scholarly journals A new CEM₄₃ thermal dose model based on Vogel-Tammann-Fulcher behaviour in thermal damage processes

2021 ◽  
Author(s):  
Hisham Assi
Keyword(s):  
High Temperature ◽  
Thermal Damage ◽  
Ex Vivo ◽  
Current Model ◽  
Damage Threshold ◽  
Thermal Therapy ◽  
Published Data ◽  
Thermal Dose ◽  
Model Based ◽  
Dose Model

Thermal dose models are metrics that quantify thermal damage in tissues based on the temperature and the time of exposure. The validity and accuracy of one of the commonly used models (CEM₄₃) for high temperature thermal therapy applications (50-90 degree Celcius) is questionable. It was found to over-estimate the accumulation of thermal damage for high-temperature applications. A new CEM₄₃ dose model based on Arrhenius type Vogel-Tammann-Fulcher equation using published data is introduced in this work. The new dose values for the same damage threshold that was produced at different in-vivo skin experiments were in the same order of magnitude, while the current dose values were 2 orders of magnitude different. The new dose values for same damage threshold in 6 lessions in ex-vivo liver experiments were more consistent than the current dose values. Computer simulations of laser interstitial thermal therapy showed that the current model usually predicts bigger volume than the new model does. The deviation in damaged volume prediction can be significant. The contribution of this work is introducing methods that can lead to more robust thermal dosimetry which will result in improved therapy modelling, monitoring and control.

scholarly journals A new CEM₄₃ thermal dose model based on Vogel-Tammann-Fulcher behaviour in thermal damage processes

2021 ◽  
Author(s):  
Hisham Assi
Keyword(s):  
High Temperature ◽  
Thermal Damage ◽  
Ex Vivo ◽  
Current Model ◽  
Damage Threshold ◽  
Thermal Therapy ◽  
Published Data ◽  
Thermal Dose ◽  
Model Based ◽  
Dose Model

Thermal dose models are metrics that quantify thermal damage in tissues based on the temperature and the time of exposure. The validity and accuracy of one of the commonly used models (CEM₄₃) for high temperature thermal therapy applications (50-90 degree Celcius) is questionable. It was found to over-estimate the accumulation of thermal damage for high-temperature applications. A new CEM₄₃ dose model based on Arrhenius type Vogel-Tammann-Fulcher equation using published data is introduced in this work. The new dose values for the same damage threshold that was produced at different in-vivo skin experiments were in the same order of magnitude, while the current dose values were 2 orders of magnitude different. The new dose values for same damage threshold in 6 lessions in ex-vivo liver experiments were more consistent than the current dose values. Computer simulations of laser interstitial thermal therapy showed that the current model usually predicts bigger volume than the new model does. The deviation in damaged volume prediction can be significant. The contribution of this work is introducing methods that can lead to more robust thermal dosimetry which will result in improved therapy modelling, monitoring and control.

Ultrasound Hyperthermia: Dose Estimation and Device Design for Intraluminal and External Delivery

2012 ◽  
Author(s):  
Danica Gordon ◽  
Chandrasekhar Thamire
Keyword(s):  
Thermal Damage ◽  
Treatment Time ◽  
The Body ◽  
Thermal Therapy ◽  
Surrounding Tissue ◽  
Temperature History ◽  
Published Data ◽  
Device Design ◽  
Treatment Protocols ◽  
Thermal Coagulation

Thermal ablation in the context of this study refers to destroying cancer cells by heating them to supraphysiological temperatures for appropriate times. Once the tumor cells and a small layer of surrounding tissue cells are killed, they are absorbed by the body over time. Compared to open surgery, radiation, and chemotherapy, thermal therapy can be less expensive and pose less risk of harmful post-procedural complications, while possessing the potential to be effective [1]. Currently microwave and radiofrequency ablation are in use for local hyperthermia; however, they lack the ability to focus heat into the target zones effectively or treat larger tumors without affecting the surrounding healthy tissue. In the current study, high frequency ultrasound (US) ablation is examined as a treatment modality because of its ability to focus and control heat effectively. Objectives of this study are to 1) develop thermal-damage correlations for US thermal therapy and 2) design delivery devices and associated treatment planning protocols. To achieve these goals, thermal damage information is first evaluated for a variety of cells and tissues from published data or pilot experiments. Required US dose levels are determined next through numerical experiments, followed by device design and estimation of thermal coagulation contours by comparing the temperature-history data against the thermal-damage data. Based on the analysis of the results for a range of parameters, namely, the applicator power, geometry, frequency, coolant parameters, treatment time, and tissue perfusion, treatment protocols are developed. Intraluminal, external, and interstitial modes of delivery are considered for focal sites in a variety of target areas. In the following sections, methods followed and sample results obtained are presented.

scholarly journals Ablation dynamics of subsequent thermal doses delivered to previously heat-damaged tissue during magnetic resonance–guided laser-induced thermal therapy

2019 ◽  
Vol 131 (6) ◽  
pp. 1958-1965 ◽  
Author(s):  
Sean M. Munier ◽  
Eric L. Hargreaves ◽  
Nitesh V. Patel ◽  
Shabbar F. Danish
Keyword(s):  
Magnetic Resonance ◽  
Thermal Damage ◽  
Total Duration ◽  
Ablation Rate ◽  
Thermal Therapy ◽  
Similar Amount ◽  
Thermal Dose ◽  
Surgical Indications ◽  
Maximum Area ◽  
Mri Guided

OBJECTIVEIntraoperative dynamics of magnetic resonance–guided laser-induced thermal therapy (MRgLITT) have been previously characterized for ablations of naive tissue. However, most treatment sessions require the delivery of multiple doses, and little is known about the ablation dynamics when additional doses are applied to heat-damaged tissue. This study investigated the differences in ablation dynamics between naive versus damaged tissue.METHODSThe authors examined 168 ablations from 60 patients across various surgical indications. All ablations were performed using the Visualase MRI-guided laser ablation system (Medtronic), which employs a 980-nm diffusing tip diode laser. Cases with multiple topographically overlapping doses with constant power were selected for this study. Single-dose intraoperative thermal damage was used to calculate ablation rate based on the thermal damage estimate (TDE) of the maximum area of ablation achieved (TDEmax) and the total duration of ablation (tmax). We compared ablation rates of naive undamaged tissue and damaged tissue exposed to subsequent thermal doses following an initial ablation.RESULTSTDEmax was significantly decreased in subsequent ablations compared to the preceding ablation (initial ablation 227.8 ± 17.7 mm2, second ablation 164.1 ± 21.5 mm2, third ablation 124.3 ± 11.2 mm2; p = < 0.001). The ablation rate of subsequent thermal doses delivered to previously damaged tissue was significantly decreased compared to the ablation rate of naive tissue (initial ablation 2.703 mm2/sec; second ablation 1.559 mm2/sec; third ablation 1.237 mm2/sec; fourth ablation 1.076 mm/sec; p = < 0.001). A negative correlation was found between TDEmax and percentage of overlap in a subsequent ablation with previously damaged tissue (r = −0.164; p < 0.02).CONCLUSIONSAblation of previously ablated tissue results in a reduced ablation rate and reduced TDEmax. Additionally, each successive thermal dose in a series of sequential ablations results in a decreased ablation rate relative to that of the preceding ablation. In the absence of a change in power, operators should anticipate a possible reduction in TDE when ablating partially damaged tissue for a similar amount of time compared to the preceding ablation.

Hyperspectral image-based analysis of thermal damage for ex-vivo bovine liver utilizing radiofrequency ablation

2021 ◽  
pp. 101564
Author(s):  
Mohamed Hisham Aref ◽  
Ibrahim H. Aboughaleb ◽  
Abou-Bakr M. Youssef ◽  
Yasser H. El-Sharkawy
Keyword(s):  
Radiofrequency Ablation ◽  
Thermal Damage ◽  
Hyperspectral Image ◽  
Ex Vivo ◽  
Bovine Liver

Retinal thermal damage threshold studies for multiple pulses

2007 ◽  
Author(s):  
Karl Schulmeister ◽  
Bernhard Seiser ◽  
Florian Edthofer ◽  
Johannes Husinsky ◽  
Letizia Farmer
Keyword(s):  
Thermal Damage ◽  
Damage Threshold ◽  
Multiple Pulses

Heterogeneity and the modelling of bacterial spore death: the case of continuously decreasing death rate

1977 ◽  
Vol 23 (11) ◽  
pp. 1501-1507 ◽  
Author(s):  
Ken Sharpe ◽  
Roger M. Bektash
Keyword(s):  
Heat Resistance ◽  
Death Rate ◽  
Bacterial Spore ◽  
Bacterial Spores ◽  
Heating Process ◽  
Published Data ◽  
Model Based

Models for the inactivation of bacterial spores for the case of continuously decreasing death rate are reviewed and extended to show that it is not possible to distinguish between one particular model based upon the innate heterogeneity of the population and that based upon the acquisition of heat resistance during the heating process. Two innate heterogeneity models have been fitted to published data.

scholarly journals Threshold of permanent cornea thermal damage due to incidental continuous wave CO2 laser irradiation

2010 ◽  
Vol 14 (2) ◽  
pp. 459-467 ◽  
Author(s):  
Mayada Tahir
Keyword(s):  
Laser Irradiation ◽  
Co2 Laser ◽  
Thermal Damage ◽  
Continuous Wave ◽  
Anterior Part ◽  
Outer Part ◽  
Human Cornea ◽  
Thermal Dose ◽  
Element Analysis ◽  
Reflex Blink

Cornea thermal damage due to incidental continuous wave CO2 laser irradiation is studied numerically based on bio-heat equation. The interaction of laser with tissue leads to a rapid temperature increased in target and the nearby tissue. As the temperature of the eye surface reaches 44?C, a sensation of pain will cause aversion response of the reflex blink and/or shifting away from the source of pain. The aim of the work is to predict numerically the threshold limit of incidental laser power that causes damage to the anterior part of the cornea, which can be healed within 2-5 days as long as damage is not exceeding the outer part of the eye (epithelium). A finite element analysis is used to predict temperature distribution through the cornea where the necroses region can be obtained using thermal dose equation. The thermal dose that required for damaging the cornea is predicted from previously published experimental data on rhesus monkeys and used later as a limit for shrinkage to human cornea. The result of this work is compared by international standard of safety and a good nearby result is obtained which verified the result of this work.

scholarly journals The Inherent Limitation of Model Based Approach of Physical Sciences to Understand Universe

2020 ◽  
Author(s):  
Jivesh Adhlakha
Keyword(s):  
Mathematical Reasoning ◽  
Current Model ◽  
Physical World ◽  
Explanatory Models ◽  
Scientific Models ◽  
Correct Description ◽  
Physical Sciences ◽  
Inherent Limitation ◽  
Model Based

In this paper, through logical and mathematical reasoning, I have shown that the current ways in Physical Sciences, especially Physics, are not only limited but may also be delusional. Moreover, if not corrected, Physical Sciences will always remain as framework for building explanatory models rather than describing the reality. Through a series of arguments, I propose a conjecture theorem – Dilemma Theorem of Scientific Models- which essentially implies that it is impossible for Physical Sciences to discover and claim the correct description of Physical World using current model based approach, hence, making them just an attempt to discover probable models and their applications, rather than a way to find true picture of Physical World.

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