Method and apparatus for compensating for b1 inhomogeneity in magnetic resonance imaging by nonselective three-dimensional tailored RF pulses
A uniform, radio frequency pulse technology, applied in the direction of using nuclear magnetic resonance imaging system for measurement, magnetic resonance measurement, and analysis by nuclear magnetic resonance, can solve the problem of non-obvious B1 inhomogeneity
Active Publication Date: 2013-04-24
COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
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This method only accounts for flip angle homogenization in slices, and assumes that B through the chosen slice 1 The inhomogeneity is not obvious
Method used
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[0047] figure 1 A very schematic illustration of a Magnetic Resonance Imaging (MRI) scanner comprising:
[0048] - a magnet M for generating a static, substantially uniform magnetic field B oriented along the direction z 0 , the patient's body (or a part of the patient's body) PB to be imaged is placed in the magnetic field;
[0049] - a radio frequency coil RFC for exposing the body to transverse radiofrequency pulses ("transverse" here means having 0 polarization, and thus in the x-y plane) and for detecting signals emitted by flipped nuclear spins within the body;
[0050] - three sets of gradient coils GC for generating gradient fields, i.e. magnetic fields oriented along the z-direction and varying linearly along corresponding spatial directions through the volume of interest (VOI);
[0051] - Oscillator OS, modulator and RF amplifier for generating radio frequency pulses supplied to the radio frequency coil. In parallel transmission, the number of times the radio fre...
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A method of exciting nuclear spins in a body, the method comprising the steps of: (a) immerging said body (PB) in a static magnetic field (B 0 ) for aligning nuclear spins along a magnetization axis (z), said static magnetic field being substantially uniform over at least a volume of interest (VOI) of said body; (b) exposing said body, or at least said volume of interest, to a time-varying magnetic field gradient having components (G x , G y , G z ) directed along at least three non-coplanar directions (x, y, z) and to a transverse radio-frequency field (B 1 ), whereby said time-varying magnetic field gradient defines a three-dimensional trajectory in k-space constituted by segments linking discrete points (k T 1 -k T 9 ), and said transverse radio-frequency field deposits radio-frequency energy along at least part of said trajectory for flipping said nuclear spins by a same predetermined flip angle, independently from their position within said volume of interest. A method of performing magnetic resonance imaging comprising a step of exciting nuclear spins in a body to be imaged, characterized in that said step is performed by carrying out a method A magnetic resonance imaging scanner for carrying out such a method.
Description
technical field [0001] The present invention relates to a radio frequency pulsed field (or "B 1 ") inhomogeneity. The invention also relates to a device or "scanner" suitable for carrying out such a method. Background technique [0002] Magnetic resonance imaging (MRI) is a very powerful tool in research and diagnosis. It includes: placing the body in a static magnetic field B 0 to orient its nuclear spin; expose the body to transverse, circularly polarized radio frequency (RF) pulses at a resonant frequency known as the "Larmor frequency"B 1 , to flip the nuclear spins by a predetermined angle; and detecting a signal from the flipped nuclear spins, from which an image of the body can be reconstructed. The "transverse" here refers to the polarization plane of the radio frequency pulse and the static magnetic field B 0 vertical, the static magnetic field B 0 Generally considered to be oriented along the "z" axis. [0003] The current trend is towards higher and higher s...
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IPC IPC(8): G01R33/483G01R33/58
CPCG01R33/44G01R33/586G01R33/246G01R33/4833G01R33/4822G01R33/34046G01R33/5659G01N24/08G01R33/4836G01R33/4818
Inventor亚历克西斯·阿马登马蒂吉恩·克鲁斯
OwnerCOMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES