Efficiency function: improvement of classical bioheat approach

1994 ◽  
Vol 77 (4) ◽  
pp. 1617-1622 ◽  
Author(s):  
H. Brinck ◽  
J. Werner
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
The Body ◽  
Tissue Temperature ◽  
Whole Body ◽  
Function Concept ◽  
Perfusion Rate ◽  
Efficiency Function ◽  
Vascular Model ◽  
The Difference

In view of the complex vascular architecture and the intricate physical heat transfer processes in the human body, convective heat transfer via the blood is generally described by simple substitutional processes (“non-vascular models”). The classical “bioheat” approach of Pennes (J. Appl. Physiol. 1: 93–122, 1948), defining the heat flow to or from the tissue as being proportional to the product of perfusion rate and the difference of arterial and tissue temperature, has been seriously questioned after having been used for > 40 yr in many applications. In our laboratory, we have at our disposal a complex three-dimensional vascular model for the special case of tissue in a human extremity. This was used to test the performance of simple nonvascular models. It turned out that the Pennes approach may deliver acceptable results if the body is in the thermoneutral zone or if heat stress acts uniformly on the whole body. However, when cold stress or local hyperthermia is present, unreliable results must be expected. As the vascular model is not generally practicable because of its extreme complexity, we offer the efficiency function concept as a simple way of correcting the classical bioheat approach by factor multiplication. Efficiency function is determined as a function of perfusion rate and tissue depth in a way that compensates for the deficiencies of the Pennes bioheat term. The results are reasonable compared with those of the vascular model and experimental results.

scholarly journals Safe Duration Of A Person Soaking Inside A Hot Tub: Theoretical Prediction of Temperature Elevations in Human Bodies Using A Whole Body Heat Transfer Model

2020 ◽  
Author(s):  
Myo Min Zaw ◽  
Manpreet Singh ◽  
Ronghui Ma ◽  
Liang Zhu
Keyword(s):  
Heat Transfer ◽  
Human Body ◽  
Energy Balance Equation ◽  
The Body ◽  
Whole Body ◽  
Equation Modeling ◽  
Transient Temperature ◽  
Transfer Model ◽  
Bioheat Equation ◽  
Arterial Blood

In this study, we first develop a whole body model based on measurements of a human body, with realistic boundary conditions incorporated before and after a person jumps into a hot tub. For the transient heat transfer simulation, the initial condition is the established steady state temperature field of the human body with appropriate clothing layer to ensure the thermal equilibrium of the body with its surroundings. Once the person is inside a hot tub, the Pennes bioheat equation is used to simulate the transient temperature elevations of the body, and the rising of the arterial blood temperature is solved by an energy balance equation modeling thermal exchange between body tissue and the blood in the body. The safe duration of soaking in hot tubs is then determined as affected by the hot tub water temperatures.

Formulation of a Statistical Model of Heat Transfer in Perfused Tissue

1994 ◽  
Vol 116 (4) ◽  
pp. 521-527 ◽  
Author(s):  
J. W. Baish
Keyword(s):  
Heat Transfer ◽  
Heat Transport ◽  
Drug Transport ◽  
Transfer Problem ◽  
Three Dimensional ◽  
Tissue Temperature ◽  
Statistical Interpretation ◽  
Transfer Equations ◽  
Vascular Geometry ◽  
Steady State Heat

A new model of steady-state heat transport in perfused tissue is presented. The key elements of the model are as follows: (1) a physiologically-based algorithm for simulating the geometry of a realistic vascular tree containing all thermally significant vessels in a tissue; (2) a means of solving the conjugate heat transfer problem of convection by the blood coupled to three-dimensional conduction in the extravascular tissue, and (3) a statistical interpretation of the calculated temperature field. This formulation is radically different from the widely used Pennes and Weinbaum-Jiji bio-heat transfer equations that predict a loosely defined local average tissue temperature from a local perfusion rate and a minimal representation of the vascular geometry. Instead, a probability density function for the tissue temperature is predicted, which carries information on the most probable temperature at a point and uncertainty in that temperature due to the proximity of thermally significant blood vessels. A sample implementation illustrates the dependence of the temperature distribution on the flow rate of the blood and the vascular geometry. The results show that the Pennes formulation of the bio-heat transfer equation accurately predicts the mean tissue temperature except when the arteries and veins are in closely spaced pairs. The model is useful for fundamental studies of tissue heat transport, and should extend readily to other forms of tissue transport including oxygen, nutrient, and drug transport.

scholarly journals Effect of Leg Dominance on The Center-of-Mass Kinematics During an Inside-of-the-Foot Kick in Amateur Soccer Players

2014 ◽  
Vol 42 (1) ◽  
pp. 51-61 ◽  
Author(s):  
Matteo Zago ◽  
Andrea Francesco Motta ◽  
Andrea Mapelli ◽  
Isabella Annoni ◽  
Christel Galvani ◽  
...  
Keyword(s):  
Body Movement ◽  
Center Of Mass ◽  
Three Dimensional ◽  
The Body ◽  
Soccer Players ◽  
Upper Body ◽  
Whole Body ◽  
Movement Velocity ◽  
Ground Support ◽  
Analysis System

Abstract Soccer kicking kinematics has received wide interest in literature. However, while the instep-kick has been broadly studied, only few researchers investigated the inside-of-the-foot kick, which is one of the most frequently performed techniques during games. In particular, little knowledge is available about differences in kinematics when kicking with the preferred and non-preferred leg. A motion analysis system recorded the three-dimensional coordinates of reflective markers placed upon the body of nine amateur soccer players (23.0 ± 2.1 years, BMI 22.2 ± 2.6 kg/m2), who performed 30 pass-kicks each, 15 with the preferred and 15 with the non-preferred leg. We investigated skill kinematics while maintaining a perspective on the complete picture of movement, looking for laterality related differences. The main focus was laid on: anatomical angles, contribution of upper limbs in kick biomechanics, kinematics of the body Center of Mass (CoM), which describes the whole body movement and is related to balance and stability. When kicking with the preferred leg, CoM displacement during the ground-support phase was 13% higher (p<0.001), normalized CoM height was 1.3% lower (p<0.001) and CoM velocity 10% higher (p<0.01); foot and shank velocities were about 5% higher (p<0.01); arms were more abducted (p<0.01); shoulders were rotated more towards the target (p<0.01, 6° mean orientation difference). We concluded that differences in motor control between preferred and non-preferred leg kicks exist, particularly in the movement velocity and upper body kinematics. Coaches can use these results to provide effective instructions to players in the learning process, moving their focus on kicking speed and upper body behavior

The Effects of Large Blood Vessels on Three-Dimensional Tissue Temperature Distributions During Electromagnetic Induced Nano-Hyperthermia: Numerical Simulation

2008 ◽  
Author(s):  
Zhong-Shan Deng ◽  
Jing Liu
Keyword(s):  
Blood Vessels ◽  
Tumor Cells ◽  
Three Dimensional ◽  
The Body ◽  
Thermal Therapy ◽  
Tissue Temperature ◽  
Surrounding Tissue ◽  
Temperature Profiles ◽  
Hyperthermia Treatment ◽  
Tumor Hyperthermia

As is well known, the blood flowing through large blood vessels acts as a heat sink and plays an important role in affecting temperature profiles of heated tissues [1]. In hyperthermia, heating is usually limited to the tumor and a small margin of the surrounding tissue. Since the temperatures in the rest of the body remain normal, the blood that supplies the tumor will be relatively cold. Consequently, the blood flow inside a large vessel will represent a sink which cools the nearby heated tissues and then limits heating lesion during tumor hyperthermia. Under this adverse condition, a part of vital tumor cells may remain in the thermally lethal area and lead to recurrence of tumors after hyperthermia treatment. More specifically, tumor cell survival in the vicinity of large blood vessels is often correlated with tumor recurrence after thermal therapy. Therefore, it is difficult to implement an effective hyperthermia treatment when a tumor is contiguous to a large blood vessel or such vessel transits the tumor. How to totally destroy tumor cells in the vicinity of large blood vessels has been a major challenge in hyperthermia [2].

Inverse Heat Transfer Analysis of Micro Heater Strength and Locations for Hyperthermia Treatment of Brain Tumors

2007 ◽  
Author(s):  
Maral Biniazan ◽  
Kamran Mohseni
Keyword(s):  
Heat Transfer ◽  
Brain Tumors ◽  
Transfer Problem ◽  
The Body ◽  
Least Square ◽  
Bioheat Transfer ◽  
Heat Transfer Analysis ◽  
Whole Body ◽  
Transient Temperature ◽  
Inverse Heat Transfer

Hyperthermia, also called thermal therapy or thermotherapy, is a type of cancer treatment in which the aim is to maintain the surrounding healthy tissue at physiologically normal temperatures and expose the cancerous region to high temperatures between 43°C–45°C. Several methods of hyperthermia are currently under study, including local, regional, and whole-body hyperthermia. In local hyperthermia, Interstitial techniques are used to treat tumors deep within the body, such as brain tumors. heat is applied to the tumor, usually by probes or needles which are inserted into the tumor. The heat source is then inserted into the probe. Invasive interstitial heating technique offer a number of advantages over external heating approaches for localizing heat into small tumors at depth. e. g interstitial technique allows the tumor to be heated to higher temperatures than external techniques. This is why an innovative internal hyperthermia research is being conducted in the design of an implantable microheater [1]. To proceed with this research we need complete and accurate data of the strength, number and location of the micro heaters, which is the objective of this paper. The location, strength, and number of implantable micro heaters for a given tumor size is calculated by solving an Inverse Heat Transfer Problem (IHTP). First we model the direct problem by calculating the transient temperature field via Pennies bioheat transfer equation. A nonlinear least-square method, modified by addition of a regularization term, Levenberg Marquardt method is used to determine the inverse problem [2].

Effects of the Heat Transfer at the Side Walls on Natural Convection in Cavities

1990 ◽  
Vol 112 (2) ◽  
pp. 370-378 ◽  
Author(s):  
Y. Le Peutrec ◽  
G. Lauriat
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Fluid Flows ◽  
Heat Losses ◽  
Transfer Rates ◽  
Side Walls ◽  
The Difference

Numerical solutions are obtained for fluid flows and heat transfer rates for three-dimensional natural convection in rectangular enclosures. The effects of heat losses at the conducting side walls are investigated. The problem is related to the design of cavities suitable for visualizing the flow field. The computations cover Rayleigh numbers from 103 to 107 and the thermal conductance of side walls ranging from adiabatic to commonly used glazed walls. The effect of the difference between the ambient temperature and the average temperature of the two isothermal walls is discussed for both air and water-filled enclosures. The results reported in the paper allow quantitative evaluations of the effects of heat losses to the surroundings, which are important considerations in the design of a test cell.

scholarly journals Determination of Some Body Measurements of Camels With Three Dimensional Modeling Method (3D)

2021 ◽  
Author(s):  
Alkan çağlı ◽  
M. Yılmaz
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Practical Method ◽  
Modeling Method ◽  
The Body ◽  
Body Measurements ◽  
3D Measurement ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
The Difference

Abstract In this study, the use of three-dimensional modeling method was tested in taking some body measurements in camels with a practical method and was compared with other measurement methods. As the animal material of the study, 12 single humped dromedary female camels and 14 double humped Camelus dromedarius X Camelus bactrianus: F1 male camels, totally 26 camels, were used in three camel farms in Incirliova district of Aydın province. The body measurements taken from each animal by using different three methods, namely by Manuel Method (MM), by Photography Method (PM), and by Three Dimensional Modeling Method (3D) were the Cidago Height (CH), the Back Height (BH), the Rump Height (RH), the Body Length (BL), the Brisket Height (BRH), the Abdominal Height (AH), the Shoulder Width (SW) and the Rump Width (RW) and these values were compared with each other. As a result of this study, the mean values of MM and 3D measurement values were very close to each other and the difference between them was found to be statistically insignificant. (P<0.05). The difference between the means of PM and MM/3D measurement values was found to be significant. (P <0.05). In the measurements taken by MM, 3D, PM methods in male camels, the values obtained by MM and 3D methods for CH, BH, RH, BRH, AH, BL, and SW were very close to each other and the differences between them were found insignificant statistically (p < 0.05). On the determined regression graph, a linear was found between MM and 3D measurement values. As a result of this study, it has been determined that the 3D modeling method can be used as a remote and more practical method in determining the morphological features of large-scale animals such as camels more reliably, more easily and more practically.

Quantifying Segmental Contributions to Center-of-Mass Motion During Dynamic Continuous Support Surface Perturbations Using Simplified Estimation Models

2020 ◽  
Vol 36 (4) ◽  
pp. 198-208
Author(s):  
Alison Schinkel-Ivy ◽  
Vicki Komisar ◽  
Carolyn A. Duncan
Keyword(s):  
Balance Control ◽  
Center Of Mass ◽  
Three Dimensional ◽  
The Body ◽  
Whole Body ◽  
Mass Motion ◽  
Support Surface ◽  
Body Segments ◽  
Body Model ◽  
Full Body

Investigating balance reactions following continuous, multidirectional, support surface perturbations is essential for improving our understanding of balance control in moving environments. Segmental motions are often incorporated into rapid balance reactions following external perturbations to balance, although the effects of these motions during complex, continuous perturbations have not been assessed. This study aimed to quantify the contributions of body segments (ie, trunk, head, upper extremity, and lower extremity) to the control of center-of-mass (COM) movement during continuous, multidirectional, support surface perturbations. Three-dimensional, whole-body kinematics were captured while 10 participants experienced 5 minutes of perturbations. Anteroposterior, mediolateral, and vertical COM position and velocity were calculated using a full-body model and 7 models with reduced numbers of segments, which were compared with the full-body model. With removal of body segments, errors relative to the full-body model increased, while relationship strength decreased. The inclusion of body segments appeared to affect COM measures, particularly COM velocity. Findings suggest that the body segments may provide a means of improving the control of COM motion, primarily its velocity, during continuous, multidirectional perturbations, and constitute a step toward improving our understanding of how the limbs contribute to balance control in moving environments.

Heat Transfer Normal to Paired Arterioles and Venules Embedded in Perfused Tissue During Hyperthermia

1988 ◽  
Vol 110 (4) ◽  
pp. 277-282 ◽  
Author(s):  
C. K. Charny ◽  
R. L. Levin
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Three Dimensional ◽  
Numerical Data ◽  
Tissue Temperature ◽  
Three Dimensional Model ◽  
Sources And Sinks ◽  
The Mean ◽  
Krogh Cylinder ◽  
Subsequent Incorporation

A numerical model of the heat transer normal to an arteriole-venule pair embedded in muscle tissue has been constructed. Anatomical data describing the blood vessel size, spacing, and density have been incorporated into the model. This model computes temperatures along the vessel walls as well as the temperature throughout the tissue which comprises an infinitely long Krogh cylinder around the vessel pair. Tissue temperatures were computed in the steady-state under resting conditions, while transient calculations were made under hyperthermic conditions. Results show that for both large- (1st generation) and medium-sized (5th generation) vessel pairs, the mean tissue temperature within the tissue cylinder is not equal to the mean of the arteriole and venule blood temperatures under both steady-state and transient conditions. The numerical data were reduced so that a comparison could be made with the predictions of a simple two-dimensional superposition of line sources and sinks presented by Baish et al. [1]. This comparison reveals that the superposition model accurately describes the heat transfer effects during hyperthermia, permitting subsequent incorporation of this theory into a realistic three-dimensional model of heat transfer in a whole limb during hyperthermia.

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