• Title/Summary/Keyword: bioheat transfer

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Thermal Distribution in Living Tissue during Warm Needling Therapy (온침 시술 시 생체 조직 내 열분포 분석에 관한 연구)

  • Kim, Jongyeon;Lee, Jong-Soo
    • Journal of Korean Medicine Rehabilitation
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    • v.24 no.3
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    • pp.111-119
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    • 2014
  • Objectives This study aims to analyze a thermal distribution in biological living tissue during warm needling therapy by using a finite element method. The analysis provides an understanding of warm needling's efficacy and safety. Methods A model which consisted of four-layered tissue and stainless steel needle was adopted to analyze the thermal distribution in living tissue with a bioheat transfer analysis. The governing equation for the analysis was a Pennes' bioheat equation. A heat source characteristic of warm needling therapy was obtained by previous experimental measurements. The first analysis of the time-dependent temperature distribution was conducted through points on a boundary between the needle and the tissue. The second analysis was conducted to visualize the horizontal temperature distribution. Results When heat source's peak temperatures was above $500^{\circ}C$ and temperature rising rates were relatively slow, the peak temperature at skin surface exceeded a threshold of pain and tissue damage ($45^{\circ}C$), whereas when the peak temperature was around $400^{\circ}C$, the peak temperature at the skin surface was within a safe limit. In addition, the conduction of combustion energy from the moxa was limited to the skin layer around the needle. Conclusions The results suggest that the skin layer around the needle can be heated effectively by warm needling therapy, but it appears to have little effect at the deeper tissue. These findings enhance our understanding of the efficacy and the safety of the warm needling therapy.

UNTEADY HEAT FLOW AND TEMPERATURE VARIATION IN HUMAN SST REGIONS

  • Sanyal, D.C.;Maji, N.K.
    • Journal of applied mathematics & informatics
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    • v.9 no.2
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    • pp.731-744
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    • 2002
  • The temperature distribution in human skin and subdermal tissue layer is presented using bioheat transfer equation. The body temperature is determined by the balance between heat produced and heat lost by our body. The time-dependent solutions have been found to be affected by the metabolic heat generation rate, blood mass flow, the rate of evaporation of perspiration and also by the atmospheric temperature. The analytic solutions for different layers have been calculated numerically and are also shown graphically.

The Effects of Warm and Cold Stimulations on the Temperature Distribution in the Prostate (냉.온열의 반복 자극이 전립선 내부의 온도 분포에 미치는 영향)

  • 문우석;백병준;박복춘;김철생
    • Journal of Biomedical Engineering Research
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    • v.23 no.6
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    • pp.467-475
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    • 2002
  • Hyperthermia using transrectal thermal probes has been used for a noninvasive treatment of prostate diseases. However it is known that heating the rectal wall at excessively high temperature can lead to destruction of the rectal mucous membrane. and it is difficult to maintain an optimum temperature over the entire prostate. Thus, a more accurate understanding of the heat transfer mechanism between prostate and hyperthermia system is needed Numerical analysis was performed to investigate how the cold/warm stimulations on the prostate surface affect the temperature distribution in the prostate model. The general purpose software "FLUENT" was used for obtaining a finite volume solution to the unsteady conduction equation and to calculate the time-varying temperature in the prostate. Effects of the warm/cold stimulations and the stimulation frequency on the temperature distribution were simulated. and we visualized how hyperthermia affected the inside of the prostate. It was found that the effect of hyperthermia by using a typical heating method is limited due to the low thermal conductivity of the prostate. Consecutive repetitions of warm and cold stimulations were considered to provide the thermal irritations inside a prostate. The effects of temperature difference and duration of warm/cold stimulations were investigated, and basic data for the optimum period and effective patterns of stimulations were obtained. A simplified bioheat equation was also solved to describe effects of the blood flow on the blood-tissue heat transfer. The effect of blood flow was not dominant compared to that of warm/cold stimulations. These results might be used as data for design of prostate treating probe, prostatic therapy and thermal stimulation effects on the prostate.

Simulation and Measurement of Thermal Ablation in a Tissue-Mimicking Phantom and Ex-Vivo Porcine Liver by Using High Intensity Focused Ultrasound

  • Lee, Kang Il
    • Journal of the Korean Physical Society
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    • v.73 no.9
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    • pp.1289-1294
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    • 2018
  • The present study aims to investigate experimentally and theoretically thermal ablation in soft tissues by using high intensity focused ultrasound (HIFU) to assess tissue damage during HIFU thermotherapy. The HIFU field was calculated by solving the axisymmetric Khokhlov-Zabolotskaya-Kuznetsov equation from the frequency-domain perspective. The temperature field was calculated by solving Pennes' bioheat transfer equation, and the thermal dose required to create a thermal lesion was calculated by using the thermal dose formula based on the thermal dose of a 240-min exposure at $43^{\circ}C$. In order to validate the simulation results, we performed thermal ablation experiments in a tissue-mimicking phantom and ex-vivo porcine liver for two different HIFU source conditions by using a 1.1-MHz, single-element, spherically focused HIFU transducer. The small difference between the measured and the predicted lesion sizes suggests that the implementation of the numerical model used here should be modified to iteratively allow for temperature-dependent changes in the physical properties of tissues.

The effects of thermal relaxation times in living tissues under the TPL bio-heat model with experimental study

  • Ibrahim A. Abbas;Aboelnour Abdalla;Fathi Anwar;Hussien Sapoor
    • Advances in materials Research
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    • v.12 no.1
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    • pp.31-42
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    • 2023
  • In the present article, the effects of three thermal relaxation times in living tissue under the three-phaselag (TPL) bioheat model are introduced. Using the Laplace transforms, the analyticalsolution of the temperature and the resulting thermal damagesin living tissues are obtained. The experimental data are used to validate the analytical solutions. By the formulations of Arrhenius, the thermal damage of tissue is estimated. Numerical outcomes for the temperature and the resulting of thermal damages are presented graphically. The effects of parameters, such as thermalrelaxation times, blood perfusion rate on tissue temperature are also discussed in detail.

Nonlocal heat conduction approach in biological tissue generated by laser irradiation

  • Abbas, Ibrahim A.;Abdalla, Aboelnour;Sapoor, Hussien
    • Advances in materials Research
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    • v.11 no.2
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    • pp.111-120
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    • 2022
  • A novel nonlocal model with one thermal relaxation time is presented to investigates the thermal damages and the temperature in biological tissues generated by laser irradiations. To obtain these models, we used the theory of the non-local continuum proposed by Eringen. The thermal damages to the tissues are assessed completely by the denatured protein ranges using the formulations of Arrhenius. Numerical results for temperature and the thermal damage are graphically presented. The effects nonlocal parameters and the relaxation time on the distributions of physical fields for biological tissues are shown graphically and discussed.

Numerical Analysis of the Wavelength Dependence in Low Level Laser Therapy (LLLT) Using a Finite Element Method

  • Yoon, Jin-Hee;Park, Ji-Won;Youn, Jong-In
    • The Journal of Korean Physical Therapy
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    • v.22 no.6
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    • pp.77-83
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    • 2010
  • Purpose: The aim of this study was to do numerical analysis of the wavelength dependence in low level laser therapy (LLLT) using a finite element method (FEM). Methods: Numerical analysis of heat transfer based on a Pennes' bioheat equation was performed to assess the wavelength dependence of effects of LLLT in a single layer and in multilayered tissue that consists of skin, fat and muscle. The three different wavelengths selected, 660 nm, 830 nm and 980 nm, were ones that are frequently used in clinic settings for the therapy of musculoskeletal disorders. Laser parameters were set to the power density of 35.7 W/$cm^2$, a spot diameter of 0.06 cm, and a laser exposure time of 50 seconds for all wavelengths. Results: Temperature changes in tissue based on a heat transfer equation using a finite element method were simulated and were dominantly dependent upon the absorption coefficient of each tissue layer. In the analysis of a single tissue layer, heat generation by fixed laser exposure at each wavelength had a similar pattern for increasing temperature in both skin and fat (980 nm > 660 nm > 830 nm), but in the muscle layer 660nm generated the most heat (660 nm ${\gg}$ 980 nm > 830 nm). The heat generation in multilayered tissue versus penetration depth was shown that the temperature of 660 nm wavelength was higher than those of 830 nm and 980 nm Conclusion: Numerical analysis of heat transfer versus penetration depth using a finite element method showed that the greatest amount of heat generation is seen in multilayered tissue at = 660 nm. Numerical analysis of heat transfer may help lend insight into thermal events occurring inside tissue layers during low level laser therapy.

A Study For Optimizing Input Waveforms In Radiofrequency Liver Tumor Ablation Using Finite Element Analysis (유한 요소 해석을 이용한 고주파 간 종양 절제술의 입력 파형 최적화를 위한 연구)

  • Lim, Do-Hyung;NamGung, Bum-Seok;Lee, Tae-Woo;Choi, Jin-Seung;Tack, Gye-Rae;Kim, Han-Sung
    • Journal of Biomedical Engineering Research
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    • v.28 no.2
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    • pp.235-243
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    • 2007
  • Hepatocellular carcinoma is significant worldwide public health problem with an estimated annually mortality of 1,000,000 people. Radiofrequency (RF) ablation is an interventional technique that in recent years has come to be used for treatment of the hepatocellualr carcinoma, by destructing tumor tissues in high temperatures. Numerous studies have been attempted to prove excellence of RF ablation and to improve its efficiency by various methods. However, the attempts are sometimes paradox to advantages of a minimum invasive characteristic and an operative simplicity in RF ablation. The aim of the current study is, therefore, to suggest an improved RF ablation technique by identifying an optimum RF pattern, which is one of important factors capable of controlling the extent of high temperature region in lossless of the advantages of RF ablation. Three-dimensional finite element (FE) model was developed and validated comparing with the results reported by literature. Four representative Rf patterns (sine, square, exponential, and simulated RF waves), which were corresponding to currents fed during simulated RF ablation, were investigated. Following parameters for each RF pattern were analyzed to identify which is the most optimum in eliminating effectively tumor tissues. 1) maximum temperature, 2) a degree of alteration of maximum temperature in a constant time range (30-40 second), 3) a domain of temperature over $47^{\circ}C$ isothermal temperature (IT), and 4) a domain inducing over 63% cell damage. Here, heat transfer characteristics within the tissues were determined by Bioheat Governing Equation. Developed FE model showed 90-95% accuracy approximately in prediction of maximum temperature and domain of interests achieved during RF ablation. Maximum temperatures for sine, square, exponential, and simulated RF waves were $69.0^{\circ}C,\;66.9^{\circ}C,\;65.4^{\circ}C,\;and\;51.8^{\circ}C$, respectively. While the maximum temperatures were decreased in the constant time range, average time intervals for sine, square, exponential, and simulated RE waves were $0.49{\pm}0.14,\;1.00{\pm}0.00,\;1.65{\pm}0.02,\;and\;1.66{\pm}0.02$ seconds, respectively. Average magnitudes of the decreased maximum temperatures in the time range were $0.45{\pm}0.15^{\circ}C$ for sine wave, $1.93{\pm}0.02^{\circ}C$ for square wave, $2.94{\pm}0.05^{\circ}C$ for exponential wave, and $1.53{\pm}0.06^{\circ}C$ for simulated RF wave. Volumes of temperature domain over $47^{\circ}C$ IT for sine, square, exponential, and simulated RF waves were 1480mm3, 1440mm3, 1380mm3, and 395mm3, respectively. Volumes inducing over 63% cell damage for sine, square, exponential, and simulated RF waves were 114mm3, 62mm3, 17mm3, and 0mm3, respectively. These results support that applying sine wave during RF ablation may be generally the most optimum in destructing effectively tumor tissues, compared with other RF patterns.