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<i>In vivo</i> blood viscosity characterization based on frequency-resolved photoacoustic measurement
摘要： In this letter, we proposed a photoacoustic (PA) method for noninvasively detecting blood viscosity in subcutaneous microvasculature with the frequency-resolved measurement. The influence of viscosity on PA generation was investigated theoretically, and a negative correlation was shown between the viscosity and the full width at half maximum (FWHM) of the PA frequency spectrum, which can be utilized to reflect the viscosity distribution. To test the feasibility and accuracy of this method, water mixed with different concentrations of glycerol was measured. FWHM of the PA frequency spectrum was also obtained in vivo in the mouse ear to characterize the blood viscosity from different vessel bifurcations, and the metabolism-induced viscosity changes were dynamically monitored in the microvasculature. Experimental results demonstrate that this technique has future potential clinical applications for real-time monitoring the viscosity changes in subcutaneous microvasculature.
关键词： in vivo,microvasculature,frequency-resolved measurement,photoacoustic,blood viscosity
更新于2025-09-23 15:21:01
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In Vivo Confocal Imaging of Fluorescently Labelled Microbubbles: Implications for Ultrasound Localization Microscopy
摘要： We report the time kinetics of fluorescently labelled microbubbles in capillary-level microvasculature as measured via confocal microscopy and compare these results to ultrasound localization microscopy. The observed 19.4 ± 4.2 microbubbles per confocal field-of-view (212 μm x 212 μm) is in excellent agreement with the expected count of 19.1 microbubbles per frame. The estimated time to fully perfuse this capillary network was 193 seconds, which corroborates the values reported in literature. We then modeled the capillary network as an empirically determined discrete-time Markov chain with adjustable microbubble transition probabilities though individual capillaries. Monte Carlo random walk simulations found perfusion times ranging from 24.5 seconds for unbiased Markov chains up to 182 seconds for heterogeneous flow distributions. This pilot study confirms a probability-derived explanation for the long acquisition times required for super-resolution ultrasound localization microscopy.
关键词： Super-resolution,Ultrasound Microvessel Imaging,Microbubble tracking,Microvasculature
更新于2025-09-23 15:19:57
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Foveal microvasculature, refractive errors, optical biometry and their correlations in school-aged children with retinopathy of prematurity after intravitreal antivascular endothelial growth factors or laser photocoagulation
摘要： Aims To compare the differences and to assess the correlations regarding to foveal microvasculature, refractive errors and optical biometry in children with history of type 1 retinopathy of prematurity (ROP) treated with either laser photocoagulation or intravitreal injection of antivascular endothelial growth factors (anti-VEGF). Methods This is a retrospective and comparative case series. Measurements of fovea microvasculature included the retinal thickness and subfoveal choroid thickness, the size of fovea avascular zone (FAZ), the fovea, parafovea and perifoveal vessel density (VD). Measurements of refractive errors and optical biometry included spherical equivalent, astigmatism, cornea curvature, anterior chamber depth (ACD), lens thickness and axial length (AXL). Results A total 47 eyes in 25 children were studied (22 laser-treated eyes from 12 children and 25 anti-VEGF treated eyes from 13 children). Laser-treated eyes had significantly smaller FAZ (p=0.004), higher fovea VD, lower parafoveal VD (p=0.02 and 0.01 in superficial capillary plexus; p=0.05 and 0.01 in deep capillary plexus), thicker inner retinal thickness (p=0.002). Laser-treated eyes had significantly higher degree of myopia (p=0.01). Regarding to optical biometry, laser-treated eyes had significant steeper cornea curvature, shallower ACD and thicker lens (p=0.01, 0.01 and 0.02, respectively) but no differences in AXL was noted (p=0.58). Significant correlations presented between inner retina thickness and FAZ to anterior segment variables. Conclusion In school-aged children with history of type 1 ROP, despite similar visual acuity outcome, those who underwent anti-VEGF injection had favourable developmental outcomes compared with laser photocoagulation. Significant correlations exist between fovea microvasculature and optical biometric components.
关键词： laser photocoagulation,anti-VEGF,foveal microvasculature,retinopathy of prematurity,optical biometry,refractive errors
更新于2025-09-23 15:19:57
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Future clinical applicability of optical coherence tomography angiography
摘要： Optical coherence tomography angiography (OCT-A) is an emerging technology that allows for the non-invasive imaging of the ocular microvasculature. Despite the wealth of observations and numerous research studies illustrating the potential clinical uses of OCT-A, this technique is currently rarely used in routine clinical settings. In this review, technical and clinical aspects of OCT-A imaging are discussed, and the future clinical potential of OCT-A is considered. An understanding of the basic principles and limitations of OCT-A technology will better inform clinicians of its future potential in the diagnosis and management of ocular diseases.
关键词： ocular microvasculature,corneal vascularisation image artifact,segmentation,optical coherence tomography angiography,optic nerve head disease,algorithm,retinal disease
更新于2025-09-23 15:19:57
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Optical coherence tomography angiography and photoacoustic imaging in dermatology
摘要： Optical coherence tomography angiography (OCTA) is a relatively novel functional extension of the widely accepted ophthalmic imaging tool named optical coherence tomography (OCT). Since OCTA’s debut in ophthalmology, researchers have also been trying to expand its translational application into dermatology. The ability of OCTA in resolving microvasculature has shown promising results in imaging skin diseases. Meanwhile, photoacoustic imaging (PAI), which uses laser pulse induced ultrasound waves as the signal, has been studied to differentiate human skin layers and to help skin disease diagnosis. This perspective article gives a short review of OCTA and PAI in the field of photodermatology. After an introduction of the principles of OCTA and PAI, we describe the most updated results of skin disease imaging using these two optical imaging modalities. We also put an emphasis on dual modality imaging combining OCTA and photoacoustic tomography (PAT) for dermatological applications. In the end, the challenges and opportunities of these two imaging modalities in dermatology are discussed.
关键词： microvasculature,dermatology,Optical coherence tomography angiography,photoacoustic imaging,skin imaging
更新于2025-09-19 17:15:36
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Optical coherence tomography angiography monitors human cutaneous wound healing over time
摘要： Background: In vivo imaging of the complex cascade of events known to be pivotal elements in the healing of cutaneous wounds is a difficult but essential task. Current techniques are highly invasive, or lack the level of vascular and structural detail required for accurate evaluation, monitoring and treatment. We aimed to use an advanced optical coherence tomography (OCT)-based angiography (OCTA) technique for the non-invasive, high resolution imaging of cutaneous wound healing. Methods: We used a clinical prototype OCTA to image, identify and track key vascular and structural adaptations known to occur throughout the healing process. Specific vascular parameters, such as diameter and density, were measured to aid our interpretations under a spatiotemporal framework. Results: We identified multiple distinct, yet overlapping stages, hemostasis, inflammation, proliferation, and remodeling, and demonstrated the detailed vascularization and anatomical attributes underlying the multifactorial processes of dermatologic wound healing. Conclusions: OCTA provides an opportunity to both qualitatively and quantitatively assess the vascular response to acute cutaneous damage and in the future, may help to ascertain wound severity and possible healing outcomes; thus, enabling more effective treatment options.
关键词： microvasculature,wound healing,skin,Optical coherence tomography angiography (OCTA)
更新于2025-09-19 17:15:36
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Photoreceptor Cells Influence Retinal Vascular Degeneration in Mouse Models of Retinal Degeneration and Diabetes
摘要： PURPOSE. Loss of photoreceptor cells is associated with retinal vascular degeneration in retinitis pigmentosa, whereas the presence of photoreceptor cells is implicated in vascular degeneration in diabetic retinopathy. To investigate how both the absence and presence of photoreceptors could damage the retinal vasculature, we compared two mouse models of photoreceptor degeneration (opsin(cid:2)/(cid:2) and RhoP23H/P23H ) and control C57Bl/5J mice, each with and without diabetes. METHODS. Retinal thickness, superoxide, expression of in?ammatory proteins, ERG and optokinetic responses, leukocyte cytotoxicity, and capillary degeneration were evaluated at 1 to 10 months of age using published methods. RESULTS. Retinal photoreceptor cells degenerated completely in the opsin mutants by 2 to 4 months of age, and visual function subsided correspondingly. Retinal capillary degeneration was substantial while photoreceptors were still present, but slowed after the photoreceptors degenerated. Diabetes did not further exacerbate capillary degeneration in these models of photoreceptor degeneration, but did cause capillary degeneration in wild-type animals. Photoreceptor cells, however, did not degenerate in wild-type diabetic mice, presumably because the stress responses in these cells were less than in the opsin mutants. Retinal superoxide and leukocyte damage to retinal endothelium contributed to the degeneration of retinal capillaries in diabetes, and leukocyte-mediated damage was increased in both opsin mutants during photoreceptor cell degeneration. CONCLUSIONS. Photoreceptor cells affect the integrity of the retinal microvasculature. Deterioration of retinal capillaries in opsin mutants was appreciable while photoreceptor cells were present and stressed, but was less after photoreceptors degenerated. This ?nding proves relevant to diabetes, where persistent stress in photoreceptors likewise contributes to capillary degeneration.
关键词： opsin,retina,microvasculature,photoreceptors
更新于2025-09-11 14:15:04
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Macular microvasculature features before and after vitrectomy in idiopathic macular epiretinal membrane: an OCT angiography analysis
摘要： Purpose To evaluate pre-operative and post-operative morphologic characteristics in idiopathic macular epiretinal membrane (ERM) by optical coherence tomography angiography (OCTA). Methods Thirty-three subjects with unilateral idiopathic ERM were enrolled and the contralateral eyes served as controls. Vascular parameters including super?cial capillary plexus (SCP), deep capillary plexus (DCP), outer capillary plexus (OCP), and choroidal capillary plexus (CCP) were evaluated by OCTA. Results The super?cial foveal avascular zone (FAZ) was signi?cantly smaller in eyes with ERM (P < 0.0001). The vessel densities (VDs) were signi?cantly increased in the fovea but dramatically decreased in the parafovea in SCP and DCP of ERM eyes (all P < 0.0001), in contrast to those in OCP and CCP. The blood ?ow was augmented in OCP but declined in choroid compared with the controls. In CCP, the mean foveal VD in ERM was signi?cantly smaller (P = 0.023), whereas parafoveal VD did not signi?cantly change (P = 0.66). At 6 months after surgery, ?ow area was decreased in OCP (P = 0.0007), and foveal and parafoveal VDs were signi?cantly altered in all layers except the foveal VD in OCP and the choroid (all P < 0.05). The total and inner retinal thickness of the fovea and parafovea were correlated with pre-operative and post-operative visual outcomes, respectively. Smaller FAZ and greater interocular differences between post-operative and fellow eyes in FAZ were associated with worse post-operative visual outcomes. Conclusions OCTA provides a better display of the vascular network of the retina and choroid to evaluate the severity and surgical prognosis of ERM patients.
关键词： Microvasculature,Vitrectomy,Epiretinal membrane,Optical coherence tomography angiography
更新于2025-09-10 09:29:36
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Diabetic Nephropathy (Pathophysiology and Clinical Aspects) || Microvascular Complications in the?Eye: Diabetic Retinopathy
摘要： Diabetic retinopathy (DR) is a major cause of vision loss and blindness among persons with diabetes mellitus. It is estimated that approximately 35% of diabetes patients develop some form of DR [1]. DR is a progressive disease that is predominantly characterized by alterations in the retinal microvasculature. It may develop from an asymptomatic nonproliferative form associated with capillary non-perfusion, microaneurysms, and retinal hemorrhages, into a vision-threating disorder such as diabetic macular edema (DME) and proliferative DR (PDR).
关键词： vision loss,Diabetic retinopathy,retinal microvasculature,blindness,microvascular complications,diabetic macular edema,diabetes mellitus,proliferative diabetic retinopathy
更新于2025-09-10 09:29:36
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Automatic Graph-based Modeling of Brain Microvessels Captured with Two-Photon Microscopy
摘要： Graph models of cerebral vasculature derived from 2-photon microscopy have shown to be relevant to study brain microphysiology. Automatic graphing of these microvessels remain problematic due to the vascular network complexity and 2-photon sensitivity limitations with depth. In this work, we propose a fully automatic processing pipeline to address this issue. The modeling scheme consists of a fully-convolution neural network to segment microvessels, a 3D surface model generator and a geometry contraction algorithm to produce graphical models with a single connected component. Quantitative assessment using NetMets metrics, at a tolerance of 60 μm, false negative and false positive geometric error rates are 3.8% and 4.2%, respectively, whereas false negative and false positive topological error rates are 6.1% and 4.5%, respectively. Our qualitative evaluation confirms the efficiency of our scheme in generating useful and accurate graphical models.
关键词： segmentation,graph,Cerebral microvasculature,deep learning,convolution neural networks,two-photon microscopy
更新于2025-09-09 09:28:46