Temperature Distributions During Thermoradiotherapy: A Sensitivity Study With a Transient Numerical Model of the Rabbit Eye

1997 ◽  
Vol 119 (2) ◽  
pp. 153-158 ◽  
Author(s):  
D. T. Tompkins ◽  
S. A. Klein ◽  
R. A. Steeves
Keyword(s):  
Numerical Model ◽  
Thermal Model ◽  
Choroidal Melanoma ◽  
Blood Perfusion ◽  
Sensitivity Study ◽  
Temperature Dependent ◽  
Rabbit Eye ◽  
Temperature Distributions ◽  
Perfusion Model ◽  
Choroidal Melanomas

An approach to the treatment of medium-sized choroidal melanomas combines radiation with ferromagnetic hyperthermia. The study herein discusses results with a numerical thermal model of a choroidal melanoma in the rabbit eye as treated with episcleral, thermoradiotherapy plaques. The sensitivity of a temperature–dependent blood perfusion model is investigated.

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.

scholarly journals Surface-Coil MRI for Small Peripheral Choroidal Melanoma: Imaging in a Rabbit Eye Model

2018 ◽  
Vol 4 (6) ◽  
pp. 364-369 ◽  
Author(s):  
Larissa Ioannidi ◽  
Konstantinos Seliniotakis ◽  
Georgios Bontzos ◽  
George Sourvinos ◽  
Viktor Haniotis ◽  
...  
Keyword(s):  
Choroidal Melanoma ◽  
Surface Coil ◽  
Eye Model ◽  
Rabbit Eye

scholarly journals Sensitivity study of diffuser angle and brim height parameters for the design of 3 kW Diffuser Augmented Wind Turbine

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Michał Lipian ◽  
Maciej Karczewski ◽  
Krzysztof Olasek
Keyword(s):  
Numerical Model ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Sensitivity Study ◽  
Flow Speed ◽  
Diffuser Angle

AbstractThe Diffuser Augmented Wind Turbine (DAWT) is an innovative mean to increase the power harvested by wind turbine. By encompassing the rotor with a diffusershaped duct it is possible to increase the flow speed through the turbine by about 40-50%. The study presents the development of a numerical model and its validation by the experiments performed in the wind tunnel of the Institute of Turbomachinery, TUL. Then, the numerical model is used for the geometry sensitivity study to optimize the shape of a diffuser. The paper presents that the DAWT technology has the potential to even double the power outcome of wind turbine when compared to a bare rotor version.

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).

scholarly journals Optical Coherence Tomography: An Adjunctive Tool for Differentiating between Choroidal Melanoma and Metastasis

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Vicktoria Vishnevskia-Dai ◽  
Dinah Zur ◽  
Shiran Yaacobi ◽  
Iris Moroz ◽  
Hadas Newman ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Retinal Thickness ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Choroidal Melanoma ◽  
Case Series ◽  
Subretinal Fluid ◽  
Optical Coherence ◽  
Choroidal Melanomas ◽  
Anterior Choroidal

Purpose.To investigate the value of optical coherence tomography (OCT) for differentiation between choroidal melanoma and metastasis based on characteristics of the anterior choroidal surface and the chorioretinal interface.Methods.This retrospective observational case series included 29 patients with untreated choroidal melanomas and 21 patients with untreated choroidal metastases. Regularity and lobularity characteristics of the anterior choroidal surface were evaluated in a masked manner. Retinal and retinal pigment epithelium (RPE) findings were documented as well.Results.OCT demonstrated a regular and smooth anterior choroidal surface in 89.7% of the eyes with melanoma and in 47.6% of the eyes with metastasis (p=0.002; sensitivity = 89.7%; specificity = 52.4%). The anterior choroidal contour was lobulated in 81.0% of the eyes with metastasis versus 17.2% of the eyes with melanoma (p<0.001; sensitivity = 82.8%; specificity = 81.0%). RPE thickness and neuroretinal characteristics (e.g., retinal thickness, the presence of cysts, and the presence of subretinal fluid) were similar in both choroidal tumors.Conclusion. OCT may serve as a noninvasive adjunctive tool for the differential diagnosis of choroidal tumors. Choroidal melanomas usually demonstrate regular surfaces on OCT, while choroidal metastases usually have an irregular and lobulated surface.

Approach to the patient in the diagnosis of Choroidal Malignant Melanoma. Question and Answer

2019 ◽  
pp. 317-320
Keyword(s):  
Risk Factor ◽  
Malignant Melanoma ◽  
Diagnostic Method ◽  
Choroidal Melanoma ◽  
Intraocular Tumors ◽  
Indirect Ophthalmoscopy ◽  
Choroidal Malignant Melanoma ◽  
Choroidal Melanomas ◽  
Venous Phase ◽  
Treatment Changes

The most valuable diagnostic method in intraocular tumors is indirect ophthalmoscopy. USG is very important in determining the thickness of the lesion and documenting post-treatment changes. However, in today's conditions, we have important auxiliary examination opportunities. OCT is especially important in detecting macular edema and fluid. In choroidal melanomas, thickening and edema of the macula may be observed before treatment due to increased VEGF levels in the eye. OCT is important in detecting such changes. Since FAF shows the amount of lipofuscin in the lesion, it reveals the activity of the lesion. Hyperotofluorescence of> 50% of the lesion surface, in other words, the diffuse pattern is a risk factor for growth and metastasis. On fluorescein angiography, choroidal melanoma shows focal hyperfluorescence starting from the late venous phase and gradually increasing.

scholarly journals Fluid Choice Based on Thermal Model and Performance Testing for Direct Cooled Electric Drive

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5867
Author(s):  
Robert Lehmann ◽  
Arthur Petuchow ◽  
Matthias Moullion ◽  
Moritz Künzler ◽  
Christian Windel ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Model ◽  
Performance Testing ◽  
Sensitivity Study ◽  
Maximum Heat ◽  
Cooling Fluid ◽  
Two Fluids ◽  
Fluid Properties ◽  
And Performance ◽  
Electric Traction

In this publication, the cooling fluid for direct oil-cooled electric traction drive is investigated. A dedicated thermal resistance model was developed in order to show the influence of the fluid properties on the continuous performance. For this purpose, the heat transfer parameters are adjusted in the simulation using an exponential approach in order to evaluate the cooling fluid. In a sensitivity study, density, heat capacity, thermal conductivity, and viscosity are investigated. Because viscosity, within the range investigated, shows the largest percentage deviation from the reference fluid, the greatest effect on performance can be seen here. In order to check the plausibility of the calculated results of the thermal simulation, two fluids were chosen for performance testing on a dedicated electro motor cooling (EMC) test. Beyond the investigation of heat transfer, aging of the defined fluid at maximum heat input over several hours is also evaluated. Only slight changes of the fluid properties are detected. This publication presents a thermal model for direct oil-cooled drive trains, which consider fluid properties. Furthermore, the model was tested for plausibility on real hardware.

Thermal Analysis of Realistic Breast Model With Tumor and Validation by Infrared Images

2021 ◽  
pp. 208-218
Author(s):  
Deepika Singh ◽  
Ashutosh Kumar Singh ◽  
Sonia Tiwari
Keyword(s):  
Breast Cancer ◽  
Thermal Analysis ◽  
Steady State ◽  
Thermal Model ◽  
Infrared Imaging ◽  
Ductal Carcinoma ◽  
Blood Perfusion ◽  
Breast Cancer Detection ◽  
Surface Geometry ◽  
Breast Thermography

Breast thermography is an emerging adjunct tool to mammography in early breast cancer detection due to its non-invasiveness and safety. Steady-state infrared imaging proves promising in this field as it is not affected by tissue density. The main aim of the present study is to develop a computational thermal model of breast cancer using real breast surface geometry and internal tumor specification. The model depicting the thermal profile of the subject's aggressive ductal carcinoma is calibrated by variation of blood perfusion and metabolic heat generation rate. The subject's IR image is used for validation of the simulated temperature profile. The thermal breast model presented here may prove useful in monitoring the response of tumor post-chemotherapy for female subjects with similar breast cancer characteristics.

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