Single-excitation fat-water separation imaging error correction system and method

Abstract

The invention discloses a single-excitation fat-water separation imaging error correction system and method. A pre-scanning module and a fat-water scanning module are installed on a host of a magnetic resonance imager and are loaded to a sequence generator of a spectrometer, for controlling a radio frequency system and a gradient system to realize excitation, space encoding and acquisition of human body proton signals. A matched data preprocessing module, a primary amplitude correction module, a primary phase correction module, a phase unwrapping module, a high-grade error correction module and a fat-water image separation module are installed on the host. According to the invention, the problem of imperfect hardware of MRI equipment is effectively overcome, a field nonuniform effect and a chemical displacement effect of a TE period are taken into consideration, the error correction precision of echo amplitude errors and phase errors and the efficiency of a phase unwrapping algorithm are improved, and the need of clinic image diagnosis is satisfied.

Description

technical field [0001] The invention relates to the technical field of medical magnetic resonance imaging, in particular to a single-shot water-fat separation imaging error correction system and method. Background technique [0002] In medical magnetic resonance imaging (MRI), fat suppression imaging is significantly better than conventional imaging techniques in showing lesions. Commonly used fat suppression methods include selective fat magnetization saturation, water selective excitation and short TI recovery (STIR). Compared with these fat suppression imaging techniques, the chemical shift imaging technique that performs separate imaging of each component based on the chemical shift of different tissue components, Δf, is more sensitive to the radiofrequency field B 1 The homogeneity and magnetic field strength have no special requirements and the image signal-to-noise ratio is not lost. It can also determine the relative proportion of fat and water in the tissue, which i...

AI Technical Summary

Problems solved by technology

However, this solution is often not effective in clinical application, and the following technical problems need to be solved to ensure its general applicability:

[0003] (1) For the imaging system with poor magnetic field uniformity and low gradient performance, the phase error caused by magnetic field inhomogeneity, magnetic susceptibility effect and eddy current effect is relatively large in the time interval between the in-phase echo peak and the anti-phase echo peak, and the In the background noise interference, the phases of the in-phase and anti-phase echoes often exceed the range of -π to +π, causing serious phase winding artifacts. This situation not only requires good shimming and eddy current suppression technology in the scanning process, but also requires The phase unwrapping algorithm for water-lipid image processing is efficient enough. Commonly used phase unwrapping algorithms (such as polynomial fitting method, region growing method, branch cutting method, etc.) need several seconds to tens of seconds to realize phase unwrapping for a single image. Even many pixels will have phase unwrapping errors, which cannot fully meet the needs of clinical applications

[0004] (2) There are differences in the amplitude, linearity, eddy current field effect and Maxwell field of the gradient system in different directions, and the filter response of the receiving channel is asymmetrical. These factors will introduce additional The phase error and magnitude error of

[0005] (3) In the case of poor magnetic field uniformity, the amplitude attenuation between the in-phase and anti-phase echoes is large, and the addition and subtraction of the water-fat in-phase map and the anti-phase map cannot fully separate the water-fat signals

[0006] (4) In the case of poor gradient performance and large RF pulse width, the chemical shift effect and field inhomogeneity effect within the echo time corresponding to the water-lipid in-phase diagram based on gradient echo cannot be ignored, otherwise it will cause water-lipid Incomplete image separation

[0007] Because of this, the phase unwrapping, phase correction and amplitude correction of fast and accurate echo signals have always been the technical bottlenecks that MRI equipment with poor hardware performance needs to solve to quickly and accurately obtain water-fat separation images.

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