Volume Correlation Research Articles

Disc degeneration influences the strain magnitude and stress distribution within the adjacent trabecular bone

IntroductionUp to one in five will suffer from osteoporotic vertebral fracture within their lifetime. Accurate fracture prediction poses challenges using bone mineral density (BMD) measures. Trabecular bone strains may be influenced by the underlying intervertebral disc (IVD). Understanding how disc degeneration alters load distribution to the vertebra may demonstrate that supplementing fracture risk tools with IVD metrics could improve predictions. The aim of this study was to assess the influence of IVD degeneration on the stress and strain magnitude and distribution in the trabecular bone of adjacent vertebrae.MethodsTen human cadaveric lumbar bi-segment specimens (20 IVDs, 9 degenerated, 11 non-degenerated) were µCT-imaged under 1000N. Digital volume correlation was used to quantify axial, principal, maximum shear, and von Mises strain in the superior and inferior regions of the vertebra. Volumetric BMD from quantitative-CT was used to calculate Young’s modulus, which was then registered with the von Mises strain field to calculate internal von Mises stress.ResultsTwo bi-segments fractured during mechanical testing, resulting in N = 8 endplate regions per group. Trabecular bone adjacent to degenerated IVDs presented higher maximum principal and shear strains in the anterior region, relative to non-degenerated (peak ε1: 6,020 ± 1,633 µε versus 3,737 ± 1,548 µε, p < 0.01; peak γmax: 6,202 ± 1948 µε versus 3,938 ± 2086 µε, p < 0.01). Von Mises stress distribution was significantly skewed towards the anterior region in the degenerated group only (28.3% ± 10.4%, p < 0.05). Reduced disc height correlated with increased central-region axial compressive strain, decreased central-region BMD, and increased anterior region von Mises stress (all p < 0.05).DiscussionDisc degeneration may encourage high strains to be experienced within the anterior region of the adjacent bone, owing to changes in load distribution. This study demonstrates the potential of utilising IVD metrics in fracture risk assessment, to inform clinical decision making and preventative treatment.

The Strain Response to Intraocular Pressure Increase in the Lamina Cribrosa of Control Subjects and Glaucoma Patients.

The purpose of this study was to measure biomechanical strains in the lamina cribrosa (LC) of living human eyes undergoing intraocular pressure (IOP) increase. Healthy control subjects and patients with glaucoma underwent optical coherence tomographic (OCT) imaging of the LC before and after wearing of swim goggles that increased IOP (57 image pairs, 39 persons). Digital volume correlation was used to measure biomechanical strains in optic nerve head tissue and change in depth of the anterior border of the LC. The mean IOP increase in both glaucoma and control eyes was 7.1 millimeters of mercury (mm Hg) after application of the goggles. Among glaucoma eyes, strains that were significant were: contractile Ezz (average = -0.33%, P = 0.0005), contractile Eθθ (average = -0.23%, P = 0.03), Emax (average = 0.83%, P < 0.0001), and Γmax (average = 0.95%, P < 0.0001), whereas the average anterior LC depth (ALD) decreased by 2.39µm (anterior; P = 0.0002). In glaucoma eyes, shear strain Ezθ was greater with worse mean deviation (MD) and visual function index (P = 0.044 and P = 0.006, respectively, multivariate models). Strain compliance for Erθ, Ezθ, and Eθθ all increased with greater MD worsening prior to imaging (P = 0.04, P = 0.007, and P = 0.03). LC strains were measurable 20 minutes after IOP increase, producing axial compression and greater peripheral strain than centrally. Some strain compliances were greater with worse existing visual field loss or with more progressive past field loss. Biomechanical strains are related to measures of glaucoma damage, supporting the hypothesis that optic nerve head biomechanical responses represent a noninvasive biomarker for glaucoma.

Biomechanics-Function in Glaucoma: Improved Visual Field Predictions from IOP-Induced Neural Strains

Purpose(1) To assess whether neural tissue structure and biomechanics could predict functional loss in glaucoma; (2) To evaluate the importance of biomechanics in making such predictions. DesignClinic-based cross-sectional study. MethodsWe recruited 238 glaucoma subjects (Chinese ethnicity, more than 50 years old). For one eye of each subject, we imaged the optic nerve head (ONH) using spectral-domain OCT under the following conditions: (1) primary gaze and (2) primary gaze with acute IOP elevation (to approximately 35 mmHg) achieved through ophthalmo-dynamometry. We utilized automatic segmentation of optic nerve head (ONH) tissues and digital volume correlation (DVC) analysis to compute intraocular pressure (IOP)-induced neural tissue strains. A robust geometric deep learning approach, known as Point-Net, was employed to predict the full Humphrey 24-2 pattern standard deviation (PSD) maps from ONH structural and biomechanical information. For each point in each PSD map, we predicted whether it exhibited no defect or a PSD value of less than 5%. Predictive performance was evaluated using 5-fold cross-validation and the F1-score. We compared the model's performance with and without the inclusion of IOP-induced strains to assess the impact of biomechanics on prediction accuracy. ResultsIntegrating biomechanical (IOP-induced neural tissue strains) and structural (tissue morphology and neural tissues thickness) information yielded a significantly better predictive model (F1-score: 0.76 ± 0.02) across validation subjects, as opposed to relying only on structural information, which resulted in a significantly lower F1-score of 0.71 ± 0.02 (p < 0.05). Our subjects had a mean age of 69±5 years. Among them, 88 were female. The cohort included a wide range of glaucoma severity, with Mean Deviation (MD) values ranging from -1.8 (mild) to -25.2 (severe), and an average MD value of -7.25±5.05. ConclusionOur study has shown that the integration of biomechanical data can significantly improve the accuracy of visual field loss predictions and highlights the importance of the biomechanics-function relationship in glaucoma.

Quantifying bone compaction and implant-bone contact in uncemented total hip arthroplasty through μCT and digital volume correlation: A cadaveric study

BackgroundThe stability of uncemented implants during total hip arthroplasty (THA) depends on bone compaction and the bone-implant contact area achieved during the surgical process, particularly during broaching and implantation. However, the evaluation of these factors in actual hip is limited through experimental studies. Therefore, the aim of this study was to quantify bone compaction, and the bone-implant contact area achieved during uncemented THA through a μCT-based cadaveric study of three femur samples. MethodsThree cadaveric femur samples underwent uncemented THA, with μCT scans conducted at intermediate surgical steps. The bone compaction resulting from the surgical process was quantified using two parameters: (a) displacement and strain induced using Digital Volume Correlation (DVC), (b) changes in bone volume fraction (BV/TV) around the bone-implant interface. Furthermore, the bone-implant contact, and its location were evaluated, including an assessment of the robustness and sensitivity of the measurements. ResultsThe DVC showed that the trabecular bone deformed plastically, with a displacement of 0.09 ± 0.13 mm, a Von-Mises strain of 7082.28 ± 9162.73 με due to the surgical process. Broken trabecular bone accumulated around the bone-implant interface, increasing BV/TV from 3.31 % to 20.69 %. Bone-implant contact (BIC) was limited, ranging from 3.05 % to 5.22 %, but 75.26 %–82.27 % of the maximum potential contact area (PBICA) was achieved. All samples established a three-point contact, and sensitivity analysis revealed a robust BIC calculation with minimal variability of ±0.87 %. ConclusionThe findings offer important insights into bone-implant behaviour during the uncemented THA process. These insights could be useful for physics-based pre-surgical planning to evaluate the stability of uncemented implants and help surgeons choose the most appropriate implants for their patients.

Correlation of weight and volume of modified radical mastectomy specimen with ptosis of breast in patients of breast cancer

BackgroundPreoperative assessment of breast features is indispensable for both cosmetic and reconstructive breast surgical procedures. In this study we aim to investigate the effect of breast ptosis on breast volume estimation by various methods. MethodsFifty patients of breast cancer planned for modified radical mastectomy were taken up. Preoperatively breast anthropometric measurement taken, grade of ptosis was noted and breast volume was calculated by anthropometry and mammography and intraopratively mastectomy specimen weight and volume was recorded. Breast volume calculated by mammography and anthropometry compared with mastectomy specimen volume and weight and correlation with ptosis was statistically analyzed. ResultsMastectomy specimen volume showed best agreement with mastectomy specimen weight (r ​= ​.993, <.001), followed by mammographic method (r ​= ​.985, P ​< ​.001), anthropometry by breast circumference in supine method (r ​= ​.982, P ​< ​.001), anthropometry by breast circumference in upright method (r ​= ​.979, P ​< ​.001) and anthropometry by breast radius and mammary projection method (r ​= ​.969, P ​< ​.001). ConclusionMammography is simple, cost effective and most accurate method for breast volume estimation followed by anthropometric breast volume calculation. As size of breast and grade of breast ptosis increases the accuracy of all methods of breast volume estimation decreases.

Interference fit of cementless tibial implants and the initial mechanical environment: A micro-CT and DVC study.

During cementless total knee arthroplasty (TKA), an overlap between the resected tibia and the implant's geometry, termed interference fit, is introduced to facilitate primary stability and direct bone-implant contact. However, little is known about the actual interference achieved and the resulting mechanical response in the surrounding cancellous bone. The aim of this study was (1) to experimentally quantify the actual interference achieved for a commercially available cementless tibial implant and (2) to assess its effect on the post-impaction cancellous bone strain. Seven human cadaveric tibiae were micro-CT scanned intact (23 µm/pixel), once prepared for TKA (46 µm/pixel) and following implantation (46 µm/pixel). The actual interference across the entire bone-implant interface was quantified and, via digital volume correlation, the compressive strains of bone in contact with the implant and at increasing distance, were extracted. An inhomogeneous actual interference was found across the implant pegs and keel (median ± std dev: 0.70 ± 0.27 mm), which was lower than the intended. Limited interference (0.02 ± 0.12 mm) was found directly under the baseplate, with immediate bone-baseplate contact of 54%. The induced compressive strains were related to the actual interference within 3.14 mm from the bone-implant interface (R2 = 0.269-0.450, p < 0.001), with higher compressive strains corresponding to higher interference, but not being related to the bone volume fraction. Clinical Significance: Insight is provided into the interaction between the variability of the resection and the resulting mechanical environment. A complex relationship is apparent, whereby the actual interference accounted for up to 45% of the variation in induced compressive strain magnitude.

Quantifying the relation between aging-related trabecular bone microstructure and mechanical properties with digital volume correlation approach

Trabecular bone, a highly porous 3D network of interconnected rods and plates known as trabeculae, plays a critical role in bone strength and integrity. Osteoporosis, a condition commonly associated with aging, leads to deteriorations in bone mass and microarchitecture, manifesting as reduced bone mineral density, thinner trabecular struts, increased trabecular spacing, and a shift from trabecular plates to rods. These microstructural alterations contribute to age-related fragility fractures. To quantitatively explore the link between microstructural changes and the mechanical properties of trabecular bone, we combined mechanical testing with micro-computed tomography (micro-CT) and digital volume correlation (DVC) to measure 3D full-field deformation in trabecular bone samples from healthy and osteoporotic human cadaver vertebrae. Our multi-step mechanical testing characterized strain concentration propagation under axial compressive loading, providing new insights into how microstructural parameters influence trabecular bone’s mechanical strength. This study demonstrates that imaging-based approaches for evaluating bone mechanical strength could serve as an alternative to traditional fracture risk assessment methods, which primarily rely on bone mineral density.

Intra-Aneurysmal High-Resolution 4D MR Flow Imaging for Hemodynamic Imaging Markers in Intracranial Aneurysm Instability.

Prediction of aneurysm instability is crucial to guide treatment decisions and to select appropriate patients with unruptured intracranial aneurysms (IAs) for preventive treatment. High-resolution 4D MR flow imaging and 3D quantification of aneurysm morphology could offer insights and new imaging markers for aneurysm instability. In this cross-sectional study, we aim to identify 4D MR flow imaging markers for aneurysm instability by relating hemodynamics in the aneurysm sac to 3D morphologic proxy parameters for aneurysm instability. In 35 patients with 37 unruptured IAs, a 3T MRA and a 7T 4D MRI flow scan were performed. Five hemodynamic parameters-peak-systolic wall shear stress (WSSMAX) and time-averaged wall shear stress (WSSMEAN), oscillatory shear index (OSI), mean velocity, and velocity pulsatility index-were correlated to 6 3D morphology proxy parameters of aneurysm instability-major axis length, volume, surface area (all 3 size parameters), flatness, shape index, and curvedness-by Pearson correlation with 95% CI. Scatterplots of hemodynamic parameters that correlated with IA size (major axis length) were created. WSSMAX and WSSMEAN correlated negatively with all 3 size parameters (strongest for WSSMEAN with volume (r = -0.70, 95% CI -0.83 to -0.49) and OSI positively (strongest with major axis length [r = 0.87, 95% CI 0.76-0.93]). WSSMAX and WSSMEAN correlated positively with shape index (r = 0.61, 95% CI 0.36-0.78 and r = 0.49, 95% CI 0.20-0.70, respectively) and OSI negatively (r = -0.82, 95% CI -0.9 to -0.68). WSSMEAN and mean velocity correlated negatively with flatness (r = -0.35, 95% CI -0.61 to -0.029 and r = -0.33, 95% CI -0.59 to 0.007, respectively) and OSI positively (r = 0.54, 95% CI 0.26-0.74). Velocity pulsatility index did not show any statistically relevant correlation. Out of the 5 included hemodynamic parameters, WSSMAX, WSSMEAN, and OSI showed the strongest correlation with morphologic 3D proxy parameters of aneurysm instability. Future studies should assess these promising new imaging marker parameters for predicting aneurysm instability in longitudinal cohorts of patients with IA.

Internal shear damage evolution of CFRP laminates ranging from −100 °C to 100 °C using in-situ X-ray computed tomography

Carbon Fiber Reinforced Polymer (CFRP) composites have been widely used in aerospace due to their high specific stiffness, strength, and fatigue properties. However, the ambient temperature significantly influences CFRP's mechanical properties and damage evolution, deriving from the temperature effect on the microstructural behavior and the mesoscopic damage evolution. In this study, the temperature-dependent in-plane shear failure behavior of CFRP composites was investigated. In-situ X-ray Computed tomography (CT) tensile experiments of laminates ([45°/-45°]2s) at RT, −100 °C, and 100 °C were carried out to study the in-plane shear failure mechanisms. The 3D fracture morphology was extracted with internal damage evolution process estimated and quantified. The in-situ 3D deformation fields of critical regions were acquired using the Digital Volume Correlation (DVC) method. The effect of temperature on strain field and the correlation between the high-strain region and the fracture location were analyzed. The results revealed the temperature correlations and failure mechanisms of CFRP's mechanical characteristics and internal damage evolution process. Compared to room temperature (RT), the delamination damage area of the sample increased by 80 % at 100 °C. Meanwhile, the shear modulus of CFRP decreases by 78.4 % from −100 °C to 100 °C, and the fracture strain increases by 95 % from RT to 100 °C. The DVC results indicated a dispersion of high-strain regions at −100 °C, reflecting the brittle damage characteristics, while an extensive ductile deformation region was captured at 100 °C. Fiber-matrix debonding is the dominant failure mode of composites under shear loading, whereas significant matrix cracking was observed at −100 °C and partial fiber pullout occurred at 100 °C.

Study of Microstructural Evolution and Strain Analysis in SiOx/C Negative Electrodes Using In‐situ X‐ray Tomography and Digital Volume Correlation

AbstractIncreasing the silicon content in batteries is expected to enhance their capacity. However, its implementation comes with challenges, as silicon exhibits a large volumetric expansion. This expansion is a significant factor contributing to the decreased lifespan of these batteries. One of the critical degradation mechanisms from a mechanical perspective is the delamination of electrode structure. The cyclability of these negative electrodes is noted to be influenced by the interaction between the binder and particles during battery cycling. The heavy local strain experienced by particles in these electrodes often leads to binder failure, resulting in particle isolation, detachment, or delamination over multiple cycles. A good understanding of the local evolution of the strain is essential in advancing the mechanical modelling of the degradation mechanism and in realizing the complete potential of silicon‐based electrodes. In this work, in situ global and local strain measurements were performed by combining synchrotron tomography with Digital Volume Correlation (DVC). The measurements showed that there is significant local strain in these electrodes which can lead to delamination. In addition to this, the spatial variability of the composite electrodes was characterized by estimating the characteristic length to strain, which can be used to replicate the strain field and model the delamination.

Proposing a Methodology for Axon-Centric Analysis of IOP-Induced Mechanical Insult.

IOP-induced mechanical insult on retinal ganglion cell axons within the optic nerve head (ONH) is believed to be a key factor in axonal damage and glaucoma. However, most studies focus on tissue-level mechanical deformations, overlooking that axons are long and thin, and that their susceptibility to damage likely depends on the insult's type (e.g. stretch/compression) and orientation (longitudinal/transverse). We propose an axon-centric approach to quantify IOP-induced mechanical insult from an axon perspective. We used optical coherence tomography (OCT) scans from a healthy monkey eye along with histological images of cryosections to reconstruct the axon-occupied volume including detailed lamina cribrosa (LC) pores. Tissue-level strains were determined experimentally using digital volume correlation from OCT scans at baseline and elevated IOPs, then transformed into axonal strains using axon paths estimated by a fluid mechanics simulation. Axons in the LC and post-LC regions predominantly experienced longitudinal compression and transverse stretch, whereas those in the pre-LC and ONH rim mainly suffered longitudinal stretch and transverse compression. No clear patterns were observed for tissue-level strains. Our approach allowed discerning axonal longitudinal and transverse mechanical insults, which are likely associated with different mechanisms of axonal damage. The technique also enabled quantifying insult along individual axon paths, providing a novel link relating the retinal nerve fiber layer and the optic nerve through the LC via individual axons. This is a promising approach to establish a clearer connection between IOP-induced insult and glaucoma. Further studies should evaluate a larger cohort.

Correlation of Preoperative Hippocampal Volume Measured with Magnetic Resonance Imaging and Emergence from General Anaesthesia in Elective Neurosurgical Patients: An Observational Study.

The electrophysiological process of emergence from general anesthesia (GA) commences from deeper structures of the brain rather than the cortex. The phylogenetically old parts of the brain (hippocampus) are the first to recover during emergence. Study objectives were to evaluate and predict the effect of preoperative hippocampal volume (HV) measured using MRI with emergence from GA and delayed extubation in patients undergoing elective neurosurgical procedures. Patients aged 18-65 years of age scheduled for elective neurosurgical procedures under GA with GCS = 15 were recruited into the prospective cohort. Those who underwent excision of the hippocampus, amygdala, and temporal lobe pathology were excluded. Bilateral HVs and total brain volume were measured preoperatively using MRI brain. GA was induced by thiopentone, fentanyl, and vecuronium and maintained with sevoflurane. At the end of the surgery, sevoflurane was turned off, and a fresh gas flow of 6 L min-1 oxygen was set, allowing patients to wake up by "no contact technique." Time elapsed from turning off sevoflurane till the onset of different phases of emergence was measured. The patterns of emergence were assessed using GCS and Riker Sedation-Agitation Scale. The complete data of 125 patients of 1192 screened for recruitment were analyzed. The median time for extubation was 13 minutes (IQR 9-16). The average bilateral standardized HV had a statistically significant negative correlation with the time to extubation (r = -0.185; P = 0.039). Average of bilateral standardized HV <2097 mm3 predicts delayed extubation with a specificity: 70.7%, sensitivity: 51.2% and AUC: 0.672, CI 0.524-0.724. Standardized dominant HV <1925 mm3 also predicts delayed extubation with specificity: 78%, sensitivity: 46.4% and AUC: 0.635, CI 0.533-0.738. Neurosurgical patients with larger average HV might lead to early extubation, vocalization, and faster gaining of orientation after GA.

Thalamic Volumes and Functional Networks Linked With Self-Regulation Dysfunction in Major Depressive Disorder.

Self-regulation (SR) dysfunction is a crucial risk factor for major depressive disorder (MDD). However, neural substrates of SR linking MDD remain unclear. Sixty-eight healthy controls and 75 MDD patients were recruited to complete regulatory orientation assessments with the Regulatory Focus Questionnaire (RFQ) and Regulatory Mode Questionnaire (RMQ). Nodal intra and inter-network functional connectivity (FC) was defined as FC sum within networks of 46 thalamic subnuclei (TS) or 88 AAL brain regions, and between the two networks separately. Group-level volumetric and functional difference were compared by two sample t-tests. Pearson's correlation analysis and mediation analysis were utilized to investigate the relationship among imaging parameters and the two behaviors. Canonical correlation analysis (CCA) was conducted to explore the inter-network FC mode of TS related to behavioral subscales. Network-based Statistics with machine learning combining powerful brain imaging features was applied to predict individual behavioral subscales. MDD patients showed no group-level volumetric difference in 46 TS but represented significant correlation of TS volume and nodal FC with behavioral subscales. Specially, inter-network FC of the orbital part of the right superior frontal gyrus and the left supplementary motor area mediated the correlation between RFQ/RMQ subscales and depressive severity. Furthermore, CCA identified how the two behaviors are linked via the inter-network FC mode of TS. More crucially, thalamic functional subnetworks could predict RFQ/RMQ subscales and psychomotor retardation for MDD individuals. These findings provided neurological evidence for SR affecting depressive severity in the MDD patients and proposed potential biomarkers to identify the SR-based risk phenotype of MDD individuals.

Correlation of coronary and carotid atheroma volume in patients with severe and familial hypercholesterolemia (VOCCA-3D HF)

Abstract Background Stratifying the risk of CV event of familial hypercholesterolemia (FH) patients is not always simple, as they usually are excluded from CV disease risk estimation scores. It has become increasingly clear over the last several years that the heterogeneity in risk among patients with FH is far greater than previously appreciated. To that end, not all patients with FH will require the use of PCSK9 inhibitors. Aim We described the type of coronary artery disease (CAD) in patients with severe and familial hypercholesterolemia and without known atherosclerotic cardiovascular disease and searched for the best determinants of CAD. We searched for correlation between epicardial adipose tissue and CAD. Methods We evaluated the atherosclerosis burden with a combination of calcium score (CAC), computed tomography angiography, and the quantification of coronary atheroma volume and the analysis of the composition of the plaques, alongside with the use of ultrasonography of supra-aortic trunks with 3D quantification of atheroma volume. We also evaluated epicardial adipose tissue volume with CT. Results We analyzed 89 individuals with LDL-c &amp;gt; 190 mg/dL, with a mean age of 56,7 years. LDL-c burden was high (maximal LDL-c level across life of 2.77 g/L in mean, duration of hypercholesterolemia of 21.5 years in mean). Forty percent of the individuals had a CAC score of zero, and only one patient had non-calcified atheroma despite a CAC score of zero. Among patients with CAD, 50% had a CAC &amp;gt; 100 AU, 9% had a stenosis &amp;gt; 50%. Coronary atheroma volume amounted to a median of 50.9 mm3 in patients with CAD, representing 4% of the analyzed coronary lumen volume, and was mainly made of calcified and non-calcified fibrous plaques. At-risk plaques were not frequent (9% of low-attenuation plaques, 15.2% of positive remodeling and 2% of napkin-ring sign) in patients with CAD. Fifty percent of the individuals had no carotid plaque. Among various clinical and biological risk factors (LDL-year-score, age, blood pressure, smoking, familial history, diabetes), the carotid atheroma volume was the only variable to be independently correlated with both CAC (t=3.1, p=0.006) and coronary atheroma volume (t=4.9, p&amp;lt;0.001). Epicardial adipose tissue was not associated with CAD. Conclusion A significant part of the patients with severe and familial hypercholesterolemia has no CAD, however half of the patients with CAD have an important atherosclerosis burden, which can be well predicted by the carotid atheroma volume. Such a screening could help identify the individuals who would benefit the most from intensive cholesterol-lowering drugs.CAC categoriesType of coronary plaques

Aortic valve tissue quantification in bicuspid aortic valve stenosis

Abstract Background The relative contribution of calcific versus noncalcific aortic valve tissue volume to aortic stenosis (AS) in bicuspid aortic valve (BAV) is unclear. Purpose We aimed to assess the association of aortic valve tissue volume quantified by contrast-enhanced CT with echocardiographic AS severity, and diagnostic implication of noncalcific tissue volume for severe AS. Methods We retrospectively identified 234 patients with BAV who had echocardiographic AS severity and contrast-enhanced CT evaluation within six months and left ventricular ejection ≥50%, including 150 severe AS (aortic valve area≤1 cm2 or indexed valve area≤0.6cm2/m2 plus mean grdient≥40mmHg or peak velocity≥4 m/s), 84 nonsevere AS (61 with at least mild AS: peak veloicty≥2.0 m/s plus mean gradient ≥10mmHg, and 23 with normal aortic valve function). Contrast-enhanced CT aortic valve calcific volume and noncalcific (fibrosis) volume were quantified using patient-specific Hounsfield unit thresholds (Figure). Noncontrast CT aortic valve calcium score (AVCscore) was quantified by the Agaston method. CT measurements were indexed to echocardiographic aortic valve annulus area and square-root transformed for the analysis. Results Of 234 patients, the mean age was 64±11 years, and 64% were men. There were positive correlations of indexed calcific volume, noncalcific volume, and inverse correlations of percentages of noncalcific volume (noncalcific volume divided by the sum of calcific and noncalcific volume) with peak velocity and mean gradient (|r|=0.30 to 0.68). Among 150 patients with severe AS, 28 had an AVCscore below the severe AVC threshold (1200 AU in women and 2000 AU in men) while exhibited a higher percentage of noncalcific volume compared to 122 patients with severe AVCscore (67±15% vs. 39±15%, p&amp;lt;0.001). After excluding 122 patients with severe AS and severe AVCscore, the indexed noncalcific volume was associated with severe AS (β±S.E: 0.18±0.07, p=0.005) with an area under the curve of 0.71; in contrast, AVCscore was not (p=0.55). Conclusion Both calcific and noncalcific aortic valve tissue volume contribute to AS severity in patients with BAV. Notably, noncalcific tissue volume is a key factor in determining severe AS in patients without severe AVCscore, suggesting its potential diagnostic value.Figure

Placental volume at gestational week 27 and subsequent fetal growth: An observational study

ObjectivesTo study if placental volume and placental to fetal ratio at gestational week (GW) 27 correlate with subsequent fetal growth. We also investigated whether the 1/3 smallest and 1/3 largest fetuses have different growth potential depending on placental volume. MethodsPlacental and fetal volume was measured by magnetic resonance imaging (MRI) at GW 27 and 37 in 86 singleton pregnancies. Placental to fetal ratio was calculated as placental volume/fetal volume. Growth was calculated as [(fetal volume at GW 37 – fetal volume at GW 27)/number of days between the MRI examinations]. To explore whether a higher placental volume affected growth of small and large fetuses differently, we performed separate analyses of the 1/3 smallest and 1/3 largest fetuses with placental volume under and above the median at GW 27. ResultsWe found a positive correlation of both placental volume and placental to fetal ratio at GW 27 with average growth velocity, r = 0.51 (p < 0.001) and r = 0.33 (p = 0.002) respectively. The correlation between fetal volume at GW 27 and average growth velocity was r = 0.48 (p < 0.001). The small fetuses had significantly lower average growth velocity if the placental volume was low compared to if the placental volume was high, 22 (SD 3) cm3/day versus 25 (SD 3) cm3/day, p = 0.02. Among the large fetuses, placental volume did not significantly affect growth. ConclusionsPlacental volume and placental to fetal ratio at GW 27 were positively correlated with subsequent fetal growth. Possibly, placental size is an indicator of fetal growth potential, especially among small fetuses.

Enhanced strain mapping Unveils internal deformation dynamics in Silicon-based lithium-ion batteries during electrochemical cycling

Silicon-based anodes have emerged as a promising advancement in lithium-ion battery technology, offering significantly higher lithium storage capacities than traditional graphite. However, the volumetric expansion of silicon-anodes can swell by up to 300 % during lithiation-presents serious challenges to their structural integrity and electrochemical stability. This study investigates the internal structural dynamics of silicon anodes during lithiation and delithiation cycles. A novel cell design for a 18,650 cylindrical cell featuring micro-sized internal speckles within the silicon anode is presented. This design improves the simulation of electrochemical conditions and allows for precise displacement tracking, mitigating impacts on capacity and cycle performance while enhancing Digital Volume Correlation (DVC) analysis. The research prioritizes reducing scan time and radiation exposure in micro-CT assessments of Li-ion cells, and improves the accuracy of internal strain mapping via DVC. Displacement fields over three charging and discharging cycles are documented. Notably, uneven volumetric changes are observed, with local displacements reaching up to 35 µm in areas smaller than 2.5 mm in radius, which contracted during charging and expanded during discharging. This protocol offers insights into the relationship between electrode mechanics and cell performance, promoting non-destructive evaluations of internal structures in commercial cells.

In-situ experimental characterization and numerical investigation of the crack initiation of SMC composite under uniaxial tension

This paper explored the crack initiation of sheet molding compound (SMC) composite under uniaxial tensile loads by integrating in-situ experimental characterization and subsequent numerical analysis. Firstly, a synchrotron micro-X-ray computed tomography was utilized to character the morphology and evolution of the microstructure and fracture features of the SMC sample with different loading conditions. Meanwhile, the digital volume correlation technology was employed to determine the internal three-dimensional deformation. Then, a numerical analysis was conducted to describe the relationships among the microstructure, deformation distribution, and position of the crack initiation. Finally, a predictive model was developed based on the internal microstructure and the deformation distribution and then utilized to predict the location and sequence of crack initiation. The good agreement between the predicted results with the experimental ones reveals the feasibility of the proposed model in exploring the fracture behaviors of carbon fiber reinforced polymer composites with complex internal microstructure.

Assessing hydrodynamic impacts of tidal range energy impoundments in UK coastal waters

Tidal range energy comprises a vast theoretical resource of 9,220 TWh per year, globally, with advantageous characteristics of predictability, generation flexibility and reliability. Approximately 13% of this resource lies within the United Kingdom’s (UK) coastal waters, where it could supply up to 12% of annual electricity demand. Tidal range energy conversion traditionally involves constructing and operating large-scale coastal or offshore impoundments (O10-100 km2), which will redefine near and far-field water levels and flow patterns. The relationship between the scale of the impoundment area and hydrodynamic impact has not been investigated for UK sites. To address this, we develop a two-dimensional (depth-averaged) TELEMAC model of the Irish Sea, and simulate six scenarios involving tidal range schemes of increasing basin area, from 25 to 150 km2, located on the North Wales coast in an open coastal basin setting. Results indicate that far-field (30−150 km) changes to the amplitude of the semi-diurnal (M2) tidal constituent exhibit a linear relationship with impoundment area and volume (correlation coefficient R=0.95 and R=0.96, respectively). The largest impoundment (150 km2) caused far-field changes in maximum surface elevation (2<ηmax<3 cm); near-field surface elevation was reduced (ηmax>3 cm).

Optimisation and Application of Entropy Weight Method-TOPSIS Model for Ranking the Importance of Urban Express Sites

With the rapid development of e-commerce, the importance of express delivery network in the modern logistics system is becoming more and more prominent. In order to scientifically assess the importance of urban express sites, this paper proposes a multi-objective decision-making method based on entropy weight method and TOPSIS model. The entropy weight method is objectively assigned by analysing the data dispersion of indicators, and the TOPSIS model is used to rank urban sites by calculating their distance from ideal and negative ideal solutions. In this paper, we firstly processed the data with multiple interpolation to ensure its accuracy, and selected four key indicators, namely, shipping volume, receiving volume, correlation and growth trend of express delivery volume. The results show that the entropy weight method-TOPSIS model can effectively assess the importance of each city site, provide a scientific basis for optimising the express delivery network, and have a wide range of application potential.