Behzad Aliahmad

Publications (2)3.43 Total impact

• Article: Does retinal vascular geometry vary with cardiac cycle?

  Hao Hao, Muhammad B Sasongko, Tien Y Wong, Mohd Zulfaezal Che Azemin, Behzad Aliahmad, Lauren Hodgson, Ryo Kawasaki, Carol Y Cheung, Jie Jin Wang, Dinesh K Kumar
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  ABSTRACT: Purpose. Changes in retinal vascular parameters have been shown to be associated with systemic vascular diseases. In this study, we assessed the physiologic variations in retinal vascular measurements during the cardiac cycle. Methods. Fundus images were taken using electrocardiogram-synchronized retinal camera at nine distinct cardiac points from 15 healthy volunteers (135 images). Analyses of retinal vessel geometric measures, including retinal vessel caliber (individual and summary), tortuosity, branching angle, length-diameter ratio (LDR), and optimality deviation, were performed using semiautomated computer software. Repeated-measures ANOVAs were used to obtain the means and to estimate the variation of each cardiac point compared with cardiac point 1. Results. There was a significant variation of the caliber of the individual arteriolar and venular vessels. However, there was no significant variation found for vessel caliber summary, represented by the central retinal arteriolar equivalent (CRAE) and the central retinal venular equivalent (CRVE). There was also no significant variation found for tortuosity and branching angle, and LDR showed none or very little variations at different cardiac points: variations in caliber ranges between 0 and 4.1%, tortuosity 0 and 1.5%, branching angle 0 and 3.5%, and LDR 0 and 2%; all values for variations, P > 0.1; linear trend, P > 0.5; and nonlinear trend, P > 0.8. Conclusions. This study showed that there were minimal variations in the CRAE, CRVE, tortuosity, and branching angle that are clinically used for two-dimensional measures of retinal vascular geometry during cardiac cycles. However, there was significant variation in the caliber of the individual vessels over the cardiac cycle.
  Investigative ophthalmology & visual science 07/2012; 53(9):5799-805. · 3.43 Impact Factor
• Article: Automatic retinal vessel profiling using multi-step regression method.

  Behzad Aliahmad, Dinesh K Kumar, Samira Janghorban, Mohd Zulfaezal Che Azemin, Hao Hao, Ryo Kawasaki
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  ABSTRACT: Caliber of the retinal blood vessel is widely used for risk assessment of cardiovascular diseases. Accurate and automatic caliber measurement requires a precise model to be made for the vessel profile. In this paper, we present a new approach for retinal vessel profiling in which the background noise, uneven illuminations and specular reflections have all been considered. In this method, regression analysis is performed with a series of second-order Gaussians to filter and up-sample the original vessel profile. This is then segmented to identify and represent the vessel edges by two Generalized Gaussian functions. The technique has been applied to retinal images and the results have been verified and compared with the state of the art automatic techniques.
  Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:2606-9.