title: Adaptive-weighted bilateral filtering and other pre-processing techniques for optical coherence tomography.
abstract: This paper presents novel pre-processing image enhancement algorithms for retinal optical coherence tomography (OCT). These images contain a large amount of speckle causing them to be grainy and of very low contrast. To make these images valuable for clinical interpretation, we propose a novel method to remove speckle, while preserving useful information contained in each retinal layer. The process starts with multi-scale despeckling based on a dual-tree complex wavelet transform (DT-CWT). We further enhance the OCT image through a smoothing process that uses a novel adaptive-weighted bilateral filter (AWBF). This offers the desirable property of preserving texture within the OCT image layers. The enhanced OCT image is then segmented to extract inner retinal layers that contain useful information for eye research. Our layer segmentation technique is also performed in the DT-CWT domain. Finally we describe an OCT/fundus image registration algorithm which is helpful when two modalities are used together for diagnosis and for information fusion.
authors.affiliation: Visual Information Laboratory, University of Bristol, Bristol, UK. Electronic address: n.anantrasirichai@bristol.ac.uk.
authors.forename: N
authors.initials: N
authors.lastname: Anantrasirichai
authors.affiliation: School of Cellular and Molecular Medicine, University of Bristol, UK.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Nicholson
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, UK.
authors.forename: James E
authors.initials: JE
authors.lastname: Morgan
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, UK.
authors.forename: Irina
authors.initials: I
authors.lastname: Erchova
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, UK.
authors.forename: Katie
authors.initials: K
authors.lastname: Mortlock
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, UK.
authors.forename: Rachel V
authors.initials: RV
authors.lastname: North
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, UK.
authors.forename: Julie
authors.initials: J
authors.lastname: Albon
authors.affiliation: Visual Information Laboratory, University of Bristol, Bristol, UK.
authors.forename: Alin
authors.initials: A
authors.lastname: Achim
mesh_terms: D000465:Algorithms; D005654:Fundus Oculi; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted; D009900:Optic Nerve / Q000033:anatomy & histology*; D041623:Tomography, Optical Coherence; D058067:Wavelet Analysis
keywords: Bilateral filter; DT-CWT; Despeckling; Image enhancement; Registration; Segmentation