Volumetric Blood Flow Rate Research Articles

Evaluation of the effect of viscosity on blood flow using viscosity models

The study of blood hemodynamics and rheological properties, particularly blood viscosity, is essential for understanding and treating certain cardiovascular conditions. Blood is a non-Newtonian fluid, meaning its viscosity varies with shear rate, a behavior driven by the aggregation and deformation of red blood cells (RBCs). Accurate modeling of blood viscosity is therefore critical for simulating blood flow in both physiological and pathological states. In this work, various viscosity models were assessed to identify the most suitable that represents the blood’s behavior in relation to shear rate. Although the Newtonian model is simple, it fails to capture the non-Newtonian characteristics of blood, particularly at varying shear rates. In comparison, the Power Law, Walburn-Schneck, and Carreau-Yasuda models offer more detailed and complex approaches to modeling blood viscosity. The Effect of blood viscosity on the overall blood flow was evaluated based on the four viscosity models. The work was carried out in a MATLAB Simulation Environment. The Volumetric blood flow rate was evaluated from the Poiseuille’s equation using three viscosity models whose values were defined by shear rates ranging from (217.5 – 226.5)s−1 . The percentage change in the blood volume resulting from changes in the viscosity was examined for each model. The two viscosity models (Power and Carreau models) concurrently reported equal percentage change of blood flux variation with the corresponding variation of the viscosity due to change in shear rate. This shows that any of the two models can be used to study the variation of blood flow to the viscosity with respect to cardiovascular complications.

Transit-time flowmetry measurement features of coronary bypass grafts after multiple percutaneous coronary interventions

The functionality of coronary bypass grafts after surgical myocardial revascularization in patients with coronary heart disease directly depends on the state of the target coronary arteries. In the presence of widespread and diff use atherosclerotic lesions or microcirculatory dysfunctions, a high frequency of coronary bypass dysfunctions is noted in the near future. In some cases, shunt dysfunction can lead to severe hemodynamic instability, accompanied by acute circulatory disorders.Aim: To assess the function of coronary bypass grafts during myocardial revascularization using the method of ultrasonic flowmetry in patients with and without a history of multiple percutaneous coronary interventions (PCI).Material and methods. The retrospective study included 47 patients who underwent coronary artery bypass surgery. A total of 145 coronary bypass grafts were performed. All patients were divided into 2 groups. Group 1 (PCI group) included patients after multiple previous PCI (n = 25; 74 coronary bypass grafts), group 2 (without PCI) included patients without previous PCI (n = 22; 71 coronary bypass grafts). All patients underwent intraoperative ultrasonic flowmetry of coronary bypass grafts using the VeriQ system (Medistim, Norway).Results. When analyzing the status of coronary bypass grafts in patients after multiple PCI, a significantly low mean volumetric blood flow rate was noted (29.5 ± 8.3 ml/min and 48.2 ± 11.6 ml/min, respectively, p = 0.0001) and lower diastolic filling (55.2 ± 8.2% and 71.9 ± 7.1%, p = 0.0001). Also in the group of patients after multiple PCI, there were 2 (2.7%) cases of revision of the distal anastomosis due to a high pulsatile index and low volumetric blood flow velocity. However, no such events were noted in the group without PCI.Conclusions. Previous percutaneous coronary interventions are compromising factors for the state of the coronary bed, which reduces the functional status of coronary bypass grafts and may increase the perioperative risk of surgical myocardial revascularization.

MRI-based parameter inference for cerebral perfusion modelling in health and ischaemic stroke

Cerebral perfusion modelling is a promising tool to predict the impact of acute ischaemic stroke treatments on the spatial distribution of cerebral blood flow (CBF) in the human brain. To estimate treatment efficacy based on CBF, perfusion simulations need to become suitable for group-level investigations and thus account for physiological variability between individuals. However, computational perfusion modelling to date has been restricted to a few patient-specific cases. This study set out to establish automated parameter inference for perfusion modelling based on neuroimaging data and thus enable CBF simulations of groups. Magnetic resonance imaging (MRI) data from 75 healthy senior adults were utilised. Brain geometries were computed from healthy reference subjects’ T1-weighted MRI. Haemodynamic model parameters were determined from spatial CBF maps measured by arterial spin labelling (ASL) perfusion MRI. Thereafter, perfusion simulations were conducted in 75 healthy cases followed by 150 acute ischaemic stroke cases representing an occlusion and CBF cessation in the left and right middle cerebral arteries. The anatomical fitness of the brain geometries was evaluated by comparing the simulated grey (GM) and white matter (WM) volumes to measurements in healthy reference subjects. Strong positive correlations were found in both tissue types (GM: Pearson’s r 0.74, P<0.001; WM: Pearson’s r 0.84, P<0.001). Haemodynamic parameter tuning was verified by comparing the total volumetric blood flow rate to the brain in healthy reference subjects and simulations (Pearson’s r 0.89, P<0.001). In acute ischaemic stroke cases, the simulated infarct volume using a perfusion-based estimate was 197±25 ml. Computational predictions were in agreement with anatomical and haemodynamic values from the literature concerning T1-weighted, T2-weighted, and phase-contrast MRI measurements in healthy scenarios and acute ischaemic stroke cases. The acute stroke simulations did not capture small infarcts (left tail of the distribution), which could be explained by neglected compensatory mechanisms, e.g. collaterals. The proposed parameter inference method provides a foundation for group-level CBF simulations and for in silico clinical stroke trials which could assist in medical device and drug development.

RELATIONSHIP BETWEEN HAEMOSTATIC AND MACRO-MICROHEMODYNAMIC PARAMETERS IN RATS UNDER EXPERIMENTAL EXPOSURE TO CADMIUM. MEANS OF PREVENTION

In experiments on Wistar rats, it was shown that the prophylactic administration of melatonin at a dose of 5 mg/kg helps to reduce the manifestations of toxic coagulopathy, preventing the development of micro- and macrohemodynamic disorders in rats with chronic cadmium intoxication. Correlations between changes in indicators of the hemostasis system with the restoration of linear and volumetric blood flow rates and a decrease in the Pourcelot peripheral resistive index were revealed. These effects correlated with a decrease in the level of lipid peroxidation products and the activity of antioxidant enzymes in the blood under the influence of melatonin. The results of the experiments suggest further studies on using melatonin for the prevention and correction of the procoagulative and pathocirculatory effects of cadmium.

Age-related changes of rats portal vein hemodynamics and morphometry

Introduction. Age-related changes of blood flow parameters and hepatic portal vein wall morphometry are one of the topical and insufficiently investigated issues of liver hemodynamics. The aim was to study changes of portal hemodynamics and to analyze the portal vein wall morphometry of rats at different age periods. Materials and methods. 60 mongrel rats of both sexes weighing 120–350 g were divided into three age groups. The first group included 20 rats aged 1 month, the second – 20 rats aged 6–12 months and the third – 20 rats aged more than 18–24 months. The qualitative and quantitative portal vein hemodynamics parameters were obtained by ultrasound scanners under zoletil-xylazine anesthesia. Morphometric examination of the portal vein was performed. Digital data were processed by methods of variational statistics. Results. The diameter of the portal vein in groups II and III was greater than the corresponding parameter in group I (R = – 0.40 and R = 0.64, respectively). The time-averaged average blood flow rate in the II age group increased by 9.11 % compared to the I group, decreased by 10.43 % in the III group (the differences are statistically unreliable). The volumetric blood flow rate increased moderately in age groups II and III compared to group I (by 13.07 and 11.13 %, respectively; the difference is statistically unreliable). The ratio of the volumetric blood flow rate to the weight of the animal in the II age group increased by 3.85 % compared to the I group, decreased by 11.54 % in the III group (the differences are statistically unreliable). Since the mass of animals significantly increased with age, the portal vein volumetric blood flow of old animals is likely to be decreased. Mature and old rats demonstrated significant decrease of the muscle membrane thickness, the Kernogan index and the width of the collagen layer. Conclusion. Age-related changes of rats portal hemodynamics resulted in a slight reliable increase of portal vein diameter and its cross-sectional area. Linear and volumetric parameters of blood flow were found not to have statistically reliable dependence on the age and weight of animals. Morphometric parameters of the rats portal vein wall were revealed to have pronounced changes in different age groups. The aging of the portal vein wall of elder rats consisted in a significant decrease of the muscle membrane thickness, the Kernogan index and the width of the collagen layer.

ULTRASOUND DIAGNOSIS OF LOWER PELVIC VARICOSITIES IN WOMEN WITH PRIMARY VALVULAR INSUFFICIENCY

The aim of the research was to study the opportunities of ultrasound diagnostics and to identify ultrasound criteria for diagnostic parameters of pelvic veins in women with pelvic varicosities against the background of primary valvular insufficiency. The study included 102 women with pelvic congestion syndrome, the average age was 35.77±7.27 years. Ultrasound examination of pelvic veins was carried out on the basis of the developed and patented technique of ultrasound examination of pelvic veins in women. The median, the mean, minimum, maximum values, standard deviation of ultrasonic parameters were determined in the general sample; grouping/classification tasks were solved using cluster analysis methods. In the general sample, when comparing the results of the study, it was revealed that the average values of ultrasound parameters on the left were greater than those on the right. The greatest differences in the average values of the ovarian veins on both sides were in volumetric and maximum blood flow rates. Sensitivity was 95%, specificity – 90%. Ultrasound examination of pelvic veins makes it possible to evaluate the hemodynamics and anatomical features of the veins' structure to reduce the recurrence of varicose veins of the pelvic varicose disease and lower extremities varicose vein disease.

Physiotherapy impact on the periodontal microcirculation during mild chronic generalized periodontitis treatment

Relevance. The high incidence of chronic generalized periodontitis indicates the relevance of this disease and its social significance. Treatment of chronic generalized periodontitis requires an integrated approach and should include conservative and surgical methods and elements of dental system rehabilitation. Physiotherapy procedures, which affect tissue blood supply and increase local immunity, form an important component of the complex treatment of chronic generalized periodontitis. Choosing the most effective physiotherapy method is essential for the complex treatment of chronic generalized periodontitis.Materials and methods. The study examined and treated 104 patients with mild chronic generalized periodontitis. All patients agreed to participate in the study and signed informed voluntary consent. The treatment type determined the allocation of three groups (group 1 – periodontium exposure to d’Arsonval currents, group 2 – the combination of physiotherapy procedures, and the control group – rinsing with antiseptics). The study consisted of the following stages: initial examination, professional controlled oral hygiene, group-dependent course of treatment, follow-up immediately after the treatment, after 3 and 6 months. Each stage included an interview, clinical examination and evaluation of periodontal microcirculation using Doppler ultraso und.Results. The study revealed a positive effect of physiotherapy procedures on the periodontal microcirculation, i.e., a significant increase in linear and volumetric blood flow rates (linear blood flow velocity – 0.411 (0.393: 0.431; 0.315-0.436) cm/s; volumetric blood flow velocity – 0.024 (0.016: 0.021; 0.015-0.019) cm3/s compared with the data of the control group patients (linear blood flow velocity – 0.305 (0.291: 0.313; 0.203-0.326) cm/s; volumetric blood flow velocity – 0.012 (0.011: 0.015; 0.007-0.090) cm3/s.Conclusion. Physiotherapy procedures in chronic generalized periodontitis treatment allowed the achievement of not only the significant immediate result but also a prolonged re mission period.

Rats caudal vena cava hemodynamics features in different age periods

Introduction. Liver hemodynamics age-related features studying is promising area of portal and caudal vena cava and hepsatic artery of rats hemodynamics exploration.Aim was to determine qualitative and quantitative hemodynamic paremeters of the laboratory rats caudal vena cava of different genders and ages.Materials and methods. The study was conducted on 60 mongrel rats (males and females, 120–170 g) divided into three age groups. The first group included 20 rats aged 1 month, the second – 20 rats aged 6–12 months and the third – 20 rats aged more than 18–24 months. The study of caudal vena cava qualitative and quantitative hemodynamic parameters was performed by ultrasound scanners. Animals were anaesthesized by zoletil-xylazine. Digital data were processed by methods of variational statistics.Results. All animals showed the antegrade caudal vena cava blood flow. The spectrum of blood flow differed in the number, shape of teeth and phase. The most animals showed three-phase spectrum not depend on the animals gender and age. The diameter of the vein did not depend on the gender. In the I and II age groups, the predominance of the volumetric blood flow rate in the CPV in males compared with females was within 10 % (R=0.98 and R=0.37, respectively), in the III age group, the relationship was not statistically significant (R=–0.03). The diameter and maximum systolic blood flow velocity in the caudal vena cava increased slightly (within 3 %) with the age of the animals (R=0.64 and R=0.43, respectively). Volumetric blood flow rate decreased within 4 % with increasing age (R=0.42).Conclusion. The spectrum of rats caudal vena cava blood flow differed in the number, shape of waves and phase. In most animals it was three-phase. In all animals the direction of blood flow was antegrade. The phase of the spectrum was not affected by the animals gender and age. There was no statistically significant dependence of the diameter and linear velocity of blood flow on the gender. The volumetric blood flow rate was slightly higher in males (within 10 %) compared to females. The diameter and the maximum systolic blood flow velocity increased slightly (within 3 %) with the age of the animals. The indicator of the volumetric blood flow rate decreased within 4 % with increasing age.

AGE-RELATED FEATURES OF PORTAL HEMODYNAMICS IN RATS

Purpose. To determine the indicators of portal hemodynamics in laboratory rats of different genders and ages based on the features of ultrasound scanning of the portal vein.&#x0D; Materials and methods. The study was conducted on 60 mongrel rats of both sexes weighing 120-270 g. The first group included 20 rats aged 1 month, the second – 20 rats aged 6-12 months and the third – 20 rats aged more than 18-24 months. The study of qualitative and quantitative indicators of portal hemodynamics was performed using ultrasound scanners with zoletil-xylazine anesthesia. Statistical analysis was performed using the application package Statistica 13.0 (StatSoft, USA).&#x0D; Results. The spectrum of blood flow in the portal vein of rats was unidirectional (monophasic), located above or below the isoline, with oscillations of the curve having a relationship with respiration. A clear dependence of blood flow fluctuations in the portal vein on cardiac activity has not been established. The diameter (by 15.4%, R= 0.64), the cross-sectional area (by 40%, R=0.68) and the maximum linear velocity of blood flow (by 1.2%, R=-0.09) in the portal vein increased with an increase in the age of the animals. The minimum linear velocity of blood flow decreased (by 32.2%, R =-0.05), which indicated an increase in the systolic-diastolic coefficient (an increase in the pulsativity of the flow). The indicator of the volumetric blood flow rate in the portal vein increased by 11.1% (R=0.06), and in relation to body weight decreased in elderly animals (by 11.5%, R=-0.05).&#x0D; Conclusion. A moderate increase in volumetric blood flow in the portal vein (by 11.1%) with a pronounced increase in body weight (by 34.9%) was found with an increase in the age of animals. The perspective of further research is to study the functional reserve of the liver in the age aspect.

Doppler ultrasound assessment results at stages of orthodontic treatment

Relevance. A modern diagnostic complex when planning orthodontic treatment is impossible without assessing the condition of periodontal tissues.Purpose. To evaluate the changes in periodontal tissues during orthodontic treatment.Material and methods. Blood velocity and flow rate in the anterior mandible were compared before and after the orthodontic treatment.Results. Blood velocity and volumetric blood flow rate significantly increased 6 ± 2 months after the beginning of orthodontic treatment.Conclusion. Orthodontic movement of crowded teeth using aligners proceeds without excessive pressure, which allows for a smooth and gradual change in the blood velocity and volumetric blood flow rate, pulsation index and peripheral resistance index.

Investigative study of hemodilution ratio: 4Vs for vein diameter, valve, velocity, and volumetric blood flow as factors for optimal forearm vein selection for intravenous infusion.

Multimodal research and guidelines recognize veins in the forearm used for peripheral intravenous catheter (PIVC) insertion can optimize dwell time. Yet, many PIVCs are still placed in areas of flexion or suboptimal locations such as the back of the hand causing premature failure of >50%. This study identified characteristics of the forearm cephalic vein that make the anatomical location highly successful for PIVC insertion. The goal was to increase the understanding of the human vasculature in association with fluid mechanics in veins above the wrist and below the antecubital fossa. A prospective in-vivo study with 10 consented healthy human volunteers (HHVs) was performed with Color Pulse Wave Doppler Ultrasound that captured high-resolution video and images of vein diameter, velocity of blood flow, and location of venous valves in the forearm. Forearm vein diameter was not directly correlated with higher or lower Velocity of Blood Flow (0.58 cm = 3.0 cm/s). However, Volumetric Blood Flow rates tended to be lower (2.51-8.28 mL/min) with Vein Diameters smaller than 0.29 cm. Ultrasound assessments and Volumetric Blood Flow calculations confirmed natural turbulence in blood and retrograde blood reflux correlated with venous valves opening and closing. Areas of turbulence, with pulse flushing, created backflow with retrograde blood flow around and into the catheter. Placement of long PIVCs in the cephalic veins of the upper forearm yield adequate flow and hemodilution capacity for veins with at least a 3 to 1 hemodilution ratio. The data from this study, along with previous research, suggest that PIVC placement in the cephalic vein, based on selection criteria, may help to reduce or eliminate intravenous complications such as chemical or mechanical thrombophlebitis causing premature catheter failure. Application of these investigational principles may result in better outcomes and catheter longevity for patients who require intravenous infusions.

AGE-RELATED ADAPTATION OF PORTAL HEMODYNAMICS IN RATS DURING 75 DAY FOLLOW-UP

The age-related adaptation of portal hemodynamics was studied in young rats by ultrasound methods. In the mode of color Doppler mapping, a color signal was visualized in the projection of the portal vein, and in the spectral Doppler mode, the spectrum of blood flow in the portal vein was visualized. The diameter and cross-section of the portal vein, linear and volumetric blood flow rates were determined. The study was performed at the beginning and after 60- and 75-day follow-up. It was found that the portal hemodynamics parameters were influenced by a change in the diameter of the portal vein. With an increase in the diameter of the portal vein, the linear velocity of blood flow in the portal vein decreased, but the volumetric velocity of blood flow in the portal vein increased. Conclusions. The mechanisms of age-related adaptation of portal hemodynamics include compensation for a decrease in the linear velocity of blood flow by increasing the volumetric velocity of blood flow in the portal vein.

Changes in the microcirculation of the oral mucosa in post-COVID-19 patients not receiving anti-coagulant therapy

Introduction. The outbreak of a new coronavirus infection has become a challenge for the global health system. The COVID-19 infection is directly related to various disorders of the cardiovascular system, including the microcirculatory bed, caused by thrombotic events and deteriorations of blood rheology. Aims. The paper reports on the results of a study of Doppler sonographic parameters changes in patients with a novel coronavirus infection over the past 6 months. Materials and methods. We assessed the oral mucosa microcirculation in three segments using the high-frequency ultrasound dopple-rography. Results. We recorded the linear and volumetric blood flow rates and the Gosling and Purselo indexes in the course of our work. When comparing the obtained average statistical parameters of blood flow velocity, the linear and volumetric blood flow rates in patients of both groups were found to be lain in the same range and the mean values of Vas, Vam, Qas were equal. The mean values of the Purselo resistance index were closer to 1,0 in patients with COVID-19, and the values of the Gosling pulsation index (PI) were on average 53.3 % higher than in the control group. Conclusion. We evaluated the screening capabilities and potential of high-frequency ultrasound dopplerography for use in patients of different age groups and different somatic status.

Incidence of Deep Vein Thrombosis (DVT) in Patients Using A Knee Scooter

Category:Ankle; TraumaIntroduction/Purpose:Functional limitations after lower extremity injury often require the use of an assistive device such as a knee scooter. Many patients find these devices to be easier and more comfortable to use than crutches or walkers. There is concern regarding the possible correlation between scooter use and DVT. Prior literature demonstrated decreased venous flow with the knee flexed, and venous stasis is a known risk factor for DVT1-3. Further, healthy volunteers using a scooter demonstrated a significant decrease in volumetric blood flow rate at the popliteal fossa4. We report the incidence of DVTs after prescription of a scooter following lower extremity injury. We hypothesized that DVT rates would be higher in patients using a scooter compared to rates of DVT in the NSQIP databaseMethods:A retrospective record review of adult patients age 18-74 within the Military Health System (MHS) database between 2010-2020 was completed to identify the total number of patients who were prescribed a knee scooter and those who subsequently developed a DVT. Additional demographic and clinical data were collected on patients who had both a scooter and a DVT. This was compared with recorded 2015 NSQIP data on DVT incidence in major orthopaedic surgery procedures.Results:Between 2010 and 2020, 46,840 of patients within the MHS database were prescribed a rolling scooter after a lower extremity injury or surgery. Of those patients who were prescribed a scooter, 377 subsequently developed a DVT within 90 days of prescription. DVTs were diagnosed on average 26.5 days after scooter prescription. The incidence of DVT of in this population was 0.8%.Conclusion:In the Military Health System database, the use of a knee scooter following lower extremity injury or surgery is associated with a higher incidence of DVT compared to the 2015 NSQIPS incidence of DVT following major orthopedic surgery (0.80% vs 0.55%), and is most frequently diagnosed within 30 days of scooter prescription. Higher level study is needed to confirm these findings and identify risk factors of patients who experience DVTs associated with scooter use after lower extremity injury or surgery.

Роль сонографічного дослідження нижньої порожнистої вени в діагностиці нейрогенної переміжної кульгавості в пацієнтів із поперековим спінальним стенозом

У 63 пацієнтів із поперековим спінальним стенозом визначено взаємозв’язок сонографічних показників параметрів нижньої порожнистої вени і нейрогенної переміжної кульгавості. Досліджувані показники зміни швидкості об’ємного кровотоку під впливом провокаційного тесту в пацієнтів із нейрогенною переміжною кульгавістю показали середнє значення чутливості даного методу (0,64), однак частота гіпердіагностики досягає значних цифр (0,71), що вимагає додаткових верифікуючих тестів для підтвердження причинно-наслідкового зв’язку.

Variant anatomy of the renal arteries with anastomosis variants in kidney transplantation

Abstract Funding Acknowledgements Type of funding sources: None. One of the most important tasks of morphology as an integral part of practical medicine is comprehensive development of theoretical knowledge pertaining to the variants and anomalies of the renal arteries anatomy. One of the main conditions required for the normal functioning and viability of the renal transplant is its adequate perfusion. Due to the variant anatomy of the renal arteries and the presence of several adjacent vessels with which anastomosis can be performed, there are many strategies for arterial allograft anastomosis. The goal of the study was to identify patterns of variant topography and anatomy of the human renal arteries according to CT angiography with three-dimensional modeling which would be further used to optimize the technique of forming vascular anastomosis during kidney transplantation. Materials and methods. The study included an assessment of computed tomograms of the abdominal organs of 130 patients, which were used to build three-dimensional models. Morphometry was carried out using the Autoplan and Luch-S programs. Based on the results of the CT scans of the kidneys and renal arteries in patients who underwent kidney transplantation, computer 3D models of the renal artery and arterial renal bed were constructed when anastomoses of the renal artery were performed with: the external iliac (group I), the internal iliac (group II) and common iliac (group III) arteries, and in the cases of multiple arteries - during the formation of a common trunk (IIa subgroup) or separate anastomosis with the common iliac artery (IIb). Afterwards, using the Abaqus program, analysis of hemodynamic parameters of intravascular blood flow was conducted, namely: volumetric blood flow rate, partial renal blood flow (the ratio of volumetric blood flow rate to graft weight), visual assessment of the blood flow turbulence. Results volumetric renal blood flow in group II (594 cm3/min) and group III (610 cm3/min) was greater than in group I (550 cm3/min); specific renal blood flow in group III exceeded groups I and II by 0.34 cm3/min/g; high turbulence was observed in the anastomosis angle region in groups I and III. The volumetric renal blood flow in subgroups IIa and IIb was 615 and 585 cm3/min respectively, and in the presence of an extra artery extending from the lower pole, a decrease in the linear blood flow velocity in the inferior polar segmental artery was visually assessed. Based on the results of the study, we can conclude that in the presence of a single renal artery, the best perfusion outcome is achieved when performing anastomosis with the common and internal iliac arteries. With multiple kidney arteries, the best perfusion option is obtained when a single renal artery fistula is formed.

On the Sensitivity Analysis of Porous Finite Element Models for Cerebral Perfusion Estimation

Computational physiological models are promising tools to enhance the design of clinical trials and to assist in decision making. Organ-scale haemodynamic models are gaining popularity to evaluate perfusion in a virtual environment both in healthy and diseased patients. Recently, the principles of verification, validation, and uncertainty quantification of such physiological models have been laid down to ensure safe applications of engineering software in the medical device industry. The present study sets out to establish guidelines for the usage of a three-dimensional steady state porous cerebral perfusion model of the human brain following principles detailed in the verification and validation (V&V 40) standard of the American Society of Mechanical Engineers. The model relies on the finite element method and has been developed specifically to estimate how brain perfusion is altered in ischaemic stroke patients before, during, and after treatments. Simulations are compared with exact analytical solutions and a thorough sensitivity analysis is presented covering every numerical and physiological model parameter. The results suggest that such porous models can approximate blood pressure and perfusion distributions reliably even on a coarse grid with first order elements. On the other hand, higher order elements are essential to mitigate errors in volumetric blood flow rate estimation through cortical surface regions. Matching the volumetric flow rate corresponding to major cerebral arteries is identified as a validation milestone. It is found that inlet velocity boundary conditions are hard to obtain and that constant pressure inlet boundary conditions are feasible alternatives. A one-dimensional model is presented which can serve as a computationally inexpensive replacement of the three-dimensional brain model to ease parameter optimisation, sensitivity analyses and uncertainty quantification. The findings of the present study can be generalised to organ-scale porous perfusion models. The results increase the applicability of computational tools regarding treatment development for stroke and other cerebrovascular conditions.

Possibilities of high-frequency Doppler ultrasound for differential diagnosis of spondylogenic muscle-tonic pain syndromes

Changes in tissue perfusion parameters indicate not only a violation of systemic hemodynamics, but can also occur with local changes in the structure of the organ pathological process. Along with degenerative and dystrophic changes in the structures of the motor segment, muscle-tonic (myofascial) pains occur in a significant number of cases. The possibilities of instrumental assessment in case of local microcirculation disorders in skeletal muscle make it possible to diagnose key manifestations — to identify an area with low blood supply. Within the framework of the study, a limited area of reduced perfusion was established in myofascial pain syndrome. With the formation of a painful muscle knot, the parameter of the volumetric blood flow velocity (Qas) is 0.006±0.0005 cm³/min, while the comparison with the control points fixes the level of blood supply at 0.0046±0.0005 cm³/min (p&lt;0.005). The method for assessing the volumetric blood flow rate in skeletal muscle allows reliably diagnosing the key symptom of myofascial syndrome — a painful muscle knot.

Influence of the cumulative effect of zoledronic acid on periodontal microcirculation in rats.

To evaluate the effect of repeated administration of zoledronic acid (ZA) on the development and severity of osteonecrosis of the jaws. In the experiment, 36 rats were used, which were divided into 4 groups: group 1 was injected with saline for 6 weeks, group 2 was injected with ZA once, group 3 was injected zoledronic acid for 3 weeks once a week, group 4 was injected with ZA for 6 weeks once a week. While taking medications, the tooth was removed. The volumetric blood flow rate was studied using laser and high-frequency ultrasound Doppler in the area of the periodontium of an extracted tooth in rats with the application of acetylcholine. Bone tissue was examined out using CBCT. In group 2, there was a violation of blood flow in the mucous membrane, bone microcirculation, but no reliable data was obtained in the bone defect in comparison with group 1. In groups 3 and 4, there was significantly disrupted blood flow. This led to an increase of the osteonecrosis (maximum at the 4th group), which was confirmed by data obtained using CBCT. An inverse relationship was observed between the blood flow of bone tissue and the size of the defect after tooth extraction. The introduction of ZA in a dose-dependent fashion resulted in impaired endothelial vasodilation and impaired blood flow to extraction sockets. These findings might explain the development of osteonecrosis of the mandible following removal of a first molar.

THE NATURE OF CHANGES IN THE HEMODYNAMICS OF THE EYES OF PATIENTS WITH CHRONIC ANTERIOR IDIOPATHIC UVEITIS COMPLICATED BY OPTIC NEURITIS WITH TRANSITION TO ATROPHY

Aim. To determine the nature and direction of changes in the hemodynamics of the eyes of patients with chronic anterior idiopathic uveitis complicated by optic neuritis with transition to atrophy. Materials and methods. The study involved 18 people with chronic anterior idiopathic uveitis complicated by optic neuritis with transition to atrophy. Ophthalmological (ophthalmoscopy, biomicroscopy, intraocular pressure, perimetry, visual acuity with maximum correction) and electrophysiological (volumetric pulse blood filling, vascular tone of the eye, volumetric blood flow rate) studies were performed before and after treatment for a year. The treatment was carried out according to the protocol: at the first visit — non-steroidal anti-inflammatory drugs, antibiotics, immunosuppressant, corticosteroids and immunomodulatory; with subsequent — metabolic and vitamin therapy, physiotherapy. Statistical analysis was performed using Statistic 12. 0 software. The t-test of Student and Wilcoxon was used. Research results. As a result of treatment, the visual functions of patients are improved: the number of people with higher visual acuity is increasing. In the period up to 6 months after treatment, the number of patients with low visual acuity (0.12–0.5) decreased from 94.4 to 50 %; in 11 of 13 visual acuity increased to 0.3–0.5 (66.7 % of all subjects). A year after the treatment, the visual acuity in the diseased eyes remained the same. The study of eye hemodynamics showed a significant (p&lt;0. 000) increase in all parameters in the diseased eye relative to the healthy one before treatment: volumetric pulse blood filling — by 64.8; the tone of large eye vessels — by 10.1, small — by 17.5; the rate of volumetric pulse blood filling — by 37.8 %. Comparative analysis of the hemodynamic data of sick eyes at different periods after treatment revealed a significant decrease in volumetric pulse blood filling to 66.4 and 52.4 %, the rate of volumetric pulse blood filling to 60. 2 and 44. 4 %. A decrease in the tone of large vessels by 3.1 and 6.4 %, and small — up to 94.6 and 92.7 % at the time of up to six months and up to a year relative to the initial data (p &lt;0.000 in all cases). Conclusions 1. As a result of treatment, the visual functions in the diseased eye improve without deteriorating until a year after treatment. 2. Before treatment, hemodynamic indices are increased (p&lt;0.000) in the diseased eye relative to the healthy one. 3. Six and 12 months after treatment, the volumetric pulse blood filling, the rate of volumetric pulse blood filling, the tone of large and small vessels were significantly reduced relative to the initial data.