An unsteady analysis of two-phase binding of drug in an asymmetric stenosed vessel

In this paper, we investigate endovascular delivery to get a step ahead of the pharmacological limitations it has due to the complexity of dealing with a patient-specific vessel through a mathematical model. We divide the domain of computation into four sub-domains: the lumen, the lumen-tissue interface, the upper tissue and the lower tissue which are extracted from an asymmetric atherosclerotic image derived by the intravascular ultrasound (IVUS) technique. The injected drug at the luminal inlet is transported with the streaming blood which is considered Newtonian. An irreversible uptake kinetics of the injected drug at the lumen-tissue interface from the luminal side to the tissue domains is assumed. Subsequently, the drug is dispersed within the tissue followed by its retention in the extracellular matrix (ECM) and by receptor-mediated binding. The Marker and Cell (MAC) method has been leveraged to get a quantitative insight into the model considered. The effect of the wall absorption parameter on the concentration of all drug forms (free as well as two-phase bound) has been thoroughly investigated, and some other important factors, such as the averaged concentration, the tissue content, the fractional effect, the concentration variance and the effectiveness of drug have been graphically analyzed to gain a clear understanding of endovascular delivery. The simulated results predict that with increasing values of the absorption parameter, the averaged concentrations of all drug forms do decrease. An early saturation of binding sites takes place for smaller values of the absorption parameter, and also rapid saturation of ECM binding sites occurs as compared to receptor binding sites. Results also predict the influence of surface roughness as well as asymmetry of the domain about the centerline on the distribution and retention of drug. A thorough sensitivity analysis has been carried out to determine the influence of some parameters involved.

A proof of concept study for machine learning application to stenosis detection

This proof of concept (PoC) assesses the ability of machine learning (ML) classifiers to predict the presence of a stenosis in a three vessel arterial system consisting of the abdominal aorta bifurcating into the two common iliacs. A virtual patient database (VPD) is created using one-dimensional pulse wave propagation model of haemodynamics. Four different machine learning (ML) methods are used to train and test a series of classifiers—both binary and multiclass—to distinguish between healthy and unhealthy virtual patients (VPs) using different combinations of pressure and flow-rate measurements. It is found that the ML classifiers achieve specificities larger than 80% and sensitivities ranging from 50 to 75%. The most balanced classifier also achieves an area under the receiver operative characteristic curve of 0.75, outperforming approximately 20 methods used in clinical practice, and thus placing the method as moderately accurate. Other important observations from this study are that (i) few measurements can provide similar classification accuracies compared to the case when more/all the measurements are used; (ii) some measurements are more informative than others for classification; and (iii) a modification of standard methods can result in detection of not only the presence of stenosis, but also the stenosed vessel.

Endovascular Treatment of Intracranial Atherosclerotic Stenosis

Background Intracranial atherosclerotic stenosis (ICAS) causes 5 – 10 % of all ischemic strokes in the European population. Indication for endovascular treatment is a special challenge and the selection of material as well as interventional techniques essentially differs from the treatment of extracranial stenoses. According to recent studies patient selection became evidence based; however the method should not be abandoned. New technical approaches can contribute to avoid complications. Method We performed a review of the literature with regard to conservative as well as endovascular treatment of ICAS. Different technical approaches are discussed and strategies to avoid complications are stressed. Based on the treatment indication, the positions of the authorities and the professional societies are taken into account. Results and Conclusion A single self-expanding stent is approved for the treatment of ICAS. Balloon mounted and other self-expanding Stents are available for off-label use. Anatomical conditions and features of the stenosis determine the choice of material. Distal wire perforations causing intracranial bleedings may occur during exchange manoeuvres and constitute one of the technical complications in the treatment of ICAS. In contrast, there is hardly any efficient way to eliminate the risk of ischemia in the territory of perforating arteries arising from the intracranial posterior circulation and the middle cerebral artery. The results of the randomized prospective trials strengthen the conservative treatment of ICAS. Endovascular treatment should not be withheld from patients with either hemodynamic stenosis, recurrent ischemic events under best medical treatment in the territory of the stenosed vessel or acute occlusions of a stenosis. Key Points: Citation Format

An Ultrasound Simulation Model for the Pulsatile Blood Flow Modulated by the Motion of Stenosed Vessel Wall

This paper presents an ultrasound simulation model for pulsatile blood flow, modulated by the motion of a stenosed vessel wall. It aims at generating more realistic ultrasonic signals to provide an environment for evaluating ultrasound signal processing and imaging and a framework for investigating the behaviors of blood flow field modulated by wall motion. This model takes into account fluid-structure interaction, blood pulsatility, stenosis of the vessel, and arterial wall movement caused by surrounding tissue’s motion. The axial and radial velocity distributions of blood and the displacement of vessel wall are calculated by solving coupled Navier-Stokes and wall equations. With these obtained values, we made several different phantoms by treating blood and the vessel wall as a group of point scatterers. Then, ultrasound echoed signals from oscillating wall and blood in the axisymmetric stenotic-carotid arteries were computed by ultrasound simulation software, Field II. The results show better consistency with corresponding theoretical values and clinical data and reflect the influence of wall movement on the flow field. It can serve as an effective tool not only for investigating the behavior of blood flow field modulated by wall motion but also for quantitative or qualitative evaluation of new ultrasound imaging technology and estimation method of blood velocity.

Revascularisatio az aortában, a veseartériákban és az alsó végtagok artériás rendszerében

Revascularisation aims to create a patent lumen in an acutely or chronically occluded or stenosed vessel. Interventional radiology has developed and used minimally invasive methods for decades concurring surgical methods and medical therapy. Innovative fields in healthcare may be handicapped since revolutionary solutions usually gain wide acceptance slowly and the results of randomized controlled trials are reported late. At present endovascular recanalization, dilatation and stent placement have achieved a well-established role in the treatment of stenosis or occlusion of the aorta, and renal and peripheral arteries. Orv. Hetil., 2015, 156(17), 665–673.