Measurement Of Tortuosity Research Articles

A computational study of the influence of wavy arteries and veins on hemodynamic characteristics in an unsteady state

The present work is focused on the study of hemodynamic characteristics for tortuous arteries/veins in a pulsatile flow. This work is an extension of an earlier work by the author, which reported the hemodynamic characteristics in a steady flow situation. It is a well-known fact that various geometric parameters affect the hemodynamics, such as the diameter of vessels, the diameter of mother and daughter tubes in bifurcation, the angle between them, and their relative magnitudes. This paper is focused on the effect of tortuosity produced in straight and bifurcating tubes under pulsatile flow conditions. A heartbeat rate of 120 bpm is considered for pulsation, covering one cycle of systole and diastole. The measure of tortuosity is defined by the varying pitch and the amplitude. The present analysis is carried out computationally using ANSYS. Results are presented through secondary flow streamline, velocity profile, and its effect on wall shear stress. Key findings are that secondary vortices are observed in the bifurcated model and counter-rotating vortices are observed in the wavy tube geometry. The velocity distribution is asymmetric in the case of the plain bifurcation geometry. In the case of the wavy tube and bifurcated geometry, there is a shift in peak velocity from the inner to the outer wall, depending on the crest and trough positions of the tortuous vein. Relative change in magnitude of velocity for wavy tube depends on the depth and pitch of wavy wall of the tortuous tube. The velocity reduces with an increase in time step for unsteady flow.

The role of Perifoveal Arteriolar Tortuosity in Optical Coherence Tomography Angiography (OCTA) images as an early indicator of hypertensive retinopathy.

To assess the value of increased perifoveal retinal vascular tortuosity in optical coherence tomography angiography (OCTA) images as a biomarker of early hypertensive retinopathy and compare its clinical sensitivity and accuracy with traditional morphological changes used for Scheie classification. OCTA images of 81 eyes (40 eyes from 20 hypertensive subjects and 41 eyes from 21 control subjects) were obtained retrospectively. Hypertensive retinopathy changes in randomized eyes were graded according to the Scheie classification, and perifoveal vessels were traced in a masked fashion. Tortuosity values of the perifoveal vessels were then calculated along with interobserver agreement in determining the morphometric values. There were no differences in perifoveal venular tortuosity between the hypertensive and control groups (Mean = 1.13 ± 0.04 vs. 1.13 ± 0.03), but significant differences existed for arterioles (Mean = 1.14 ± 0.05 vs. 1.11 ± 0.04). Tortuosity measurements demonstrated a significant interobserver agreement (p < 0.001), while Scheie ratings had a poor interobserver agreement (p = 0.735). There was a significant difference in Scheie classification between the hypertensive and control groups (Mean = 1.06 ± 0.54 vs. 0.50 ± 0.43, p = 0.005). OCTA-based perifoveal retinal arteriolar tortuosity may be a potential reliable biomarker with certain advantages for detecting early hypertensive retinopathy than morphological changes used for the Scheie classification. This may have broad applications and establish important parameters in utilizing OCTA for screening protocols, considering the importance of early detection of systemic hypertension.

The Effect of Silicon Nanoparticle Size on Cycle and Calendar Life

Lithium-ion batteries are now ubiquitous in modern electronics, electric vehicles, and many other applications. As the battery industry continues to push for better, longer lasting batteries, many have turned to using a different anode material that would provide higher-energy density and require less frequent charges. While graphite is the tried-and-true anode material for lithium-ion batteries, a silicon anode battery could provide up to ten times higher theoretical energy density than graphite. However, there are a lot of challenges standing in the way between silicon anode batteries and commercialization—the large volume expansion of silicon (around 200-300% expansion, compared to graphite at 10%) and the unstable solid-electrolyte-interface (SEI) of silicon results in anodes that mechanically degrade and calendar age faster than their graphite counterparts.Previous research has demonstrated that plasma-enhanced chemical vapor deposition (PECVD) silicon nanoparticles with a hydrophilic coating such as polyethylene oxide (PEO) results in silicon anodes with good cycle life [1, 2, 3, 4]. In this system, smaller particle sizes typically yielded better cyclability than larger particle sizes, which is contrary to conventional wisdom that more surface area is detrimental as it allows for more SEI formation and side reactions. However, since silicon anodes experience large volume changes during cycling, the surface area might not be the dominant contribution to capacity fade. Larger silicon particles result in larger total expansions of the electrode, which causes more mechanical damage like cracks to form, exposing fresh surface area to electrolyte and SEI formation.This research investigates the performances of PEO-coated PECVD Si electrodes with nanoparticles ranging from 3 to 27 nm in diameter. We measure the cycle life at a rate of 0.333C, as well as the calendar lifetimes of each electrode. We characterize each electrode with SEM imaging, tortuosity measurements, and electrochemical impedance spectroscopy to understand the differences in microstructure that contribute to capacity fade and impedance rise.

Computer-aided detection of retinopathy of prematurity severity assessment via vessel tortuosity measurement in preterm infants' fundus images.

To develop a computer-aided diagnostic system for retinopathy of prematurity (ROP) disease using retinal vessel morphological features. A total of 200 fundus images from 136 preterm infants with stage 1 to 3 ROP were analysed. Two methods were developed to measure vessel tortuosity: the peak-and-valley method and the polynomial curve fitting method. Correlations between temporal artery tortuosity (TAT) and temporal vein tortuosity (TVT) with ROP severity were investigated, and vessel tortuosity relationships with vessel angles (TAA and TVA) and vessel widths (TAW and TVW). A separate dataset from Japan containing 126 images from 97 preterm patients was used for verification. Both methods identified similar tortuosity in images without ROP and mild ROP cases. However, the polynomial curve fit method demonstrated enhanced tortuosity detection in stages 2 and 3 ROP compared to the peak and valley method. A strong positive correlation was revealed between ROP severity and increased arterial and venous tortuosity (P < 0.0001). A significant negative correlation between TAA and TAT (r = -0.485, P < 0.0001) and TVA and TVT (r = -0.281, P < 0.0001), and a significant positive correlation between TAW and TAT (r = 0.204, P value = 0.0040) were identified. Similar results were found in the test dataset from Japan. ROP severity was associated with increased retinal tortuosity and retinal vessel width while displaying a decrease in retinal vascular angle. This quantitative analysis of retinal vessels provides crucial insights for advancing ROP diagnosis and understanding its progression.

Association between cervicocerebral artery dissection and tortuosity - a review on quantitative and qualitative assessment.

Cervicocerebral artery dissection stands out as a significant contributor to ischemic stroke in young adults. Several studies have shown that arterial tortuosity is associated with dissection. We searched Pubmed and Embase to identify studies on the association between arterial tortuosity and cervicocerebral artery dissection, and to perform a review on the epidemiology of cervicocerebral artery tortuosity and dissection, pathophysiology, measurement of vessels tortuosity, strength of association between tortuosity and dissection, clinical manifestation and management strategies. The prevalence of tortuosity in dissected cervical arteries was reported to be around 22%-65% while it is only around 8%-22% in non-dissected arteries. In tortuous cervical arteries elastin and tunica media degradation, increased wall stiffness, changes in hemodynamics as well as arterial wall inflammation might be associated with dissection. Arterial tortuosity index and vertebrobasilar artery deviation is used to measure the level of vessel tortuosity. Studies have shown an independent association between these two measurements and cervicocerebral artery dissection. Different anatomical variants of tortuosity such as loops, coils and kinks may have a different level of association with cervicocerebral artery dissection. Symptomatic patients with extracranial cervical artery dissection are often treated with anticoagulant or antiplatelet agents, while patients with intracranial arterial dissection were often treated with antiplatelets only due to concerns of developing subarachnoid hemorrhage. Patients with recurrent ischemia, compromised cerebral blood flow or contraindications for antithrombotic agents are usually treated with open surgery or endovascular technique. Those with subarachnoid hemorrhage and intracranial artery dissection are often managed with surgical intervention due to high risk of re-hemorrhage.

Determination and Engineering of Li‐Ion Tortuosity in Electrode Toward High Performance of Li‐Ion Batteries

AbstractWith the progressively widespread application of lithium‐ion batteries, their energy density and power density are being pursued to the extremely high. However, both cannot be reached simultaneously at present. Tortuosity depicts the relationship in ionic diffusion between bulk electrolyte and the electrolyte in a porous electrode, provides information about channels within electrodes, and correlates the current dilemma between energy density and power capability of the lithium‐ion batteries. It is crucial to upgrade the fast charging and discharging performance of LIBs electrodes without losing volumetric energy density and using tortuosity as a guide is able to achieve this goal fundamentally. Meanwhile, tortuosity can serve as an evaluation parameter for production quality assessment, but this demands a fast, accurate, and cost‐effective measuring method. After the definition and measurement of tortuosity are provided, this article analyzes the structural influencing factors of tortuosity which have impacts on ion transportation and subsequently on tortuosity to facilitate a more systematic and comprehensive picture. Through the discussion of contradictions and influencing factors, a more refined transmission line model (the refined TLM) is perceived as the very first step to drive both aforementioned goals toward success and is discussed in the perspective part.

Coronary Tortuosity Index vs. Angle Measurement Method for the Quantification of the Tortuosity of Coronary Arteries in Non-Obstructive Coronary Disease.

Coronary tortuosity has been recognized as a potential pathophysiological mechanism in the development of non-obstructive coronary artery disease (CAD). The aim of this study was to examine the role of two coronary tortuosity measurement methods in the detection of clinically significant coronary tortuosity. The study included 160 patients with angina symptoms and myocardial ischemia detected by cardiac stress tests in chronic settings and those diagnosed with acute coronary syndrome. After coronary angiography, tortuosity of coronary arteries was assessed by two methods, including measurement of tortuosity angles and calculating of tortuosity index. Significantly more tortuous coronary arteries were detected in the group with non-obstructive CAD (p < 0.01 for all three arteries), with significantly higher tortuosity index (TI) for all three coronary arteries in this group of patients, compared to patients with obstructive CAD. The highest TI for LCX was found in patients with lateral ischemia (p < 0.001) and for LAD in patients with anterior ischemia (p < 0.001). When measured by the angle method, the only association was found between LCX tortuosity and lateral ischemia (OR 4.9, p = 0.046). In conclusion, coronary tortuosity represents a pathophysiological mechanism for myocardial ischemia in non-obstructive CAD. The coronary tortuosity index could be a reliable and widely applicable tool for the quantification of coronary tortuosity.

Evaluation of surface tortuosity on the corrosion resistance of organic coatings using laser texturing process

Surface tortuosity is a quantitative measure of the complexity of a material's surface. It is commonly defined as the ratio between the real length of the surface over the shortest distance between two points on the surface. An increase in surface tortuosity has been found to have advantageous effects on the durability of coated parts when exposed to corrosive and humid conditions. Laser surface texturing, a versatile process, can be used to modify the surface tortuosity by creating various structure patterns on the surface of steel. This study aims to investigate the impact of V-shaped groove dimensions on the resistance against corrosion creep of an organic coating applied to textured surfaces. Comparative surface tortuosity measurements were obtained for different groove dimensions while keeping the aspect ratio and textured areas constant. V-shaped grooves with an aspect ratio of 1 and sizes of 50, 100, and 200 μm were machined on carbon steel AISI-A36. The distance between adjacent grooves was varied to achieve different textured areas, ranging from 10% to 60%. The surface roughness (Sa) and surface tortuosity were characterized. The performance of the coating was evaluated using an accelerated corrosion test based on ISO 12944-9. The results indicate that V-shaped grooves with dimensions of 100 μm and a textured area of 40% exhibit the lowest coating delamination. It is worth to mention that the performance of organic coatings is enhanced up to a certain optimal point by an increase in surface tortuosity. However, beyond this optimal point, further increases in tortuosity do not lead to an increased resistance to the propagation of corrosion.

A Comparison of the Tortuosity Phenomenon in Retinal Arteries and Veins Using Digital Image Processing and Statistical Methods

The tortuosity of retinal blood vessels is an important phenomenon, and it can act as a biomarker in the diagnosis of several eye diseases. The study of abnormalities in the tortuosity of retinal arteries and veins provides ophthalmologists with important information for disease diagnosis. Our study aims to compare the tortuosity relation between retinal arteries and veins by quantifying the vessels’ tortuosity in the retina using 14 tortuosity measures applied to the AV-classification retinal dataset. Two feature sets are created, one for arteries and the other for veins. The comparison between the tortuosity of arteries and veins is based on a two-sample T-test statistical method, a regression analysis between the quantified tortuosity features, principal component analysis at the dataset level, and the introduction of the arteriovenous length ratios concept to compare the variations in these new ratios to see the tortuosity behavior in each image. The methods’ results have shown that the tortuosity of retinal arteries and veins is similar. The result of the two-sample T-test supports the research hypothesis, as the P-value obtained was greater than 0.05. Furthermore, the regression analysis between arteries and veins features showed a high correlation (r2 = 89.39% and 89.11%) for arteries and veins, respectively. The study concludes that the retinal vessel type has no statistical significance in the tortuosity calculation results.

Automated airway quantification associates with mortality in idiopathic pulmonary fibrosis

ObjectivesThe study examined whether quantified airway metrics associate with mortality in idiopathic pulmonary fibrosis (IPF).MethodsIn an observational cohort study (n = 90) of IPF patients from Ege University Hospital, an airway analysis tool AirQuant calculated median airway intersegmental tapering and segmental tortuosity across the 2nd to 6th airway generations. Intersegmental tapering measures the difference in median diameter between adjacent airway segments. Tortuosity evaluates the ratio of measured segmental length against direct end-to-end segmental length. Univariable linear regression analyses examined relationships between AirQuant variables, clinical variables, and lung function tests. Univariable and multivariable Cox proportional hazards models estimated mortality risk with the latter adjusted for patient age, gender, smoking status, antifibrotic use, CT usual interstitial pneumonia (UIP) pattern, and either forced vital capacity (FVC) or diffusion capacity of carbon monoxide (DLco) if obtained within 3 months of the CT.ResultsNo significant collinearity existed between AirQuant variables and clinical or functional variables. On univariable Cox analyses, male gender, smoking history, no antifibrotic use, reduced DLco, reduced intersegmental tapering, and increased segmental tortuosity associated with increased risk of death. On multivariable Cox analyses (adjusted using FVC), intersegmental tapering (hazard ratio (HR) = 0.75, 95% CI = 0.66–0.85, p < 0.001) and segmental tortuosity (HR = 1.74, 95% CI = 1.22–2.47, p = 0.002) independently associated with mortality. Results were maintained with adjustment using DLco.ConclusionsAirQuant generated measures of intersegmental tapering and segmental tortuosity independently associate with mortality in IPF patients. Abnormalities in proximal airway generations, which are not typically considered to be abnormal in IPF, have prognostic value.Clinical relevance statementQuantitative measurements of intersegmental tapering and segmental tortuosity, in proximal (second to sixth) generation airway segments, independently associate with mortality in IPF. Automated airway analysis can estimate disease severity, which in IPF is not restricted to the distal airway tree.Key Points• AirQuant generates measures of intersegmental tapering and segmental tortuosity.• Automated airway quantification associates with mortality in IPF independent of established measures of disease severity.• Automated airway analysis could be used to refine patient selection for therapeutic trials in IPF.Graphical

Binary fluids in mesoporous materials: Phase separation studied by NMR relaxation and diffusion

Relaxation and diffusion measurements were carried out on single and binary liquids filling the pore space of controlled porous glass Vycor with an average pore size of about 4 nm. The dispersion of the longitudinal relaxation time T1 is discussed as a means to identify liquid-surface interaction based on existing models developed for metal-free glass surfaces. In addition, the change of T1 and T2 with respect to their bulk values is discussed, in particular T2 serves as a probe for the strength of molecular interactions. As the native glass surface is polar and contains a large amount of hydroxyl groups, a pronounced interaction of polar and protic adsorbate liquids is expected; however, the T1 dispersion, and the corresponding reduction of T2, are also observed for non-polar liquids such as alkanes and cyclohexane. Deuterated liquids are employed for simplifying data analysis in binary systems, but also for separating the respective contributions of intra- and intermolecular interactions to the overall relaxation rate. Despite the lack of paramagnetic impurities in the glass material, 1H and 2H relaxation dispersions of equivalent molecules are frequently found to differ from each other, suggesting intermolecular relaxation mechanisms for the 1H nuclei. The variation of the T1 dispersion when comparing single and binary systems gives clear evidence for the preferential adsorption of one of the two liquids, suggesting complete phase separation in several cases. Measurement of the apparent tortuosity by self-diffusion experiments supports the concept of a local variation of sample composition within the porespace.

Retinal Vessel Local Tortuosity under a Macula-to-Optic Disc Central-Framing Change

Some ocular and cardiovascular diseases can be detected through the increased tortuosity of retinal blood vessels. Objective tortuosity measures can be obtained from digital image analysis of a retinography. This study tested a set of local tortuosity indices under a change in the frame center (macula, optic disc) of the eye fundus image. We illustrate the effects of such a change on 40 pairs of vessels evaluated with eight tortuosity indices. We show that the frame center change caused significant differences in the mean values of the vast majority of the tortuosity indices analyzed. The index defined as the ratio of the curvature to the arc length of a vessel segment proved to be the most robust in relation to a frame center change. Experimental results obtained from the analysis of clinical images are provided and discussed.

Abstract Number ‐ 11: Automated Measurement Of Vascular Tortuosity: Association With Baseline Clinical Characteristics And Impact On Mechanical Thrombectomy

Introduction Vascular tortuosity is considered one of the main hurdles that may negatively impact mechanical thrombectomy in stroke treatment, delaying catheter access to the occluded vessel. Automatic characterization of anatomical vascular features may help in the planification of endovascular interventions. We developed a fully automatic algorithm for vascular tortuosity measurement and explored the association of several anatomical features with baseline characteristics and procedural outcomes. Methods An automatic software integrating segmentation, centerline extraction and vessel labelling, was used to extract features directly from computed tomography angiograms (CTA) of stroke patients undergoing transfemoral endovascular treatment.Mean vessel diameter and tortuosity index (TI) of the carotid arteries and brachiocephalic trunk were used as relevant tortuosity indicators. Patients were compared according to six different clinical conditions(gender, hypertension, dyslipidemia, diabetes, obesity and atrial fibrillation). Tortuosity values were also correlated with age.Patients with an anterior circulation stroke were further classified according to four procedural measures:time from groin puncture to first angiographic run, time to first retrieval attempt, time to revascularization. Results A sample of 558 patients with acute ischemic stroke who underwent mechanical thrombectomy at our medical center were included in this study. Forty patients (7.2%) were discarded due to sub‐optimal segmentation (n = 30) or processing errors (n = 10), leaving a final sample size of N = 518 (51% female, 74.8±12.9 years). Women presented significantly smaller mean diameter for all analyzed vessels (p &lt; 0.01) and an increased TI for both carotid arteries(p &lt; 0.01). Age was significantly correlated with increased TI in all analyzed vessels (0.35£r£0.52;p &lt; 0.01) Patients with hypertension and/or atrial fibrillation displayed significantly higher TI in both carotid arteries (p &lt; 0.01). Additionally, the brachiocephalic trunk was found to be more tortuous in patients with atrial fibrillation (p &lt; 0.01). A higher TI in all ipsilateral carotid segments was associated with higher times to first angiographic run and to final revascularization (p &lt; 0.05). A TI from the ipsilateral carotid segment over 0.28 independently predicted difficult catheter access (time to first angiographic run &gt;40 min, 3.8% of cases) with a sensitivity of 0.92 and a specificity of 0.68. Conclusions An automated software was successfully used to characterize the anatomical vascular features from CTA. Gender, age, hypertension and atrial fibrillation were found to significantly influence vascular tortuosity in anterior circulation arteries. Patients with difficult catheter access and/or delayed revascularization presented higher TI of ipsilateral carotid arteries. Carotid TI emerged as a potential predictor of difficult catheter access.

Retinal Vascular Changes in Alzheimer's Dementia and Mild Cognitive Impairment: A Pilot Study Using Ultra-Widefield Imaging.

Retinal microvascular abnormalities measured on retinal images are a potential source of prognostic biomarkers of vascular changes in the neurodegenerating brain. We assessed the presence of these abnormalities in Alzheimer's dementia and mild cognitive impairment (MCI) using ultra-widefield (UWF) retinal imaging. UWF images from 103 participants (28 with Alzheimer's dementia, 30 with MCI, and 45 with normal cognition) underwent analysis to quantify measures of retinal vascular branching complexity, width, and tortuosity. Participants with Alzheimer's dementia displayed increased vessel branching in the midperipheral retina and increased arteriolar thinning. Participants with MCI displayed increased rates of arteriolar and venular thinning and a trend for decreased vessel branching. Statistically significant differences in the retinal vasculature in peripheral regions of the retina were observed among the distinct cognitive stages. However, larger studies are required to establish the clinical importance of our findings. UWF imaging may be a promising modality to assess a larger view of the retinal vasculature to uncover retinal changes in Alzheimer's disease. This pilot work reports an investigation into which retinal vasculature measurements may be useful surrogate measures of cognitive decline, as well as technical developments (e.g., measurement standardization), that are first required to establish their recommended use and translational potential.

Clinical Implications of Internal Carotid Arterial Tortuosity in Patients with White Matter Hyperintensities

AbstractBackgroundWhite matter hyperintensities (WMHs) are observed frequently on MRI in elderly and associated with cognitive dysfunction. Many studies focused on intracranial small vessel disease (SVD), however, few studies linked WMHs with changes of extracranial large feeding arteries. We aimed to investigate the effects of internal carotid artery (ICA) tortuosity changes through quantitative MR Angiography.MethodFifty‐seven patients (age: 72.98±5.62; 32 females/25 males) with WMHs were included. WMHs lesions were semi‐automatically segmented on FLAIR images. ICAs were segmented on the TOF images to generate tortuosity quantitative metrics, including tortuosity index (TI), inflection count metric (ICM), and ICA angle (Figure 1). According to the Fazekas scores, patients were categorized into mild, moderate and severe groups as summarized in Table 1. One‐way ANOVA analyses were applied to reveal the difference of averaged bilateral ICAs' tortuosity measurements. Pearson's correlation coefficients were calculated to quantitatively investigate the relationship between tortuosity and volumes of lesions that are apart from the ventricle in subcortical white matter, i.e., deep white matter lesions (DWMLs), as well as the lesions attached with the ventricular system, i.e., periventricular white matter lesions (PVWMLs).ResultPatients with higher Fazekas scores have higher TI and ICM, indicating higher tortuosity (Figure 2). The correlation results showed that TI and ICM were positively correlated with DWMLs volumes (r = 0.33, P&lt; 0.05; r = 0.4, P&lt; 0.01), however, they did not show associations with PVWMLs. While there's no correlation between averaged bilateral ICA angles and DWMLs or PVWMLs, we found significant correlations between left ICA angles and DWML volumes on left brain (r =0.56, P &lt; 0.005) as well as between right ICA angles and DWML volumes on right brain (r = 0.49, P &lt; 0.05) (Figure 3).ConclusionTortuosity measurements derived from TOF images showed that subjects with higher degree of ICA tortuosity had higher lesion volumes of DWMLs not PVWMLs, indicating DWMLs may have different etiologies such as ischemic origin. The findings also highlight the importance of ICA angle as a risk factor for WMHs development which might be associated with the local hemodynamic shear stress at the bulb, where the ICA plaques are often developed.

Quantifying acid diversion efficiency through NMR tortuosity measurements

The diversion efficiency measures the acid capacity to change its flow direction to the lower permeability reservoir sections. A good acid diverter creates a tortuous (zigzagged) wormhole within the acidized core sample in a laboratory setup. Here, we studied two different acid diverters compared to the conventional hydrochloric acid (HCl) to investigate their efficiency in changing the wormhole direction inside the rock core. Nuclear magnetic resonance (NMR) can be used to measure the 3D tortuosity of a rock sample; hence, we propose it as a tool to measure acid diversion efficiency because it can be applied in the field and in the laboratory. Two acid systems were utilized: straight 15 wt.% HCl acid and gelled acid consisting of 15 wt.% HCl acid and polyacrylamide polymer (PAM). Four coreflooding experiments were conducted on 1.5 inch-diameter × 3 inch-length Indiana limestone samples, two with straight HCl acid and two with gelled HCl acid at different PAM concentrations. NMR was utilized to measure the T2 distribution of the rock samples and diffusion tortuosity in two orthogonal directions. Also, X-ray computed tomography (CT) of the acidized samples was taken to visualize the wormholes. Results showed that the polymer-based acid-created zigzagged paths, and more acid volume was consumed to create the wormholes using CT. NMR diffusion tortuosity measurements showed that the tortuosity was reduced along the wormhole direction in all experiments. Nevertheless, the gelled acid treatments showed a significant reduction of the tortuosity orthogonal to the main wormhole path. The diversion efficiency of the 50 lbm/ 1000 gal PAM-gelled acid was 35% higher compared to the straight HCl acid. On the contrary, the 30 lbm/ 1000 gal PAM-gelled acid gave only 10% improvement in the diversion. The index could screen quantitatively which diverting acid is more efficient. We introduced a new diversion index based on the NMR diffusion measurements in this study to quantify the diversion capacity of an acid system in carbonate rock.

Mathematical Models and Experiments on the Acoustic Properties of Granular Packing Structures (Measurement of Tortuosity in Hexagonal Close-Packed and Face-Centered Cubic Lattices).

In this study, the sound absorption characteristics of hexagonal close-packed and face-centered cubic lattices were estimated by theoretical analysis. Propagation constants and characteristic impedances were obtained by dividing each structure into elements perpendicular to the incident direction of sound waves and by approximating each element to a clearance between two parallel planes. Consequently, the propagation constant and the characteristic impedance were treated as a one-dimensional transfer matrix in the propagation of sound waves, and the normal incident sound absorption coefficient was calculated by the transfer matrix method. The theoretical value of the sound absorption coefficient was derived by using the effective density applied to the measured tortuosity. As a result, the theoretical value was becoming closer to the measured value. Therefore, the measured tortuosity is reasonable.

New Method for the Automated Assessment of Corneal Nerve Tortuosity Using Confocal Microscopy Imaging

An automated tool for corneal nerve fiber tortuosity quantification from in vivo confocal microscopy (IVCM) is described and evaluated. The method is a multi-stage process based on the splitting of the corneal nerve fibers into individual segments, whose endpoints are an extreme or intersection of white pixels on a binarized image. Individual segment tortuosity is quantified in terms of the arc-chord ratio. Forty-three IVCM images from 43 laser-assisted in situ keratomileusis (LASIK) surgery patients were used for evaluation. Images from symptomatic dry eye disease (DED) post-LASIK patients, with (n=16) and without (n=7) ocular pain, and non-DED post-LASIK controls (n=20) were assessed. The automated tortuosity measure was compared to a manual grading one, obtaining a moderate correlation (Spearman’s rank correlation coefficient = 0.49, p=0.0008). The new tortuosity index was significantly higher in post-LASIK patients with ocular pain than in control patients (p=0.001), while no significant differences were detected with manual measurement (p&gt;0.28). The tortuosity quantification was positively correlated with the ocular surface disease index (OSDI) and a numeric rating scale (NRS) assessing pain (p=0.0012 and p=0.0051, respectively). The results show good performance of the proposed automated methodology for the evaluation of corneal nerve tortuosity.

Four Severity Levels for Grading the Tortuosity of a Retinal Fundus Image.

Hypertensive retinopathy severity classification is proportionally related to tortuosity severity grading. No tortuosity severity scale enables a computer-aided system to classify the tortuosity severity of a retinal image. This work aimed to introduce a machine learning model that can identify the severity of a retinal image automatically and hence contribute to developing a hypertensive retinopathy or diabetic retinopathy automated grading system. First, the tortuosity is quantified using fourteen tortuosity measurement formulas for the retinal images of the AV-Classification dataset to create the tortuosity feature set. Secondly, a manual labeling is performed and reviewed by two ophthalmologists to construct a tortuosity severity ground truth grading for each image in the AV classification dataset. Finally, the feature set is used to train and validate the machine learning models (J48 decision tree, ensemble rotation forest, and distributed random forest). The best performance learned model is used as the tortuosity severity classifier to identify the tortuosity severity (normal, mild, moderate, and severe) for any given retinal image. The distributed random forest model has reported the highest accuracy (99.4%) compared to the J48 Decision tree model and the rotation forest model with minimal least root mean square error (0.0000192) and the least mean average error (0.0000182). The proposed tortuosity severity grading matched the ophthalmologist’s judgment. Moreover, detecting the tortuosity severity of the retinal vessels’, optimizing vessel segmentation, the vessel segment extraction, and the created feature set have increased the accuracy of the automatic tortuosity severity detection model.

Retinal microvascular associations with cardiometabolic risk factors differ by diabetes status: results from the UK Biobank

Aims/hypothesisThe aim of the study was to examine the association of retinal vessel morphometry with BP, body composition and biochemistry, and to determine whether these associations differ by diabetes status.MethodsThe UK Biobank ocular assessment included 68,550 participants aged 40-70 years who underwent non-mydriatic retinal photography, BP and body composition measurements, and haematological analysis. A fully automated image analysis program provided measurements of retinal vessel diameter and tortuosity. The associations between retinal vessel morphology and cardiometabolic risk factors by diabetes status were examined using multilevel linear regression, to provide absolute differences in vessel diameter and percentage differences in tortuosity (allowing for within-person clustering).ResultsA total of 50,233 participants (a reduction from 68,550) were included in these analyses. Overall, those with diabetes had significantly more tortuous venules and wider arteriolar diameters compared with those without. Associations between venular tortuosity and cardiometabolic risk factors differed according to diabetes status (p interaction <0.01) for total fat mass index, HbA1c, C-reactive protein, white cell count and granulocyte count. For example, a unit rise in white cell count was associated with a 0.18% increase (95% CI 0.05, 0.32%) in venular tortuosity for those without diabetes and a 1.48% increase (95% CI 0.90, 2.07%) among those with diabetes. For arteriolar diameter, significant interactions were evident for systolic BP, diastolic BP, mean arterial pressure (MAP) and LDL-cholesterol. For example, a 10 mmHg rise in systolic BP was associated with a −0.92 μm difference (95% CI −0.96 to −0.88 μm) in arteriolar diameter for those without diabetes, and a −0.58 μm difference (95% CI −0.76 to −0.41 μm) among those with diabetes. No interactions were observed for arteriolar tortuosity or venular diameters.Conclusions/interpretationWe provide clear evidence of the modifying effect of diabetes on cardiometabolic risk factor associations with retinal microvascular architecture. These observations suggest the occurrence of preclinical disease processes, and may be a sign of impaired autoregulation due to hyperglycaemia, which has been suggested to play a pivotal role in the development of diabetes-related microvascular complications.Data AvailabilityThe data supporting the results reported here are available through the UK Biobank (https://www.ukbiobank.ac.uk/enable-your-research/apply-for-access).Graphical abstract