title: Classification of image artefacts in optical coherence tomography angiography of the choroid in macular diseases.
abstract: BACKGROUND
  To evaluate and classify image artefacts in optical coherence tomography (OCT) angiography (OCTA) of the choroid in a group of patients with macular diseases.
  
  
  METHODS
  Retrospective observational study.
  
  
  METHODS
  Five patients with age-related macular degeneration, three with central serous retinopathy, one with polypoidal choroidal vasculopathy and one with multiple evanescent white dot syndrome.
  
  
  METHODS
  OCTA and OCT reflectivity (OCTR) maps were reviewed along with their fluorescein angiography and indocyanine green angiography. Sixty OCTA images (20 outer retina, 20 Sattler and 20 Haller layers) were graded for image artefacts by two examiners independently.
  
  
  METHODS
  OCTA artefacts and their correlation with OCTR maps, angiography and OCT B-scans.
  
  
  RESULTS
  Artefacts (frequency) were classified into (i) motion (70-100%), (ii) fringe washout (100%), (iii) decorrelation projection (0-20%), (iv) masking and unmasking (50-65%) and (v) stromal decorrelation signal (100%). Motion artefact in OCTA is characterized by horizontal dark lines or bands not apparent on OCTR map. Fringe washout creates signal void within choroidal vessels because of fast blood flow. Decorrelation projection from retinal vasculature and choroidal new vessels above the Bruch's membrane are seen within the choroidal OCTA image. Masking and unmasking artefacts occur in regions of pigment epithelial detachment and atrophy. Decorrelation signals can also be seen in the choroidal stroma.
  
  
  CONCLUSIONS
  Our classification system of artefact in choroidal OCTA establishes a common terminology for clinical interpretation. This is important in enhancing our understanding of the principles of OCTA acquisition, and it also serves as a bench mark for reading centres.
authors.affiliation: Centre for Ophthalmology and Visual Science (incorporating Lions Eye Institute), The University of Western Australia, Perth, Western Australia, Australia.|Department of Ophthalmology, Royal Perth Hospital, Perth, Western Australia, Australia.
authors.forename: Fred K
authors.initials: FK
authors.lastname: Chen
authors.affiliation: Department of Ophthalmology, Royal Perth Hospital, Perth, Western Australia, Australia.
authors.forename: Rian D
authors.initials: RD
authors.lastname: Viljoen
authors.affiliation: Centre for Ophthalmology and Visual Science (incorporating Lions Eye Institute), The University of Western Australia, Perth, Western Australia, Australia.
authors.forename: Danuta M
authors.initials: DM
authors.lastname: Bukowska
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D056833:Central Serous Chorioretinopathy / Q000000981:diagnostic imaging* / Q000503:physiopathology; D020256:Choroidal Neovascularization / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004396:Coloring Agents / Q000008:administration & dosage; D005260:Female; D005451:Fluorescein Angiography; D006801:Humans; D007208:Indocyanine Green / Q000008:administration & dosage; D008268:Macular Degeneration / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011127:Polyps / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000145:classification*
chemical_list: D004396:Coloring Agents; D007208:Indocyanine Green
keywords: choroidal vasculature; image artefact; optical coherence tomography angiography; retinal diseases