Computational Bioheat Modeling in Human Eye with Local Blood Perfusion Effect

2012 ◽  
pp. 327-344
Keyword(s):  
Blood Perfusion ◽  
Human Eye

The Thermal Behavior Analysis of a Human Eye Subjected to Laser Radiation Under the Non-Fourier Law of Heat Conduction

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Najat A. Alghamdi ◽  
Hamdy M. Youssef
Keyword(s):  
Heat Conduction ◽  
Laser Irradiation ◽  
Power Density ◽  
Evaporation Rate ◽  
Relaxation Times ◽  
Blood Perfusion ◽  
Absolute Temperature ◽  
Ambient Temperatures ◽  
Human Eye ◽  
Fourier Heat Conduction

Abstract Purpose: The physiological conditions and environment have vital roles in the heat transfer in the human tissues, such as the multilayered human-eye. In this paper, a mathematical model of the human eye subjected to an exponential laser beam concerning the change in blood perfusion, porosity, evaporation rate, and ambient temperatures has been constructed based on non-Fourier heat conduction law. Methods: The human eye has been divided into six layers. Appropriate boundary and interface conditions have been considered. A separable function has been assumed, and the twelve equations have been formulated in matrix form. The solutions have been calculated by using maple 17 software. Results: The results have been shown in figures with different cases. The absolute temperature distribution based on various values of the power density of laser irradiation and relaxation times parameters have been discussed first. The effect of the blood perfusion, porosity, evaporation rate, time, and ambient temperatures have also been discussed. Conclusions: The power density of laser irradiation, blood perfusion, porosity, evaporation rate, time, and ambient temperatures significantly affects the value of the temperature passing through the human eye layers.

Repeatability of Arterial Spin Labeling MRI in Measuring Blood Perfusion in the Human Eye

2018 ◽  
Vol 49 (4) ◽  
pp. 966-974 ◽  
Author(s):  
Safal Khanal ◽  
Philip R.K. Turnbull ◽  
Ehsan Vaghefi ◽  
John R. Phillips
Keyword(s):  
Arterial Spin Labeling ◽  
Blood Perfusion ◽  
Spin Labeling ◽  
Human Eye

Mathematical model of thermal effects of blinking in human eye

2015 ◽  
Vol 09 (01) ◽  
pp. 1650006 ◽  
Author(s):  
D. B. Gurung ◽  
K. C. Gokul ◽  
P. R. Adhikary
Keyword(s):  
Thermal Effects ◽  
Extreme Values ◽  
Choroidal Melanoma ◽  
Transient State ◽  
Blood Perfusion ◽  
Heat Transfer Process ◽  
Eyelid Closure ◽  
Ambient Temperatures ◽  
Human Eye ◽  
Palpebral Conjunctiva

Blinking is regarded as the continuous interrupted eyelid closure or opening and its thermal effect will compromise between these two. During a blink, the heat loss via convection, radiation and tear evaporation from cornea is prevented, warm tear is layered across corneal surface and the vessels of the palpebral conjunctiva provide heat to anterior eye. In most of the thermal models in human eye that are found in literatures, effect of blinking is not included, simulation is carried out only in open eye. Thus, in this paper, thermal effects of blinking are investigated using one-dimensional finite element method in transient state case. The bio-heat transfer process is simulated during different blinking rates, lid closure and opening. The simulation is carried out using normal and extreme values of ambient temperatures, blood temperatures, evaporation rates, blood perfusion rates, and lens thermal conductivities. Blinking is found to increase corneal and lens temperature by 1.29°C and 0.78°C respectively when compared to open eye. The results obtained from this model are useful in predicting temperature distribution in different laser eye surgeries, hyperthermia and cryosurgery treatment of eyelid carcinoma, choroidal melanoma and can be used for diagnosing temperature-related diseases.

Bio-Heat Transfer Model of Human Eye Subjected to Retinal Laser Irradiation

2010 ◽  
Author(s):  
Arunn Narasimhan ◽  
Kaushal Kumar Jha
Keyword(s):  
Heat Transfer ◽  
Laser Radiation ◽  
Numerical Model ◽  
Laser Irradiation ◽  
Laser Power ◽  
Blood Perfusion ◽  
Transient Temperature ◽  
Transfer Model ◽  
Two Dimensional ◽  
Human Eye

Retinopathy is a surgical process in which maladies of the human eye are treated by laser irradiation. A two-dimensional numerical model of the human eye geometry has been developed to investigate steady and transient thermal effects due to laser radiation. In particular, the influence of choroidal pigmentations and choroidal blood convection — parameterized as a function of choroidal blood perfusion are investigated in detail. The Pennes bio-heat transfer equation is invoked as the governing equation and a finite volume formulation is employed in the numerical method. The numerical model is validated with available experimental and two-dimensional numerical results. For a 500 μm diameter spot size, laser power of 0.2 W, with 100% absorption of laser radiation in the Retinal Pigmented Epithelium (RPE) region, the peak RPE temperature is observed to be 175 °C at steady state, with no blood perfusion in choroid. It reduces to 168.5 °C when the choroidal blood perfusion rate is increased to 23.3 kgm−3s−1. However, under transient simulations, the peak RPE temperature is observed to remain constant at 104 °C after 100 ms of the laser surgery period. A truncated three-dimensional model incorporating multiple laser irradiation spots is also developed to observe the spatial effect of choroidal blood perfusion. For a circular array of seven uniformly distributed spots of identical diameter and laser power of 0.2 W, steady and transient temperature evolution are presented with analysis.

A New System For Optomanual Semiautomatic Quantitative Image Analysis

1977 ◽  
Vol 35 ◽  
pp. 210-211
Author(s):  
H.P. Rohr
Keyword(s):  
Image Analysis ◽  
Volume Density ◽  
List Type ◽  
Distribution Analysis ◽  
Type Number ◽  
Point Counting ◽  
Human Eye ◽  
Quantitative Image ◽  
Point Density ◽  
Electronic Counting

Today, in image analysis the broadest possible rationalization and economization have become desirable. Basically, there are two approaches for image analysis: The image analysis through the so-called scanning methods which are usually performed without the human eye and the systems of optical semiautomatic analysis completely relying on the human eye.The new MOP AM 01 opto-manual system (fig.) represents one of the very promising approaches in this field. The instrument consists of an electronic counting and storing unit, which incorporates a microprocessor and a keyboard for choice of measuring parameters, well designed for easy use.Using the MOP AM 01 there are three possibilities of image analysis:the manual point counting,the opto-manual point counting andthe measurement of absolute areas and/or length (size distribution analysis included).To determine a point density for the calculation of the corresponding volume density the intercepts lying within the structure are scanned with the light pen.

The Human Eye and the Photographic Camera

1913 ◽  
Vol 76 (1960supp) ◽  
pp. 51-51
Author(s):  
A. Gleichen
Keyword(s):  
Human Eye ◽  
Photographic Camera

Partition Coefficient Ratios and Tumour Perfusion Studied with 85mKr and 133Xe

1987 ◽  
Vol 26 (06) ◽  
pp. 253-257
Author(s):  
M. Mäntylä ◽  
J. Perkkiö ◽  
J. Heikkonen
Keyword(s):  
Partition Coefficient ◽  
Partition Coefficients ◽  
Regional Blood Flow ◽  
Blood Perfusion ◽  
Compartmental Analysis ◽  
Malignant Tumour ◽  
Mean Value ◽  
Perfusion Rate ◽  
Biological Variables ◽  
The Mean

The relative partition coefficients of krypton and xenon, and the regional blood flow in 27 superficial malignant tumour nodules in 22 patients with diagnosed tumours were measured using the 85mKr- and 133Xe-clearance method. In order to minimize the effect of biological variables on the measurements the radionuclides were injected simultaneously into the tumour. The distribution of the radiotracers was assumed to be in equilibrium at the beginning of the experiment. The blood perfusion was calculated by fitting a two-exponential function to the measuring points. The mean value of the perfusion rate calculated from the xenon results was 13 ± 10 ml/(100 g-min) [range 3 to 38 ml/(100 g-min)] and from the krypton results 19 ± 11 ml/(100 g-min) [range 5 to 45 ml/(100 g-min)]. These values were obtained, if the partition coefficients are equal to one. The equations obtained by using compartmental analysis were used for the calculation of the relative partition coefficient of krypton and xenon. The partition coefficient of krypton was found to be slightly smaller than that of xenon, which may be due to its smaller molecular weight.

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