Simple and convenient nuclear magnetic resonance gradient waveform distortion pre-correction method

Abstract

The invention provides a simple and convenient nuclear magnetic resonance gradient waveform distortion pre-correction method. The method comprises the following steps: 1, correcting: loading an ideal gradient waveform, namely Sgg (i = 1, t) = Sideal (t), in a gradient generator, generating distortion after the gradient waveform passes through a gradient system, obtaining a gradient waveform Svol (i = 1, t) in an imaging space through a sequence method, and estimating a gradient system response according to the Svol (i = 1, t) and the Sideal (t) to obtain a system impulse response h (t); correcting distortion of the Svol (i = 1, t) relative to the Sideal (t), performing next iteration, and updating an output gradient waveform Sgg (i + 1, t); and iterating for multiple times until the distortion of the Svol (i = 1, t) is minimum, and repeating the following steps to obtain a pre-corrected gradient waveform database. The method does not need to specially measure the frequency response of the gradient system, is more stable and reliable, does not need pre-scanning, and can adapt to scanning in any geometric orientation.

Description

technical field [0001] The invention relates to the technical field of magnetic resonance imaging, in particular to a simple pre-correction method for nuclear magnetic resonance gradient waveform distortion. Background technique [0002] Gradient pulse is very important in magnetic resonance imaging (MRI). On the one hand, combined with radiofrequency pulses, it determines the excitation profile of the tissue; on the other hand, although current MRI introduces the concepts of RF coding and coil sensitivity coding, gradient coding is still the most important spatial coding method. However, due to the inductance of the gradient coil, the bandwidth limitation of the gradient amplifier, and the conductor structure in the magnet space, the actual magnetic field gradient generated in the imaging space always deviates from the ideal gradient waveform designed in the MRI imaging sequence. This is the so-called gradient waveform deformation or waveform distortion. Distortion of the...

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Problems solved by technology

[0004] For the above two methods, the first gradient waveform distortion correction method needs to measure the frequency response of the gradient system, the process is complicated, the measurement time is long, and it is often difficult to measure accurately in practice; the second method prolongs the scan time, and In practical applications, the accuracy of measuring gradient waveforms is also easily affected by the geometric structure of the object, and there is a certain risk of measurement failure

In addition, in some cases, such as the half-pulse design of two-dimensional ultra-short echo time imaging, the slice selection gradient must approach the ideal waveform, and the second type of method cannot be applied at this time

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