlinear equations to a set of linear equations involving Fourier transforms. Due to the P-coil, the linearized excitation expression is as follows:

[0030] m ...

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Abstract

The invention provides a method for designing RF excitation pulses in magnetic resonance tomography. Waveforms for radio-frequency (RF) excitations pulses used in magnetic resonance imaging are designed according to a Least Squares QR (LSQR) algorithm or a Conjugate Gradient Least Squares (CGLS) algorithm, to solve the linear system of equations that arises in a multi-channel RF transmit arrangement. Better management of SAR and other factors is achieved with RF pulses designed according to these algorithms, compared to the conventionally employed singular value decomposition (SVD) algorithm.

Description

technical field [0001] The present invention relates to a method for designing RF pulse shapes for excitation sequences in magnetic resonance tomography. technical background [0002] Current clinical magnetic resonance (MR) systems use a single RF transmit channel to transmit radio frequency pulses to excite nuclear spins in an object under examination. The use of a single RF transmit channel limits the application of several MR imaging such as high field and whole body imaging. [0003] The use of multiple, independent RF modulators as well as RF coils is the object of current research and promises to remove some of the limitations imposed by using a single RF transmit channel by providing an additional degree of freedom. [0004] A significant problem associated with multi-channel transmission is potentially higher specific absorption (SAR) due to the large number of simultaneous transmission channels. [0005] When RF pulses are designed using conventional matrix inver...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R33/32G01R33/20A61B5/055
CPCG01R33/288G01R33/3415G01R33/5611G01R33/5612G01R33/5659
Inventor 埃尔法·阿德尔斯坦森乔格·U·方修斯卡温·塞特松波普劳伦斯·L·伟德亚当·C·泽林斯基
Owner SIEMENS AG
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