title: Image artefacts in swept-source optical coherence tomography angiography.
abstract: OBJECTIVE
  To describe optical coherence tomography angiography (OCTA) image artefacts in eyes with and without ocular pathologies.
  
  
  METHODS
  The OCTA images of healthy subjects and patients with age-related macular degeneration, diabetic retinopathy and retinal vascular occlusions were retrospectively reviewed. All OCTA images were obtained using a swept-source OCTA instrument (Triton, Topcon). The frequency of various image artefacts including segmentation, banding, motion, projection, masking, unmasking, doubling of the retinal vessels, blink, stretching, out-of-window and crisscross artefacts was assessed. The impact of the artefact on the grading of the images for the foveal avascular zone in deep and superficial retinal layers, capillary non-perfusion and choroidal neovascularisation (CNV) was evaluated.
  
  
  RESULTS
  OCTA images of 57 eyes of 48 subjects including 23 eyes (40.3%) with CNV, 13 eyes (22.8%) with dry age-related macular degeneration, 9 eyes (15.7%) with cystoid macular oedema due to diabetic retinopathy or retinal vein occlusion and 12 normal eyes (21.1%) were available for evaluation. At least one type of artefact was present in the images from 51 eyes (89.4%). Banding artefact, segmentation, motion, unmasking, blink, vessel doubling, masking and out-of-window artefacts were found in 51 (89.4%), 35 (61.4%), 28 (49.1%), 9 (15.8%), 5 (8.8%), 1 (1.7%), 1 eye (1.7%) and 1 eye (1.7%), respectively. Projection artefact, stretch artefact or crisscross artefact was not observed. Banding, motion and segmentation artefacts were statistically significantly more frequent in eyes with ocular pathology compared with control eyes (all p<0.001). Eyes with choroidal diseases had significantly higher rate of segmentation error in the choriocapillaris slab compared with eyes with only retinal disease (p=0.02). In nine eyes (17.6%), the artefacts were deemed severe enough by the graders to preclude accurate grading of the image.
  
  
  CONCLUSIONS
  Image artefacts occur frequently in OCTA images. The artefacts are more frequent in eyes with pathology.
authors.affiliation: Department of Ophthalmology, Doheny Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.|Eye Research Center, Rassoul Akram Hospital, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Khalil
authors.initials: K
authors.lastname: Ghasemi Falavarjani
authors.affiliation: Department of Ophthalmology, Doheny Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Mayss
authors.initials: M
authors.lastname: Al-Sheikh
authors.affiliation: Department of Ophthalmology, Doheny Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Handan
authors.initials: H
authors.lastname: Akil
authors.affiliation: Department of Ophthalmology, Doheny Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Srinivas R
authors.initials: SR
authors.lastname: Sadda
mesh_terms: D000368:Aged; D016477:Artifacts; D016022:Case-Control Studies; D002829:Choroid / Q000098:blood supply; D003930:Diabetic Retinopathy / Q000000981:diagnostic imaging*; D005260:Female; D005451:Fluorescein Angiography / Q000379:methods*; D006801:Humans; D008268:Macular Degeneration / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012170:Retinal Vein Occlusion / Q000000981:diagnostic imaging*; D012171:Retinal Vessels / Q000473:pathology; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: Imaging; Retina