Magnetic resonance imaging method to eliminate motion artifacts

Title: Magnetic resonance imaging method to eliminate motion artifacts Author: Tan Pei Degree awarded: China University of Science and Technology Keywords: magnetic resonance imaging;; motion artifacts;; motion estimation;; image reconstruction;; PROPELLER;; grid Abstract:
MRI (Magnetic Resonance Imaging, MRI) based on in vivo nuclear magnetic resonance in the static magnetic field within the imaging characteristics of the signal with high image resolution, more imaging parameters, the fault can be in any direction, the human body without ionizing radiation damage, etc. significant advantages, as the most neodymium magnets advanced medical imaging methods in clinical and scientific research has been more widely used.
Magnetic resonance imaging process, the patient's autonomy and physical movement is often difficult to avoid, it will undermine the data collection process and the formation of the image into artifacts, allowing physicians to make the correct diagnosis difficult. Uncertainty due to movement and movement is difficult to obtain a priori knowledge of the motion artifact correction also very difficult to seriously affect and impede the development of magnetic resonance imaging technology and applications. Therefore, to eliminate motion artifacts in magnetic resonance methods of research, attracted wide attention from foreign scholars, is the current medical imaging field of research focus, progress of any research in this area will have magnetic resonance imaging technology and applications from to the active role.
This familiar and master in magnetic resonance imaging based on the principles and techniques of motion artifacts in-depth research, analysis of motion artifacts on magnetic resonance imaging in the process of data collection and final imaging these two important aspects of impact, proposed several artifacts in image reconstruction algorithms and post-processing correction algorithms for magnetic resonance imaging motion artifact can be effectively suppressed. This study from the analysis of a kind to eliminate motion artifacts in functional imaging algorithm PROPELLER data acquisition to start, right in the application on the basis of implementing the algorithm proposed can improve the speed of the circular grid algorithms, and grid algorithm has been improved to further improve the imaging speed and quality of the algorithm, then presents several practical value of the magnetic resonance image post-processing correction algorithm, on which the translational motion and rotational motion http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php artifact correction, to improve the final image quality.
To sum up, this completed the following distinctive research work:
1) PROPELLER imaging algorithm to improve data collection, proposed a new algorithm based on circular grid. PROPELLER magnetic resonance imaging is a new algorithm, it by changing the way data acquisition and imaging reconstruction step in the reconstruction process by adding correction algorithms, which can more effectively eliminate motion artifacts. Based on the analysis of the algorithm to achieve its basic principles and steps, based on the correction algorithm for the rotation which takes many shortcomings, propose a new circular grid algorithm, grid and interpolation operations to reduce the number of times, improved estimation of rotation parameters PROPELLER accuracy and the speed of the algorithm. Improved PROPELLER imaging data acquisition scanning algorithm not only can effectively inhibit the formation process of motion artifacts, and fast, high image quality.
2) proposed two improved sampling-based data grid PROPELLER imaging algorithm. PROPELLER imaging grid is an important step in the algorithm, the imaging results of the final plays a decisive role in improvement of the meshing algorithm, mesh-based imaging can significantly improve the speed and quality. Algorithms for the Voronoi grid mesh size density compensation value as a function of closure and proposed the establishment of the grid method, the grid-based imaging algorithm has been improved. Algorithm II to a large matrix of grid-based algorithm not only improves the quality of the grid, but also the use of matrix operations to speed up the computing process.
3) for two magnetic resonance translational motion artifact correction algorithms. First, a new algorithm based directly on the artifact zone correction algorithm. It is based on artifacts zone data to establish the constraint equations translation exercise, using a differential evolution algorithm for optimization of the value function, shift to get exercise, to achieve translational motion artifact correction. Algorithm based on two non-sports related, respectively, x and y direction translational motion processing. Fourier projection algorithm, to get x-amount of the entire pixel motion pan, quickly correct the x direction of motion artifacts; parameters based on polynomial fitting, correct use of genetic algorithms and x-y direction, the direction of the sub-pixel motion artifacts. Experimental results show that two algorithms of translational motion artifacts can play a better inhibitory effect.
4) rapid scanning sequence for the MRI, we propose a rotational motion artifact correction algorithms. Algorithm includes the following new ideas: the uniformly rectangular K-space data, the idea of ​​a new striping plan; given new similarity measure formula used to estimate the rotation parameters; proposed compensation Hermitian conjugate algorithm, after correction for the position to compensate for uneven data space; design a fast grid-based algorithm, the process of accelerated computing. Experimental results show that the algorithm can effectively correct rotation motion artifacts, and by the signal to noise ratio is small, has a certain robustness. Degree Year: 2009