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Karlsson RA, Hardarson SH. Artery vein classification in fundus images using serially connected U-Nets. Comput Methods Programs Biomed 2022; 216:106650. [PMID: 35139461 DOI: 10.1016/j.cmpb.2022.106650] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 01/12/2022] [Accepted: 01/18/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND AND OBJECTIVE Retinal vessels provide valuable information when diagnosing or monitoring various diseases affecting the retina and disorders affecting the cardiovascular or central nervous systems. Automated retinal vessel segmentation can assist clinicians and researchers when interpreting retinal images. As there are differences in both the structure and function of retinal arteries and veins, separating these two vessel types is essential. As manual segmentation of retinal images is impractical, an accurate automated method is required. METHODS In this paper, we propose a convolutional neural network based on serially connected U-nets that simultaneously segment the retinal vessels and classify them as arteries or veins. Detailed ablation experiments are performed to understand how the major components contribute to the overall system's performance. The proposed method is trained and tested on the public DRIVE and HRF datasets and a proprietary dataset. RESULTS The proposed convolutional neural network achieves an F1 score of 0.829 for vessel segmentation on the DRIVE dataset and an F1 score of 0.814 on the HRF dataset, consistent with the state-of-the-art methods on the former and outperforming the state-of-the-art on the latter. On the task of classifying the vessels into arteries and veins, the method achieves an F1 score of 0.952 for the DRIVE dataset exceeding the state-of-the-art performance. On the HRF dataset, the method achieves an F1 score of 0.966, which is consistent with the state-of-the-art. CONCLUSIONS The proposed method demonstrates competitive performance on both vessel segmentation and artery vein classification compared with state-of-the-art methods. The method outperforms human experts on the DRIVE dataset when classifying retinal images into arteries, veins, and background simultaneously. The method segments the vasculature on the proprietary dataset and classifies the retinal vessels accurately, even on challenging pathological images. The ablation experiments which utilize repeated runs for each configuration provide statistical evidence for the appropriateness of the proposed solution. Connecting several simple U-nets significantly improved artery vein classification performance. The proposed way of serially connecting base networks is not limited to the proposed base network or segmenting the retinal vessels and could be applied to other tasks.
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Affiliation(s)
- Robert Arnar Karlsson
- Faculty of Medicine at the University of Iceland, Sæmundargata 2, Reykjavík, 102, Iceland; Faculty of Electrical and Computer Engineering at the University of Iceland, Sæmundargata 2, Reykjavík, 102, Iceland.
| | - Sveinn Hakon Hardarson
- Faculty of Medicine at the University of Iceland, Sæmundargata 2, Reykjavík, 102, Iceland.
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Karlsson RA, Olafsdottir OB, Helgadottir V, Belhadj S, Eliasdottir TS, Stefansson E, Hardarson SH. Automation improves repeatability of retinal oximetry measurements. PLoS One 2021; 16:e0260120. [PMID: 34914738 PMCID: PMC8675673 DOI: 10.1371/journal.pone.0260120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 11/02/2021] [Indexed: 11/19/2022] Open
Abstract
Purpose Retinal oximetry is a technique based on spectrophotometry where images are analyzed with software capable of calculating vessel oxygen saturation and vessel diameter. In this study, the effect of automation of measurements of retinal vessel oxygen saturation and vessel diameter is explored. Methods Until now, operators have had to choose each vessel segment to be measured explicitly. A new, automatic version of the software automatically selects the vessels once the operator defines a measurement area. Five operators analyzed image pairs from the right eye of 23 healthy subjects with semiautomated retinal oximetry analysis software, Oxymap Analyzer (v2.5.1), and an automated version (v3.0). Inter- and intra-operator variability was investigated using the intraclass correlation coefficient (ICC) between oxygen saturation measurements of vessel segments in the same area of the retina. Results For semiautomated saturation measurements, the inter-rater ICC was 0.80 for arterioles and venules. For automated saturation measurements, the inter-rater ICC was 0.97 for arterioles and 0.96 for venules. For semiautomated diameter measurements, the inter-rater ICC was 0.71 for arterioles and venules. For automated diameter measurements the inter-rater ICC was 0.97 for arterioles and 0.95 for venules. The inter-rater ICCs were different (p < 0.01) between the semiautomated and automated version in all instances. Conclusion Automated measurements of retinal oximetry values are more repeatable compared to measurements where vessels are selected manually.
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Affiliation(s)
- Robert Arnar Karlsson
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Faculty of Electrical and Computer Engineering, University of Iceland, Reykjavik, Iceland
- * E-mail:
| | - Olof Birna Olafsdottir
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- The National University Hospital of Iceland, Reykjavik, Iceland
| | | | | | - Thorunn Scheving Eliasdottir
- The National University Hospital of Iceland, Reykjavik, Iceland
- Faculty of Nursing, University of Iceland, Reykjavik, Iceland
| | - Einar Stefansson
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- The National University Hospital of Iceland, Reykjavik, Iceland
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Olafsdottir OB, Saevarsdottir HS, Hardarson SH, Hannesdottir KH, Traustadottir VD, Karlsson RA, Einarsdottir AB, Jonsdottir KD, Stefansson E, Snaedal J. Retinal oxygen metabolism in patients with mild cognitive impairment. Alzheimers Dement (Amst) 2018; 10:340-345. [PMID: 30014033 PMCID: PMC6024244 DOI: 10.1016/j.dadm.2018.03.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Introduction We have previously reported that retinal vessel oxygen saturation is increased in mild-to-moderate dementia of Alzheimer's type when compared with healthy individuals. Mild cognitive impairment (MCI) is the predementia stage of the disease. The main purpose was to investigate if these changes are seen in MCI. Methods Retinal vessel oxygen saturation was measured in 42 patients with MCI and 42 healthy individuals with a noninvasive retinal oximeter, Oxymap T1. The groups were paired according to age. Results Arteriolar and venular oxygen saturation was increased in MCI patients compared to healthy individuals (arterioles: 93.1 ± 3.7% vs. 91.1 ± 3.4%, P = .01; venules: 59.6 ± 6.1% vs. 54.9 ± 6.4%, P = .001). Arteriovenous difference was decreased in MCI compared to healthy individuals (33.5 ± 4.5% vs. 36.2 ± 5.2%, P = .01). Discussion Increased retinal vessel oxygen saturation and decreased arteriovenous difference in MCI could reflect less oxygen extraction by retinal tissue. This indicates that retinal oxygen metabolism may be affected in patients with MCI. The need for reliable, noninvasive techniques for diagnosis of dementia is widely recognized. This research indicates that retinal metabolism is decreased in patients in the predementia stage of mild cognitive impairment. Retinal oximetry is a novel noninvasive method that could help as a diagnostic tool in dementia.
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Affiliation(s)
- Olof Birna Olafsdottir
- Department of Ophthalmology, Landspitali - National University Hospital, Reykjavik, Iceland.,University of Iceland, Reykjavik, Iceland
| | | | | | | | | | - Robert Arnar Karlsson
- Department of Ophthalmology, Landspitali - National University Hospital, Reykjavik, Iceland
| | | | | | - Einar Stefansson
- Department of Ophthalmology, Landspitali - National University Hospital, Reykjavik, Iceland.,Department of Geriatrics, Landspitali - National University Hospital, Reykjavik, Iceland
| | - Jon Snaedal
- Department of Geriatrics, Landspitali - National University Hospital, Reykjavik, Iceland
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Hardarson SH, Gottfredsdottir MS, Halldorsson GH, Karlsson RA, Benediktsson JA, Eysteinsson T, Beach JM, Harris A, Stefansson E. Glaucoma Filtration Surgery and Retinal Oxygen Saturation. ACTA ACUST UNITED AC 2009; 50:5247-50. [DOI: 10.1167/iovs.08-3117] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Sveinn Hakon Hardarson
- From the Department of Ophthalmology, University of Iceland/Landspítali–University Hospital, Reykjavik, Iceland; 2Oxymap ehf., Reykjavik, Iceland
| | | | | | | | - Jon Atli Benediktsson
- the Department of Electrical and Computer Engineering, University of Iceland, Reykjavik, Iceland; and
| | - Thor Eysteinsson
- From the Department of Ophthalmology, University of Iceland/Landspítali–University Hospital, Reykjavik, Iceland
| | | | - Alon Harris
- the School of Medicine, Indiana University, Indianapolis, Indiana
| | - Einar Stefansson
- From the Department of Ophthalmology, University of Iceland/Landspítali–University Hospital, Reykjavik, Iceland
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Traustason S, Hardarson SH, Gottfredsdottir MS, Eysteinsson T, Karlsson RA, Stefansson E, Harris A. Dorzolamide-timolol combination and retinal vessel oxygen saturation in patients with glaucoma or ocular hypertension. Br J Ophthalmol 2009; 93:1064-7. [DOI: 10.1136/bjo.2008.148460] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Hardarson SH, Basit S, Jonsdottir TE, Eysteinsson T, Halldorsson GH, Karlsson RA, Beach JM, Benediktsson JA, Stefansson E. Oxygen Saturation in Human Retinal Vessels Is Higher in Dark Than in Light. ACTA ACUST UNITED AC 2009; 50:2308-11. [DOI: 10.1167/iovs.08-2576] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Sveinn Hakon Hardarson
- From the Department of Ophthalmology, University of Iceland/Landspi´tali University Hospital, Reykjavik, Iceland
| | - Samy Basit
- From the Department of Ophthalmology, University of Iceland/Landspi´tali University Hospital, Reykjavik, Iceland
| | - Thora Elisabet Jonsdottir
- From the Department of Ophthalmology, University of Iceland/Landspi´tali University Hospital, Reykjavik, Iceland
| | - Thor Eysteinsson
- From the Department of Ophthalmology, University of Iceland/Landspi´tali University Hospital, Reykjavik, Iceland
| | | | | | | | - Jon Atli Benediktsson
- Department of Electrical and Computer Engineering, University of Iceland, Reykjavik, Iceland
| | - Einar Stefansson
- From the Department of Ophthalmology, University of Iceland/Landspi´tali University Hospital, Reykjavik, Iceland
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Troglio G, Benediktsson JA, Serpico SB, Moser G, Karlsson RA, Halldorsson GH, Stefansson E. Automatic registration of retina images based on genetic techniques. Annu Int Conf IEEE Eng Med Biol Soc 2009; 2008:5419-24. [PMID: 19163943 DOI: 10.1109/iembs.2008.4650440] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The aim of this paper is to develop an automatic method for the registration of multitemporal digital images of the fundus of the human retina. The images are acquired from the same patient at different times by a color fundus camera. The proposed approach is based on the application of global optimization techniques to previously extracted maps of curvilinear structures in the images to be registered (such structures being represented by the vessels in the human retina): in particular, a genetic algorithm is used, in order to estimate the optimum transformation between the input and the base image. The algorithm is tested on two different types of data, gray scale and color images, and for both types, images with small changes and with large changes are used. The comparison between the registered images using the implemented method and a manual one points out that the proposed algorithm provides an accurate registration. The convergence to a solution is not possible only when dealing with images taken from very different view-points.
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Affiliation(s)
- G Troglio
- University of Genoa, Dept. of Biophysical and Electronic Eng. (DIBE), Via Opera Pia 11a, I-16145, Italy.
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Hardarson SH, Harris A, Karlsson RA, Halldorsson GH, Kagemann L, Rechtman E, Zoega GM, Eysteinsson T, Benediktsson JA, Thorsteinsson A, Jensen PK, Beach J, Stefánsson E. Automatic Retinal Oximetry. ACTA ACUST UNITED AC 2006; 47:5011-6. [PMID: 17065521 DOI: 10.1167/iovs.06-0039] [Citation(s) in RCA: 171] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE To measure hemoglobin oxygen saturation (SO(2)) in retinal vessels and to test the reproducibility and sensitivity of an automatic spectrophotometric oximeter. METHODS Specialized software automatically identifies the retinal blood vessels on fundus images, which are obtained with four different wavelengths of light. The software calculates optical density ratios (ODRs) for each vessel. The reproducibility was evaluated by analyzing five repeated measurements of the same vessels. A linear relationship between SO(2) and ODR was assumed and a linear model derived. After calibration, reproducibility and sensitivity were calculated in terms of SO(2). Systemic hyperoxia (n = 16) was induced in healthy volunteers by changing the O(2) concentration in inhaled air from 21% to 100%. RESULTS The automatic software enhanced reproducibility, and the mean SD for repeated measurements was 3.7% for arterioles and 5.3% venules, in terms of percentage of SO(2) (five repeats, 10 individuals). The model derived for calibration was SO(2) = 125 - 142 . ODR. The arterial SO(2) measured 96% +/- 9% (mean +/- SD) during normoxia and 101% +/- 8% during hyperoxia (n = 16). The difference between normoxia and hyperoxia was significant (P = 0.0027, paired t-test). Corresponding numbers for venules were 55% +/- 14% and 78% +/- 15% (P < 0.0001). SO(2) is displayed as a pseudocolor map drawn on fundus images. CONCLUSIONS The retinal oximeter is reliable, easy to use, and sensitive to changes in SO(2) when concentration of O(2) in inhaled air is changed.
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Affiliation(s)
- Sveinn Hakon Hardarson
- Department of Ophthalmology, University of Iceland, National Univbersity Hospital, Reykjavik, Iceland
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