Mathematical Modeling of Thermal Ablation in Tissue Surrounding a Large Vessel

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Xin Chen ◽  
Gerald M. Saidel
Keyword(s):  
Temperature Distribution ◽  
Blood Vessel ◽  
Thermal Ablation ◽  
Large Vessel ◽  
Tissue Temperature ◽  
Maximum Temperature ◽  
Capillary Perfusion ◽  
Distribution Dynamics ◽  
Large Blood Vessel ◽  
Power Inputs

Thermal ablation of a solid tumor in a tissue with radio-frequency (rf) energy can be accomplished by using a probe inserted into the tissue under the guidance of magnetic resonance imaging. The extent of the ablation can be significantly reduced by heat loss from capillary perfusion and by blood flow in a large vessel in the tissue. A mathematical model is presented of the thermal processes that occur during rf ablation of a tissue near a large blood vessel, which should not be damaged. Temperature distribution dynamics are described by the combination of a 3D bioheat transport in tissue together with a 1D model of convective-dispersive heat transport in the blood vessel. The objective was to determine how much of the tissue can be ablated without damaging the blood vessel. This was achieved by simulating the tissue temperature distribution dynamics and by determining the optimal power inputs so that a maximum temperature increase in the tissue was achieved without inducing tissue damage at the edge of the large vessel. The main contribution of this study is to provide a model analysis for pretreatment and, eventually, for intra-operative application to thermal ablation of a tumor located near a large blood vessel.

The Comparison of Two Simulation Methods on the Thermal Ablation with Large Blood Vessel

2013 ◽  
Vol 444-445 ◽  
pp. 1177-1181
Author(s):  
Fei Zhai ◽  
Qun Nan ◽  
Hui Juan Zhang ◽  
Xue Mei Guo
Keyword(s):  
Heat Exchange ◽  
Blood Vessel ◽  
Thermal Ablation ◽  
Blood Flow Rate ◽  
Bioheat Transfer ◽  
Microwave Antenna ◽  
Simulation Methods ◽  
Large Blood Vessel ◽  
Significant Difference ◽  
Coupling Algorithm

Purpose: The aim of this study is to contrast the coupling algorithm (CEE) and boundary heat exchange coefficients (Nu) used in treatment of the large blood vessel in thermal ablation. Methods: Based on the Pennes bioheat transfer equation, the models with blood vessel parallel to microwave antenna were built with finite element method. In two kind of simulation, blood flow rate was set in 0.2 m/s or boundary heat exchange coefficients was set in 1750 W / (m2 °C), respectively. Results and conclusions : There was no significant difference on shape of effective ablation areas and 54°C temperature contours by using two kinds of simulation methods, especially the place far away from the blood vessel. At the place near the blood vessel, the method of CEE is closer to real condition which considers directivity of blood. Whats more, there are higher temperature by using method of Nu inside effective ablation areas.

Effect of the SAR Distribution of a Radio Frequency (RF) Coil on the Temperature Field Within a Human Leg: Numerical Studies

1999 ◽  
Author(s):  
J. X. Ling ◽  
Jeffrey W. Hand ◽  
Ian R. Young
Keyword(s):  
Temperature Distribution ◽  
Temperature Change ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Source Term ◽  
Fdtd Method ◽  
Tissue Temperature ◽  
Maximum Temperature ◽  
Rf Coil ◽  
Specific Absorption

Abstract This paper presents a three dimensional Finite Element Model for studying the effect of the specific absorption rate (SAR) distribution of a RF coil on the temperature distribution within a human leg due to the energy deposit. The model consists of fat, muscle, and bone, and has 21,158 uniform elements. The 3-D leg model was derived from the tissue maps that are obtained from the 79 sequential MR images of a volunteer’s leg. The specific absorption rate (SAR) data are from the solution to the fundamental Maxwell’s electromagnetic equations of the leg with RF coil in place using finite difference time domain (FDTD) method. The blood perfusion term, which is a function of the local tissue temperature, along with the metabolic heat as well as the SAR term, are treated as one heat source term in the classical bio-heat transfer equation. A commercial FEA code, ANSYS, was used to solve the 3-D heat conduction equation with an additional iteration method to deal with the temperature dependent source term. The 3-D temperature fields without and with the SAR term were computed, as well as the changes in temperature. They predict that the maximum temperature change occurs in approximately the same location as the maximum local SAR. The map of the temperature change clearly shows how the presence of the RF coil affect the temperature distribution within the leg. With 2 watts absorbed in the leg, about 8.8 w/kg of peak SAR value, the maximum change in temperature of the leg is about 1.74° C.

Nano-Cryosurgery to Tackle the Deficiency in Conventional Freezing of Tumors With Large Blood Vessels

2010 ◽  
Author(s):  
Zhong-Shan Deng ◽  
Jing Liu
Keyword(s):  
Temperature Distribution ◽  
Blood Vessel ◽  
Blood Vessels ◽  
Large Vessel ◽  
Research Focus ◽  
Thermal Distribution ◽  
Tumor Tissues ◽  
Warm Blood ◽  
Large Vessels ◽  
Conventional Freezing

Recently, nano-cryosurgery was proposed to improve freezing efficiency of the conventional cryosurgery. As is well known, the effect of thermally significant large blood vessel on temperature has long been a research focus for conventional cryosurgery, since the warm blood flowing through large vessel may result in insufficient freezing and tumor residual. However, there is little information concerning the effects of large vessels on the temperature distribution and freezing lesion in nano-cryosurgery. In this study, two typical vascular models were applied to investigate the effects of large blood vessels to the thermal distribution and freezing lesion during nano-cryosurgery. The numerical results indicated that, after localized introduction of nanoparticles, large vessels embedding in tumor tissues can be totally frozen during cryosurgery and thus the insufficient freezing region surrounding large vessels can be effectively eliminated. The results also suggested that adjuvant use of nanoparticles is expected to serve as a promising method to tackle the deficiency in conventional freezing of tumors with large blood vessels in future oncological clinics.

Theoretical Analysis of the Large Blood Vessel Influence on the Local Tissue Temperature Decay After Pulse Heating

1993 ◽  
Vol 115 (2) ◽  
pp. 175-179 ◽  
Author(s):  
L. X. Xu ◽  
M. M. Chen ◽  
K. R. Holmes ◽  
H. Arkin
Keyword(s):  
Temperature Field ◽  
Blood Vessel ◽  
Point Source ◽  
Blood Perfusion ◽  
Tissue Temperature ◽  
Surrounding Tissue ◽  
Heating Pulse ◽  
Local Tissue ◽  
Large Blood Vessel ◽  
Temperature Decay

The influence of a large blood vessel (larger than 500 μm in diameter) on the local tissue temperature decay following a point source heating pulse was determined numerically using a sink/source method. It was assumed that the vessel was large enough so that the temperature of blood flowing within it remained essentially constant and was unaffected by any local tissue temperature transients. After the insertion of a point source heating pulse, the vessel influence on the local tissue transient temperature field was estimated by representing the vessel as a set of negative fictitious instantaneous heat sources with strength just sufficient to maintain the vessel at a constant temperature. In the surrounding tissue, the Pennes’ tissue heat transfer equation was used to describe the temperature field. Computations have been performed for a range of vessel sizes, probe-vessel spacings and local blood perfusion rates. It was found that the influence of a large vessel on the local tissue temperature decay is more sensitive to its size and location rather than to the local blood perfusion rate. For a heating pulse of 3s duration and 5 mW of power, there is a critical probe-vessel center distance 7R (R, vessel radius) beyond which the larger vessel influence on tissue temperature at the probe can be neglected.

Electromagnetic performance and thermal analysis of a novel permanent magnet fluxed-switching coupler

2021 ◽  
pp. 1-18
Author(s):  
Lezhi Ye ◽  
Yulong Zhang ◽  
Mingguang Cao
Keyword(s):  
Temperature Distribution ◽  
Permanent Magnet ◽  
Permanent Magnets ◽  
Three Dimensional ◽  
Load Condition ◽  
Maximum Load ◽  
Maximum Temperature ◽  
The Novel ◽  
Transient Field ◽  
Three Dimensional Finite Element

To solve the problem of complex operating device and permanent magnets (PMs) demagnetization at high temperature, a new type of permanent magnet fluxed-switching coupler (PMC) with synchronous rotating adjuster is proposed. Its torque can be adjusted by rotating a switched flux angle between the adjuster and PMs along the circumferential direction. The structural feature and working principle of the PMC are introduced. The analytical model of the novel PMC was established. The torque curves are calculated in transient field by using the three-dimensional finite element method (3-D FEM). The temperature distribution of the novel PMC under rated condition is calculated by 3-D FEM, and the temperature distribution of the PM is compared with that of the conventional PMC. The simulation and test results show that the maximum temperature of copper disc and PM of the novel PMC are 100 °C and 48 °C respectively. The novel PMC can work stably for a long time under the maximum load condition.

scholarly journals Research on Influence of Different Simulation Methods of Bypass Flow in Thermal Hydraulic Analysis on Temperature Distribution in HTR-10

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Shiyan Sun ◽  
Youjie Zhang ◽  
Yanhua Zheng
Keyword(s):  
Temperature Distribution ◽  
Reactor Core ◽  
Flow Distribution ◽  
Maximum Temperature ◽  
Flow Ratio ◽  
Hydraulic Analysis ◽  
Bypass Flow ◽  
Pebble Bed ◽  
The Core ◽  
Thermal Hydraulic Analysis

In pebble-bed high temperature gas-cooled reactor, gaps widely exist between graphite blocks and carbon bricks in the reactor core vessel. The bypass helium flowing through the gaps affects the flow distribution of the core and weakens the effective cooling of the core by helium, which in turn affects the temperature distribution and the safety features of the reactor. In this paper, the thermal hydraulic analysis models of HTR-10 with bypass flow channels simulated at different positions are designed based on the flow distribution scheme of the original core models and combined with the actual position of the core bypass flow. The results show that the bypass coolant flowing through the reflectors enhances the heat transfer of the nearby components efficiently. The temperature of the side reflectors and the carbon bricks is much lower with more side bypass coolant. The temperature distribution of the central region in the pebble bed is affected by the bypass flow positions slightly, while that of the peripheral area is affected significantly. The maximum temperature of the helium, the surface, and center of the fuel elements rises as the bypass flow ratio becomes larger, while the temperature difference between them almost keeps constant. When the flow ratio of each part keeps constant, the maximum temperature almost does not change with different bypass flow positions.

The Effect of Curvature and Torsion on the Temperature Distribution in a Helix

1985 ◽  
Vol 52 (3) ◽  
pp. 529-532 ◽  
Author(s):  
D. D. Sayers ◽  
M. C. Potter
Keyword(s):  
Differential Equation ◽  
Finite Element Method ◽  
Partial Differential Equation ◽  
Temperature Distribution ◽  
Strong Dependence ◽  
Maximum Temperature ◽  
Nonuniform Heating ◽  
The Finite Element Method ◽  
Curvature Parameter ◽  
Curvature And Torsion

Traditional analysis treats the helix as a straight wire with the effects of nonuniform heating, torsion, and large curvature ignored. Using a helical coordinate system the governing partial differential equation including these effects is derived. The equation is then solved numerically using the finite element method. The results indicate a strong dependence of the temperature on the torsion parameter when the curvature parameter is significant. As the curvature parameter increases, the temperature distribution becomes skew-symmetric and the maximum temperature in the helix increases. Nonuniform heating influences the temperature distribution independent of the curvature and torsion.

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