title: Repeatability of autofluorescence lifetime imaging at the human fundus in healthy volunteers.
abstract: OBJECTIVE
  We aim to evaluate the repeatability of a new fluorescence lifetime imaging (FLIM) technique which measures time-resolved autofluorescence to assess metabolism of the retina.
  
  
  METHODS
  We performed FLIM with two spectral channels (channel 1: 490-560 nm and channel 2: 560-700 nm) on 10 healthy volunteers, with 10 replicates per volunteer. From the 30° fundus FLIM images, we selected three regions: the fovea, the optic disc and the papillo-macular bundle. For each channel in these regions, we determined an average multi-exponential approximation with three components, and the six resulting parameters, α1-α3 (amplitudes) and τ1-τ3 (fluorescence lifetimes), were analyzed in terms of the coefficient of variation (CV).
  
  
  RESULTS
  Repeatability was highest in the papillo-macular bundle, followed by the fovea and the optic disc. Repeatability was higher in channel 1 (mean CV of 7.9%) than in channel 2 (mean CV of 17.7%). The average CV for the diagnostically most relevant channel 1 and the most relevant parameters was as follows: τ1 (5.5%) and τ2 (4.7%) in the papillo-macular bundle, and τ1 (6.8%) and τ2 (6.9%) in the fovea.
  
  
  CONCLUSIONS
  We demonstrated repeatability of FLIM measurement results within acceptable ranges of variation. Based on the detailed coefficients of variation, we derived recommendations for parameter ranges suitable for diagnostic applications.
authors.affiliation: Institute of Biomedical Engineering and Informatics, Ilmenau University of Technology, Ilmenau, Germany . matthias.klemm@tu-ilmenau.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Klemm
authors.forename: Alexander
authors.initials: A
authors.lastname: Dietzel
authors.forename: Jens
authors.initials: J
authors.lastname: Haueisen
authors.forename: Edgar
authors.initials: E
authors.lastname: Nagel
authors.forename: Martin
authors.initials: M
authors.lastname: Hammer
authors.forename: Dietrich
authors.initials: D
authors.lastname: Schweitzer
mesh_terms: D000328:Adult; D005451:Fluorescein Angiography; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D064368:Healthy Volunteers; D006801:Humans; D061848:Optical Imaging / Q000379:methods; D015203:Reproducibility of Results; D012160:Retina / Q000378:metabolism*; D012235:Rhodamines / Q000737:chemistry; D012395:Rose Bengal / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D012235:Rhodamines; D012395:Rose Bengal; C029773:rhodamine B