Self-adaptive MRI gradient pre-emphasis waveform generating device and method

Abstract

The invention discloses a self-adaptive MRI (Magnetic Resonance Imaging) gradient pre-emphasis waveform generating device. The device includes a user computer, a sampling computer, a gradient controlmodule, a gradient power amplifier module and a gradient signal collection module. The invention also discloses a self-adaptive MRI gradient pre-emphasis waveform generating method. According to the invention, based on a gradient current pre-emphasis compensation principle, first, when pre-emphasis treatment is not performed, distorted actual gradient magnetic field waveform data on a gradient coil is collected through a current monitoring port of the gradient power amplifier module and in uploaded to the user computer, and then the offset between preset gradient magnetic field waveform data and the actual gradient magnetic field waveform data is calculated. An eddy curve is acquired based on the offset, a group of amplitude constants and time constants are acquired through least squares fitting, and pre-emphasis treatment is performed on gradient pre-emphasis parameters through the amplitude constants and time constants are acquired through fitting, so that influence on gradient magnetic field by eddy currents is eliminated through neutralization.

Description

technical field [0001] The present invention relates to the technical field of nuclear magnetic resonance instruments, in particular to an adaptive nuclear magnetic resonance gradient pre-emphasis waveform generation device, and also to a method for generating adaptive nuclear magnetic resonance gradient pre-emphasis waveforms, which is used to reduce gradient eddy currents in nuclear magnetic resonance experiments The gradient magnetic field distortion and distortion caused by it. Background technique [0002] In the MRI system, the gradient system is responsible for generating a linearly changing gradient magnetic field for spatially encoding the object to be measured. The gradient system generates the required gradient magnetic field by applying a gradient current to the gradient coil. Since the gradient coil is located inside the magnet, and the magnet contains many metal parts, such as magnetic shielding shell, superconducting coil, shim coil and radio frequency coil, e...

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Problems solved by technology

[0007] Although the above-mentioned gradient pre-emphasis adjustment method based on NMR signal strength can obtain eddy current compensation parameters, it still has the following deficiencies: 1. It is necessary for the debugger to manually repeatedly set the gradient pre-emphasis parameters to obtain a better compensation effect, and the debugging process is time-consuming and laborious; 2. .The setting of time constant and amplitude constant depends on the experience of professional debugging personnel, and it is difficult for ordinary users to complete debugging; 3. This method can only obtain the compensation current constant generated by the falling edge of the gradient, but the compensation parameters of the rising edge of the gradient cannot be obtained. Accurately compensates for the effects of eddy currents

4. Since the pre-emphasis parameters need to be adjusted by observing the NMR signal intensity, the debugging results are easily affected by factors such as magnetic field inhomogeneity, sample relaxation time, and pulse sequence parameters.

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