title: Validation of spectral domain optical coherence tomographic Doppler shifts using an in vitro flow model.
abstract: OBJECTIVE
  To validate velocity measurements produced by spectral domain optical coherence tomography (SD-OCT) in an in vitro laminar flow model.
  
  
  METHODS
  A 30-mL syringe filled with skim milk was inserted into a syringe pump. Intravenous (i.v.) tubing connected the syringe within the pump to a glass capillary tube (internal diameter, 0.579 mm) shallowly embedded in agarose gel, then to a collection reservoir. SD-OCT imaging was performed with an anterior segment eye scanner and optics engine coupled with a 100-nm bandwidth broadband superluminescent diode. Scan density of 128 x 128 A-scans was spread over a 4 x 4 mm area, and each A-scan was 2 mm in length. Fifteen sequential stationary A-scans were obtained at each 128 x 128 position, and Doppler shifts were calculated from temporal changes in phase. The beam-to-flow vector Doppler angle was determined from three-dimensional scans.
  
  
  RESULTS
  In all reflectance and Doppler images, a clear laminar flow pattern was observed, with v(max) appearing in the center of the flow column. Phase wrapping was observed at all measured flow velocities, and fringe washout progressively shattered reflectance and phase signals beyond the Nyquist limit. The observed percentages of the velocity profile at or below Nyquist frequency was highly correlated with the predicted percentages (R(2)=0.934; P=0.007).
  
  
  CONCLUSIONS
  SD-OCT provides objective Doppler measurements of laminar fluid flow in an in vitro flow system in a range up to the Nyquist limit.
authors.affiliation: UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Larry
authors.initials: L
authors.lastname: Kagemann
authors.forename: Gadi
authors.initials: G
authors.lastname: Wollstein
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Townsend
authors.forename: Joel S
authors.initials: JS
authors.lastname: Schuman
mesh_terms: D001783:Blood Flow Velocity; D017078:Laser-Doppler Flowmetry; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D012039:Regional Blood Flow; D041623:Tomography, Optical Coherence / Q000295:instrumentation / Q000379:methods*