A Study On Visualization Of Diffusion Tensor Imaging Of Magnetic Resonance

In the middle of twenty century, investigators used the pulsed gradient to encode the motion effect of water molecular and produced the diffusion weighted image (DWI). A new Magnetic Resonance imaging (MRI) method called diffusion tensor imaging (DTI) has emerged, which utilizes the diffusion tensor of each voxel calculated from multiple direction DWI(at least 6 directions).As a new technology which can reflect the direction of molecule diffusion, DTI can shows the information of the structure of the tissues and the exchanges of water molecule with each tissues in pathology. It has great advantages on showing the distribution of white matter fiber pathway and its three-dimensional structures because of the distinct anisotropy of the diffusion in water molecule of the brain white matter. Without any other methods can measure the character of the live white matter presently, DTI has great significance for the study of the anatomization of the brain and the diagnosis of the diseases of white matter.As a non-invasive and very important tool for study of the internal structure of the brain, DTI has been widely used in the research of neurophysiology, neurosurgery, and diagnosis of brain cancer, etc. There is a second order tensor corresponding to each voxel in the DTI image, and the representation of those tensor data and digging of the meaningful information in those data become the main issues for the research of DTI and its applications, including the processing of diffusion tensor data, fiber tracking, seeking the real and intuitive representation or display of these results.This paper introduces the basic theory and the concept of DTI. It reviews the visualization methods in common used with DTI data. Ellipsoidal visualization with diffusion tensor is a regular method of glyph, and the ellipsoid is one of the most direct glyph. It is hard to distinguish different diffusion shapes according to the different observing positions. This paper addresses a new method of ellipsoidal visualization based on the anisotropy of the diffusion tensor shaped color-encoding. It uses different colors for different anisotropy shapes in the ellipsoid and puts the information of anisotropy level into the image. Moreover, it is expanded to three-dimensional space. According to the method of ellipsoidal visualization, it can give better visual effect to distribution and pathway of the white matter in the brain. It's advantaged for the basic research of brain functions, the clinic diagnosis and treatment for brain diseases.Nowadays, various techniques of three-dimensional visualization with nerve fibers have been mentioned, and the technique of tractography is the most popular method in visualizing and analyzing with white matter fibers. According to the limitation of the traditional algorithms, this dissertation presents a new fiber tracking algorithm based on the diffusion shape. Absorbing the advantages of Streamline Tracking (STT) and Tensor Deflection (TEND), this algorithm uses different tracking strategies on corresponding diffusion shape. It results in a better tracking pathway which is closer to real fiber in case of planar diffusion and visualizes the fibers of the brain white matter more accurately.