title: Signal quality assessment of retinal optical coherence tomography images.
abstract: OBJECTIVE
  The purpose of this article was to assess signal quality of retinal optical coherence tomography (OCT) images from multiple devices using subjective and quantitative measurements.
  
  
  METHODS
  A total of 120 multiframe OCT images from 4 spectral domain OCT devices (Cirrus, RTVue, Spectralis, and 3D OCT-1000) were evaluated subjectively by trained graders, and measured quantitatively using a derived parameter, maximum tissue contrast index (mTCI). An intensity histogram decomposition model was proposed to separate the foreground and background information of OCT images and to calculate the mTCI. The mTCI results were compared with the manufacturer signal index (MSI) provided by the respective devices, and to the subjective grading scores (SGS).
  
  
  RESULTS
  Statistically significant correlations were observed between the paired methods (i.e., SGS and MSI, SGS and mTCI, and mTCI and MSI). Fisher's Z transformation indicated the Pearson correlation coefficient ρ ≥ 0.8 for all devices. Using the Deming regression, correlation parameters between the paired methods were established. This allowed conversion from the proprietary MSI values to SGS and mTCI that are universally applied to each device.
  
  
  CONCLUSIONS
  The study suggests signal quality of retinal OCT images can be evaluated subjectively and objectively, independent of the devices. Together with the proposed histogram decomposition model, mTCI may be used as a standardization metric for OCT signal quality that would affect measurements.
authors.affiliation: Fundus Photograph Reading Center, and Ocular Epidemiology Reading Center, Department of Ophthalmology, University of Wisconsin-Madison, Madison, Wisconsin 53717, USA. yhuang@rc.ophth.wisc.edu
authors.forename: Yijun
authors.initials: Y
authors.lastname: Huang
authors.forename: Sapna
authors.initials: S
authors.lastname: Gangaputra
authors.forename: Kristine E
authors.initials: KE
authors.lastname: Lee
authors.forename: Ashwini R
authors.initials: AR
authors.lastname: Narkar
authors.forename: Ronald
authors.initials: R
authors.lastname: Klein
authors.forename: Barbara E K
authors.initials: BE
authors.lastname: Klein
authors.forename: Stacy M
authors.initials: SM
authors.lastname: Meuer
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Danis
mesh_terms: D003930:Diabetic Retinopathy / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000592:standards; D008268:Macular Degeneration / Q000473:pathology*; D012160:Retina / Q000033:anatomy & histology* / Q000473:pathology*; D012170:Retinal Vein Occlusion / Q000473:pathology*; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000295:instrumentation / Q000592:standards*