April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Measurement of retina vascular flow across small and large vessel sizes
Author Affiliations & Notes
  • J Ramella-Roman
    Biomedical Engineering Department, Florida International University, Miami, FL
    Herbert Wertheim College of Medicine, Florida International University, Miami, FL
  • Footnotes
    Commercial Relationships J Ramella-Roman, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 227. doi:
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      J Ramella-Roman; Measurement of retina vascular flow across small and large vessel sizes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):227.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

The quantitative estimation of blood flow is an important tool for exploring the etiology, and the treatment of many diseases of the eye including diabetic retinopathy. Current imaging technique focus on limited ranges of vessel sizes. We introduce a novel retinal flow imaging system that combines Speckle Imaging and TRacking of Red blood cells (SITAR). The system provides not only quantitative values of flow but does so across multiple vessels sizes (250µm to 20 µm in diameter).

 
Methods
 

The SITAR imaging system consists of a fundus camera, a fast high sensitivity cooled CCD, and a laser light source, (520 nm). The RBC tracking system utilizes the same laser source as the speckle imaging system but requires amplitude modulation and coherence scrambling. Calibration and characterization of the system was conducted by imaging several micro-fluidic devices of different diameters. Physiologic flow velocities of whole human blood were observed and compared to Finite Element simulations of capillary flow. A self-calibration scheme is utilized to expand the values of flow rate to the full range under study.

 
Results
 

Test conducted with SITAR in-vitro showed high accuracy of flow determination in small vasculature size (20 to 60 µm in diameter) where error between measured flow and predicted flow was less than 3%. When expanding to larger vessel (200µm in diameter) the error grew to up to 6%. An example of this scheme is shown in Fig. 1.

 
Conclusions
 

We propose the combination of two flow measuring techniques, Laser Speckle Contrast Imaging and red blood cell tracking to truly quantify flow on all retina vessels regardless of their size or location for the first time. We also propose a set of in vitro and measurements to explore the limit and strengths of the technique. We believe that this procedure (instrumentation and processing algorithms) will find use in a variety of clinical and research applications where ever the assessment of perfusion within superficial vascular beds is important.

 
 
Fig. 1 RBC tracking at small vessels (Diameter 60µm and 100µm) and self-calibration of flow for large vessels (Diameter =200µm)
 
Fig. 1 RBC tracking at small vessels (Diameter 60µm and 100µm) and self-calibration of flow for large vessels (Diameter =200µm)
 
Keywords: 551 imaging/image analysis: non-clinical  
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