Blood Mass Flow Rate Research Articles

Computational analysis of the blood hemodynamic inside internal cerebral aneurysm in the existence of endovascular coiling

The precise evaluations of intracranial aneurysms (IAs) are highly prominent for the treatment and control of aneurysm rupture. Computational fluid dynamic (CFD) simulations based on angiography image is a reliable tool for the recognition of high-risk region and aneurysm status in recent years. In our study, the CFD is used to investigate the impacts of blood hematocrit and coiling techniques on the risk of aneurysm rupture. To do this, wall shear stress (WSS), oscillatory shear index (OSI) and pressure distribution on the wall of an aneurysm are comprehensively evaluated in various coding porosities and blood viscosities. One-way Fluid Solid Interaction (FSI) technique is applied to investigate the non-Newtonian, pulsatile blood stream inside the sac of the aneurysm. Impacts of two coiling porosities and blood hematocrits of 0.3 and 0.5 on blood features inside the sac are also analyzed. The influence of the blood mass flow rate in four different time instants of blood cycles on the size of the high-risk region on the aneurysm wall is demonstrated. Our results show that more than 40% reduction is noticed when the hematocrit (HCT) of blood is reduced from 0.5 to 0.3 in different time instants. Our findings also reveal that decreasing the porosity from 0.96 to 0.74 in the peak systolic stage results in a 28% reduction in the maximum OSI at specific HCT = 0.4.

Bio-heat transfer in cancer treatment using cryo-freezing method

The objective of this study is to investigate the effect of bio-heat transfer from large blood vessels on freezing region size of tumorous liver tissue using cryo-freezing method. Bio-heat transfer, one of the cancer treatment method, in tumorous tissue has been investigated experimentally using cryo-freezing method for vessels. Investigated parameters are the blood mass flow rate, the diameter of vessel, the number of vessel, and the location of tumorous tissue. Study is carried out for nine different blood mass flow rates varying from 10 g/min to 1200 g/min. Tissues without blood vessel, with single, double and branched vessels are used for the experimental study. Vessels with inner diameter of 2.4, 3.2 and 4.0 mm are used. Liver of beef is employed as a tissue. Refrigerant is the nitrogen protoxide gas. Results show that the number of vessel, the diameter of vessel, the location of tumorous tissue, and the blood mass flow rate affect the freezing region size. Freezing region size decreases with increasing in diameter of vessel, number of vessel and blood mass flow rate. The large blood vessel located near the tumorous tissue affects the freezing time to destroy the tumor. The desired freezing region obtained in tumorous tissue with vessel develops later than the tumorous tissue without vessel. Results indicate that a tumorous tissue about 23 mm may be destroyed in a short time using cryo-freezing method when nitrogen protoxide gas is used as refrigerant gas.

Numerical simulation of thermal changes in tissues of woman's breast during menstrual cycle in different stages of its development

A model is proposed to study thermal changes taking place in a woman's breast in different stages of its development due to the menstrual cycle. The changes in the physical and physiological parameters such as blood mass flow rate, metabolic heat generation and thermal conductivity due to benign changes in the breast, have been incorporated in the model. Appropriate boundary conditions have been framed based on the physical conditions of the problem. The temperature profiles have been computed and the thermal changes in the breast have been analysed during the follicular and luteal phases of the menstrual cycle in different stages of its development. The finite element method has proved to be quite flexible and powerful in the present study as it was possible to incorporate the physiology of the breast in the proposed model to generate the thermal information of the breast due to benign changes occurring in the breast such as the menstrual cycle, etc.

Numerical simulation of thermal changes in tissues of woman's breast during menstrual cycle in different stages of its development

A model is proposed to study thermal changes taking place in a woman's breast in different stages of its development due to the menstrual cycle. The changes in the physical and physiological parameters such as blood mass flow rate, metabolic heat generation and thermal conductivity due to benign changes in the breast, have been incorporated in the model. Appropriate boundary conditions have been framed based on the physical conditions of the problem. The temperature profiles have been computed and the thermal changes in the breast have been analysed during the follicular and luteal phases of the menstrual cycle in different stages of its development. The finite element method has proved to be quite flexible and powerful in the present study as it was possible to incorporate the physiology of the breast in the proposed model to generate the thermal information of the breast due to benign changes occurring in the breast such as the menstrual cycle, etc.

Three-dimensional finite element model to study temperature distribution in peripheral layers of human limbs immediately after physical exercise

The physical exercise imposes challenges on the human thermoregulatory system, as heat exchange between the body and environment is substantially impaired, which can lead to decrease in performance and increased risk of heat illness. In view of above a three-dimensional finite element model is proposed to study the effect of different intensities of physical exercise on temperature distribution in peripheral regions of human limbs under moderate climatic conditions. Human limb is assumed to have a cylindrical cross-section. The peripheral region of the human limb is divided into three natural components, namely epidermis, dermis and subdermal tissues. The model incorporates the effect of important physiological parameters like blood mass flow rate, metabolic heat generation, and thermal conductivity of the tissues. Appropriate boundary conditions have been framed based on the physical conditions of the problem. The model is transformed into the discretized variational form and finite element method (FEM) has been employed to obtain the solution. The numerical results have been used to obtain the temperature profiles in the region immediately after exercise for an unsteady state case. The thermal information generated from the model can be useful for developing protocols for improving performance of sportsmen, military persons and labor-intensive workers.

Thermal stability of biological tissues and their behavior in cold conditions — A mathematical model

This paper presents an application of finite element method to study the thermoregulatory behavior of three layers of human dermal parts with varying properties. The investigation of temperature distributions in epidermis, dermis and subcutaneous tissue together with Crank–Nicholson scheme at various atmospheric conditions was carried out. The finite element method has been applied to obtain the numerical solution of governing differential equation for one-dimensional unsteady state bioheat equation using suitable values of parameters that affect the heat transfer in human body. The outer skin is assumed to be exposed to cold atmospheric temperatures and the loss of heat due to convection, radiation and evaporation has been taken into consideration. The important parameters like blood mass flow rate, metabolic heat generation rate and thermal conductivity are taken heterogeneous in each layer according to their distinct physiological and biochemical activities. The temperature profiles at various nodal points of the skin and in vivo tissues have been calculated with respect to the severe cold ambient temperatures. The conditions under which hypothermia, non-freezing and freezing injuries develop were illustrated in the graphs.

Finite element model to study the thermal effect of tumors in dermal regions of irregular tapered shaped human limbs

The present study deals with the temperature variation in dermal layers of irregular tapered shaped human limb involving metastasis of tumors. Two uniformly perfused tumors are assumed to be present at different axial and angular positions of the dermal regions of the human limb. The model incorporates the effect of blood mass flow rate, metabolic activity and thermal conductivity in different tissue layers. The self controlled and uncontrolled rates of metabolic heat generation are incorporated respectively for the normal and malignant tissues. Appropriate boundary conditions have been incorporated based on the physical conditions of the problem. The appropriate variations in biophysical parameters are also incorporated in the model. The finite element method has been employed for the solution. The numerical results have been used to analyze the thermal effect of metastasis of tumors on temperature distribution in dermal regions of human limbs. The thermal information generated from the numerical results can be useful for clinical applications.

Steady state temperature distribution in dermal regions of an irregular tapered shaped human limb with variable eccentricity

The investigators in the past have developed some models of temperature distribution in the human limb assuming it as a regular circular or elliptical tapered cylinder. But in reality the limb is not of regular tapered cylindrical shape. The radius and eccentricity are not same throughout the limb. In view of above a model of temperature distribution in the irregular tapered elliptical shaped human limb is proposed for a three dimensional steady state case in this paper. The limb is assumed to be composed of multiple cylindrical substructures with variable radius and eccentricity. The mathematical model incorporates the effect of blood mass flow rate, metabolic activity and thermal conductivity. The outer surface is exposed to the environment and appropriate boundary conditions have been framed. The finite element method has been employed to obtain the solution. The temperature profiles have been computed in the dermal layers of a human limb and used to study the effect of shape, microstructure and biophysical parameters on temperature distribution in human limbs. The proposed model is one of the most realistic model as compared to conventional models as this can be effectively employed to every regular and nonregular structures of the body with variable radius and eccentricity to study the thermal behaviour.

Variational Finite Element Approach to Study Radial Heat Distribution Problem in Human Limbs

This paper is based on bio heat transfer equation and demonstrates its application in solving one dimensional physiological heat distribution problems pertaining to limbs. The biological properties are assumed to vary along the radial direction. The dermal region is made up of three layers, namely epidermis, dermis, and subcutaneous tissues. The model incorporates significant variations of physical and physiological parameters like blood mass flow rate, rate of metabolic heat generation, and thermal conductivity in each layer. Numerical results have been obtained for various cases of practical interest. Keywords: Rate of metabolism 1, blood mass flow rate 2, thermal conductivity 3, heat generation 4, finite element method 5.

Two dimensional temperature distribution model in human dermal region exposed at low ambient temperatures with air flow

This paper deals with thermo-regulation in human dermal part in a cold atmosphere with significant air flow. The mathematical model involving bio-heat equation has been solved using finite element method and Crank-Nicolson technique to numerically investigate two dimensional temperature distributions. The natural three layers of dermal part – epidermis, dermis, and subcutaneous tissue are considered for the study. The important parameters like blood mass flow rate, metabolic heat generation rate and thermal conductivity are taken distinct in each layer according to their distinct sub-regional activities. The human subject is assumed in static condition. The wind speed is considered in the range from the start of forced convection (? 0.2 m/s) and up to 5 m/s. The loss of heat from the skin surface to the environment is taken due to convection, radiation, and insensible perspiration. Kathmandu University Journal of Science, Engineering and Technology Vol. 8, No. II, December, 2012, 11-24 DOI: http://dx.doi.org/10.3126/kuset.v8i2.7320

Flow resistance analysis of extracranial-to-intracranial (EC–IC) vein bypass

Although brain bypass surgery has often been selected to treat internal carotid arteries (ICA) which are restricted by aneurysm or artery stenosis, its effectiveness has not been quantitatively evaluated. The purpose of this study is to propose an innovative approach for the evaluation of brain extracranial-to-intracranial (EC–IC) vein bypass surgery, based on the analysis of flow resistance in vein bypasses and within their contralateral carotid arteries through the use of computational fluid dynamics (CFD). Seven patients who underwent vein bypass surgery were examined with the use of high-resolution; computed tomography angiogram (CTA). The reconstructed three-dimensional (3D) geometries were segmented to create CFD calculation domains. Colour Doppler ultrasound (CDU) was used to measure blood flow velocities at the common carotid arteries (CCA), in order to determine inflow conditions. Based on the pipe flow theory, pressure drop was expressed as Aṁ2+Bṁ where A and B represent flow resistance coefficients and ṁ represents blood mass flow rate. The CFD results revealed that for a healthy ICA, the average values of A and B were 0.013088Pa/(ml/min)2 and 3.105Pa/(ml/min), respectively. For the vein bypass, an average value of A was 0.0143Pa/(ml/min)2 and B 3.402Pa/(ml/min), which was approximately that of a healthy ICA. However, in the case of a bypass utilising a venous conduit possessing a large-sized valve or existing size alteration, the flow resistance in that bypass would be higher than those found in the healthy ICA. An imbalance of flow resistances may impose conditions that could predispose hemodynamic failure or distal aneurysm development.

FINITE ELEMENT MODEL TO STUDY THERMAL EFFECT OF UNIFORMLY PERFUSED TUMOR IN DERMAL LAYERS OF ELLIPTICAL SHAPED HUMAN LIMB

In this paper, a two-dimensional finite element model has been developed to study thermal disturbances in elliptical shaped human limbs involving uniformly perfused tumor. The model incorporates the effect of important physiological parameters like blood mass flow rate, self-controlled metabolic activity and thermal conductivity in dermal regions. For tumor regions the uncontrolled rate of metabolic activity and abnormal rate of blood flow have been incorporated. The outer surface of the limb is exposed to the environment where heat loss takes place via the conduction, convection, radiation and evaporation. Appropriate boundary conditions have been framed. The model has been simulated using MATLAB 7.5 to obtain numerical results.

AN INFINITE ELEMENT MODEL TO STUDY TEMPERATURE VARIATIONS DURING WOUND HEALING PROCESS AFTER PLASTIC SURGERY

The study of temperature regulation of human body will help to better understand the physiology and functioning of every biological system. Skin is the largest organ of the integumentory system playing an important role to maintain the body core temperature (Tb) at 37°C. Any disturbance in the temperature regulation may cause lots of abnormality in the body. The purpose of this paper is to present an overview of temperature variations of tissues of human peripheral region during wound healing process after plastic surgery. An attempt has been made to study temperature variations of normal region (region before surgery) as well as abnormal region (region after surgery) of human peripheral region after the plastic surgery at different atmospheric temperatures and rates of evaporation for an undressed wound by extending finite domain to infinite using infinite element method (IEM). The two-dimensional peripheral region (skin and subcutaneous tissues) consists of finite triangular elements of very small size and the infinitely long rectangular elements. The appropriate shape functions are used for the elements. Physiological parameters like thermal conductivity, rate of metabolism, blood mass flow rate, latent heat, rate of evaporation etc. are used along with the proper initial and boundary conditions. The temperature variations are noted for tissue of donor site (normal region) as well as tissues after surgery (abnormal region). The information obtained from this model can be of great use for biomedical scientists for application in treatment of various diseases as well as helpful to develop protocols for medical purpose.

Three dimensional finite element model to study heat flow in dermal regions of elliptical and tapered shape human limbs

In this paper a three-dimensional steady state model has been developed to study heat flow in dermal regions of tapered shape human limbs, which are elliptical in shape. The model incorporates the important biophysical parameters like blood mass flow rate, thermal conductivity and rate of metabolic heat generation. Appropriate boundary conditions have been framed using biophysical conditions. The finite element method has been employed using coaxial elliptical hexahedral elements to solve the problem. MATLAB 7.0 has been used to simulate the model and obtain numerical results.

SEMINUMERICAL MODEL TO STUDY TEMPERATURE DISTRIBUTION IN PERIPHERAL LAYERS OF ELLIPTICAL AND TAPERED SHAPED HUMAN LIMBS

In this article, a seminumerical approach has been developed to study temperature distribution in peripheral layers of tapered shaped human limbs, which are elliptical in shape. The model is three-dimensional which incorporates the important biophysical parameters such as blood mass flow rate, thermal conductivity and rate of metabolic heat generation. Appropriate boundary conditions have been framed using biophysical conditions. The finite element method has been employed along radial and angular directions and Fourier series method along axial direction to obtain temperature profiles in the region. The results have been used to study relationships among various physical and physiological parameters. MATLAB 7.0 has been used to simulate the model and obtain numerical results.

A study of systemic-to-pulmonary artery shunt deformation shape by CFD (computational fluid dynamics)

Hypoplastic left heart syndrome (HLHS) is rare but serious. It is the most common cause of death from heart disease during the first week of life. With surgical repair or a heart transplant, about 70% of children born with HLHS live for at least 5 years. The purpose of this study is to achieve an optimization of the systemic-topulmonary artery shunt. In this study, computational fluid dynamic (CFD) models were used to determine the velocity profile in a systemic-to-pulmonary artery shunt and we suggest a simplified method of calculating the blood mass flow rate in the shunt based on ultrasound systems. We analyzed the flow characteristic variations and Oscillatory Shear Index (OSI) due to the anastomosis angle and changing shunt diameter.

A Two Dimensional Infinite Element Model to Study Temperature Distribution in Human Dermal Regions due to Tumors

In this study, a two dimensional infinite element model has been developed to study thermal effect in human dermal regions due to tumors. This model incorporates the effect of blood mass flow rate, metabolic heat generation and thermal conductivity of the tissues.The dermal region is divided into three natural layers, namely, epidermis, dermis and subdermal tissues. A uniformly perfused tumor is assumed to be present in the dermis. The domain is assumed to be finite along the depth and infinite along the breadth. The whole dermis region involving tumor is modelled with the help of triangular finite elements to incorporate the geometry of the region. These elements are surrounded by infinite domain elements along the breadth. Appropriate boundary conditions has been incorporated. A computer program has been developed to obtain the numerical results.

3D numerical reconstruction of the hyperthermia induced temperature distribution in human sarcomas using DE-MRI measured tissue perfusion: validation against non-invasive MR temperature measurements.

Essential to the success of optimized thermal treatment during hyperthermia is accurate modelling. Advection of energy due to blood perfusion significantly affects the temperature. Without accurate estimates of the magnitude of the local tissue blood perfusion, accurate estimates of the temperature distribution can not be made. It is shown here that the blood mass flow rate per unit volume of tissue in the Pennes' bio-heat equation can be modelled using a relative perfusion index (RPI) determined with dynamic-enhanced magnetic resonance imaging (DE-MRI). Temperature distributions in two patients treated with hyperthermia at Duke University Medical Center for high-grade leg tissue sarcomas are modelled, and the resultant temperatures are compared to measured temperatures using a non-invasive MR thermometry technique. Significant correlations are found between the DE-MRI perfusion images, the MR temperature images, and the numerical simulation of the temperature field. The correlation between DE-MRI measured values and advective heat loss in tissue is used to scale the perfusion distribution, thereby allowing the continuum model to account for the local thermal impact of vasculature in the tumour. Large vessels in tumour and neighbouring healthy tissue need to be taken into account in order to accurately describe the complete temperature distribution.

Coaxial circular sector elements to study two-dimensional heat distribution problem in dermal regions of human limbs

A finite element model using two-dimensional coaxial circular sector elements has been developed to study radial and angular heat distribution problem in dermal regions of human limbs. The dermal region is made up of three layers, namely epidermis, dermis, and subcutaneous tissues. The muscles, bones, major blood vessels and fats form the inner core of the human limb. The model incorporates significant variations of physical and physiological parameters like blood mass flow rate, rate of metabolic heat generation, and thermal conductivity in each layer. The core temperature of the limb is at variable temperature along angular direction. The outer surface is exposed to the environment, and heat loss at the outer boundary takes place due to conduction, convection, radiation, and evaporation. Appropriate boundary conditions have been framed in view of the physical conditions. A computer program has been developed for the entire problem and simulated on an ICIM-6040 machine to compute numerical results. The model developed here makes the use of a finite element method easier in this situation and reduces the amount of computation in comparison to triangular elements in a finite element method.

Variational finite element approach to a heat flow problem in human limbs

An attempt has been made to study cross sectional temperature distribution in in‐vivo tissues of a human limb employing variational finite element approach. The outermost surface of the limb is assumed to be exposed to the atmosphere. The physiological and physical parameters like rate of metabolic heat generation (rmhg), blood mass flow rate (bmfr) and thermal conductivity are assumed to vary in the subregions independently. Numerical results have been obtained for various cases of practical interest.