فشرده سازي تصاوير MRI سه بعدي مغز براساس تقارن

چكيده انگليسي :

Compression of 3D MRI Images of Brain Based on Symmetry Somaieh Amraee s amraee@ec iut ac ir Jan 23 2010 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiS Samavi Prof Supervisor samavi96@cc iut ac irM Davarpanah Jazi Assist Prof Supervisor mdjazi@cc iut ac irAbstractMagnetic Resonance Imaging MRI is a medical imaging technique which is most commonly used in radiologyto visualize the internal structure and function of the body MRI provides better contrast between the differentsoft tissues of the body than computed tomography CT does This makes it especially useful in the brain andcancer imaging An MRI scan can be used as an extremely accurate method of disease detection throughout thebody In the head trauma to the brain can be seen as bleeding or swelling Other abnormalities often foundinclude brain aneurysms stroke tumors of the brain as well as tumors or inflammation of the spine Medical images such as MRI can be produced in three forms A two dimensional slice is a single snapshot ofthe tissue Three dimensional or structural MRI is a 3D sequence composed of 2D slices Third form of MRIdata is four dimensional or functional MRI scans which are 3D scans over time Hence each functional MRIscan is composed of a number of 3D sequences Large number of MRI images is routinely generated For follow ups and further study these images need to bestored which requires large amount of storage space With tele medicine becoming more popular there is also aneed for reduction in transmission time Hence compression of medical images plays an important role forefficient storage and transmission Different methods for lossy compression of images and video sequences are available The exact reconstructionof the images is not possible for the lossy compressed images For medical diagnosis purposes lossycompression of images is not desired since it may lead to loss of critical clinical information and may causemisdiagnosis In the lossless compression of volumetric medical images an important number of technical advances have beenreported Some of the existing works have assumed that all slices are independent and can be compressedseparately This means that no correlation among adjacent slices inter slice correlation is exploited It isshown that even for data sets with a small number of 2D slices and a high slice distance there is significant gainin compression ratio by compressing the 3D data compared to compressing the 2D slices independently Generally there is an important shortcoming in most of the available 3D medical image compression schemes These methods often do not exploit some of the inherent characteristics of medical image data such as theinherent symmetry in the ROI In this thesis we propose a lossless compression method for the brain 3D MRIdata that extracts inherent symmetrical property of these images To achieve higher compression ratios theproposed method works on the symmetrical characteristics that exist in the prediction error field of these

امرايي، سميه

فشرده سازي تصاوير MRI سه بعدي مغز براساس تقارن

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