A Perspective Review on Numerical Simulations of Hemodynamics in Aortic Dissection

Aortic dissection, characterized by separation of the layers of the aortic wall, poses a significant challenge for clinicians. While type A aortic dissection patients are normally managed using surgical treatment, optimal treatment strategy for type B aortic dissection remains controversial and requires further evaluation. Although aortic diameter measured by CT angiography has been clinically used as a guideline to predict dilation in aortic dissection, hemodynamic parameters (e.g., pressure and wall shear stress), geometrical factors, and composition of the aorta wall are known to substantially affect disease progression. Due to the limitations of cardiac imaging modalities, numerical simulations have been widely used for the prediction of disease progression and therapeutic outcomes, by providing detailed insights into the hemodynamics. This paper presents a comprehensive review of the existing numerical models developed to investigate reasons behind tear initiation and progression, as well as the effectiveness of various treatment strategies, particularly the stent graft treatment

Comparison of diametric and volumetric changes in Stanford type B aortic dissection patients in assessing aortic remodeling post-stent graft treatment

Background: The study aims to analyze the correlation between the maximal diameter (both axial and orthogonal) and volume changes in the true (TL) and false lumens (FL) after stent-grafting for Stanford type B aortic dissection. Method: Computed tomography angiography was performed on 13 type B aortic dissection patients before and after procedure, and at 6 and 12 months follow-up. The lumens were divided into three regions: the stented area (Region 1), distal to the stent graft to the celiac artery (Region 2), and between the celiac artery and the iliac bifurcation (Region 3). Changes in aortic morphology were quantified by the increase or decrease of diametric and volumetric percentages from baseline measurements. Results: At Region 1, the TL diameter and volume increased (pre-treatment: volume =51.4±41.9 mL, maximal axial diameter =22.4±6.8 mm, maximal orthogonal diameter =21.6±7.2 mm; follow-up: volume =130.7±69.2 mL, maximal axial diameter =40.1±8.1 mm, maximal orthogonal diameter =31.9+2.6 mm, P<0.05 for all comparisons), while FL decreased (pre-treatment: volume =129.6±150.5 mL; maximal axial diameter =43.0±15.8 mm; maximal orthogonal diameter =28.3±12.6 mm; follow-up: volume =66.6±95.0 mL, maximal axial diameter =24.5±19.9 mm, maximal orthogonal diameter =16.9±13.7, P<0.05 for all comparisons). Due to the uniformity in size throughout the vessel, high concordance was observed between diametric and volumetric measurements in the stented region with 93% and 92% between maximal axial diameter and volume for the true/false lumens, and 90% and 92% between maximal orthogonal diameter and volume for the true/false lumens. Large discrepancies were observed between the different measurement methods at regions distal to the stent graft, with up to 46% differences between maximal orthogonal diameter and volume. Conclusions: Volume measurement was shown to be a much more sensitive indicator in identifying lumen expansion/shrinkage at the distal stented region

Development of brain tissue swelling predictive tools for ischaemic stroke patient post-treatment

Ischaemic stroke is one of the causes of death worldwide. Treatments such as thrombolysis and catheterisation must be given within 3 hours after stroke onset, in which treatments beyond this time may pose risk of brain tissue swelling. Thus, a prediction system must be made to determine the suitability of a stroke treatment to avoid the risk of failure. In this report, a mathematical model based on poroelastic theory and asymptotic expansion homogenization has been developed to study the formation of brain tissue swelling after ischaemia-reperfusion treatment. Firstly, the mathematical model of brain tissue swelling after ischaemia-reperfusion treatment is investigated using an ideal 2D brain geometry. The objective here is to observe the effect of infarct size and location towards the formation and severity of brain herniation, which will form due to brain tissue swelling. However, this model assumed that the blood pressure is constant and homogeneous throughout the brain, while in fact, the blood capillaries vary in sizes and shapes. Therefore, asymptotic expansion homogenization technique is applied to allow for the inclusion of capillaries sizes into the initial model. This method transforms the initial model into two types of equations: (1) macroscale governing equations; and (2) microscale cell problems. In order to solve for the macroscale governing equations, the microscale cell problems must first be solved on a brain tissue geometry to calculate the effective parametric tensors, which later be used in the macroscale governing equations. Lastly, the mathematical model is solved in a realistic brain geometry to evcaluate the effect of different mechanical properties of the brain towards brain tissue swelling formation

Harga Diri Pada Remaja Menengah Putri Di SMA Negri 15 Kota Semarang

Self-esteem is a individual appraisal, feeling, view to her self or something related to her self that is expressed to the dimension Significance, Power, Competence,Virtue. This studywas aimedtoidentifythe relationshipbetween Self-Esteem anddietary behaviorin femaleadolescent (age 15-17 years) inSMAN 15 Semarang.Design used in this study are correlational descriptive with cross sectional design. Sampling was stratified random sampling method of 170 respondents and using chi-square analysis. The results of the study note that as many as 113 respondents (66.9%) had high self esteem and 57 respondents (33.1) has a low self esteem.Foryoung womenwhowant Togo on a dietshould pay attention tonutrition, health andnurses canplay a roleasan educator andcounselo

The role of infarct transmural extent in infarct extension: a computational study

Infarct extension, a process involving progressive extension of the infarct zone (IZ) into the normally perfused border zone (BZ), leads to continuous degradation of the myocardial function and adverse remodelling. Despite carrying a high risk of mortality, detailed understanding of the mechanisms leading to BZ hypoxia and infarct extension remains unexplored. In the present study, we developed a 3D truncated ellipsoidal left ventricular model incorporating realistic electromechanical properties and fibre orientation to examine the mechanical interaction among the remote, infarct and BZs in the presence of varying infarct transmural extent (TME). Localized highly abnormal systolic fibre stress was observed at the BZ, owing to the simultaneous presence of moderately increased stiffness and fibre strain at this region, caused by the mechanical tethering effect imposed by the overstretched IZ. Our simulations also demonstrated the greatest tethering effect and stress in BZ regions with fibre direction tangential to the BZ–remote zone boundary. This can be explained by the lower stiffness in the cross-fibre direction, which gave rise to a greater stretching of the IZ in this direction. The average fibre strain of the IZ, as well as the maximum stress in the sub-endocardial layer, increased steeply from 10% to 50% infarct TME, and slower thereafter. Based on our stress–strain loop analysis, we found impairment in the myocardial energy efficiency and elevated energy expenditure with increasing infarct TME, which we believe to place the BZ at further risk of hypoxia

Left ventricular flow propagation velocity measurement: is it cast in stone?

This study aims to investigate the measurement of left ventricular flow propagation velocity, V, using phase contrast magnetic resonance imaging and to assess the discrepancies resulting from inflow jet direction and individual left ventricular size. Three V measuring techniques, namely non-adaptive (NA), adaptive positions (AP) and adaptive vectors (AV) method, were suggested and compared. We performed the comparison on nine healthy volunteers and nine post-infarct patients at four measurement positions, respectively, at one-third, one-half, two-thirds and the conventional 4\ua0cm distances from the mitral valve leaflet into the left ventricle. We found that the V measurement was affected by both the inflow jet direction and measurement positions. Both NA and AP methods overestimated V, especially in dilated left ventricles, while the AV method showed the strongest correlation with the isovolumic relaxation myocardial strain rate (r\ua0=\ua00.53, p\ua

The impact of the number of tears in patient-specific Stanford type B aortic dissecting aneurysm: CFD simulation

It is believed that the progression of Stanford type B aortic dissection is closely associated with vascular geometry and hemodynamic parameters. The hemodynamic differences owing to the presence of greater than two tears have not been explored. The focus of the present study is to investigate the impact of an additional re-entry tear on the flow, pressure and wall shear stress distribution in the dissected aorta. A 3D aorta model with one entry and one re-entry tear was generated from computed tomography (CT) angiographic images of a patient with Stanford Type B aortic dissection. To investigate the hemodynamic effect of more than two tear locations, an additional circular re-entry tear was added 24mm above the original re-entry tear. Our simulation results showed that the presence of an additional re-entry tear provided an extra return path for blood back to the true lumen during systole, and an extra outflow path into the false lumen during diastole. The presence of this additional path led to a decrease in the false lumen pressure, particularly at the distal region. Meanwhile, the presence of this additional tear causes no significant difference on the time average wall shear stress (TAWSS) distribution except at regions adjacent to re-entry tear 2. Moderate and concentrated TAWSS was observed at the bottom region of this additional tear which may lead to further extension of the tear distally

Biomechanical analysis of distal stent graft induced new entry (SINE) formation in aortic dissection patient

This is the first study to investigate the effect of material models and properties on stress and strain distributions in Type IIIb aortic dissection patient with distal stent graft induced new entry. Both elastic and hyperelastic models consistently showed a reduction in all stress and strain parameters (i.e. 5.4% - 59.1%) at neighboring region distal to the stent-wall composite when the disease progressed from acute to chronic. We found that the maximum shear stress (SS) presents a potential inducer for SINE formation, while the maximum shear elastic strain (SE) could be an indicator for the location of such formation

Treatment of chronic back pain using indirect vibroacoustic therapy: A pilot study

BACKGROUND: Low frequency sound wave stimulation therapy has become increasingly popular in the rehabilitation fields,due to its ease, less fatiguing and time efficient application.OBJECTIVE: This 12-week pilot study examines the efficacy of applying low frequency sound wave stimulation (between16-160 Hz) through both hands and feet on relieving pain and improving functional ability in patients with chronic back pain.METHODS: Twenty-three participants with chronic shoulder (eleven participants) or low back pain (twelve participants) underwent a 12-week vibration therapy program of three sessions per week. A low frequency sound wave device comprising fourpiezoelectric vibration-type tactile tranducers enclosed in separate 5-cm diameter circular plates, which generate sinusoidal vibratory stimuli at a frequency of 16-160 Hz, was used in this study. Primary outcome measure was pain sensation measuredusing the Visual Analogue Scale (P-VAS). The secondary outcome measures were pain-related disability measured using thepain disability index (PDI) and quality of life measured using the SF-12.RESULTS: At week 12, significant reductions in pain sensation and pain-related disability were observed, with mean reductionsof 3.5 points in P-VAS and 13.5 points in the PDI scores. Sixty-five percent of the participants had a reduction of at least 3 pointson the P-VAS score, while 52% participants showed a decrease of at least 10 points in the PDI score. Significant improvementwas observed in the SF-12 physical composite score but not the mental composite score.CONCLUSIONS: The preliminary findings showed that passive application of low frequency sound wave stimulation therapythrough both hands and feet was effective in alleviating pain and improving functional ability in patients with chronic back pain

Classification of electrocardiogram and auscultatory blood pressure signals using machine learning models

In this paper, two real-world medical classification problems using electrocardiogram (ECG) and auscultatory blood pressure (Korotkoff) signals are examined. A total of nine machine learning models are applied to perform classification of the medical data sets. A number of useful performance metrics which include accuracy, sensitivity, specificity, as well as the area under the receiver operating characteristic curve are computed. In addition to the original data sets, noisy data sets are generated to evaluate the robustness of the classifiers against noise. The 10-fold cross validation method is used to compute the performance statistics, in order to ensure statistically reliable results pertaining to classification of the ECG and Korotkoff signals are produced. The outcomes indicate that while logistic regression models perform the best with the original data set, ensemble machine learning models achieve good accuracy rates with noisy data sets