title: Automated estimation of choroidal thickness distribution and volume based on OCT images of posterior visual section.
abstract: A variety of vision ailments are indicated by anomalies in the choroid layer of the posterior visual section. Consequently, choroidal thickness and volume measurements, usually performed by experts based on optical coherence tomography (OCT) images, have assumed diagnostic significance. Now, to save precious expert time, it has become imperative to develop automated methods. To this end, one requires choroid outer boundary (COB) detection as a crucial step, where difficulty arises as the COB divides the choroidal granularity and the scleral uniformity only notionally, without marked brightness variation. In this backdrop, we measure the structural dissimilarity between choroid and sclera by structural similarity (SSIM) index, and hence estimate the COB by thresholding. Subsequently, smooth COB estimates, mimicking manual delineation, are obtained using tensor voting. On five datasets, each consisting of 97 adult OCT B-scans, automated and manual segmentation results agree visually. We also demonstrate close statistical match (greater than 99.6% correlation) between choroidal thickness distributions obtained algorithmically and manually. Further, quantitative superiority of our method is established over existing results by respective factors of 27.67% and 76.04% in two quotient measures defined relative to observer repeatability. Finally, automated choroidal volume estimation, being attempted for the first time, also yields results in close agreement with that of manual methods.
authors.affiliation: Department of Electrical Engineering, Indian Institute of Technology Hyderabad, Telangana 502205, India. Electronic address: ee11p012@iith.ac.in.
authors.forename: Kiran Kumar
authors.initials: KK
authors.lastname: Vupparaboina
authors.affiliation: Department of Electrical Engineering, Indian Institute of Technology Hyderabad, Telangana 502205, India.
authors.forename: Srinath
authors.initials: S
authors.lastname: Nizampatnam
authors.affiliation: L. V. Prasad Eye Institute, Hyderabad, Telangana 500034, India.
authors.forename: Jay
authors.initials: J
authors.lastname: Chhablani
authors.affiliation: L. V. Prasad Eye Institute, Hyderabad, Telangana 500034, India.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Richhariya
authors.affiliation: Department of Electrical Engineering, Indian Institute of Technology Hyderabad, Telangana 502205, India.
authors.forename: Soumya
authors.initials: S
authors.lastname: Jana
mesh_terms: D000465:Algorithms; D002829:Choroid / Q000473:pathology*; D015862:Choroid Diseases / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D015588:Observer Variation; D009887:Ophthalmoscopy / Q000379:methods; D057972:Posterior Eye Segment / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: Choroidal thickness; Choroidal volume; Optical coherence tomography (OCT); Structural similarity (SSIM) index; Tensor voting