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Liposomes
Published in Sourav Bhattacharjee, Principles of Nanomedicine, 2019
Visudyne®: This is a unilamellar liposomal (150–300 nm) formulation of photosensitive drug verteporfin for intravenous administration to prevent choroidal neovascularization in patients suffering from age-related macular degeneration. Developed by Novartis AG, Switzerland, and approved by the FDA in 2000, the formulation has a lipid composition of DMPC and egg phosphatidyl glycerol while the molar ratio of photosensitive verteporfin to total lipid is 1:8. Verteporfin is a synthetic porphyrin that accumulates in the abnormal blood vessels with proliferating endothelial cells, such as in wet macular degeneration, and then eliminates them by producing toxic oxygen radicals upon activation by absorbing light of 692 nm wavelength. High lipophilicity of verteporfin ensures ~100% entrapment efficiency and the freeze-dried powder can be readily reconstituted into injectable fluid. Results from phase III clinical trials have shown a superior effect of Visudyne® compared to that of only verteporfin in the reduction of abnormal blood vessels in macular degeneration and in halting progression toward blindness [169]. In mice tumor models, Visudyne® showed marginally higher intratumoral accumulation, reduced side effects, and comparable t1/2 (16.1 hours) to 16.9 hours for verteporfin only [170].
Studies on Registration and Fusion of Retinal Images
Published in Rick S. Blum, Zheng Liu, Multi-Sensor Image Fusion and Its Applications, 2018
France Laliberté, Langis Gagnon
The eye (Figure 3.1) can be imaged under many modalities with various sensors. We focus on the imaging conditions of the eye fundus (Figure 3.2). There are two main diseases associated to the retina and choroid: diabetic retinopathy and age-related macular degeneration. Diabetes can cause a weakening of blood vessel bodies, in particular within the retina. The capillaries can leak and become potential hosts for microaneurisms (small bulges that develop in the capillary walls and are the first indicator of diabetic retinopathy). The development of new weak capillaries (neovascularization), which leak easily, can also occur. An edema appears when fluids accumulate in the retina. These fluids are also responsible for exudates, which are metabolic waste products. Closure of capillaries is another possible change that may lead to a lack of oxygen in the retina (ischemia). The cotton wool spots indicate the areas of oxygen-starved retina. Figure 3.3 shows the fundus of a normal eye with the principal anatomical components identified. Figure 3.4 shows the fundus of an eye with diabetic retinopathy on which some common lesions are identified. Choroidal neovascularization associated with age-related macular degeneration leads to irreversible damage in retinal tissue. Early and complete photocoagulation of the affected areas is the only treatment for delaying or preventing decreases in visual acuity.
Controlled Drug Delivery in Photodynamic Therapy and Fluorescence-Based Diagnosis of Cancer
Published in Mary-Ann Mycek, Brian W. Pogue, Handbook of Biomedical Fluorescence, 2003
Pharmacokinetically, the targeting of neovascular structures is a “one-compartment” problem in which the main input parameters are vascular permeability and interstitial pressure. Furthermore, this approach overcomes the problem of producing specific targeting agents for each cancer, thereby generalizing the problem. However, tumor development is a highly complex process in which angiogenesis is generally preceded by an avascular phase, where the primary tumor is still localized. Superficial and microinvasive tumors as well as carcinoma in situ often lack the presence of a developed neovasculature. Thus, the targeting of angiogenesis-associated antigens by antibody fragment-photosensitizer conjugates can only help to manage or detect advanced tumors. Besides tumor development, angiogenesis is a process that is associated with many other human diseases, such as choroidal neovascularization (CNV) associated with age-related macular degeneration, diabetic retinopathy, cardiovascular diseases, psoriasis, and rheumatoid arthritis. Thus, the targeting of neovessels in such disorders with scFv-pho-tosensitizer conjugates and subsequent irradiation of the site of the lesion can improve current treatment strategies. Using their scFv(L19), Neri et al. recently demonstrated selective occlusion of neovessels in a rabbit cornea micropocket angiogenesis assay, when coupling chlorin e6 to this targeting moiety [58].
OCT image denoising algorithm based on discrete wavelet transform and spatial domain feature fusion
Published in Journal of Modern Optics, 2023
Wenyu Wei, Huaiguang Chen, Jing Gao, Shujun Fu, Jin Li
Optical coherence tomography (OCT) is a biomedical imaging technology, which has the characteristics of fast imaging, high resolution, non-invasive and high safety performance [1]. This technology has become one of the important tools for material detection, biological research and medical clinical application, especially for the diagnosis and treatment of ophthalmic diseases, such as age-related macular degeneration (AMD), diabetic macular edema (DME) and choroidal neovascularization (CNV), etc. [2]. Since OCT adopts low coherence interferometry, the generated image is inevitably damaged by speckle noise, which seriously affects the imaging quality [1,3]. Low-quality OCT images blur the fine features of images, which have adverse effects on subsequent processing such as edge detection, structure segmentation, and lesion identification [4,5]. Therefore, removing the speckle noise of the OCT image while retaining its fine detail features is of great significance for the subsequent processing of the OCT image. Especially in the diagnosis and treatment of retinal diseases, high-quality OCT images can reduce the rate of misdiagnosis of diseases and improve the accuracy and cure rate of doctors' diagnosis.
Swept-source optical coherence tomography imaging of the retinochoroid and beyond
Published in Expert Review of Medical Devices, 2020
Jayesh Vira, Alessandro Marchese, Rohan Bir Singh, Aniruddha Agarwal
The fast-paced evolution of technology is resulting in rapid developments of tools useful to the clinicians in their practice and management of patients. SS-OCT imaging has significant advantages over the available SD technology and finds utility in various retinochoroidal conditions. SS-OCT and SS-OCTA are very useful in determining the anatomical location of the disease, and understanding the disease pathophysiology. This is exemplified by the SS-OCTA imaging in MEWDS, where this technology clearly shows a lack of choriocapillaris flow abnormality, which was otherwise thought to exist based on indocyanine green angiography. SS-OCT also aids in better imaging of patients with pachychoroid over conventional imaging, as this entity primarily involves the choroid. In our experience, SS-OCT imaging is desirable in most entities where imaging the deeper retinal layers and the choroid is essential, especially retinal vasculopathies including diabetic retinopathy, pachychoroid including polypoidal choroidal vasculopathy (and differentiating it from choroidal neovascularization due to age-related macular degeneration), inflammatory pathologies (including choriocapillaritis and stromal choroiditis), and neoplastic pathologies.
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 allows for depth-resolved, high-resolution imaging of retinal and choroidal vasculature. Qualitative and quantitative analysis using OCTA has been essential in further understanding the pathogenesis and progression of various vascular pathologies, such as diabetic retinopathy.A limitation of OCTA is that it offers an image depicting either the presence or absence of flow, without information about flow velocities.Variable interscan time analysis (VISTA) overcomes the grayscale limitation of OCTA and provides a color-coded map of relative retinal blood flow speeds. VISTA has been used to further analyze retinal vascular diseases, such as age-related macular degeneration, including choroidal neovascularization and geographic atrophy, diabetic retinopathy, and aneurysmal type 1 neovascularization.Further development of VISTA and its flow speed mapping capabilities may allow OCTA to become an essential tool for screening purposes.