The Application Research On Improving The Image Qualitt Of Upper Abdomen Using VIBE RADIAL Sequence

Abdominal imaging is one of the important clincal application areas of magnetic resonance imaging(MRI).Many low-end equipment inhibit respiratory movement by suppressing breath to reduce motion artifact.However,it's difficult for many patients suppressing scan for a long time.Especially the elderly patients and the patients who hard hold their breath.If the respiratory motion is not processed,the reconstructed image will produce ghost,blur,or even lose important diagnostic information,making diagnosis difficult or even impossible.RADIAL sampling is a non-Cartesian sampling method.The traditional Cartesian sampling method is senstive to motion,which result in motion artifact in the direction of phase coding.RADIAL sampling method acquires the data along rotated spokes,which leads to a high density of K space center data.It's not senstive to motion and can reduce motion ghosting effectively.The overlap in K space center has a motion-averaing effect.Data in consistencies can instead lead to ‘streak' artifacts.‘streak' artifacts have only a mlid effect on the image quality.and they can easily be identified as artifacts due to their characteristic visual appearance.The main contents of this thesis:1.The design of VIBE RADIAL sequence and data acquisitionThe traditional VIBE sequence is a Cartesian approach to abdominal data acquisition sequences.In this thesis,the acquisition of this sequence is changed to RADIAL data acquisition,and the pressure pulse is added to the sequence to improve the signal to noise ratio(SNR)of the image.The upper abdominal image data were acquired with the sequence as the basis of the reconstruction experiment.2.Data correction and image reconstruction.The system delay correction of original data by the method of pre-scan leads to improvement of Image contrast and resolution greatly comparing with conventional method.The reconstruction image using Min-Max nufft instead of Gridding can improve image contrast and resolution.3.Fast scan implementationThe conventional TV iterative algorithm is used to restore the RADIAL under-sampled data.To balance image detail and resolution,this paper choose the appropriate TV weight coefficient.Reconstruction of upper abdominal image with undersampled data using TV iterative algorithm can satisfy basic requirements for rapid scanning.