Multi-echo multi-slice spatio-temporal encoding magnetic resonance imaging method based on segmented excitation

Abstract

The invention discloses a segmented excitation based multi-echo multi-layer space-time coding magnetic resonance imaging method, and relates to a magnetic resonance imaging method. The method comprises the following steps: dividing an imaging object into several segments; selecting an imaging segment through a 90-degree segment selection pulse; performing time-space coding of intra-segment core spinning through a 180-degree linear frequency sweep pulse; enabling the core of non-imaging segment to spin to a heat balance state by using a 180-degree hard pulse; storing the spinning information byusing the same pulse as the 90-degree segment selection pulse; sequentially exciting multiple target layers by using multiple 90-degree layer selection pulses; in combination with the specific dispersed phase gradient of frequency coding dimension, enabling the signals on different layers to form echoes at different sampling moments; changing the center frequency of the layer selection pulse andrelevant pulse gradient, to obtain magnetic resonance data on each layer in the segment; modifying the center frequency of the segment selection pulse, and selecting different imaging segments; repeating the above operations to obtain data of the whole imaging object; dividing the data of multiple echoes acquired at the same time, according to the echo number; and performing super-resolution reconstruction of the data on each layer, to obtain a multi-layer high-resolution magnetic resonance image.

Description

technical field [0001] The invention relates to a magnetic resonance imaging method, in particular to a multi-echo multi-layer space-time encoding magnetic resonance imaging method based on segmental excitation. Background technique [0002] Ultra-fast magnetic resonance imaging (MRI) has good temporal resolution, and it is very useful in functional MRI (fMRI) [1-3] , Diffusion tensor imaging (DTI) [4-6] , free-breathing heart imaging [7] and other fields play an important role. In ultra-fast MRI, echo planar imaging (EPI) is currently the most widely used, and it has excellent performance in both temporal and spatial resolution. [8-10] . EPI is sampled through a series of rapidly switched gradient echoes, and all the data required for a two-dimensional magnetic resonance image can be obtained with one radio frequency pulse excitation. However, EPI images are susceptible to distortion due to inhomogeneous magnetic fields and chemical shift effects [11,12] . [0003] I...

AI Technical Summary

Problems solved by technology

However, the current spatio-temporal encoding imaging method still has the following defects: First, due to the fast positive and negative gradient switching in the sampling stage for data acquisition, the image is susceptible to artifacts caused by the eddy current effect [16,17] Second, the specific absorption rate (SAR) of the linear sweep pulse used in space-time coding is relatively large, which has no effect on single-slice imaging, but in multi-layer imaging, the repeated application of linear sweep pulses will cause the SAR value to be too large, thus limiting its application in clinical

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