Research On Affine Motion Artifacts Suppression Methods In MRI Based On PROPELLER Sampling

Magnetic Resonance Imaging (MRI) is a non-invasive approach of mapping the internal structure and function of the human body. Compared with other modalities of medical imaging, MRI has many advantages, such as with no ionizing radiation, imaging with multiple parameters in arbitrary plane, and providing excellent soft-tissue contrast. All those advantages make MR a very important tool for both research and clinical applications.However, long data acquisition time makes MRI susceptible to patient motion. Patient's rigid motion causes artifacts during his magnetic resonance imaging examination, and it affects the diagnosis of doctors seriously. Due to the uncertainty of motion, the prior motion knowledge can't be acquired, so it's very difficult to eliminate the motion artifacts, which will affect and hinder the development step of magnetic resonance imaging technology. Thus the study of MRI motion artifacts, which causes the wide concern of the domestic and foreign scientific research institutions and scholars, is a hot topic in the research area of medical imaging. Any research progress in this field will play an active role in the development and application of magnetic resonance imaging technology.After mastering the principle of magnetic resonance imaging, we do an in-depth study on motion artifacts and PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) MRI. PROPELLER MRI offers an effective means for compensating rigid motion during data collection. So far, this method has been evaluated clinically and found to be able to improve image quality through quantification and correction for head motion, where hypothetically only rotation and translation is present. During imaging of other parts of body, especially in abdomen, soft tissue such as liver, deformation occurs frequently. Traditional PROPELLER reconstruction can't model this kind of non-rigid body motion and can only attain limited compensation through correlation weighting.In this paper, a new method was proposed for affine motion correction, which extracted affine motion information from image space and compensated it in k-space. The experimental results show that the proposed method could correct artifacts due to not only the rigid motion but also the affine motion.To improve affine compensation algorithm for PROPELLER MRI, we proposed a new affine estimate method based on the algorithm of correlation in frequency domain (CF). The original method took a third-order unit matrix as initial value into the estimation of affine parameters. However, the proposed method obtained the rigid motion parameters in each k-space strip by CF, and then the rigid parameters will be initial value into the estimation of affine parameters. The experimental results show that the proposed method is better than the conventional method, and the proposed method is an effective and practical algorithm of affine parameter estimation in PROPELLER MRI.