title: Choroidal thickness maps from spectral domain and swept source optical coherence tomography: algorithmic versus ground truth annotation.
abstract: OBJECTIVE
  The purpose of the study was to create a standardised protocol for choroidal thickness measurements and to determine whether choroidal thickness measurements made on images obtained by spectral domain optical coherence tomography (SD-OCT) and swept source (SS-) OCT from patients with healthy retina are interchangeable when performed manually or with an automatic algorithm.
  
  
  METHODS
  36 grid cell measurements for choroidal thickness for each volumetric scan were obtained, which were measured for SD-OCT and SS-OCT with two methods on 18 eyes of healthy volunteers. Manual segmentation by experienced retinal graders from the Vienna Reading Center and automated segmentation on >6300 images of the choroid from both devices were statistically compared.
  
  
  RESULTS
  Model-based comparison between SD-OCT/SS-OCT showed a systematic difference in choroidal thickness of 16.26±0.725 μm (p<0.001) for manual segmentation and 21.55±0.725 μm (p<0.001) for automated segmentation. Comparison of automated with manual segmentations revealed small differences in thickness of -0.68±0.513 μm (p=0.1833). The correlation coefficients for SD-OCT and SS-OCT measures within eyes were 0.975 for manual segmentation and 0.955 for automatic segmentation.
  
  
  CONCLUSIONS
  Choroidal thickness measurements of SD-OCT and SS-OCT indicate that these two devices are interchangeable with a trend of choroidal thickness measurements being slightly thicker on SD-OCT with limited clinical relevance. Use of an automated algorithm to segment choroidal thickness was validated in healthy volunteers.
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria.
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Philip
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria.
authors.forename: Bianca S
authors.initials: BS
authors.lastname: Gerendas
authors.affiliation: Iowa Institute for Biomedical Imaging, L300 Pappajohn Biomedical Discovery Building, Iowa City, Iowa, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria.
authors.forename: Henrik
authors.initials: H
authors.lastname: Faatz
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria.
authors.forename: Dominika
authors.initials: D
authors.lastname: Podkowinski
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria Iowa Institute for Biomedical Imaging, L300 Pappajohn Biomedical Discovery Building, Iowa City, Iowa, USA.
authors.forename: Hrvoje
authors.initials: H
authors.lastname: Bogunovic
authors.affiliation: Iowa Institute for Biomedical Imaging, L300 Pappajohn Biomedical Discovery Building, Iowa City, Iowa, USA Stephen R Wynn Institute for Vision Research, Iowa City, Iowa, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Abramoff
authors.affiliation: Center for Medical Statistics, Informatics, and Intelligent Systems, Medical University of Vienna, Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Hagmann
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Leitner
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Simader
authors.affiliation: Iowa Institute for Biomedical Imaging, L300 Pappajohn Biomedical Discovery Building, Iowa City, Iowa, USA.
authors.forename: Milan
authors.initials: M
authors.lastname: Sonka
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria.
authors.forename: Sebastian M
authors.initials: SM
authors.lastname: Waldstein
authors.affiliation: Christian Doppler Laboratory for Ophthalmic Image Analysis, Department of ophthalmology, Medical University of Vienna, Vienna, Austria.
authors.forename: Ursula
authors.initials: U
authors.lastname: Schmidt-Erfurth
mesh_terms: D000328:Adult; D000465:Algorithms; D002829:Choroid / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult
keywords: Choroid; Imaging