Significance: Evaluation of vessel patency and blood flow direction is important in various medical situations, including diagnosis and monitoring of ischemic diseases, and image-guided vascular surgeries. While optical coherence tomography angiography (OCTA) is the most widely used functional extension of optical coherence tomography that visualizes three-dimensional vasculature, inability to provide information of blood flow direction is one of its limitations.
Aim: We demonstrate two-dimensional (2D) transverse blood flow direction imaging in en face OCTA.
Approach: A series of triangular beam scans for the fast axis was implemented in the horizontal direction for the first volume scan and in the vertical direction for the following volume scan, and the inter A-line OCTA was performed for the blood flow direction imaging while the stepwise pattern was used for each slow axis scan. The decorrelation differences between the forward and the backward inter A-line OCTA were calculated for the horizontal and the vertical fast axis scans, and the ratio of the horizontal and the vertical decorrelation differences was utilized to show the 2D transverse flow direction information.
Results: OCTA flow direction imaging was verified using flow phantoms with various flow orientations and speeds, and we identified the flow speed range relative to the scan speed for reliable flow direction measurement. We demonstrated the visualization of 2D transverse blood flow orientations in mouse brain vascular networks in vivo.
Conclusions: The proposed OCTA imaging technique that provides information of 2D transverse flow direction can be utilized in various clinical applications and preclinical studies.
Kidney transplantation is currently the most favorable treatment for patients with end stage renal disease (ESRD).1,2 Although transplantation from living donors (LD) promises higher survival rate, transplantation from deceased donors (DD) accounts for more than half of all kidney transplantation in the United States.5 Minimizing the ischemic damage on donor kidneys is essential for successful DD kidney transplantation because manifestations of the reperfusion injury after transplantation depend on the extent of ischemic insult.6 In this study, we investigate the correlation between the extent of ischemia and the renal microvasculature damage in an animal model of kidney ischemia and reperfusion injury using Optical Coherence Tomography Angiography (OCTA).
KEYWORDS: Optical coherence tomography, In vivo imaging, Heart, Visualization, Information visualization, Angiography, Tissue optics, Spatial resolution, Temporal resolution, Imaging systems
Optical coherence tomography (OCT) is a useful imaging method for in vivo tissue imaging with deep penetration and high spatial resolution. However, imaging of the beating mouse heart is still challenging due to limited temporal resolution or penetration depth. Here, we demonstrate a multifunctional OCT system for a beating mouse heart, providing various types of visual information about heart pathophysiology with high spatiotemporal resolution and deep tissue imaging. Angiographic imaging and polarization-sensitive (PS) imaging were implemented with the electrocardiogram (ECG)-triggered beam scanning scheme on the high-speed OCT platform (A-line rate: 240 kHz). Depth-resolved local birefringence and the local orientation of the mouse myocardial fiber were visualized from the PS-OCT. ECG-triggered angiographic OCT (AOCT) with the custom-built motion stabilization imaging window provided myocardial vasculature of a beating mouse heart. Mice underwent coronary artery ligation to derive myocardial infarction (MI) and were imaged with the multifunctional OCT system at multiple time points. AOCT and PS-OCT visualize change of functionality of coronary vessels and myocardium respectively at different phases (acute and chronic) of MI in an ischemic mouse heart. Taken together, the integrated imaging of PS-OCT and AOCT would play an important role in study of MI providing multi-dimensional information of the ischemic mouse heart in vivo.
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