title: Speckle reduction in optical coherence tomography by two-step image registration.
abstract: The image quality of optical coherence tomography can be severely influenced by speckle noise (i.e., signal-degrading speckle). Averaging multiple B-scans can effectively suppress speckle noise. Because of sample motion, images subject to averaging must be aligned exactly. We propose a two-step image registration scheme that combines global and local registrations for speckle reduction by the averaging of multiple B-scans. The method begins with a global registration to compensate for overall motion, which is estimated based on the rigid transformation model involving translation and rotation. Then each A-scan is aligned by cross-correlation using a graph-based algorithm, followed by a pixel subdivision method to improve smoothness in local registration. The method does not rely on any information about the retinal layer boundaries. We have applied this method to the registration of macular optical coherence tomography images. The results show the reduction of speckle noise and the enhanced visualization of layer structures. A signal-to-noise ratio improvement of nearly the square root of the number of averaged B-scans and a contrast-to-noise ratio improvement of around 11 are achieved through our method.
authors: Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Laboratory of Information Optics and Opto-Electronic Technology, Shanghai 201800, ChinabUniversity of Chinese Academy of Sciences, Beijing 100049, China.
authors: Hang
authors: H
authors: Zhang
authors: Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Laboratory of Information Optics and Opto-Electronic Technology, Shanghai 201800, ChinabUniversity of Chinese Academy of Sciences, Beijing 100049, China.
authors: Zhongliang
authors: Z
authors: Li
authors: Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Laboratory of Information Optics and Opto-Electronic Technology, Shanghai 201800, ChinabUniversity of Chinese Academy of Sciences, Beijing 100049, China.
authors: Xiangzhao
authors: X
authors: Wang
authors: Jiangnan University, School of Science, Wuxi 214122, China.
authors: Xiangyang
authors: X
authors: Zhang
mesh_terms: D000465:Algorithms; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008266:Macula Lutea / Q000000981:diagnostic imaging; D000075530:Organ Motion; D012160:Retina / Q000000981:diagnostic imaging*; D059629:Signal-To-Noise Ratio; D041623:Tomography, Optical Coherence / Q000379:methods*