title: Enhancing the signal-to-noise ratio in ophthalmic optical coherence tomography by image registration--method and clinical examples.
abstract: Optical coherence tomography (OCT) has already proven an important clinical tool for imaging and diagnosing retinal diseases. Concerning the standard commercial ophthalmic OCT systems, speckle noise is a limiting factor with respect to resolving relevant retinal features. We demonstrate successful suppression of speckle noise from mutually aligning a series of in vivo OCT recordings obtained from the same retinal target using the Stratus system from Humphrey-Zeiss. Our registration technique is able to account for the axial movements experienced during recording as well as small transverse movements of the scan line from one scan to the next. The algorithm is based on a regularized shortest path formulation for a directed graph on a map formed by interimage (B-scan) correlations. The resulting image enhancement typically increases the contrast-to-noise ratio (CNR) with a factor of three or more and facilitates segmentation and quantitative characterization of pathologies. The method is currently successfully being applied by medical doctors in a number of specific retinal case studies.
authors.affiliation: Technical University of Denmark, Riso National Laboratory, Optics and Plasma Research Department, Roskilde, Denmark. thomas.martini@risoe.dk
authors.forename: Thomas Martini
authors.initials: TM
authors.lastname: Jørgensen
authors.forename: Jakob
authors.initials: J
authors.lastname: Thomadsen
authors.forename: Ulrik
authors.initials: U
authors.lastname: Christensen
authors.forename: Wael
authors.initials: W
authors.lastname: Soliman
authors.forename: Birgit
authors.initials: B
authors.lastname: Sander
mesh_terms: D000465:Algorithms; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012160:Retina / Q000033:anatomy & histology*; D012164:Retinal Diseases / Q000473:pathology; D042262:Retinoscopy / Q000379:methods*; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D041623:Tomography, Optical Coherence / Q000379:methods*