Characterizing relationship between optical microangiography signals and capillary flow using microfluidic channels

Abstract

Optical microangiography (OMAG) is a powerful optical angiographic tool to visualize micro-vascular flow in vivo. Despite numerous demonstrations for the past several years of the qualitative relationship between OMAG and flow, no convincing quantitative relationship has been proven. In this paper, we attempt to quantitatively correlate the OMAG signal with flow. Specifically, we develop a simplified analytical model of the complex OMAG, suggesting that the OMAG signal is a product of the number of particles in an imaging voxel and the decorrelation of OCT (optical coherence tomography) signal, determined by flow velocity, interframe time interval, and wavelength of the light source. Numerical simulation with the proposed model reveals that if the OCT amplitudes are correlated, the OMAG signal is related to a total number of particles across the imaging voxel cross-section per unit time (flux); otherwise it would be saturated but its strength is proportional to the number of particles in the imaging voxel (concentration). The relationship is validated using microfluidic flow phantoms with various preset flow metrics. This work suggests OMAG is a promising quantitative tool for the assessment of vascular flow. Chen, and R. K. Wang, "Repeatability and reproducibility of optic nerve head perfusion measurements using optical coherence tomography angiography," J. Biomed. Opt. 21(6), 065002 (2016). 42. Z. Chu, J. Lin, C. Gao, C. Xin, Q. Zhang, C. L. Chen, L. Roisman, G. Gregori, P. J. Rosenfeld, and R. K. Wang, "Quantitative assessment of the retinal microvasculature using optical coherence tomography angiography," J.

Optical coherence tomography angiography monitors human cutaneous wound healing over time

“…The angiogenic vessels visualized here also appeared brighter than their surrounding counterparts (Figure 4). Studies have shown that the OMAG signal is proportional to the flux of red blood cells passing through the vessels (70,71).…”

Hematocrit dependence of flow signal in optical coherence tomography angiography

“…It is interesting to compare our works with the intralipid phantom study [20] which also employed similar microfluidic chip. The primary difference between these two studies is the different scattering media used.…”

“…(1). In the model by Choi et al, the phase term was taken into consideration when a complex OCT value based OCTA was used [20]. In a previous publication [13], it has been shown that OCT amplitude based OCTA and OCT complex value based OCTA show very similar trends although the unnormalized OCTA values from these methods are different.…”

“…In addition, due to pulsatile nature of the blood flow, the RBC velocity will not be constant. Recently, similar expressions has been used by other groups for quantitative description of OCTA [20,27]. So this model is suitable for modeling hematocrit dependence of flow signal in OCTA.…”

“…Ruminski et al used a 280-μm silicon capillary filled with 2% intralipid to investigate the contrast-to-noise ratio for the angiographic images derived from different OCTA algorithms [14]. Very recently, Choi et al [20] as well as our group [21] have investigated the relationship between OCTA and flow speed in channels with different size using microfluidic chips.…”