Thermal feedback control of laser coagulation of biological tissues /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
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| Subjects: | |
| Online Access: | Link to ProQuest copy Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | Laser thermal coagulation of biological tissue was studied in an egg white model and in beef tissues using an Argon laser. Understanding the laser coagulation process in biological tissue is essential in order to achieve the ultimate goal of control of the laser coagulation process. Using egg white (albumin) samples mixed with absorbing and scattering agents, results showed coagulation diameter and depth increase with an increase in scatterer concentration. In general, the coagulated diameter was more strongly affected by variation of scatterer concentration. An approach to obtain the maximum coagulation effect was implemented in an in vitro experimental study for beef myocardium, kidney and liver by maintaining the surface temperature within a desired range using by thermal feedback control. A special two layer setup composed of a clear gel on top and tissue on the bottom was designed for this purpose. Optimal coagulative behavior was obtained through feedback control by monitoring temperature using thermocouple sensors placed at the tissue-gel interface. Continuous wave (488nm) Argon laser power of 1W, 2W and 3W with electronically controlled shutter on/off output was delivered on the surface of fresh beef tissues for 6, 3 and 2 minutes, respectively. Measurements of temperature by thermocouples were carried out at the center of the irradiated beam on the surface of tissue. A pulsatile exposure regimen was used so that thermocouple readings without self absorption effect may be obtained. It was found in uncontrolled temperature responses that the temperature on the surface of tissue was due to several factors, such as optical properties, incident powers (intensities) and exposure times. Controlled coagulation using thermal feedback resulted in coagulation propagation which is less affected by variabilities in various tissue properties. Coagulation depths in the controlled temperature experiment consistently increased when using lower power and the coagulation diameters increased as the incident powers increased. Coagulation sizes (diameters and depths) of the lesions produced by longer exposure resulted in more damage. |
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| Item Description: | "Major subject: Bioengineering." Vita. |
| Physical Description: | xvii, 133 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |