title: An improved level set method for brain MR images segmentation and bias correction.
abstract: Intensity inhomogeneities cause considerable difficulty in the quantitative analysis of magnetic resonance (MR) images. Thus, bias field estimation is a necessary step before quantitative analysis of MR data can be undertaken. This paper presents a variational level set approach to bias correction and segmentation for images with intensity inhomogeneities. Our method is based on an observation that intensities in a relatively small local region are separable, despite of the inseparability of the intensities in the whole image caused by the overall intensity inhomogeneity. We first define a localized K-means-type clustering objective function for image intensities in a neighborhood around each point. The cluster centers in this objective function have a multiplicative factor that estimates the bias within the neighborhood. The objective function is then integrated over the entire domain to define the data term into the level set framework. Our method is able to capture bias of quite general profiles. Moreover, it is robust to initialization, and thereby allows fully automated applications. The proposed method has been used for images of various modalities with promising results.
authors.affiliation: School of math and phy, Nanjing University of Information Science and Technology, Nanjing, Jiangsu Province 210044, China. generalcyj@yahoo.com.cn
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Chen
authors.forename: Jianwei
authors.initials: J
authors.lastname: Zhang
authors.forename: Jim
authors.initials: J
authors.lastname: Macione
mesh_terms: D015982:Bias; D001921:Brain / Q000033:anatomy & histology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000706:statistics & numerical data*; D015233:Models, Statistical