title: Dual-wavelength retinal images denoising algorithm for improving the accuracy of oxygen saturation calculation.
abstract: Noninvasive measurement of hemoglobin oxygen saturation ( SO 2 ) in retinal vessels is based on spectrophotometry and spectral absorption characteristics of tissue. Retinal images at 570 and 600 nm are simultaneously captured by dual-wavelength retinal oximetry based on fundus camera. SO 2 is finally measured after vessel segmentation, image registration, and calculation of optical density ratio of two images. However, image noise can dramatically affect subsequent image processing and SO 2 calculation accuracy. The aforementioned problem remains to be addressed. The purpose of this study was to improve image quality and SO 2 calculation accuracy by noise analysis and denoising algorithm for dual-wavelength images. First, noise parameters were estimated by mixed Poisson–Gaussian (MPG) noise model. Second, an MPG denoising algorithm which we called variance stabilizing transform (VST) + dual-domain image denoising (DDID) was proposed based on VST and improved dual-domain filter. The results show that VST + DDID is able to effectively remove MPG noise and preserve image edge details. VST + DDID is better than VST + block-matching and three-dimensional filtering, especially in preserving low-contrast details. The following simulation and analysis indicate that MPG noise in the retinal images can lead to erroneously low measurement for SO 2 , and the denoised images can provide more accurate grayscale values for retinal oximetry.
authors.affiliation: Chinese Academy of Sciences, The Key Laboratory of Adaptive Optics, No. 1 Guangdian Avenue Xihang Port Shuangliu, Chengdu 610209, ChinabUniversity of Electronic Science and Technology of China, School of Optoelectronic Information, No. 4 Block 2 N. Jianshe Road, Chengdu 610054, ChinacChinese Academy of Sciences, Institute of Optics and Electronics, No. 1 Guangdian Avenue Xihang Port Shuangliu, Chengdu 610209, ChinadUniversity of Chinese Academy of Sciences, No. 19, Yuquan Road, Shijingshan, Beijing 100049, China.
authors.forename: Yong-Li
authors.initials: YL
authors.lastname: Xian
authors.affiliation: Chinese Academy of Sciences, The Key Laboratory of Adaptive Optics, No. 1 Guangdian Avenue Xihang Port Shuangliu, Chengdu 610209, ChinacChinese Academy of Sciences, Institute of Optics and Electronics, No. 1 Guangdian Avenue Xihang Port Shuangliu, Chengdu 610209, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Dai
authors.affiliation: University of Electronic Science and Technology of China, School of Optoelectronic Information, No. 4 Block 2 N. Jianshe Road, Chengdu 610054, China.
authors.forename: Chun-Ming
authors.initials: CM
authors.lastname: Gao
authors.affiliation: Chinese Academy of Sciences, The Key Laboratory of Adaptive Optics, No. 1 Guangdian Avenue Xihang Port Shuangliu, Chengdu 610209, ChinacChinese Academy of Sciences, Institute of Optics and Electronics, No. 1 Guangdian Avenue Xihang Port Shuangliu, Chengdu 610209, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Du
mesh_terms: D000465:Algorithms; D007091:Image Processing, Computer-Assisted; D016011:Normal Distribution; D010092:Oximetry; D010100:Oxygen / Q000032:analysis*; D016012:Poisson Distribution; D012160:Retina / Q000000981:diagnostic imaging* / Q000378:metabolism; D012171:Retinal Vessels / Q000000981:diagnostic imaging* / Q000378:metabolism; D059629:Signal-To-Noise Ratio
chemical_list: D010100:Oxygen