A multi-layer ultrafast magnetic resonance imaging method based on segmented excitation spatiotemporal encoding

Abstract

The invention relates to a multilayer super-rapid magnetic resonance imaging method based on segmental excitation space-time coding and relates to the magnetic resonance imaging method. According to the method, an imaging object is divided into multiple segments, at an excitation stage, a 90-degree segment selection sinc pulse is utilized to select an imaging segment, in-segment protons are made to spin through a 180-degree linear frequency modulation pulse to acquire a secondary phase, and time-space coding for the spinning protons in the imaging segment is carried out; the secondary phase information is stored through a phase identical to the 90-degree segment selection pulse; a layer selection 90-degree sinc pulse is connected, decoding and sampling for the protons are carried out. Through designing the center frequency and the decoding sampling gradient of the layer selection pulse, the magnetic resonance data of multiple layers of the segment can be acquired, different imaging segments are selected through correcting the center frequency of the segment selection pulse, and the multilayer data of the whole imaging object is acquired through repeated operation, high resolution reconstruction for the acquired magnetic resonance data of each layer is sequentially carried out, and the multilayer high resolution magnetic resonance image is acquired.

Description

technical field [0001] The invention relates to a magnetic resonance imaging method, in particular to a multi-layer ultra-fast magnetic resonance imaging method based on segmental excitation space-time encoding. Background technique [0002] Ultra-fast magnetic resonance imaging plays an important role in some medical applications and research that require high time resolution, such as diffusion tensor imaging (DTI), functional MRI (functional MRI, fMRI), real-time dynamic imaging ( real-time imaging), etc. Among many ultra-fast methods, single-scan echo planar imaging (EPI) has become the most popular ultra-fast imaging technology due to its high time resolution. EPI performs fast sampling through a series of rapidly switched gradient echoes, and one magnetic resonance image can be obtained with one excitation. However, the EPI imaging method is easily affected by the inhomogeneity of the magnetic field and the chemical shift effect, resulting in geometric distortion of t...

AI Technical Summary

Problems solved by technology

[0003] Although the single-layer space-time coding technology has the above advantages, if the multi-layer imaging technology is introduced, the specific absorption rate (SAR) will be too large due to the application of multiple chirp pulses, so it cannot be really applied

In 2013, the Frydman group proposed a multi-layer spatiotemporal coding imaging technique with global spatial coding layered sampling (Schmidt R, Frydman L. Newspatiotemporal approaches for fully refocused, multislice ultrafast 2DMRI. Magn Reson Med 2014; 71:711-722), although the technology greatly reduces the SAR, but as the number of layers increases, due to the T 1 However, the relaxation effect caused the sampling signal to be greatly attenuated, and the signal-to-noise ratio of the image was also reduced.

Images