Publication: Bias field in-homogeneity correction of magnetic resonance images (mri)
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Date
2008-03-01
Authors
Yeoh, Yan Pore
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Abstract
Magnetic resonance (MR) imaging has opened up new avenues of diagnosis and treatment that were not previously available. However, there are a number of artifacts which can arise in the MR imaging process and make subsequent analysis more challenging. The most drastic visual effect is the intensity in-homogeneity of the output MR images. Therefore, study on correcting this in-homogeneity problem is essential and important to extract information on MR image correctly. In this project, we present various types of methods to correct the in-homogeneity of the MRI which are histogram matching, histogram equalization, data driven method, and homomorphic unsharp masking method. Histogram matching and histogram equalization are used to uniform the intensity of the input MR images as a pre-processing technique, so that the input MRI with uniform intensity can be process later efficiently. Then, a data driven method for solving in-homogeneity in MRI is presented. Small variations within tissue type are modeled and a correction function is generated. This method is based on image features and does not need any phantom nor user interaction. A modified data driven method with iteration is designed to give better result in MRI in-homogeneity correction. Another method which is homomorphic unsharp masking method is presented and used as a post – processing method to remove in-homogeneity in MRI. This method is function as a sort of band notch filter, where a certain spatial frequency range in the image is selected and removed. It removes low frequency components from an image and it does not alter the tissue boundaries. This method is the simplest method and it can be done by using different kind of filter such as mean and median. From the result provided by the methods mention above, some methods do remove the in-homogeneity of MRI successfully while some methods do not. As a result, different methods do correct the in-homogeneity of the MRI in different ways.