Rise of Tissue Temperature Induced by Reduced Blood Perfusion Caused by External Pressure

1996 ◽  
pp. 391-397
Author(s):  
Y. Yamada ◽  
H. Ishiguro ◽  
M. Yamashita ◽  
T. Tanaka ◽  
M. Takeuchi ◽  
...  
Keyword(s):  
Blood Perfusion ◽  
External Pressure ◽  
Tissue Temperature

Lumped Parameter Thermal Model for the Study of Vascular Reactivity in the Fingertip

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
O. Ley ◽  
C. Deshpande ◽  
B. Prapamcham ◽  
M. Naghavi
Keyword(s):  
Heat Flux ◽  
Blood Flow ◽  
Thermal Model ◽  
Vascular Reactivity ◽  
Arterial Occlusion ◽  
Blood Perfusion ◽  
Cost Effective ◽  
Venous Occlusion ◽  
Cardiovascular Complications ◽  
Tissue Temperature

Vascular reactivity (VR) denotes changes in volumetric blood flow in response to arterial occlusion. Current techniques to study VR rely on monitoring blood flow parameters and serve to predict the risk of future cardiovascular complications. Because tissue temperature is directly impacted by blood flow, a simplified thermal model was developed to study the alterations in fingertip temperature during arterial occlusion and subsequent reperfusion (hyperemia). This work shows that fingertip temperature variation during VR test can be used as a cost-effective alternative to blood perfusion monitoring. The model developed introduces a function to approximate the temporal alterations in blood volume during VR tests. Parametric studies are performed to analyze the effects of blood perfusion alterations, as well as any environmental contribution to fingertip temperature. Experiments were performed on eight healthy volunteers to study the thermal effect of 3min of arterial occlusion and subsequent reperfusion (hyperemia). Fingertip temperature and heat flux were measured at the occluded and control fingers, and the finger blood perfusion was determined using venous occlusion plethysmography (VOP). The model was able to phenomenologically reproduce the experimental measurements. Significant variability was observed in the starting fingertip temperature and heat flux measurements among subjects. Difficulty in achieving thermal equilibration was observed, which indicates the important effect of initial temperature and thermal trend (i.e., vasoconstriction, vasodilatation, and oscillations).

ANALYTICAL SOLUTIONS OF NON-FOURIER PENNES AND CHEN–HOLMES EQUATIONS

2012 ◽  
Vol 05 (04) ◽  
pp. 1250022 ◽  
Author(s):  
WEIPING ZHU ◽  
FANGBAO TIAN ◽  
PENG RAN
Keyword(s):  
Heat Transfer ◽  
Analytical Solutions ◽  
Laplace Transformation ◽  
Solution Method ◽  
Thermal Relaxation ◽  
Blood Perfusion ◽  
Good Alternative ◽  
Tissue Temperature ◽  
Particular Solution ◽  
Insight Into

The analytical solutions of non-Fourier Pennes and Chen–Holmes equations are obtained using the Laplace transformation and particular solution method in the present paper. As an application, the effects of the thermal relaxation time τ, the blood perfusion wb, and the blood flow velocity v on the biological skin and inner tissue temperature T are studied in detail. The results obtained in this study provide a good alternative method to study the bio-heat and a biophysical insight into the understanding of the heat transfer in the biotissue.

Prediction of skin burn injury. Part 2: Parametric and sensitivity analysis

2002 ◽  
Vol 216 (3) ◽  
pp. 171-183 ◽  
Author(s):  
E Y-K Ng ◽  
L T Chua
Keyword(s):  
Thermal Conductivity ◽  
Sensitivity Analysis ◽  
Burn Injury ◽  
Convective Heat Transfer Coefficient ◽  
Blood Perfusion ◽  
Tissue Temperature ◽  
Two Dimensional ◽  
Perfusion Rate ◽  
Injury Threshold ◽  
Blood Perfusion Rate

Part 2 of this paper presents an analysis of variance (ANOVA) for investigating the precedence of the various parameters, and the effects of varying these parameters, in assessment of burn injury resulting from the exposure of skin surface to heat sources. A one-dimensional model based on the finite difference method (FDM), as implemented in a spreadsheet software application, is applied to the assessment of burn injury. Henriques' theory of skin burns is used for determining the spatial and temporal extent of tissue damage. The ranks of the effects of various factors were obtained. It was found that the highest ranked factor is the initial tissue temperature followed by the thermal conductivity of the epidermal layer. The effect of blood perfusion rate is ranked much below the combinations of other factors. The results from the present numerical experiment agree well with the results obtained by Palla. Sensitivity analysis of the critical exposure levels was also carried out and results are discussed. In this study, the effects of the various parameters on injury threshold were investigated. Again, the results indicate that the four parameters: thermal conductivity of the epidermis and dermis, convective heat transfer coefficient and initial tissue temperature, have a pronounced influence on assessing the burn injury threshold. It was also found that fat thermal conductivity and blood perfusion rate have no obvious effect on injury threshold. A two-dimensional analysis was further conducted to determine the sensitivity of the predicted injury to the values of frequency factor, P, and apparent activation energy, Δ E, used in the models. Part 1 of this study details the development of the computer models based on the one- and two-dimensional bioheat equations.

A Comparative Evaluation of Unconstrained Optimization Methods Applied to the Thermal Tomography Problem

1985 ◽  
Vol 107 (3) ◽  
pp. 228-233 ◽  
Author(s):  
S. T. Clegg ◽  
R. B. Roemer
Keyword(s):  
Unconstrained Optimization ◽  
Blood Perfusion ◽  
Optimization Methods ◽  
Sensitivity Study ◽  
Initial Guess ◽  
Optimization Techniques ◽  
Temperature Fields ◽  
Tissue Temperature ◽  
Initial Attempt ◽  
Error Space

In cancer hyperthermia treatments, it is important to be able to predict complete tissue temperature fields from sampled temperatures taken at the limited number of locations allowed by clinical constraints. An initial attempt to do this automatically using unconstrained optimization techniques to minimize the differences between experimental temperatures and temperatures predicted from treatment simulations has been previously reported [1]. This paper reports on a comparative study which applies a range of different optimization techniques (relaxation, steepest descent, conjugate gradient, Gauss, Box-Kanemasu, and Modified Box-Kanemasu) to this problem. The results show that the Gauss method converges more rapidly than the others, and that it converges to the correct solution regardless of the initial guess for the unknown blood perfusion vector. A sensitivity study of the error space is also performed, and the relationships between the error space characteristics and the comparative speeds of the optimization techniques are discussed.

scholarly journals Analysis of the effect of external heating in the human tissue: A finite element approach

2020 ◽  
Vol 26 (4) ◽  
pp. 251-262
Author(s):  
Mridul Sannyal ◽  
Abul Mukid Mohammad Mukaddes ◽  
Md. Matiar Rahman ◽  
M. A. H. Mithu
Keyword(s):  
Finite Element ◽  
Human Tissue ◽  
Transfer Problem ◽  
Thermal Response ◽  
Blood Perfusion ◽  
Element Model ◽  
Bioheat Transfer ◽  
Tissue Temperature ◽  
Blood Temperature ◽  
External Heating

AbstractThermal therapy which involves either raising or lowering tissue temperature to treat malignant cells needs precise acknowledgment of thermal history inside the biological system to ensure effective treatment. For this purpose, this study presents a two-dimensional unsteady finite element model (FEM) of the bioheat transfer problem based on Pennes bio-heat equation to analyze the thermal response of tissue subject to external heating. Crank-Nikolson scheme was used for the unsteady solution. A finite element code was developed using C language to calculate results. The obtained numerical result was compared with the analytical and other numerical results available in the literature. A good agreement was found from the comparison. Temperature distribution inside the human body due to constant and sinusoidal spatial and surface heating were analyzed. Response to point heating was also investigated. Moreover, a sensitivity analysis was carried out to know the effect of various parameters, i.e. blood temperature, thermal conductivity, and blood perfusion rate on tissue temperature. The outcome of this study will be helpful for the researchers and physicians involved in the thermal treatment of human tissue.

scholarly journals Possible Error in Reflection Pulse Oximeter Readings as a Result of Applied Pressure

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Ilya Fine ◽  
Alexander Kaminsky
Keyword(s):  
Blood Flow ◽  
Pulse Oximetry ◽  
Applied Pressure ◽  
Form Factors ◽  
Blood Perfusion ◽  
Modern Medicine ◽  
External Pressure ◽  
Reflection Mode ◽  
Local Pressure ◽  
Arterial Blood

Pulse oximetry is one of the most widely used techniques in modern medicine. In pulse oximetry, photoplethysmography (PPG) signals are measured at two different wavelengths and converted into the parameter Gamma, which is used to calculate the oxygen saturation of arterial blood. Although most pulse oximetry sensors are based on transmission geometry, the reflection mode is required for different form factors such as the forehead or wrists. In reflection oximetry, local pressure is applied to the measurement surface. We investigated the relationship between applied pressure and Gamma and found that for the reflection mode, Gamma tends to increase with increasing applied pressure. To explain this, we described the PPG signal in terms of two alternative models: a volumetric model and a Scattering-Driven Model (SDM). We assumed that the application of external pressure results in a decrease in local blood flow. We showed that only SDM correctly qualitatively describes Gamma as a function of the decrease in blood flow. We concluded that both described models coexist and that the relative influence of each depends on the measurement geometry and blood perfusion in the skin.

Simulation of Empirical Correlations Between Temperatures and Blood Perfusion During Heating Using a Temperature-Dependent Blood Perfusion Model

2004 ◽  
Author(s):  
Cuiye Chen ◽  
Robert B. Roemer
Keyword(s):  
Blood Flow ◽  
Blood Perfusion ◽  
Step Function ◽  
Human Muscle ◽  
Tissue Temperature ◽  
Thigh Muscle ◽  
Temperature Dependent ◽  
In Vivo Experiments ◽  
Perfusion Model

This study applies a recently developed temperature-dependent blood perfusion model (TDBPM) coupled with a modified, one-dimensional Pennes bioheat transfer equation to predict the blood perfusion and temperature responses to step function microwave heating applied in the in vivo experiments performed by Sekins’ et al. [1] on human thigh muscle. The TDBPM model links the perfusion increase to the tissue temperature elevation based on physiological mechanisms underlying this temperature-blood-perfusion change phenomenon, i.e., a pharmacokinetic compartmental model. This physiology-based model avoids using ad hoc time delays between blood perfusion increases and tissue temperature elevations as done in previous efforts. It also includes a mechanism that produces the threshold temperature for blood flow increases that has been observed in vivo. In our recent study [2], the TDBPM model was used to simulate both the constant temperature water bath heating used in the in vivo experiments on rat leg muscle performed by Song et al. [3], and the step function microwave heating applied in the in vivo experiments on canine thigh muscle performed by Roemer et al. [4]. The blood perfusion rates predicted by the model are compared with those in vivo experimental data obtained in rat muscle and human muscle and good agreement was obtained. The TDBPM provides a possible explanation to the biochemical and biophysical origins of the relationships between temperature and blood flow that observed in rat muscle and human muscle. The physiology-based TDBPM is a simple, generic model of muscle blood flow responses of different animals to different heating conditions, which provides the type of fundamental information needed for the design of methods to thermally control blood flow in medical applications.

Temperature Elevation in the Human Eye Due To Intraocular Projection Prosthesis Device

2021 ◽  
Vol 13 (6) ◽  
Author(s):  
Dipika Gongal ◽  
Siddhant Thakur ◽  
Ashay Panse ◽  
John A. Stark ◽  
Charles Q. Yu ◽  
...  
Keyword(s):  
Power Dissipation ◽  
Corneal Transplantation ◽  
Blood Perfusion ◽  
Element Model ◽  
Corneal Opacity ◽  
Implantable Devices ◽  
Tissue Temperature ◽  
Eye Model ◽  
Bionic Eye ◽  
Transient Thermal

Abstract Corneal opacity is a leading cause of blindness worldwide. Corneal transplantation and keratoprosthesis can restore vision but have limitations due to the shortage of donor corneas and complications due to infection. A proposed alternative treatment using an intraocular projection prosthesis device can treat corneal disease. In this study, we perform a transient thermal analysis of the bionic eye model to determine the power the device can produce without elevating the eye tissue temperature above the 2°C limit imposed by the international standard for implantable devices. A 3D finite element model, including blood perfusion and natural convection fluid flow of the eye, was created. The device was placed 1.95 mm from the iris, which experienced less than 2°C rise in the tissue temperature at a maximum power dissipation of LED at 100 mW and microdisplay at 25 mW.

scholarly journals Level of Cutaneous Blood Flow Depression During Cryotherapy Depends on Applied Temperature: Criteria for Protocol Design

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Sepideh Khoshnevis ◽  
R. Matthew Brothers ◽  
Kenneth R. Diller
Keyword(s):  
Exposure Time ◽  
Tissue Injury ◽  
Soft Tissue Injury ◽  
Blood Perfusion ◽  
Dose Effect ◽  
Tissue Temperature ◽  
Vascular Response ◽  
Local Skin ◽  
Skin Perfusion ◽  
And Control

Cryotherapy is commonly used for the management of soft tissue injury. The dose effect of the applied cooling temperature has not been quantified previously. Six subjects were exposed during five different experiments to local skin temperatures of 16.6 °C, 19.8 °C, 24.7 °C, 27.3 °C, and 37.2 °C for 1 h of active heat transfer followed by 2 h of passive environmental interaction. Skin blood perfusion and temperature were measured continuously at treatment and control sites. All treatments resulted in significant changes in cutaneous vascular conductance (CVC, skin perfusion/mean arterial pressure) compared to baseline values. The drop in CVC for cooling to both 19.8 °C and 16.6 °C was significantly larger than for 27.3 °C (P < 0.05 and P < 0.0005, respectively). The depression of CVC for cooling to 16.6 °C was significantly larger than at 24.7 °C (P < 0.05). Active warming at 37.2 °C produced more than a twofold increase in CVC (P < 0.05). A simulation model was developed to describe the coupled effects of exposure time and temperature on skin perfusion. The model was applied to define an equivalent cooling dose defined by exposure time and temperature that produced equivalent changes in skin perfusion. The model was verified with data from 22 independent cryotherapy experiments. The equivalent doses were applied to develop a nomogram to identify therapeutic time and temperature combinations that would produce a targeted vascular response. The nomogram may be applied to design cryotherapy protocols that will yield a desired vascular response history that may combine the benefits of tissue temperature reduction while diminishing the risk of collateral ischemic injury.

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