A New Fundamental Bioheat Equation for Muscle Tissue—Part II: Temperature of SAV Vessels

2001 ◽  
Vol 124 (1) ◽  
pp. 121-132 ◽  
Author(s):  
Liang Zhu ◽  
Lisa X. Xu ◽  
Qinghong He ◽  
Sheldon Weinbaum
Keyword(s):  
Source Term ◽  
Vascular Anatomy ◽  
Blood Perfusion ◽  
Surrounding Tissue ◽  
Inlet Temperature ◽  
Bioheat Equation ◽  
Temperature Variations ◽  
Relative Contribution ◽  
Branching Patterns ◽  
Vascular Branching

In this study, a new theoretical framework was developed to investigate temperature variations along countercurrent SAV blood vessels from 300 to 1000 μm diameter in skeletal muscle. Vessels of this size lie outside the range of validity of the Weinbaum-Jiji bioheat equation and, heretofore, have been treated using discrete numerical methods. A new tissue cylinder surrounding these vessel pairs is defined based on vascular anatomy, Murray’s law, and the assumption of uniform perfusion. The thermal interaction between the blood vessel pair and surrounding tissue is investigated for two vascular branching patterns, pure branching and pure perfusion. It is shown that temperature variations along these large vessel pairs strongly depend on the branching pattern and the local blood perfusion rate. The arterial supply temperature in different vessel generations was evaluated to estimate the arterial inlet temperature in the modified perfusion source term for the s vessels in Part I of this study. In addition, results from the current research enable one to explore the relative contribution of the SAV vessels and the s vessels to the overall thermal equilibration between blood and tissue.

A New Fundamental Bioheat Equation for Muscle Tissue: Part I—Blood Perfusion Term

1997 ◽  
Vol 119 (3) ◽  
pp. 278-288 ◽  
Author(s):  
S. Weinbaum ◽  
L. X. Xu ◽  
L. Zhu ◽  
A. Ekpene
Keyword(s):  
Heat Transfer ◽  
Muscle Tissue ◽  
Source Term ◽  
Venous Return ◽  
Blood Perfusion ◽  
Efficiency Coefficient ◽  
Bioheat Equation ◽  
Or Efficiency ◽  
Cross Sectional ◽  
Transfer Unit

A new model for muscle tissue heat transfer has been developed using Myrhage and Eriksson’s [23] description of a muscle tissue cylinder surrounding secondary (s) vessels as the basic heat transfer unit. This model provides a rational theory for the venous return temperature for the perfusion source term in a modified Pennes bioheat equation, and greatly simplifies the anatomical description of the microvascular architecture required in the Weinbaum-Jiji bioheat equation. An easy-to-use closed-form analytic expression has been derived for the difference between the inlet artery and venous return temperatures using a model for the countercurrent heat exchange in the individual muscle tissue cylinders. The perfusion source term calculated from this model is found to be similar in form to the Pennes’s source term except that there is a correction factor or efficiency coefficient multiplying the Pennes term, which rigorously accounts for the thermal equilibration of the returning vein. This coefficient is a function of the vascular cross-sectional geometry of the muscle tissue cylinder, but independent of the Peclet number in contrast to the recent results in Brinck and Werner [8]. The value of this coefficient varies between 0.6 and 0.7 for most muscle tissues. In part II of this study a theory will be presented for determining the local arterial supply temperature at the inlet to the muscle tissue cylinder.

The Bleed Off Perfusion Term in the Weinbaum-Jiji Bioheat Equation

1992 ◽  
Vol 114 (4) ◽  
pp. 539-542 ◽  
Author(s):  
S. Weinbaum ◽  
L. M. Jiji ◽  
D. E. Lemons
Keyword(s):  
Energy Equation ◽  
Source Term ◽  
Venous Return ◽  
Effective Conductivity ◽  
Blood Perfusion ◽  
Tissue Temperature ◽  
Bioheat Equation ◽  
Countercurrent System ◽  
Thermal Equilibration ◽  
Arteries And Veins

The microvascular organization and thermal equilibration of the primary and secondary arteries and veins that comprise the bleed off circulation to the muscle fibers from the parent countercurrent supply artery and veins are analyzed. The blood perfusion heat source term in the tissue energy equation is shown to be related to this vascular organization and to undergo a fundamental change in behavior as one proceeds from the more peripheral tissue, where the perfusion term is proportional to the Ta - Tv difference in the parent supply vessels, to the deeper tissue layers where the bleed off vessels themselves form a branching countercurrent system for each muscle tissue cylinder and the venous return temperature can vary between the local tissue temperature and Ta. The consequences of this change in behavior are examined for the Weinbaum-Jiji bioheat equation and a modified expression for the effective conductivity of perfused tissue is derived for countercurrent bleed off exchange.

scholarly journals Mechanisms of Venoarteriolar Reflex in Type 2 Diabetes with or without Peripheral Neuropathy

Biology ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 333
Author(s):  
Cécile Reynès ◽  
Antonia Perez-Martin ◽  
Houda Ennaifer ◽  
Henrique Silva ◽  
Yannick Knapp ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Peripheral Neuropathy ◽  
Spectral Power ◽  
Blood Perfusion ◽  
Doppler Flowmetry ◽  
Relative Contribution ◽  
Total Spectral Power ◽  
Underlying Mechanisms ◽  
Endothelial Nitric Oxide

The aim of this study is to investigate the underlying mechanisms of the venoarteriolar reflex (VAR) in type 2 diabetes mellitus (T2DM), with and without peripheral neuropathy. Laser Doppler flowmetry (LDF) recordings were performed on the medial malleus and dorsal foot skin, before and during leg dependency in healthy controls, in persons with obesity, in those with T2DM, in those with T2DM and subclinical neuropathy, and in those with T2DM and confirmed neuropathy. LDF recordings were analyzed with the wavelet transform to evaluate the mechanisms controlling the flowmotion (i.e., endothelial nitric oxide-independent and -dependent, neurogenic, myogenic, respiratory and cardiac mechanisms). Skin blood perfusion decreased throughout leg dependency at both sites. The decrease was blunted in persons with confirmed neuropathy compared to those with T2DM alone and the controls. During leg dependency, total spectral power increased in all groups compared to rest. The relative contribution of the endothelial bands increased and of the myogenic band decreased, without differences between groups. Neurogenic contribution decreased in controls, in persons with obesity and in those with T2DM, whereas it increased in subclinical- and confirmed neuropathy. In conclusion, this study provides evidence that confirmed diabetic neuropathy alters the VAR through the neurogenic response to leg dependency.

scholarly journals Thermal changes in Human Abdomen Exposed to Microwaves: A Model Study

2019 ◽  
Vol 8 (3) ◽  
pp. 64-75
Author(s):  
J. Kaur ◽  
S. A. Khan
Keyword(s):  
Heat Transfer ◽  
Wave Model ◽  
Biological Tissues ◽  
Bioheat Transfer ◽  
Biological Medium ◽  
Bioheat Equation ◽  
Temperature Variations ◽  
Microwave Exposure ◽  
Model Study ◽  
Speed Of Propagation

The electromagnetic energy associated with microwave radiation interacts with the biological tissues and consequently, may produce thermo-physiological effects in living beings. Traditionally, Pennes’ bioheat equation (BTE) is employed to analyze the heat transfer in biological medium. Being based on Fourier Law, Pennes’ BTE assumes infinite speed of propagation of heat transfer. However, heat propagates with finite speed within biological tissues, and thermal wave model of bioheat transfer (TWBHT) demonstrates this non-Fourier behavior of heat transfer in biological medium. In present study, we employed Pennes’ BTE and TWMBT to numerically analyze temperature variations in human abdomen model exposed to plane microwaves at 2450 MHz. The numerical scheme comprises coupling of solution of Maxwell's equation of wave propagation within tissue to Pennes’ BTE and TWMBT. Temperatures predicted by both the bioheat models are compared and effect of relaxation time on temperature variations is investigated. Additionally, electric field distribution and specific absorption rate (SAR) distribution is also studied.  Transient temperatures predicted by TWMBT are lower than that by traditional Pennes’ BTE, while temperatures are identical in steady state. The results provide comprehensive understanding of temperature changes in irradiated human body, if microwave exposure duration is short.

scholarly journals Prediction human skin temperature in comfort level

2019 ◽  
Vol 1 (3) ◽  
pp. 1-4
Author(s):  
Zaina Norhallis Zainol ◽  
Masine Md. Tap ◽  
Haslinda Mohamed Kamar
Keyword(s):  
Thermal Comfort ◽  
Skin Temperature ◽  
Human Skin ◽  
Blood Perfusion ◽  
Comfort Level ◽  
Working Environment ◽  
Percentage Error ◽  
Bioheat Equation ◽  
Acceptable Error ◽  
Human Arm

Thermal comfort is the human subject perceive satisfaction to the work environment. The thermal comfort need to be achieve towards productive working environment. The comfort level of the subject is affected by the human skin temperature. To assess the skin temperature with the sorrounding by conducting human experiment in the climatic chamber. It is rigorous and complex experiment.This study was developed to predict human skin temperature in comfort level with the finite element method and the bioheat equation. The bioheat equation is a consideration of metabolic heat generation and the blood perfusion to solve heat transfer of the living tissue. It is to determine the skin temperature focussing at the human arm. From the study, it is found that the predicted skin temperature value were in well agreement with the experimental results. The percentage error insignificant with acceptable error of 1.05%.

Design of Laser Treatment Protocols for Bacterial Disinfection in Root Canals Using Theoretical Modeling and MicroCT Imaging

2012 ◽  
Vol 4 (3) ◽  
Author(s):  
Jennifer Gill ◽  
Dwayne Arola ◽  
Ashraf F. Fouad ◽  
Liang Zhu
Keyword(s):  
Root Canal ◽  
Thermal Damage ◽  
Elevated Temperatures ◽  
Surrounding Tissue ◽  
Tooth Root ◽  
Bioheat Equation ◽  
Human Teeth ◽  
Treatment Protocols ◽  
Theoretical Simulations ◽  
Bacterial Disinfection

Theoretical simulations of temperature elevations in root dentin are performed to evaluate, how heating protocols affect the efficacy of using erbium, chromium; yttrium, scandium, gallium, garnet (Er,Cr;YSGG) pulsed lasers for bacterial disinfection during root canal treatments. The theoretical models are generated based on microcomputer tomography (microCT) scans of extracted human teeth. Heat transfer simulations are performed using the Pennes bioheat equation to determine temperature distributions in tooth roots and surrounding tissue during 500 mW pulsed Er,Cr;YSGG laser irradiation on the root canal for eradicating bacteria. The study not only determines the heat penetration within the deep dentin but also assesses potential thermal damage to the surrounding tissues. Thermal damage is assumed to occur when the tissue is subject to a temperature above at least 47 °C for a minimum duration of 10 s. Treatment protocols are identified for three representative tooth root sizes that are capable of maintaining elevated temperatures in deep dentin necessary to eradicate bacteria, while minimizing potential for collateral thermal tissue damage at the outer root surfaces. We believe that the study not only provides realistic laser heating protocols for various tooth root geometries but also demonstrates utility of theoretical simulations for designing individualized treatments in the future.

Photodynamic therapy and diagnostic measurements of basal cell carcinomas using esterified and non-esterified δ-aminolevulinic acid

2001 ◽  
Vol 05 (02) ◽  
pp. 147-153 ◽  
Author(s):  
MARCELO SOTO THOMPSON ◽  
LOTTA GUSTAFSSON ◽  
SARA PÅLSSON ◽  
NIELS BENDSOE ◽  
MARIA STENBERG ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Basal Cell ◽  
Aminolevulinic Acid ◽  
Normal Skin ◽  
Continuous Light ◽  
Blood Perfusion ◽  
Surrounding Tissue ◽  
Ir Camera ◽  
Fluorescence Measurements ◽  
Basal Cell Carcinomas

Various optical techniques were used to investigate relevant parameters involved in photodynamic therapy (PDT) of human basal cell carcinomas (BCCs). The aim of the study was to compare the diagnostic and therapeutic outcome when using topically applied methyl-esterified δ-aminolevulinic acid (ALA-ME) and δ-aminolevulinic acid (ALA). A total of 35 pathologically verified BCCs in 14 patients were investigated. A diode laser, emitting continuous light at 633 nm, was used to induce PDT. The diagnostic measurements were performed before, during, and after PDT. Laser-induced fluorescence (LIF) was used to monitor the build-up of the ALA/ALA-ME-induced protoporphyrin IX ( PpIX ). The superficial tissue perfusion was measured with laser-Doppler perfusion imaging (LDPI) and the temperature of the lesion and the surrounding tissue was imaged with an IR-camera. A clear demarcation between the lesion and the normal skin was detected with LIF before the treatment for both PpIX precursors. The fluorescence measurements suggest that PpIX builds up to a higher degree and more selectively in the tumour following ALA-ME as compared to ALA. The LDPI measurements indicate a local transient restriction in blood perfusion immediately post-PDT. The measurement with the IR-camera revealed a temperature rise of about 1–2 °C during the treatment.

scholarly journals Experimental Evaluation of the Energy Performance of an Air Vortex Tube when the Inlet Parameters are Varied

2013 ◽  
Vol 7 (1) ◽  
pp. 98-107 ◽  
Author(s):  
E. Torrella ◽  
J. Patiño ◽  
D. Sánchez ◽  
R. Llopis ◽  
R. Cabello
Keyword(s):  
Vortex Tube ◽  
Experimental Tests ◽  
Energy Performance ◽  
Cooling Capacity ◽  
Inlet Temperature ◽  
Temperature Variations ◽  
Cold Flow ◽  
Air Inlet ◽  
Cold Stream ◽  
Cooling Tube

The paper presents the analysis of the energy performance of an air vortex cooling tube under variations of the air inlet properties, with three independent experimental tests validated through the energy balance in the device. The experimental analysis includes the following variations of the input conditions: First, the effect of the air inlet pressure to the vortex tube, focused on the analysis of temperature variations in the output cold stream and in the cooling capacity when the cold flow fraction varies. Second, we studied air inlet temperature variations to the vortex tube under different cold flow fractions, which is an analysis not found in the literature. And finally, is studied the performance of the vortex tube when the insulation is provided or in absence of insulation.

scholarly journals Daytime eyeshine contributes to pupil camouflage in a cryptobenthic marine fish

2017 ◽  
Author(s):  
Matteo Santon ◽  
Pierre-Paul Bitton ◽  
Ulrike K. Harant ◽  
Nico K. Michiels
Keyword(s):  
Marine Fish ◽  
Teleost Fish ◽  
Pigment Epithelium ◽  
Field Measurements ◽  
Surrounding Tissue ◽  
Prey Fish ◽  
Relative Contribution ◽  
Visual Models ◽  
Dim Light ◽  
Scorpaena Porcus

ABSTRACTOcular reflectors enhance eye sensitivity in dim light, but can produce reflected eyeshine when illuminated. Most teleost fish occlude their reflectors during the day. The opposite is observed in cryptic sit-and-wait predators such as scorpionfish and toadfish, where reflectors are occluded at night and exposed during the day. This results in daytime eyeshine, proposed to enhance pupil camouflage by reducing the contrast between the otherwise black pupil and the surrounding tissue. In this study, we test this hypothesis in the scorpionfish Scorpaena porcus and show that eyeshine is the result of two mechanisms: the previously described Stratum Argenteum Reflected (SAR) eyeshine, and Pigment Epithelium Transmitted (PET) eyeshine, a newly described mechanism for this species. We confirm that the ocular reflector is exposed only when the eye is light-adapted, and present field measurements to show that eyeshine reduces pupil contrast against the iris. We then estimate the relative contribution of SAR and PET eyeshine to pupil brightness. Visual models for different light scenarios in the field show that daytime eyeshine enhances pupil camouflage from the perspective of a prey fish. We propose that the reversed occlusion mechanism of some cryptobenthic predators has evolved as a compromise between camouflage and vision.

Evaluation of Effectiveness of Er,Cr:YSGG Laser For Root Canal Disinfection: Theoretical Simulation of Temperature Elevations in Root Dentin

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
L. Zhu ◽  
M. Tolba ◽  
D. Arola ◽  
M. Salloum ◽  
F. Meza
Keyword(s):  
Alternative Treatment ◽  
Root Canal ◽  
Thermal Damage ◽  
Treatment Time ◽  
Treatment Protocol ◽  
Surrounding Tissue ◽  
Bioheat Equation ◽  
Canal Surface ◽  
Theoretical Simulation ◽  
Bacterial Disinfection

Erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) lasers are currently being investigated for disinfecting the root canal system. Prior to using laser therapy, it is important to understand the temperature distribution and to assess thermal damage to the surrounding tissue. In this study, a theoretical simulation using the Pennes bioheat equation is conducted to evaluate how heat spreads from the canal surface using an Er,Cr:YSGG laser. Results of the investigation show that some of the proposed treatment protocols for killing bacteria in the deep dentin are ineffective, even for long heating durations. Based on the simulation, an alternative treatment protocol is identified that has improved effectiveness and is less likely to introduce collateral damage to the surrounding tissue. The alternative protocol uses 350 mW laser power with repeating laser tip movement to achieve bacterial disinfection in the deep dentin (800 μm lateral from the canal surface), while avoiding thermal damage to the surrounding tissue (T<47°C). The alternative treatment protocol has the potential to not only achieve bacterial disinfection of deep dentin but also shorten the treatment time, thereby minimizing potential patient discomfort during laser procedures.

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