Author: Nathan Jowett
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"Background: Despite significant advances in surgery over the last century, most surgical approaches necessitate cold steel instruments under the control of the surgeon's hand. Lasers provide a means of precise surgical ablation, but their clinical use has remained limited due to undesired thermal, free-radical producing, or mechanical effects causing significant cellular insult. A novel ultrafast, non-ionizing, picosecond infrared laser (PIRL) system has recently been developed, capable in theory of ablation with negligible thermal or mechanical collateral damage.Objective: The purpose of this work is to provide the reader with an overview of laser-tissue interactions and laser ablation mechanisms in addition to presenting novel experimental data comparing heat generation during ablation of ex vivo porcine skin and chicken bone by conventional microsecond pulsed erbium doped yttrium aluminum garnet (Er:YAG) laser versus PIRL.Methods: Ex vivo porcine skin and chicken bone was ablated with both Er:YAG laser and PIRL at fluence levels above ablation threshold. Temperature rises were determined using infrared thermography and compared using appropriate statistical methods. Ablation craters were assessed by means of digital microscopy.Results: Mean peak rise in skin surface temperature for the Er:YAG laser and PIRL was 15.0°C and 1.68°C, respectively (p
Author: Patrick Joseph Morris
Publisher:
ISBN:
Category :
Languages : en
Pages : 92
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Book Description
Author: Ashley J. Welch
Publisher: Springer Science & Business Media
ISBN: 9048188318
Category : Science
Languages : en
Pages : 951
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Book Description
The second edition maintains the standard of excellence established in the first edition, while adjusting the content to reflect changes in tissue optics and medical applications since 1995. The material concerning light propagation now contains new chapters devoted to electromagnetic theory for coherent light. The material concerning thermal laser-tissue interactions contains a new chapter on pulse ablation of tissue. The medical applications section now includes several new chapters on Optical Coherent Tomography, acoustic imaging, molecular imaging, forensic optics and nerve stimulation. A detailed overview is provided of the optical and thermal response of tissue to laser irradiation along with diagnostic and therapeutic examples including fiber optics. Sufficient theory is included in the book so that it is suitable for a one or two semester graduate or for senior elective courses. Material covered includes (1) light propagation and diagnostic application; (2) the thermal response of tissue and therapeutic application; (3) denaturation; and (4) ablation. The theory and applications provide researchers with sufficient detail that this volume will become the primary reference for laser-tissue interactions and medical applications.
Author: Lana S. Krause
Publisher:
ISBN:
Category :
Languages : en
Pages : 132
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Book Description
Author: Mark A. Mackanos
Publisher:
ISBN:
Category : Cornea
Languages : en
Pages : 199
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Book Description
Author: Bruno Girard
Publisher:
ISBN: 9780494395455
Category :
Languages : en
Pages : 316
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Book Description
Laser ablation of tissues for surgical purposes has been under investigation for decades. Hard biological tissues, such as bone, possess an inherent molecular complexity that lead to a broad absorption spectrum, and current lasers are inefficient and cause thermal damage that delays healing. Recently, amplified femtosecond laser systems have demonstrated ablation of materials with little thermal damage. The goal of this thesis was to better characterize the damage in bone following femtosecond laser irradiation using both in vitro and in vivo models as well as evaluating the healing outcomes in order to determine if a fs laser system has the potential to be used in a surgical operating room. Using calcified bone samples we determined that the ablation rates of a fs laser system would be at best comparable to current mechanical instruments. We were the first to report on healing of wounds created by femtosecond lasers. Evaluation of the healing of mice calvaria demonstrated that femtosecond laser cutting displays unsurpassed precision when compared to mechanical instruments. Healing was similar among wounding techniques, albeit a trend in lesser bone formation was observed in the laser group. We accelerated the healing using bone morphogenetic protein-7 and showed that the laser cutting does not negatively influence wound closure when compared to mechanical instruments. Tissue damage was assessed in vitro using freshly excised mice calvaria with fluorescence-based tissue staining techniques to monitor the extracellular and intracellular enzymatic activity. We demonstrated that the fs laser produces a damage zone of only 14 +/- 5mum from the cut boundary, the smallest measure reported following laser ablation of viable tissues. Further, we used transgenic VEGF-luc mice to compare inflammation and neovascularization in wounds created by mechanical instruments or fs laser and the results suggested that more trauma is created with mechanical instruments. Finally, we performed preliminary bone ablation experiments using two novel laser sources irradiating at 1560nm (fs range) and 3mum (ps range) and found evidence of photomechanical effects in bone. Our studies have shown that fs lasers could be used in a clinical setting although major technological advances are required before implementation is recommended.
Author: Mohit Ganguly
Publisher:
ISBN:
Category :
Languages : en
Pages : 164
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Book Description
Pulsed lasers are known for their spatial and temporal specificity in delivering heat energy to the tissues. This is useful in laser ablation treatment mechanism where damage to the healthy tissues is highly undesired. However, the efficacy of the process is limited by the damage caused by the pulsed laser. A pulsed laser has both photothermal and photomechanical interaction with tissues. Photothermal interaction is caused by the rise in temperature due to the laser irradiation. This includes the denaturation of proteins, increased mitochondrial membrane permeability and ultimately vaporization. Photomechanical interaction causes the generation of pressure waves produced as a result of the pulse-laser interaction. This arises due to the thermoelastic expansion of the tissues due to heating. Photothermal and photomechanical interactions combined lead to damage in the tissues and are a potential threat to the surrounding tissues. In this thesis, the effects of both the mechanisms are studied using finite element models of the skin. A three-layered model of the skin is considered which is irradiated upon by a focused Nd:YAG infrared laser beam. The finite-element solver COMSOL Multiphysics is used to simulate the thermal and mechanical interaction due to the laser irradiation. Thermal effects of the irradiation are evaluated using the Arrhenius damage integral and the equivalent thermal dose administered to the tissue. The results obtained are validated using the histology results when mouse tissues are irradiated with a focused beam Q-switched Nd:YAG laser which leads to temperature rise and tissue removal. The mechanical interaction is evaluated in terms of the stress generated in the tissue during the laser ablation damage. Results obtained here are useful in characterizing the parameters of laser ablation like the repetition rate, laser power and pulse width. This helps us in optimizing the laser ablation process for a more effective treatment with minimum damage to surrounding tissues.
Author: Vivek Krishna Nagarajan
Publisher:
ISBN:
Category : Biomedical materials
Languages : en
Pages : 111
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Book Description
Real-time assessment of thermal tissue damage during ablation is necessary to achieve optimal tumor ablation. Histological assessment of thermal damage remains to be the gold standard. However, histological assessment is not real-time and requires experienced pathologists to grade thermal damage. Therefore, real-time monitoring of tissue status during thermal ablation of tumors would significantly advance the state of the art by ensuring complete destruction of tumor mass while avoiding tissue charring and excessive damage to normal tissues. Currently, Arrhenius damage model is the widely used method for real-time assessment of thermal tissue damage. This model uses a priori tissue information, such as tissue composition, empirically determined activation energy and pre-exponential factor along with the local tissue temperature, to calculate a damage index. Magnetic resonance thermometry (MRT) along with magnetic resonance imaging (MRI) is the most commonly used method for temperature mapping and assessing thermal ablation of soft tissues. However, MRT/MRI is bulky, very expensive and often subjected to motion artifacts. Light propagation within tissues is sensitive to changes in the tissue microstructure and physiology that is used to directly quantify the extent of tissue damage. In the past decade, several groups have reported differences in the absorption coefficient ([micron]a(¿)) and reduced scattering coefficient ([micron]s'(¿)) of native and coagulated tissues. However, a robust and low-cost system for determining [micron]a(¿) and [micron]s'(¿) during a thermal ablation process is yet to be realized in a clinical setting. More importantly, the relationship between microscopic changes in tissue and the resultant change in optical properties needs to be studied so that tissue damage can be predicted using changes in optical properties. The main objective of this dissertation research is to establish a correlation between changes in tissue optical properties ([micron]a(¿) and [micron]s'(¿)) and the status of tissue coagulation/damage during heating of ex vivo tissues. Successfully relating thermal damage to changes in [micron]a (¿) and [micron]s'(¿) during heating would help in realizing a compact, cost-effective real-time ablation solution that could benefit many clinics and hospitals that currently lack adequate funds to access ablative treatments.
Author: Yu Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 52
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Book Description
Cancer is one of the serious public health problems in the world. In order to reduce the side effect of the traditional cancer therapies, such as chemotherapy and radiotherapy, researchers have been working on developing new cancer treatments and photothermal therapy (PTT) is one of them. Irradiated by a NIR laser, nanoparticles targeted in the tumor tissue can generate heat. When the temperature is above 42 & degC, the tumor regions will begin to become ablated. Compared with the traditional therapy, PTT could increase the specificity of the treatment and reduce the side effects. Iron oxide magnetic nanoparticles are widely used for PTT due to their stability and multimodal functionality. The stability and innate toxicity of PS coated and uncoated nanoparticles were evaluated and it was found that PS coating significantly increases the stability and reduces the innate toxicity. Furthermore, hyperthermic ablation of MDA-MB-231 due to the photothermal effect of PS coated nanoparticles was observed. This observation was made using a 785 nm NIR laser for irradiation. The tissue-depth is of a concern for clinical therapy because the body tissues can absorb NIR laser. An agar gel layer was used to mimic the body tissue. The transmittance of laser through agar gel layers of varying thickness were examined and the effect of the tissue depth on hyperthermic ablation was evaluated. The absorbance of NIR light increases as the agar gel depth increases and as a result viability decreases. However, the significant viability loss was still observed at 3cm agar gel layer, indicates that the thickness of agar gel layer has a limiting impact on hyperthermia ablation of MDA-MB-231.
Author: Markolf H. Niemz
Publisher: Springer Science & Business Media
ISBN: 3662047179
Category : Science
Languages : en
Pages : 310
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Book Description
Basic concepts such as the optical and thermal properties of tissue, the various types of tissue ablation, and optical breakdown and its related effects are treated in detail. Special attention is given to mathematical tools (Monte Carlo simulations, the Kubelka—Munk theory etc.) and approved techniques (photodynamic therapy, laser-induced interstitial thermotherapy etc.). The part on applications reviews clinically relevant methods in modern medicine using the latest references. The last chapter covers today’s standards of laser safety, with a careful selection of essential guidelines published by the Laser Institute of America. With numerous research photographs, illustrations, tables and comprehensive summaries.
