Ultrafast Laser Radiation and Conduction Heat Transfer in Biological Tissues

2005 ◽  
Author(s):  
Kyunghan Kim ◽  
Zhixiong Guo
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Thermal Wave ◽  
Pulse Train ◽  
Thermal Relaxation ◽  
Temperature Response ◽  
Single Pulse ◽  
Biological Tissues ◽  
Heat Diffusion ◽  
Local Temperature

Ultrafast laser radiation heat transfer in biological tissues is governed by time-dependent equation of radiative transfer and modeled using the transient discrete ordinates method. The divergence of radiative heat flux is then obtained and used for predicting the local temperature response due to radiation energy absorption within the ultrashort time period. To this end, the lumped method is employed and heat diffusion is negligible. Both single pulse and pulse train irradiations are considered. For the single pulse irradiation, the transient radiation field is obtained and the local temperature keeps rising until a time of about 20 times of the short pulse width; and then a stable local temperature profile is reached and maintained until the start of heat conduction. For the pulse train case (104 ultrashort pulses until 1 ms), the local temperature response is an accumulation of continuous single pulses because the thermal relaxation time of biological tissues was reported in the range of 1-100 sec and is much longer than the pulse train duration (1 ms). After a stable local temperature field is achieved, the hyperbolic heat conduction model is adopted to describe the heat conduction. MacCormark’s scheme is utilized for solving the thermal wave equations. Thermal wave behavior is observed during the heat transfer process. It is found that the hyperbolic wave model predicts a higher temperature rise than the classical heat diffusion model. After several thermal relaxation times the thermal wave behavior is substantially weakened and the predictions between the hyperbolic and diffusion models match.

Heat Transfer in Ultrafast Laser Tissue Welding

2005 ◽  
Author(s):  
Kyunghan Kim ◽  
Zhixiong Guo ◽  
Sunil Kumar
Keyword(s):  
Heat Transfer ◽  
Thermal Wave ◽  
Temperature Response ◽  
Ultrafast Laser ◽  
Heat Diffusion ◽  
Local Temperature ◽  
Hyperbolic Heat Conduction ◽  
Tissue Welding ◽  
Laser Tissue Welding ◽  
Ultrashort Laser

The objective of this research is to develop an appropriate model for simulating the transient heat transfer processes in tissue welding subject to irradiation of ultrashort laser pulses. The ultrafast laser tissue welding process is modeled in three steps. First, there is an immediate local temperature response due to radiation absorption during an ultrashort time period. The transient discrete ordinate method is employed to simulate the ultrashort laser pulse transport in tissue. The temporal radiation field is obtained and the lumped method is used for predicting the local temperature response. After a stable local temperature profile is achieved, the second step starts, in which the hyperbolic heat conduction model is adopted to describe the heat transfer. The thermal wave behavior is observed. It is found that the hyperbolic wave model predicts a higher temperature rise than the classical diffusion model. After about five thermal relaxation times the thermal wave behavior is substantially weakened and the heat diffusion predominates. The heat diffusion equation can accurately describe the heat transfer thereafter.

Nonclassical Heat Transfer Models for Laser-Induced Thermal Damage in Biological Tissues

2011 ◽  
Author(s):  
Jianhua Zhou ◽  
J. K. Chen ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Conduction ◽  
Temperature Gradient ◽  
Thermal Wave ◽  
Thermal Damage ◽  
Blood Perfusion ◽  
Biological Tissues ◽  
Phase Lag ◽  
Fourier Heat Conduction

To ensure personal safety and improve treatment efficiency in laser medical applications, one of the most important issues is to understand and accurately assess laser-induced thermal damage to biological tissues. Biological tissues generally consist of nonhomogeneous inner structures, in which heat flux equilibrates to the imposed temperature gradient via a thermal relaxation mechanism which cannot be explained by the traditional parabolic heat conduction model based on Fourier’s law. In this article, two non-Fourier heat conduction models, hyperbolic thermal wave model and dual-phase-lag (DPL) model, are formulated to describe the heat transfer in living biological tissues with blood perfusion and metabolic heat generation. It is shown that the non-Fourier bioheat conduction models could predict significantly different temperature and thermal damage in tissues from the traditional parabolic model. It is also found that the DPL bioheat conduction equations can be reduced to the Fourier heat conduction equations only if both phase lag times of the temperature gradient (τT) and the heat flux (τq) are zero. Effects of laser parameters and blood perfusion on the thermal damage simulated in tissues are also studied. The result shows that the overall effects of the blood flow on the thermal response and damage are similar to those of the time delay τT. The two-dimensional numerical results indicate that for a local heating with the heated spot being smaller than the tissue bulk, the variations of the non-uniform distributions of temperature suggest that the multi-dimensional effects of thermal wave and diffusion not be negligible.

Bio-Heat Transfer in a Model Skin Subject to a Train of Short Pulse Irradiation

2008 ◽  
Author(s):  
Jian Jiao ◽  
Zhixiong Guo
Keyword(s):  
Heat Transfer ◽  
Temperature Rise ◽  
Ultrashort Pulse ◽  
Short Pulse ◽  
Temperature Response ◽  
Biological Tissues ◽  
Skin Tissue ◽  
Discrete Ordinates ◽  
Transfer Model ◽  
Pulse Irradiation

Thermal analysis of biological tissues subject to a train of ultrashort pulse irradiations was made of developing a combined time-dependent radiation and conduction bio-heat transfer model. A model skin tissue stratified as three layers with different optical, thermal and physiological properties was considered. Temperature response of the skin tissue exposed to a single ultrashort pulse irradiation was firstly analyzed by the finite volume method in combination with the transient discrete ordinates method. This temperature rise was found to reach pseudo steady state within an extremely short time period in which thermal diffusion is negligible. Since the tissue properties were assumed to be constant during a train of pulse irradiation, this temperature rise subject to a single pulse can be employed for repeated pulses. In the same time, Pennes’ equation was employed to study the bio-heat transfer in the meso-time scale. The effects of pulse strengths and repetition rate on the temperature response in the multi-layer skin tissue were investigated.

scholarly journals Assessment of Hyperbolic Heat Transfer Equation in Theoretical Modeling for Radiofrequency Heating Techniques

2008 ◽  
Vol 2 (1) ◽  
pp. 22-27 ◽  
Author(s):  
Juan A López-Molina ◽  
Maria J Rivera ◽  
Macarena Trujillo ◽  
Fernando Burdío ◽  
Juan L Lequerica ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Transfer Equation ◽  
Cardiac Tissue ◽  
Thermal Relaxation ◽  
Propagation Speed ◽  
Biological Tissues ◽  
Heating Time ◽  
Theoretical Modeling ◽  
Rf Heating ◽  
Heat Transfer Equation

Theoretical modeling is a technique widely used to study the electrical-thermal performance of different surgical procedures based on tissue heating by use of radiofrequency (RF) currents. Most models employ a parabolic heat transfer equation (PHTE) based on Fourier’s theory, which assumes an infinite propagation speed of thermal energy. We recently proposed a one-dimensional model in which the electrical-thermal coupled problem was analytically solved by using a hyperbolic heat transfer equation (HHTE), i.e. by considering a non zero thermal relaxation time. In this study, we particularized this solution to three typical examples of RF heating of biological tissues: heating of the cornea for refractive surgery, cardiac ablation for eliminating arrhythmias, and hepatic ablation for destroying tumors. A comparison was made of the PHTE and HHTE solutions. The differences between their temperature profiles were found to be higher for lower times and shorter distances from the electrode surface. Our results therefore suggest that HHTE should be considered for RF heating of the cornea (which requires very small electrodes and a heating time of 0.6 s), and for rapid ablations in cardiac tissue (less than 30 s).

Numerical simulation of non-Fourier effects in combined heat transfer

2010 ◽  
Vol 225 (2) ◽  
pp. 429-436
Author(s):  
E Izadpanah ◽  
S Talebi ◽  
M H Hekmat
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Heat Conduction Equation ◽  
Splitting Method ◽  
Thermal Relaxation ◽  
Conduction Equation ◽  
Hyperbolic Heat Conduction ◽  
Wave Nature ◽  
Fourier Heat Conduction ◽  
Combined Heat Transfer

The non-Fourier effects on transient and steady temperature distribution in combined heat transfer are studied. The processes of coupled conduction and radiation heat transfer in grey, absorbing, emitting, scattering, one-dimensional medium with black boundary surfaces are analysed numerically. The hyperbolic heat conduction equation is solved by flux splitting method, and the radiative transfer equation is solved by P1 approximate method. The transient thermal responses obtained from non-Fourier heat conduction equation are compared with those obtained from the Fourier heat conduction equation. The results show that the non-Fourier effect can be important when the conduction to radiation parameter and the thermal relaxation time are larger. Further, the radiation effect is more pronounced at small values of single scattering albedo and conduction to radiation parameters. Analysis results indicate that the internal radiation in the medium significantly influences the wave nature.

scholarly journals Теплопроводность за пределами закона Фурье

2021 ◽  
Vol 91 (1) ◽  
pp. 5
Author(s):  
А.И. Жмакин
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Conduction ◽  
Fractional Derivatives ◽  
Nonlinear Effects ◽  
Biological Tissues ◽  
Phase Lag ◽  
Fourier Law

The Fourier law adequately describes heat conduction in most practical problems. However for heat transfer in fast processes and at micro/nano scales, in materials with inner structure (porous media, biological tissues) other models are needed that account for the nonlinear effects and both time (memory) and space nonlocality. Such models including phase lag models, phonon and thermodynamics models as well as fractional derivatives models are reviewed. .

Mass Nature of Heat and Its Applications IV: Thermal Wave and Periodic Temperature Oscillation in Metallic Films Heated by Ultra-Short Pulsed Lasers

2010 ◽  
Author(s):  
Haidong Wang ◽  
Weigang Ma ◽  
Xing Zhang ◽  
Wei Wang
Keyword(s):  
Heat Transfer ◽  
Femtosecond Laser ◽  
Electron Temperature ◽  
Thermal Wave ◽  
Laser Heating ◽  
Rear Surface ◽  
Temperature Response ◽  
Propagation Speed ◽  
Pulsed Lasers ◽  
Metallic Films

The ultra-fast heat transfer in metallic films has attracted great interest in modern femtosecond laser processing and metallic film manufacturing. Considering the unphysical infinite propagation speed of heat disturbances based on Fourier’s model, some hyperbolic heat transfer models have been developed in the past decades, leading to the character of thermal wave in metallic films under ultra-fast laser heating conditions. In this paper the thermomass model is applied to obtain the governing equation for heat conduction in the thin films under pulsed laser heating, which is a damped wave equation and identical with that based on the Hyperbolic Two-Step (HTS) model. The semi-implicit Crank-Nicholson scheme is used to solve governing equations. Numerical results show that there may be two kinds of temperature oscillations existed in metallic films heated by ultra-short pulsed lasers, and the thermally oscillating boundary condition usually dominates over that caused by thermal wave induced oscillation of the electron temperature, which is validated by the measurement of the temperature response at the rear surface using a femtosecond laser pump-probe system. The measured electron temperature curve agrees well with the theoretically predicted one.

Nonclassical Thermal Effects in Stokes’ Second Problem for Micropolar Fluids

2004 ◽  
Vol 72 (4) ◽  
pp. 468-474 ◽  
Author(s):  
F. S. Ibrahem ◽  
I. A. Hassanien ◽  
A. A. Bakr
Keyword(s):  
Heat Transfer ◽  
Relaxation Time ◽  
Heat Conduction ◽  
Velocity Field ◽  
Angular Velocity ◽  
Thermal Effects ◽  
Thermal Relaxation ◽  
Micropolar Fluids ◽  
Displacement Thickness ◽  
Stokes Second Problem

The MCF model is used to study the nonclassical heat conduction effects in Stokes’ second problem of a micropolar fluid. The effects of the thermal relaxation time and the structure wave on angular velocity, velocity field, and temperature are investigated. The skin friction, the displacement thickness, and the rate of the heat transfer at the plate are determined.

scholarly journals Twenty-first century regional temperature response in Chile based on empirical-statistical downscaling

2021 ◽  
Author(s):  
Sebastian G. Mutz ◽  
Samuel Scherrer ◽  
Ilze Muceniece ◽  
Todd A. Ehlers
Keyword(s):  
Statistical Models ◽  
Temperature Response ◽  
Local Scale ◽  
First Century ◽  
Local Temperature ◽  
Future Climate Change ◽  
Weather Station ◽  
Temperature Changes ◽  
Scale Temperature ◽  
Twenty First Century

AbstractLocal scale estimates of temperature change in the twenty-first century are necessary for informed decision making in both the public and private sector. In order to generate such estimates for Chile, weather station data of the Dirección Meteorológica de Chile are used to identify large-scale predictors for local-scale temperature changes and construct individual empirical-statistical models for each station. The geographical coverage of weather stations ranges from Arica in the North to Punta Arenas in the South. Each model is trained in a cross-validated stepwise linear multiple regression procedure based on (24) weather station records and predictor time series derived from ERA-Interim reanalysis data. The time period 1979–2000 is used for training, while independent data from 2001 to 2015 serves as a basis for assessing model performance. The resulting transfer functions for each station are then directly coupled to MPI-ESM simulations for future climate change under emission scenarios RCP2.6, RCP4.5 and RCP 8.5 to estimate the local temperature response until 2100 A.D. Our investigation into predictors for local scale temperature changes support established knowledge of the main drivers of Chilean climate, i.e. a strong influence of the El Niño Southern Oscillation in northern Chile and frontal system-governed climate in central and southern Chile. Temperature downscaling yields high prediction skill scores (ca. 0.8), with highest scores for the mid-latitudes. When forced with MPI-ESM simulations, the statistical models predict local temperature deviations from the 1979–2015 mean that range between − 0.5–2 K, 0.5–3 K and 2–7 K for RCP2.6, RCP4.5 and RCP8.5 respectively.

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