Simultaneous Multi-slice Echo Planar Imaging Sequence Design And Image Reconstruction For MRI

Magnetic resonance imaging not only imaging for structures but also perform functional imaging.Therefore,functional magnetic resonance imaging is widely used in brain function research.In magnetic resonance scanner equipment with the main magnetic field strength(B0)of 3.0T or below,GRE-based echo planar imaging sequences are the most commonly used for functional imaging.The echo planar imaging sequence implements the acquisition of the entire k-space data with one radiofrequency pulse excitation due to its unique gradient encoding method.It can complete the whole brain scan in a short time,but this special imaging approach also leads to artifacts and lowresolution.Functional magnetic resonance imaging requires repeated scanning at multiple time points using an echo planar imaging sequence.It takes at least seven to nine minutes for a functional imaging.Such a long scanning process is difficult to obtain high-quality functional image data for subjects with poor compliance.Therefore,enhancing the artifact suppression capability and reducing the scanning time of the echo planar imaging sequence will improve the quality and efficiency of functional magnetic resonance imaging and expand the scope of application of functional imaging.In this paper,we have completed the design of simultaneous multi-slice echo planar imaging sequence and image reconstruction for MRI.The simultaneous multi-slice and parallel imaging technology are applied to the echo planar imaging sequence to achieve2 times and 3 times acceleration in the slice and phase encoding direction respectively,which improves the scanning speed of the echo planar imaging sequence.In addition,the reference scan method and fat suppression technology are used to remove the N/2 artifacts and chemical shift artifacts in the echo planar image,so as to ensure that the functional magnetic resonance scan will obtain high-quality echo planar images.The simultaneous multi-slice echo planar imaging sequence implemented in this paper has stable image reconstruction results for consecutive repeated scans,without obvious residual artifacts and geometric distortions.At the same image quality,the scanning time of the simultaneous multi-slice echo planar imaging sequence while achieving 6 times acceleration in both directions is half of the convention echo planar imaging sequence.After the resting and task state functional magnetic resonance experiments,the verification results show that the experimental data obtained by the simultaneous multi-slice echo planar imaging sequence can accurately calculate the corresponding activation area.Simultaneous multi-slice echo planar imaging pulse sequence has higher temporal or spatial resolution and can complete functional magnetic resonance imaging faster.For subjects with poor compliance,sufficient data can be obtained in a short time to reduce the error on the results of functional magnetic resonance analysis caused by the subject's movement.For subjects with good compliance,it is possible to increase the number of repeated acquisitions or obtain data with a higher spatial resolution to improve the accuracy of functional magnetic resonance analysis results.