Microvascular Parameters Research Articles

Perfused boundary region as biomarker for endothelial integrity in former preterms in adolescence.

Extremely low birth weight (ELBW) survivors have microvascular structural differences already described in kidney and retina, suggesting changes in endothelial integrity. A biomarker of endothelial integrity is perfused boundary region (PBR), which measures glycocalycal thickness. The endothelial glycocalyx is a complex, highly versatile structure with essential roles in vascular integrity and function. We explored PBR patterns together with other microvascular markers in healthy controls and former ELBW children. In the PREMATCH cohort (87 healthy controls, 93 ELBW survivors), we assessed endothelial integrity by calculating PBR (sidestream dark-field imaging), several microvascular markers (blood pressure, estimated glomerular filtration rate (eGFRcysC)), and retinal imaging in early adolescence. We explored differences between both groups, and searched for perinatal determinants of PBR and correlations between different microvascular markers. We provided reference values for PBR (average 1.90 µm, SD 0.30) in children. PBR was not different from ELBW survivors during early adolescence, despite their higher blood pressure, lower eGFRcysC, and different retinal vessel width and tortuosity. We generated reference values for PBR in early adolescence. Despite some correlations between microvascular parameters, there seem to be numerous confounders to propose PBR as a marker for endothelial integrity in ELBW survivors. The endothelial glycocalyx is a complex and versatile structure. Changes in blood pressure and retinal and renal vascularization suggest a disturbance of its integrity in extremely low birth weight (ELBW) survivors. Its thickness can be measured by calculating perfused boundary region (PBR) using sidestream dark-field imaging, with a higher PBR indicating a thinner glycocalyx. We generated reference values for PBR in healthy adolescents. These values were not different in former ELBW children. Despite some correlations of PBR with other microvascular biomarkers, these are not strong enough to describe endothelial integrity and its covariates in former ELBW children.

A narrative review on the association of high intraocular pressure and glaucoma in patients with retinal vein occlusion.

Retinal vein occlusion (RVO) is a major cause of vision loss and elevated intraocular pressure (IOP), high ocular perfusion pressure, and glaucoma are known ophthalmic risk factors for RVO. The aim of this paper is to provide the update on the association and management of high IOP/glaucoma and RVO. A literature review was performed in PubMed and Medline until May 2022 utilizing specific keywords and cross-matched reference lists. The association of RVO with high IOP/glaucoma may be attributed to retinal ganglion cell loss due to retinal ischemia in high IOP and glaucoma. As new modalities showed, decreased optic disc perfusion, reduced density of blood vessels in the optic nerve head of glaucoma patients, changes in the peripapillary microvascular parameters, and decreased retinal nerve fiber layer (RNFL) thickness of the optic nerve head of eyes with RVO suggest a common pathway between RVO and glaucoma. Literature suggests the close follow up for glaucoma development among patients with non-arteriovenous (AV) crossing (optic cup or optic nerve sited) RVO in fellow eye and management of elevated IOP among RVO cases treated with anti-vascular endothelial growth factor (VEGF) antibodies/corticosteroids and those with preexisting primary open angle glaucoma (POAG). Determining potential patient responses to treatment and considering therapeutic options are challenging among patients with RVO and glaucoma. However, IOP lowering managements in preventing IOP spikes in patients with preexisting glaucoma and early treatment of macular edema in eyes with RVO is recommended.

Evaluation of macular microvascular structure with optical coherence tomography angiography in children with history of treatment for retinopathy of prematurity.

To compare macula vascular parameters in optical coherence tomography angiography (OCTA) of children with history of retinopathy of prematurity (ROP) who were treated with laser photocoagulation (LPC) or intravitreal Bevacizumab therapy. Forty eyes of 28 ROP children treated with LPC and 36 eyes of 22 ROP children treated with intravitreal Bevacizumab and 40 eyes of 40 age-gender matched term children were included the study. Capillary plexus densities in macula, FAZ parameters, outer retina and choriocapillaris flow rates, and central foveal thickness were measured. Foveal superficial and deep capillary plexus densities were found significantly higher in LPC and intravitreal Bevacizumab injection (IBI) groups compared to control group. FAZ area was found significantly lower in LPC and IBI groups compared to control group (p ‹ 0.001). Higher foveal superficial capillary plexus density, higher central foveal thickness, and lower FAZ area were found to be associated with poorer visual acuity in correlation analysis (p ‹ 0.05). In IBI group, earlier anti-VEGF therapy was found to be associated with lower foveal superficial capillary plexus density. Microvascular characteristics such as FAZ area and capillary plexus densities of macula are deteriorated in ROP. There is no significant difference between the treatment alternatives of ROP in terms of macular microvascular parameters.

Comparison of microvascular parameters and diagnostic ability of optical coherence tomography angiography between eyes with primary angle closure glaucoma and primary open angle glaucoma

BackgroundTo investigate and compare the peripapillary and macular microvascular parameters between eyes with primary angle closure glaucoma (PACG) and primary open-angle glaucoma (POAG) using optical coherence tomography angiography (OCTA). MethodsSeventy-nine eyes of 43 patients with primary angle closure glaucoma (PACG), 78 eyes of 43 patients with primary open-angle glaucoma (POAG), 64 eyes of 35 patients with primary angle closure (PAC), and 73 eyes of 40 control subjects underwent imaging with OCTA. Perfusion density (PD) and vessel density (VD) for the macular area, and PD and flux index (FI) for the peripapillary area were calculated automatically. The area under receiver operator characteristic curves (AUC) were constructed to distinguish PACG and POAG eyes from healthy control eyes. ResultsThe peripapillary FI in all quadrants and PD and VD of the macular outer circle in superior and inferior quadrants were significantly lower in PACG and POAG eyes than in control eyes. The peripapillary FI in the inferior quadrant was significantly lower in the POAG group than in the PACG group (0.348 ± 0.06 vs. 0.369 ± 0.06, p = 0.04). The remaining OCTA parameters in the peripapillary and macular area did not show a significant difference between the POAG and PACG groups. Eyes with PAC presented significantly lower PD and VD than healthy control eyes at the superior and inferior quadrant of the macular outer circle, while retinal nerve fiber layer and ganglion cell inner complex thickness were not significantly different from than control eyes. The best diagnostic parameter was peripapillary FI in both PACG (AUC: 0.922) and POAG (AUC: 0.938) eyes. ConclusionsWe found significantly lower peripapillary FI in the inferior quadrant in POAG eyes compared to the PACG eyes, which may indicate the different underlying pathogenesis between POAG and PACG. The PAC eyes had lower macular PD and VD than normal eyes. This suggests that retinal vascular impairment may develop earlier than structural damage in PAC eyes.

Effect of direct stenting on microvascular dysfunction during percutaneous coronary intervention in acute myocardial infarction: a randomized pilot study.

ObjectiveWhether direct stenting (DS) without predilatation during primary percutaneous coronary intervention (PPCI) reduces microvascular dysfunction in patients with ST-elevation myocardial infarction is unclear. We performed a randomized study to assess the effect of DS on microvascular reperfusion.MethodsSeventy-two patients undergoing PPCI were randomly assigned to the DS or conventional stenting (CS) with predilatation groups. The primary endpoint was the post-PPCI index of microcirculatory resistance (IMR). We compared thrombolysis in myocardial infarction myocardial perfusion (TMP) grades, ST-segment resolution, and long-term clinical outcomes between the groups.ResultsMicrovascular reperfusion parameters immediately after PPCI (e.g., the IMR, TMP grade, and ST-segment resolution) were not different between the groups. However, significantly fewer patients in the DS group had the IMR measured because of no-reflow or cardiogenic shock during PPCI than those in the CS group. No differences were found in left ventricular functional recovery or clinical outcomes between the groups.ConclusionsThis trial showed no effect of DS on the IMR. However, our finding should be interpreted with caution because the number of patients who could not have the IMR measured was higher in the CS group than in the DS group. A larger randomized trial is required (Research Registry number: 8079).

Is there a potential biomarker in distinguishing invasive breast carcinomas with elevated Ki-67 levels among 2D-SWE, SMI, and 18F-FDG PET-CT/MRI-derived parameters?: A single-center data.

To investigate the strength of quantitative imaging and metabolic parameters in differentiating invasive breast carcinomas with elevated Ki-67 levels. A total of 123 patients with 129 breast lesions confirmed as invasive breast carcinoma underwent shear wave elastography (SWE), superb microvascular imaging (SMI) and positron emission tomography (PET)/CT or MRI. Adler's grade (classifying the microvascularity into four types) and Vascular Index (VI) was obtained by SMI as microvascular parameters. In addition, the stiffness value (Emean ) was evaluated in kilopascal by SWE. The average of consecutive measurements was recorded as mean VI and mean Emean . PET scan parameters were obtained as SUVmax and SULpeak . Lesions were divided into two groups according to the Ki-67 expression, low as 14 and high as >14. Adler's grading was the most correlated imaging parameter with high Ki-67 expression (p< 0.05), while VI and Emean had poor correlation (p> 0.05). SUVmax and SULpeak indicated a significant linear correlation with Ki-67 but a moderate correlation with the high levels of Ki-67 (p< 0,001). The sensitivity of VI, Emean , SUVmax and SULpeak was 64.6%, 66.7%, 65.7%, and 66.7% when the cut-off point was set to 5.25, 102.5, 6.59, and 2.63, respectively. SUVmax had the highest AUC value of 0.740, according to the ROC curve analysis. Our results suggest that the quantitative parameters obtained by advanced imaging methods may be useful in predicting the high proliferation in invasive breast carcinomas. But none of them is eligible to be used as an independent biomarker in distinguishing aggressive behavior. Nevertheless, as a noninvasive method, visual assessment of microvascular morphology using SMI increases the prognostic efficiency in invasive breast carcinomas.

Numerical simulation on mechanical properties and damage behavior of CFRP with self-healing microvascular channels

In this study, 3D representative volume element models with microchannels were established based on measured data. And the periodic boundary conditions were moderately modified to adapt to the actual constraints of the studied object. The effects of different microvascular parameters on the tensile and compressive properties of composites were studied. And the damage pattern of carbon fiber as the main load-bearing phase under the force was analyzed. The models were verified by tensile testing and micromorphology experiments. The research results are of application to the design and analysis of CFRP laminates containing similar microchannel structures.

Characterization of the Structural and Functional Alteration in Eyes with Diabetic Macular Ischemia

To investigate the relative effect of disorganization of the retinal inner layers (DRIL) and ellipsoid zone (EZ) loss on visual function in diabetic macular ischemia (DMI). Prospective cross-sectional observational study. Patients with stable treated proliferative diabetic retinopathy (PDR) without center-involved diabetic macular edema were recruited at the Moorfields Eye Hospital from December 2019 to November 2021. The main inclusion criteria were best-corrected visual acuity (BCVA) of ≥ 40 ETDRS letters (Snellen equivalent 20/160) with OCT angiography (OCTA) evidence of DMI in ≥ 1 eye. Each eligible eye of the recruited patients was assessed for BCVA, OCT, and OCTA metrics. The prespecified OCT parameters were DRIL and subfoveal EZ loss. Generalized estimating equations were used. The frequency of DRIL and EZ loss, their relative contributions to vision loss, and their associations with microvascular alterations were evaluated. A total of 125 eyes of 86 patients with PDR were enrolled; 104 (83%) eyes had a BCVA of ≥ 70 letters. Disorganization of the retinal inner layers was more prevalent than EZ loss (46% [58 eyes] vs. 19% [24 eyes]). On average, the presence of DRIL had a more pronounced impact on vision, retinal thickness, and microvascular parameters than EZ loss. After multivariable adjustment, the odds of coexisting DRIL increased by 12% with every letter decrease in BCVA; however, there was no statistically significant association of subfoveal EZ loss with BCVA. In eyes with DRIL in the absence of EZ loss, the BCVA declined significantly by 6.67 letters compared with eyes with no DRIL nor EZ loss (95% confidence interval [CI],-9.92 to-3.41; P < 0.001). However, if DRIL and EZ loss coexisted, the resultant BCVA was 13.22 letters less than eyes without these structural abnormalities (95% CI,-18.85 to-7.59; P < 0.001). In patients with DMI with a Snellen visual acuity of 20/160 or better, eyes with DRIL were associated with more visual function loss and retinal blood circulation alterations than those with subfoveal EZ loss only.

Retinal Neurovascular Changes in Patients With Ischemic Stroke Investigated by Optical Coherence Tomography Angiography.

BackgroundTo investigate retinal neurovascular structural changes in patients with ischemic stroke (IS) using optical coherence tomography angiography (OCTA).Materials and MethodsThe cross-sectional study was conducted in Guangdong Provincial People’s Hospital, China, consisting of 159 eyes from IS patients and 109 eyes from age-matched control subjects. Retinal microvascular parameters including the vessel density (VD) of the superficial capillary plexus (SCP), deep capillary plexus (DCP) and radial peripapillary capillary (RPC), and neural parameters such as ganglion cell complex thickness (GCCt) and retinal nerve fibre layer thickness (RNFLt) were measured by OCTA.ResultsThe VD of SCP and DCP in the macular area were significantly reduced in IS patients compared to the control group (all p < 0.001). The VD of RPC at the optic disc was also significantly reduced in IS patients (all p < 0.05). IS patients showed reduced GCCt and RNFLt and increased GCC focal loss volume and global loss volume compared with the controls (all p < 0.05). Among patients with IS, the parafovea SCP VD was positively correlated with GCCt (r = 0.346–0.408, all p < 0.001) but not with DCP VD (all p > 0.1). In the optic disc region, the whole image RPC VD was positively correlated with mean RNFLt (r = 0.467–0.548, all p < 0.001).ConclusionReduction of retinal VD, GCCt and RNFLt was observed in patients with IS. The parafovea SCP VD and RPC VD were positively correlated with GCCt and RNFLt, respectively.

RELATIONSHIP OF 24-HOUR AMBULATORY BLOOD PRESSURE VARIABILITY WITH MICRO- AND MACROVASCULAR PARAMETERS AND HYPERTENSION STATUS

Objective: Existing evidence shows that increased values of blood pressure variability (BPV) are associated with a higher risk of subclinical organ damage and cardiovascular events, independently of elevated average BP values. We sought to investigate the relation of novel BPV indices with micro- and macrovascular parameters that have not all been previously studied and to identify differences according to hypertension status. Design and method: We evaluated the relationship between BPV indices and micro- and macrovascular parameters in a selected population of 344 individuals (233 never-treated, newly diagnosed hypertensive and 111 normotensive individuals).Using data from 24-h ambulatory blood pressure monitoring device, BPV was assessed by average real variability (ARV) during 24-hours, daytime and nighttime and as systolic weighted standard deviation (wSD). Nonmydriatic retinal photography was used to assess retinal microvascular diameters. Arterial stiffness was evaluated by measurement of pulse wave velocity(PWV) and aortic augmentation index (AIx). Myocardial perfusion was evaluated using subendocardial variability ratio (SEVR).The carotid intima-media thickness (cIMT) was measured by ultrasound. We performed a multiple regression analysis for all the parameters which were statistically significant in the univariate analyses. Results: After adjusting for potential confounders, all vascular parameters [venular retinal diameter (p = 0.036), PWV (p &lt; 0.007), cIMT (p &lt; 0.06)], except for SEVR were independently associated with ARV components in the total population. Further analysis based on hypertension status showed that in hypertensives only macrocirculation indices such as PWV and cIMT were independently associated with ARV (for PWV: 24-h systolic, p = 0.025, nighttime systolic, p = 0.001 and nighttime diastolic, p = 0.012 respectively; and for cIMT, p = 0.001 for both 24-h and daytime systolic). In normotensive individuals, venular diameter was associated with 24-h systolic and diastolic and daytime systolic and diastolic ARV (p = 0.004, p = 0.002, p = 0.001 and p = 0.049 respectively). The arteriovenous ratio was associated with daytime systolic ARV (p = 0.022), and AIx was associated with daytime diastolic ARV (p = 0.022). None of the univariate correlations between vascular parameters and wSD remained significant after adjustment for potential confounders. Conclusions: We concluded that short-term BPV represented by ARV is independently associated with macrovascular parameters in untreated hypertensive patients and microvascular parameters in normotensives.

HIGH MOBILITY GROUP BOX-1 IS INCREASED IN NEWLY DIAGNOSED ESSENTIAL HYPERTENSIVES AND CORRELATES WITH HYPERTENSION-MEDIATED TARGET ORGAN DAMAGE

Objective: Chronic immune-mediated inflammation is increasingly recognized as an important contributor to target organ damage (TOD) in essential hypertension (EH). High mobility group box-1 (HMGB1) is a damage-associated molecular pattern (DAMP) molecule which stimulates innate immunity, hence exerting significant proinflammatory properties including vascular inflammation and thrombosis. So far, no clinical data exist regarding the role of HMGB1 in EH and its association with vascular damage. Our objective was to measure HMGB1 levels in newly diagnosed, untreated patients with EH (UHTs) compared to normotensive controls (NTs) and correlate them with indices of macro- and microvascular dysfunction, which play a core role in the pathogenesis of TOD in EH. Design and method: HMGB1 was measured in serum with ELISA. Ambulatory and central blood pressure (BP) parameters, and pulse wave velocity (PWV), were measured by using the Mobil-O-Graph device. Skin microcirculation was assessed with Laser Speckle Contrast Imaging (LSCI) coupled with post-occlusive reactive hyperemia (PORH). Results are expressed as a percentage increase between peak and baseline perfusion (%), and the amplitude of PORH response defined as peak Cutaneous Vascular Conductance (CVC) minus baseline CVC. The CVC was calculated as the flux in each period divided by mean arterial pressure [(PUs)/mmHg]. Results: We consecutively enrolled 55 UHTs and 25 NTs matched for age and sex. HMGB1 levels were significantly higher in UHTs compared to NTs. HMGB1 showed a significant positive association with measures of macrocirculation including 24 h central systolic (0.325, p &lt; 0.01) and diastolic BP (0.371, p &lt; 0.01), day central systolic (0.353, p &lt; 0.01) and diastolic BP (0.402, p &lt; 0.01), and 24 h PWV (0.224, p &lt; 0.05) and day PWV (0.230, p &lt; 0.05) in the total study population. In addition, HMGB1 presented a significant negative association with skin microvascular parameters including base to peak flux (-0.247, p &lt; 0.05) and PORH amplitude (-0.225, p &lt; 0.01). Conclusions: HMGB1 is significantly increased in UHTs compared to NTs and correlates with indices of macro- and microvascular damage. These results reinforce the concept that immune system activation contributes to hypertension-mediated TOD from the very early stages and point towards intense research in order to investigate novel potential therapeutic targets related to EH.

Abnormalities of retinal structure and microvasculature are associated with cerebral white matter hyperintensities.

Whilst retinal microvasculature represents cerebral small vessels, the retinal nerve fiber layer is the extended white matter of the brain. The aim was to investigate the correlation between changes in retina and white matter hyperintensities (WMHs). Sixty-four candidates with WMHs received an optical coherence tomography angiography examination. WMHs were divided into mild or moderate/severe groups according to the Fazekas score. After imaging the superficial capillary plexus (SCP) and deep capillary plexus (DCP), the microvascular density parameters (vascular perfusion density [VPD], vascular length density [VLD] and fovea avascular zone area) and morphological parameters (vessel diameter index [VDI], fractal dimension [FD] and vessel tortuosity) were identified. A software algorithm measured the thickness of the peripapillary retina nerve fiber layer (PRNFL). Thirty-two were classified as having mild WMHs and 32 were moderate/severe. The median (interquartile range) ages of the two groups were 58 (54-64) and 61 (57-67) years, respectively. A decrease of FD, VPD and VLD in either SCP or DCP appeared with an increased risk of moderate/severe WMHs. Although changes of capillary plexus were not associated with paraventricular WMHs, decreased FD, VPD, VLD and fovea avascular zone area in either SCP or DCP were associated with an increased risk of moderate/severe deep WMHs (DWMHs). Participants with moderate/severe WMHs demonstrated reduced PRNFL thickness, particularly in the DWMHs, compared with mild WMHs. Abnormalities of retinal microvascular density, morphological parameters and PRNFL thickness are correlated with the incidence of moderate/severe WMHs, particularly the DWMHs, suggesting that arteriosclerosis and hypoperfusion are the causes of DWMHs.

EFFECT OF ORAL CARBONIC ANHYDRASE INHIBITOR ON CYSTOID MACULAR EDEMA ASSOCIATED WITH RETINITIS PIGMENTOSA: An OCT and OCT Angiography Study.

To investigate the factors associated with visual improvement in response to oral carbonic anhydrase inhibitors (CAIs) and the occurrence of microvascular changes in patients with retinitis pigmentosa-associated cystoid macular edema (RP-CME). This retrospective cohort study included 59 eyes from 39 patients with RP-CME who underwent at least 3 months of oral CAI treatment. The eyes were divided into responding and nonresponding groups based on optical coherence tomography (OCT) criteria (resolution of cyst and reduction of foveal or parafoveal volume). All eyes were assessed before and after treatment using OCT and OCT angiography. Thirty-three eyes (55.9%) demonstrated a positive response to treatment, and 26 eyes (44.1%) did not. Compared with nonresponding eyes, responding eyes had a significantly higher frequency of multilayer CME than CME limited to the inner nuclear layer ( P = 0.016). Subgroup analysis within the responding group revealed that improvements in visual acuity were more likely in eyes with fovea-involving CME and a higher baseline external limiting membrane and ellipsoid zone width. Microvascular parameters showed no significant changes after treatment. Eyes with CME extending to the outer nuclear layer or central fovea, and higher initial photoreceptor integrity may be prognostic factors associated with structural and functional improvements after carbonic anhydrase inhibitors treatment. Early treatment of multilayer CME with foveal involvement seems to be crucial in preventing irreversible photoreceptor damage.

Methylene Blue Reduces Fluid Loading and Norepinephrine Requirements for Post-Resuscitation Syndrome in a Pig Model of Refractory Cardiac Arrest Resuscitated with Veno-Arterial ECMO.

Background: Refractory cardiac arrest management relies on extracorporeal cardiopulmonary resuscitation (ECPR), requiring the use of veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Circulatory flow recovery can be associated with an ischemia–reperfusion injury, leading to vasoplegia and vasopressor requirement. The aim of this work was to evaluate the impact on hemodynamics of a methylene blue bolus infusion in a porcine model of ischemic refractory cardiac arrest. Methods: Ischemic refractory cardiac arrest was induced in 20 pigs. After a low flow period of 30 min, VA-ECMO was initiated and the pigs were randomly assigned to the standard care group (norepinephrine + crystalloids) or methylene blue group (IV 2 mg·kg−1 bolus of methylene blue over 30 min + norepinephrine and crystalloids). Macrocirculatory parameters and lactate clearance were measured. Sublingual microcirculation was evaluated with sidestream dark field (SDF) imaging. The severity of the ischemic digestive lesions was assessed according to the histologic Chiu/Park scale. Results: Eighteen pigs were included. The total crystalloid load (5000 (6000–8000) mL vs. 17,000 (10,000–19,000) mL, p = 0.007, methylene blue vs. standard care group) and catecholamine requirements (0.31 (0.14–0.44) μg·kg−1·min−1 vs. 2.32 (1.17–5.55) μg·kg−1·min−1, methylene blue vs. standard care group, p = 0.004) were significantly reduced in the methylene blue group. There were no significant between-group differences in lactate clearance, sublingual capillary microvascular parameters assessed by SDF or histologic Chiu/Park scale. Conclusions: In our refractory cardiac arrest porcine model treated with ECPR, methylene blue markedly reduced fluid loading and norepinephrine requirements in comparison to standard care during the first 6 h of VA-ECMO.

CapillaryNet: An automated system to quantify skin capillary density and red blood cell velocity from handheld vital microscopy

Capillaries are the smallest vessels in the body which are responsible for delivering oxygen and nutrients to surrounding cells. Various life-threatening diseases are known to alter the density of healthy capillaries and the flow velocity of erythrocytes within the capillaries. In previous studies, capillary density and flow velocity were manually assessed by trained specialists. However, manual analysis of a standard 20-s microvascular video requires 20 min on average and necessitates extensive training. Thus, manual analysis has been reported to hinder the application of microvascular microscopy in a clinical environment. To address this problem, this paper presents a fully automated state-of-the-art system to quantify skin nutritive capillary density and red blood cell velocity captured by handheld-based microscopy videos. The proposed method combines the speed of traditional computer vision algorithms with the accuracy of convolutional neural networks to enable clinical capillary analysis. The results show that the proposed system fully automates capillary detection with an accuracy exceeding that of trained analysts and measures several novel microvascular parameters that had eluded quantification thus far, namely, capillary hematocrit and intracapillary flow velocity heterogeneity. The proposed end-to-end system, named CapillaryNet, can detect capillaries at ~0.9 s per frame with ~93% accuracy. The system is currently used as a clinical research product in a larger e-health application to analyse capillary data captured from patients suffering from COVID-19, pancreatitis, and acute heart diseases. CapillaryNet narrows the gap between the analysis of microcirculation images in a clinical environment and state-of-the-art systems.

Peripapillary Microvascular and Structural Parameters in Atrophic Nonarteritic Anterior Ischemic Optic Neuropathy and Their Unaffected Fellow Eyes.

This cross-sectional study aimed to evaluate the peripapillary vessel density (VD), peripapillary retinal nerve fiber layer (RNFL) thickness values of eyes with atrophic nonarteritic anterior ischemic optic neuropathy (NAION), and unaffected fellow eyes. Peripapillary VDs and RNFL thicknesses in the peripapillary region and 4 sectors (superior, inferior, nasal, and temporal) were evaluated using optical coherence tomography angiography among 19 atrophic NAION eyes, 19 unaffected fellow eyes, and 22 age-matched and sex-matched healthy controls. The NAION eyes had lower peripapillary VD and RNFL thickness values in all areas compared with both the fellow and the healthy control eyes ( P < 0.001 for all). The fellow eyes also demonstrated lower peripapillary VD values ( P = 0.02) despite similar RNFL thickness values ( P = 0.99) in the peripapillary region compared with the age-matched and sex-matched healthy controls. The peripapillary RNFL thickness values significantly correlated with peripapillary VD values in both NAION and fellow eyes. Diminished RNFL thickness and peripapillary VD values were observed in atrophic NAION eyes. In addition, a tendency for a lower peripapillary VD despite similar RNFL thickness values in the fellow eyes may indicate the potential vascular risk factors for NAION.

Microvascular rarefaction in patients with cerebrovascular events.

Capillary density rarefaction and endothelial dysfunction contribute to chronic hypoperfusion and cerebral small vessel disease. Previous animal experiments revealed spatiotemporal microvascular remodeling directing post-stroke brain reorganization. We hypothesized that microcirculatory changes during acute cerebrovascular events could be reflected systemically and visualized sublingually. In a prospective observational trial in vivo sublingual sidestream darkfield videomicroscopy was performed in twenty-one patients with either acute stroke (n=13 ischemic, n=1 ischemic with hemorrhagic transformation and n=2 hemorrhagic stroke) or transitory ischemic attacks (n=5) within 24h after hospital admission and compared to an age- and sex-matched control group. Repetitive measurements were performed on the third day and after one week. Functional and perfused total capillary density was rarefied in the overall patient group (3060 vs 3717μm/mm2, p=0.001 and 5263 vs 6550μm/mm2, p=0.002, respectively) and in patients with ischemic strokes (2897 vs. 3717μm/mm2, p<0.001 and 5263 vs. 6550μm/mm2, p=0.006, respectively) when compared to healthy controls. The perfused boundary region (PBR), which was measured as an inverse indicator of glycocalyx thickness, was markedly related to red blood cell (RBC) filling percentage (regarded as an estimate of microvessel perfusion) in the overall patient group (r=-0.843, p<0.001), in patients with ischemic strokes (r=-0.82, p=0.001) as well as in healthy volunteers (r=-0.845, p<0.001). In addition, there were significant associations between platelet count or platelet aggregation values (as measured by whole blood impedance aggregometry) and microvascular parameters in the overall patient collective, as well as in patients with ischemic strokes. In conclusion, cerebrovascular events are associated with altered systemic microvascular perfusion.

Macular and Optic Nerve Microvascular Alteration in Relation to Axial Length, by Optical Coherence Tomography Angiography (OCTA).

AimTo study the effect of axial length (AL) on quantitative characterization of macular and optic nerve microvasculature using optical coherence tomography angiography (OCTA) in healthy individuals.MethodsA cross-sectional study where participants were divided into 3 groups according to AL; A: ≤22.5 mm, B: 22.6–24.5 mm, C: >24.5 mm. Superficial vascular density (SVD), deep vascular density (DVD), foveal avascular zone (FAZ), and radial peripapillary capillary density (RPCD) were calculated using OCTA. Pearson correlation was run to identify the relation between AL and study parameters.ResultsOne hundred and twelve eyes of 56 participants (20 males, 36 females) were included. Mean FAZ was 0.33 ± 0.15 mm2, 0.27 ± 0.1 mm2 and 0.28 ± 0.2 mm2 in Groups A, B, and C, respectively (p value 0.073). No significant difference was found between 3 groups, as regards superficial foveal density and vessel density inside the disc. Deep foveal density was significantly lower in Group A in comparison to Groups B and C (p value 0.021 and 0.005, respectively). As for other parameters of SVD, DVD and RPCD, no significant difference was observed between Groups A and B; however, the same parameters were significantly lower in Group C when compared to Group A and B. AL was found to be negatively correlated to FAZ (r −0.191, p value 0.043) and most of parameters of SVD, DVD, and RPCD (p value < 0.0001).ConclusionMost of optic nerve and macular microvascular parameters were significantly lower in eyes with longer axial lengths when compared to those with shorter axial lengths. Moreover, most of these parameters were negatively correlated with AL.

Quantitative Analysis of DCE and DSC-MRI: From Kinetic Modeling to Deep Learning.

Perfusion MRI is a well-established imaging modality with a multitude of applications in oncological and cardiovascular imaging. Clinically used processing methods, while stable and robust, have remained largely unchanged in recent years. Despite promising results from novel methods, their relatively minimal improvement compared to established methods did not generally warrant significant changes to clinical perfusion processing. Machine learning in general and deep learning in particular, which are currently revolutionizing computer-aided diagnosis, may carry the potential to change this situation and truly capture the potential of perfusion imaging. Recent advances in the training of recurrent neural networks make it possible to predict and classify time series data with high accuracy. Combining physics-based tissue models and deep learning, using either physics-informed neural networks or universal differential equations, simplifies the training process and increases the interpretability of the resulting models. Due to their versatility, these methods will potentially be useful in bridging the gap between microvascular architecture and perfusion parameters, akin to MR fingerprinting in structural MR imaging. Still, further research is urgently needed before these methods may be used in clinical practice. · Machine learning offers promising methods for processing of perfusion data.. · Recurrent neural networks can classify time series with high accuracy.. · Data augmentation is essentially especially when using small datasets.. · Rotkopf LT, Zhang KS, Tavakoli AA et al. Quantitative Analysis of DCE and DSC-MRI: From Kinetic Modeling toDeep Learning. Fortschr Röntgenstr 2022; 194: 975 - 982.

Evaluation of peripapillary - macular microvascularity and choroidal vascularity index after refractive surgery

BackgroundTo evaluate the microvascularity and choroidal vascularity index (CVI) using optical coherence tomography angiography (OCTA) and OCT following femtosecond laser-assisted in-situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE) procedures. MethodsPatients with myopia (<-6.0D sphere) or myopic astigmatism (<-4.0D astigmatism) were enroled. The percentage of vessel density and foveal avascular zone (FAZ) size, optic disc flux index and perfusion were noted and the CVI was calculated before and after surgery. ResultsTwenty-nine eyes of 16 patients in the FS-LASIK group and 30 eyes of 16 patients in the SMILE group were enroled. Macular vessel density, FAZ size, and optic disc flux index were significantly higher on postoperative 1st day compared to preoperative day (p = 0.001, p = 0.007, and p < 0.001, respectively). There was no significant difference in terms of macular and peripapillary CVI between postoperative 1st day and preoperative day (p > 0.05). All microvascular parameters were similar on postoperative 7th day and preoperative day (p > 0.05). ConclusionsIt was detected that there is a transient alteration in macular and peripapillary microvascularity after FS-LASIK/SMILE, whereas choroidal circularity is not significantly affected by these refractive surgeries.