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Dynamic shimming method of multi-order harmonics for magnetic resonance imaging

A technology of magnetic resonance imaging and dynamic shimming, which is applied in the direction of magnetic resonance measurement, application, and measurement of magnetic variables, which can solve the problem of time-consuming and achieve the effect of improving uniformity.

Inactive Publication Date: 2012-06-20
SUZHOU LONWIN MEDICAL SYST
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The maximum signal method needs to iteratively calculate the supplementary current of each harmonic coil, which is too time-consuming for multi-order dynamic shimming and is no longer applicable

Method used

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  • Dynamic shimming method of multi-order harmonics for magnetic resonance imaging
  • Dynamic shimming method of multi-order harmonics for magnetic resonance imaging
  • Dynamic shimming method of multi-order harmonics for magnetic resonance imaging

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Embodiment

[0017] Embodiment: A multi-order harmonic dynamic shimming method for magnetic resonance imaging. After the patient enters the imaging workspace and before the formal magnetic resonance sequence scan, the main magnetic field B in the selected imaging region volume 0 The distribution of the harmonics is measured through the imaging phase map, and the distribution of the harmonic weights of each order is analyzed. According to the results of the harmonic analysis, the compensation current value in the corresponding harmonic shim coil is dynamically adjusted in real time, and the main magnetic field of the selected imaging area is improved. B 0 The uniformity, the specific process is as follows:

[0018] After the patient enters the imaging workspace and before the formal MRI sequence scan, for the main magnetic field B 0 For the measurement of the distribution, the sequence used is a three-dimensional gradient echo sequence, which is collected twice. The other parameters of the...

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Abstract

The invention discloses a method for carrying out dynamic and real-time shimming on any multi-order harmonic component in a selected area for magnetic resonance imaging, and the method can be used for improving the uniformity degree of a main magnetic field in an imaging area through cancelling out non-uniform harmonic items. According to the method provided by the invention, the weight distribution of any-order harmonic of the main magnetic field in the selected area can be analyzed once through phase information of images which are acquired by a three-dimensional gradient echo sequence twice, wherein a series of technical means of carrying out water-fat phase synchronization, eliminating low-signal noise pollution by virtue of an amplitude template and unwinding a three-dimensional phase are adopted, so that the weight component coefficient of any-order harmonic in the selected imaging area can be accurately and rapidly analyzed; a reversed compensating current is added into a corresponding harmonic shimming coil so as to accurately cancel out non-uniform high-order harmonics and only reserve zero-order harmonics, namely a uniform field; and the method provided by the invention has the advantage of maximally improving the uniformity degree of the main magnetic field by combining owned hardware conditions.

Description

technical field [0001] The invention belongs to the field of magnetic resonance imaging, and in particular relates to a multi-order harmonic dynamic shimming method for magnetic resonance imaging. Background technique [0002] In magnetic resonance imaging, the main magnetic field B 0 The uniformity of the film is an important indicator, and its quality is directly related to the quality of the image. For general conventional sequences, the main magnetic field B 0 The uniformity of the imaging will affect the imaging deformation, signal-to-noise ratio, and layer selection accuracy. For some high-order sequences, mainly high-speed sequences and sequences related to chemical shift spectra, the B 0 The requirements for field uniformity are more stringent. For example in an echo planar imaging (EPI) sequence, if the B of the imaging area 0 If the field uniformity cannot be controlled at a good level (within 1ppm), the EPI imaging will produce large image geometric distortion...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R33/38A61B5/055
CPCG01R33/3875
Inventor 唐昕姜忠德刘文韬
Owner SUZHOU LONWIN MEDICAL SYST
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