title: The EM Method in a Probabilistic Wavelet-Based MRI Denoising.
abstract: Human body heat emission and others external causes can interfere in magnetic resonance image acquisition and produce noise. In this kind of images, the noise, when no signal is present, is Rayleigh distributed and its wavelet coefficients can be approximately modeled by a Gaussian distribution. Noiseless magnetic resonance images can be modeled by a Laplacian distribution in the wavelet domain. This paper proposes a new magnetic resonance image denoising method to solve this fact. This method performs shrinkage of wavelet coefficients based on the conditioned probability of being noise or detail. The parameters involved in this filtering approach are calculated by means of the expectation maximization (EM) method, which avoids the need to use an estimator of noise variance. The efficiency of the proposed filter is studied and compared with other important filtering techniques, such as Nowak's, Donoho-Johnstone's, Awate-Whitaker's, and nonlocal means filters, in different 2D and 3D images.
authors.affiliation: Laboratorio de Procesado de Imagen, Escuela Técnica Superior de Ingenieros de Telecomunicación, Campus Miguel Delibes s.n., 47011 Valladolid, Spain.
authors.forename: Marcos
authors.identifier: 0000-0001-9342-9989
authors.initials: M
authors.lastname: Martin-Fernandez
authors.affiliation: Departamento de Álgebra, Análisis Matemático, Geometría y Topología, Facultad de Ciencias, Campus Miguel Delibes s.n., 47011 Valladolid, Spain.
authors.forename: Sergio
authors.identifier: 0000-0003-2508-3861
authors.initials: S
authors.lastname: Villullas
mesh_terms: D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology; D019295:Computational Biology; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000706:statistics & numerical data; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D015233:Models, Statistical; D016011:Normal Distribution; D059629:Signal-To-Noise Ratio; D058067:Wavelet Analysis