Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications.

Optical coherence tomography (OCT)-based angiography (OCTA) provides in vivo, three-dimensional vascular information by the use of flowing red blood cells as intrinsic contrast agents, enabling the visualization of functional vessel networks within microcirculatory tissue beds non-invasively, without a need of dye injection. Because of these attributes, OCTA has been rapidly translated to clinical ophthalmology within a short period of time in the development. Various OCTA algorithms have been developed to detect the functional micro-vasculatures in vivo by utilizing different components of OCT signals, including phase-signal-based OCTA, intensity-signal-based OCTA and complex-signal-based OCTA. All these algorithms have shown, in one way or another, their clinical values in revealing micro-vasculatures in biological tissues in vivo, identifying abnormal vascular networks or vessel impairment zones in retinal and skin pathologies, detecting vessel patterns and angiogenesis in eyes with age-related macular degeneration and in skin and brain with tumors, and monitoring responses to hypoxia in the brain tissue. The purpose of this paper is to provide a technical oriented overview of the OCTA developments and their potential pre-clinical and clinical applications, and to shed some lights on its future perspectives. Because of its clinical translation to ophthalmology, this review intentionally places a slightly more weight on ophthalmic OCT angiography.

Optical coherence tomography based angiography [Invited].

Retinal Microvascular Network and Microcirculation Assessments in High Myopia

PURPOSE To evaluate the perifoveolar retinal capillary network at different depths and to quantify the foveal avascular zone (FAZ) in eyes with retinal vein occlusion (RVO) compared with their fellow eyes and healthy controls using spectral-domain optical coherence tomography angiography (SD-OCTA). METHODS We prospectively recruited 23 patients with RVO including 15 eyes with central RVO (CRVO) and 8 eyes with branch RVO (BRVO), their fellow eyes, and 8 age-matched healthy controls (8 eyes) for imaging on prototype OCTA software within RTVue-XR Avanti. The 3 × 3 mm and 6 × 6 mm en face angiograms of superficial and deep retinal capillary plexuses were segmented. Perifoveolar retinal capillary network was analyzed and FAZ was quantified. RESULTS Decrease in vascular perfusion at the deep plexus was observed in all eyes with CRVO (8/8, 100%) and BRVO (6/6, 100%) without cystoid macular edema, and in 8 of 15 (53%) and 2 of 8 (25%) of the fellow eyes, respectively. Vascular tortuosity was observed in 13 of 15 (87%) CRVO and 5 of 8 (63%) BRVO eyes. Collaterals were seen in 10 of 15 (67%) CRVO and 5 of 8 (63%) BRVO eyes. Mean FAZ area was larger in eyes with RVO than their fellow eyes (1.13 ± 0.25 mm2 versus 0.58 ± 0.28 mm2; P = 0.007) and controls (1.13 ± 0.25 mm2 versus 0.30 ± 0.09 mm2; P < 0.0001), and in fellow eyes of RVO patients when compared to controls (0.58 ± 0.28 mm2 versus 0.30 ± 0.09 mm2; P = 0.01). CONCLUSIONS Spectral-domain OCTA reveals abnormalities at different levels of perifoveolar retinal capillary network and is able to quantify the FAZ in RVO. Longitudinal studies may be considered to evaluate the clinical utility of OCTA in RVO and other retinal vascular diseases.

Retinal Capillary Network and Foveal Avascular Zone in Eyes with Vein Occlusion and Fellow Eyes Analyzed With Optical Coherence Tomography Angiography.

Vascularization and efficient perfusion are long-standing challenges in cardiac tissue engineering. Here we report engineered perfusable microvascular constructs, wherein human embryonic stem cell-derived endothelial cells (hESC-ECs) are seeded both into patterned microchannels and the surrounding collagen matrix. In vitro, the hESC-ECs lining the luminal walls readily sprout and anastomose with de novo-formed endothelial tubes in the matrix under flow. When implanted on infarcted rat hearts, the perfusable microvessel grafts integrate with coronary vasculature to a greater degree than non-perfusable self-assembled constructs at 5 days post-implantation. Optical microangiography imaging reveal that perfusable grafts have 6-fold greater vascular density, 2.5-fold higher vascular velocities and >20-fold higher volumetric perfusion rates. Implantation of perfusable grafts containing additional hESC-derived cardiomyocytes show higher cardiomyocyte and vascular density. Thus, pre-patterned vascular networks enhance vascular remodeling and accelerate coronary perfusion, potentially supporting cardiac tissues after implantation. These findings should facilitate the next generation of cardiac tissue engineering design.

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Patterned human microvascular grafts enable rapid vascularization and increase perfusion in infarcted rat hearts.

Optical coherence tomography angiography (OCTA) allows for the evaluation of functional retinal vascular networks without a need for contrast dyes. For sophisticated monitoring and diagnosis of retinal diseases, OCTA capable of providing wide-field and high definition images of retinal vasculature in a single image is desirable. We report OCTA with motion tracking through an auxiliary real-time line scan ophthalmoscope that is clinically feasible to image functional retinal vasculature in patients, with a coverage of more than 60 degrees of retina while still maintaining high definition and resolution. We demonstrate six illustrative cases with unprecedented details of vascular involvement in retinal diseases. In each case, OCTA yields images of the normal and diseased microvasculature at all levels of the retina, with higher resolution than observed with fluorescein angiography. Wide-field OCTA technology will be an important next step in augmenting the utility of OCT technology in clinical practice.

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Wide-field optical coherence tomography based microangiography for retinal imaging.

Optical coherence tomography based microangiography (OMAG) is a new, non-invasive imaging modality capable of providing three dimentional (3D) retinal and choroidal microvascular maps without a need for exogenous dye. In this study, we evaluated the retinal and choroidal microvascular architecture of the macula in a patient with hydroxychloroquine (HCQ) toxicity using OMAG. Detailed microvascular information of the retina and the underlying choroid showed loss of parafoveal outer retinal vasculature with sparing of the central fovea vasculature.

Optical coherence tomography based microangiography findings in hydroxychloroquine toxicity

IntroductionTo evaluate and identify early microvascular changes in patient with choroidal rupture using optical coherence tomography (OCT) based microangiography (OMAG).Case descriptionOne patient (one eye) with confirmed diagnosis of choroidal rupture after sustained ocular blunt trauma underwent OMAG imaging. OMAG was performed by Zeiss spectral domain OCT-angiography prototype using a “6.5 mm × 6.5 mm” field of view around macular region. The resulting images were presented into bilayers: the retinal layer and the choroidal layer.Discussion and evaluationChoroidal rupture sites were easily shown on OMAG images with clear evidence of multiple breaks in Bruch’s membrane involving macula and the region superior to nerve. OMAG provided detailed vascular network patterns in the areas of choroidal rupture, showing a concern for choroidal neovascularization (CNV). The OMAG demonstrated cross sectional area to visualize CNV location relative to the other layers of the retina, identifying functional blood vessels through the lesion. The patient’s progress was followed using OMAG.ConclusionThe images provided by OMAG give detailed microvascular findings about the macula and adjacent retinal region along with the underlying choroidal alternations. In our case, details of the architecture and vascular flow of CNVM in choroidal rupture was delivered by OMAG, which were used to follow the progression of the disease progression. Further studies are needed to assess the role of quantitative and qualitative OCT microangiography in the evaluation and treatment of choroidal rupture.

Optical coherence tomography based microangiography as a non-invasive imaging modality for early detection of choroido-neovascular membrane in choroidal rupture.

Introduction
To evaluate and identify early microvascular changes in patient with choroidal rupture using optical coherence tomography (OCT) based microangiography (OMAG).

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Optical coherence tomography based microangiography as a non-invasive imaging modality for early detection of choroido-neovascular membrane in choroidal rupture

Jin Liu

Papers

Wide-field optical coherence tomography based microangiography for retinal imaging.

Optical coherence tomography based microangiography findings in hydroxychloroquine toxicity

Optical coherence tomography based microangiography as a non-invasive imaging modality for early detection of choroido-neovascular membrane in choroidal rupture.

Optical coherence tomography based microangiography as a non-invasive imaging modality for early detection of choroido-neovascular membrane in choroidal rupture