The Effect of Laser Parameters on the Zone of Thermal Injury Produced by Laser Ablation of Biological Tissue

1994 ◽  
Vol 116 (1) ◽  
pp. 62-70 ◽  
Author(s):  
V. Venugopalan ◽  
N. S. Nishioka ◽  
B. B. Mikic´
Keyword(s):  
Laser Ablation ◽  
Pulse Duration ◽  
Biological Tissue ◽  
Thermal Injury ◽  
Thermal Damage ◽  
Optical Scattering ◽  
Published Data ◽  
Laser Parameters ◽  
Model Predictions ◽  
Key Parameter

A thermal model to predict the effect of laser parameters on the zone of thermal injury produced by laser ablation of biological tissue is presented. The model suggests that the Pe´cle`t number based on the optical penetration depth of laser radiation is the key parameter in determining the resulting zone of thermal injury. We show that the zone of thermal injury is minimized for Pe´cle`t numbers greater than one since the transport of energy via conduction beyond the ablation front is minimized. We also show that for Pe´cle`t numbers less than one, larger zones of thermal damage are unavoidable regardless of the laser pulse duration. The predictions of the model are compared with data available in the literature. Deviations between the model predictions and published data are discussed and the potential effects of the model assumptions, optical scattering, pyrolysis, temporal pulse shape, pulse duration, irradiance and pulse repetition rate are explored.

scholarly journals Modeling of thermal injury produced by laser ablation of biological tissue

1993 ◽  
Author(s):  
Vasan Venugopalan ◽  
Norman S. Nishioka ◽  
B. B. Mikic
Keyword(s):  
Laser Ablation ◽  
Biological Tissue ◽  
Thermal Injury

Effect of optical pulse duration on the XeCl laser ablation of polymers and biological tissue

1987 ◽  
Vol 50 (25) ◽  
pp. 1779-1781 ◽  
Author(s):  
R. S. Taylor ◽  
D. L. Singleton ◽  
G. Paraskevopoulos
Keyword(s):  
Laser Ablation ◽  
Pulse Duration ◽  
Biological Tissue ◽  
Optical Pulse ◽  
Xecl Laser

Er:YAG laser ablation of tissue: Effect of pulse duration and tissue type on thermal damage

1989 ◽  
Vol 9 (4) ◽  
pp. 314-326 ◽  
Author(s):  
Joseph T. Walsh ◽  
Thomas J. Flotte ◽  
Thomas F. Deutsch
Keyword(s):  
Laser Ablation ◽  
Pulse Duration ◽  
Thermal Damage ◽  
Er:Yag Laser ◽  
Tissue Type ◽  
Tissue Effect

Influence of pulse duration on erbium and holmium laser ablation under water

1995 ◽  
Author(s):  
Michael Ith ◽  
Martin Frenz ◽  
Hans S. Pratisto ◽  
Heinz P. Weber ◽  
Hans J. Altermatt ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Pulse Duration ◽  
Holmium Laser

Assessment of Possible Thermal Damage of Tissue due to Atherectomy by Means of a Mechanical Debulking Device

2008 ◽  
Author(s):  
Ryang D. Lovik ◽  
John P. Abraham ◽  
Eph M. Sparrow
Keyword(s):  
Numerical Simulations ◽  
Thermal Injury ◽  
Thermal Damage ◽  
Threshold Value ◽  
Posterior Tibial Artery ◽  
Artery Wall ◽  
Flow Rates ◽  
Injury Index ◽  
Orbital Atherectomy

In vitro and cadaver experiments, coupled with numerical simulations, were performed to assess the possibility that orbital atherectomy might cause thermal damage of tissue. The experiments involved debulking operations on a surrogate artery and on the plaque-lined posterior tibial artery of a cadaver. Temperatures and coolant flow rates measured during these experiments enabled a numerical simulation of the debulking of a plaque-lined artery in a living human. The temperature variations from the numerical simulations were used to evaluate a thermal injury index. The resulting values of the index were found to be several orders of magnitude below the threshold value for thermal injury. It is concluded that it is extremely unlikely that the use of an orbital debulking device, the Diamondback 360°™ (Cardiovascular Systems, Inc.), can lead to thermal injury of the artery wall.

scholarly journals Study of the formation of 3-D titania nanofibrous structure by MHz femtosecond laser in ambient air

2021 ◽  
Author(s):  
Amirhossein Tavangar ◽  
Bo Tan ◽  
Krishnan Venkatakrishnan
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Deposition Rate ◽  
Femtosecond Laser Ablation ◽  
Ambient Air ◽  
Experimental Results ◽  
Laser Parameters ◽  
Nanofibrous Structure ◽  
Titania Nanostructures ◽  
Multiple Pulses

In this study, we describe the formation mechanism of web-like three-dimensional (3-D) titania nanofibrous structures during femtosecond laser ablation of titanium (Ti) targets in the presence of background air. First, we demonstrate the mechanism of ablation of Ti targets by multiple femtosecond laser pulses at ambient air in an explicit analytical form. The formulas for evaporation rates and the number of ablated particles, which is analogous to the deposition rate of the synthesized nanofibers, for the ablation by a single pulse and multiple pulses as a function of laser parameters, background gas, and material properties are predicted and compared to experimental results. Afterwards, the formation of nanofibrous structures is demonstrated by applying an existing simplified kinetic model to Ti targets and ambient conditions. The predicted theory provides nanofiber diameter dependency with the combination of laser parameters, target properties, and ambient gas characteristics. Experimental studies are then performed on titania nanofibrous structures synthesized by laser ablation of Ti targets using MHz repletion-rate femtosecond laser at ambient air. The models' predictions are then compared with the experimental results, where nanostructures with different morphologies are manufactured by altering laser parameters. Our results indicate that femtosecond laser ablation of Ti targets at air background yields crystalline titania nanostructures. The formation of crystalline titania nanostructures is preceded b thermal mechanism of nucleation and growth. The results point out that laser pulse repetition and dwell time can control the density, size, and pore size of the engineered nanofibrous structure. As the deposition rate of nanostructures is analogous to the ablation rate of the target, higher density of nanofibrous structure is seen at greater laser fluences. The predicted theory can be applied to predict ablation mechanism and nanofiber formation of different materials.

scholarly journals PECULIARITIES OF THE WOUND PROCESS DEVELOPMENT IN PATIENTS WITH THERMAL INJURY WHEN USED SILVER PREPARATIONS IN BURN WOUNDS SURGICAL TREATMENT

2021 ◽  
pp. 81-87
Author(s):  
N. V. Tuzyuk
Keyword(s):  
Metabolic Activity ◽  
Functional Activity ◽  
Thermal Injury ◽  
Thermal Damage ◽  
Main Group ◽  
The Body ◽  
Metabolic Reaction ◽  
Neutrophilic Granulocytes ◽  
Burn Wound ◽  
Significant Activation

Fundamental research in the field of burn wound development process highlights new pathogenetic mechanisms that underlie the improvement of medical practice, the main purpose of which is to create optimal conditions for early regeneration of the affected skin, as well as to eliminate the development of local and general complications. Irrational general and local treatment of wounds contribute to the slowing down of regenerative processes, thereby worsening the prognosis and consequences of thermal injury. It was found out that in patients of both study groups in the first period of the study the characteristics of the cellular composition of the wound impressions of the wound bottom of the area of thermal damage correspond to the degenerative type. In patients of the main group in the second term of the study in the area of thermal damage cells with high levels of functional and metabolic activity begin to appear, which increase antimicrobial resistance and reduce the risk of generalization of the infectious process which is the main source of burns. In patients of the main group, an increase in the activity of neutrophilic granulocytes in the induced test was found in the second term of the study, which, in our opinion, indicates the involvement of neutrophilic granulocytes with high functional and metabolic activity. Under conditions of significant activation of resident monocytes in response to injury in patients of the main group in the second and third term, the area of thermal damage migrates functionally effective monocytes. In patients of the main group the preservation of the activity of myeloperoxidase - the main enzyme of the oxygen-dependent phase of phagocytosis at the minimum subcompensated level, which leads to the preservation of the oxygen-dependent metabolic reaction of neutrophilic granulocytes in the subsequent study, Increases in the content of PAS-positive substances in neutrophilic granulocytes indicate the preservation of the functional reserve for activation and completion of the oxygen-independent phase of phagocytosis. The use of the developed treatment promotes the involvement of functionally active phagocytic cells in the burn wound, reduces the toxic load on monocytes and neutrophils, which helps to maintain their functional activity at the subcompensated level. These trends in patients of the main group reduce the risk of both local and general infectious complications of burn disease. It was found that the level of spontaneous functional activity in the HCT test is associated with the activity of resident monocytes. They form the primary barrier that protects the body from infection or harmful macromolecular complexes. Monocytes - "inflammatory", which constantly come from the free pool and their functional activity against microbial antigens is much higher than resident monocytes. An indicator of the activity of monocytes - "inflammatory" is an indicator of functional activity in the induced HCT test. The results of the study indicate that under conditions of significant activation of resident monocytes in response to injury in patients of the main group in the second and third terms of the area of thermal damage migrate functionally effective monocytes.

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