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Imaging the Living Eye
Published in Margarida M. Barroso, Xavier Intes, In Vivo, 2020
Brian T. Soetikno, Lisa Beckmann, Hao F. Zhang
While OCTA holds promise for answering translational research questions, as highlighted by the previous examples, OCTA is also being adopted rapidly for answering clinical questions (Kashani et al., 2017). There are several commercial OCT systems for imaging the retina in patients, with the ability to perform an OCTA scan pattern (Tan et al., 2018). Each device includes its own OCTA algorithm, as discussed previously, and automated segmentation software to segment each of the retinal vascular networks. Because OCTA is still considered an emerging technology, studies using OCTA in clinics have compared OCTA images with that revealed by accepted gold-standard methods of fundus fluorescein angiography or indocyanine green angiography (Ang et al., 2016; Inoue et al., 2016; Tanaka et al., 2017; Abucham-Neto et al., 2018). Thus far, OCTA studies in patients have found promise in a wide variety of retinal diseases, such as diabetic retinopathy, AMD, vascular occlusion, and choroidal neovascularization. OCTA imaging could also have potential to study the anterior segment for diseases, such as glaucoma or corneal neovascularization. OCTA imaging will likely become a key complementary imaging technique for monitoring the healing process after a corneal transplantation, or the effect of anti-VEGF treatments in a patient with diabetic retinopathy (Hagag et al., 2017).
Automatic Detection of Early Signs of Diabetic Retinopathy Based on Feature Fusion from OCT and OCTA Scans
Published in Ayman El-Baz, Jasjit S. Suri, Big Data in Multimodal Medical Imaging, 2019
Nabila Eladawi, Ahmed ElTanboly, Mohammed Elmogy, Mohammed Ghazal, Ali Mahmoud, Ahmed Aboelfetouh, Alaa Riad, Magdi El-Azab, Jasjit S. Suri, Guruprasad Giridharan, Ayman El-Baz
Diabetic retinopathy (DR) affects the blood circular system in the eye. It is the most common cause of vision loss among people with diabetes. In addition, it is the leading cause of vision impairment and blindness among working-age people. The earlier stage of DR is called non-proliferative diabetic retinopathy (NPDR). In the NPDR stage, abnormalities, such as microaneurysms, vessel dilation and tortuosity, foveal avascular zone (FAZ) enlargement, and capillary dropout, start to appear [1–8]. The more advanced stage of the disease is proliferative diabetic retinopathy (PDR). PDR is characterized by retinal and/or optic nerve neovascularization. Ophthalmologists aim to prevent and treat DR to avoid vision loss, not to restore it. To be able to do so, early detection of DR is needed. Since microvascular pathology causes DR, we need imaging techniques that can visualize retinal vasculature. The standard clinical techniques to visualize the ocular vasculature are fluorescein angiography (FA) and indocyanine green angiography (ICGA). Due to their invasiveness and cost, they cannot be used routinely to examine DR. Optical coherence tomography angiography (OCTA) depends on repeated B-scans that are taken in rapid succession. Due to the noninvasiveness character of OCTA, it is ideal for monitoring and detecting DR in diabetic patients. OCTA can easily detect capillary dropout among other abnormalities that appear in the early stage of DR [4,9–15].
Multimodal macula mapping by deformable image registration
Published in João Manuel, R. S. Tavares, R. M. Natal Jorge, Computational Modelling of Objects Represented in Images, 2018
P. Baptista, J. Ferreira, R. Bernardes, J. Dias, J. Cunha-Vaz
Multimodal macula mapping is the combination of a variety of diagnostic imaging modalities to examine the macular region in order to obtain information on its structure and function. The macula is located in the posterior pole of the retina and is responsible for detailed and color vision, thus constituting an important area for human vision, as any macular alteration will, sooner or later, affect visual acuity (Bernardes, Lobo, and Cunha-Vaz 2002). Currently, a wealth of retina imaging modalities exists, either on daily clinical practice or research environments, such as color fundus photography, red-free fundus photography, fluorescein angiography, indocyanine green angiography, optical coherence tomography, retina flowmeter, fundus autofluorescence, leakage analysis, multifocal electroretinography, etc. The potential for multimodal macular mapping was demonstrated in (Bernardes, Lobo, and Cunha-Vaz 2002).
Optical coherence tomography angiography (OCTA) flow speed mapping technology for retinal diseases
Published in Expert Review of Medical Devices, 2018
Malvika Arya, Ramy Rashad, Osama Sorour, Eric M. Moult, James G. Fujimoto, Nadia K. Waheed
Optical coherence tomography angiography (OCTA) is a noninvasive imaging technique that provides depth-resolved imaging of retinal vasculature. While fluorescein angiography (FA) has been the gold standard for the diagnosis of retinal and choroidal vasculopathies, OCTA is now able to provide most of the same information. FA and indocyanine green angiography (ICGA) allow for the visualization of chorioretinal vessels, but their procedures require the injection of a contrast agent. Dye-based angiography provides two-dimensional images and requires imaging of initial, intermediate, and late phases, extending over several minutes. Potential systemic adverse effects, such as nausea, vomiting, and anaphylaxis further limit the frequency with which FA/ICGA can be performed in a clinical setting. Kwan et al. found 132 adverse events from 11,898 FA injections, with nausea and vomiting being the most common [1]. However, despite these drawbacks, FA and ICGA currently offer certain advantages over OCTA, such as the ability to image a wider field, the visualization of vessel leakage, and the improved detection of microaneurysms and areas of slow flow [2–6].