Evaluation of Temperature Rise and Thermal Lesion Dimensions in Liver Laser Interstitial Thermotherapy

Gorjiara, T. and Mokhtari-Dizaji, M. and Ghanaati, H. (2005) Evaluation of Temperature Rise and Thermal Lesion Dimensions in Liver Laser Interstitial Thermotherapy. Iranian Journal of Medical Physics, 2 (2). pp. 55-66.

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Abstract

Introduction:  Laser  interstitial  thermotherapy  (LITT)  is  an  internal  ablation  therapy  method consisting of a percutaneous or intraoperative insertion of laser fibers directly into the liver tumor with maximum diameter of 5 cm. In this treatment method, there isnâ��t any general information about the relationship  between  increasing  the  exposure  power,  coagulation  and  carbonization  areas  with  the changes  in  temperature.  In  this  study,  according  to  the  power  range  of  LITT  the  changes  in  the temperature of liver tissue and the diameter of the necrotic area were measured.  Materials and Methods: In vitro LITT was performed on fleshly sheep liver tissue using a bare-tip optical  fiber  from  a  Nd:Yag  laser.  A  power  setting  of  2,  2.4,  3,  3.4,  and  4  watt  were  used  for  an exposure time of 300 sec. The temperature monitoring was performed during the heating and cooling down by fixing micro thermocouples at 2.5 mm from the fiber tip. The thermal lesions which include necrosis and carbonization areas were compared for each power.  Results: The result of the temperature monitoring was expressed as the mean value for each power. The temperature charts show that at 2.5 mm from the fiber tip the max. tissue temperature is increased from 276.20 ºC (for a power setting of 2 watt and a 308 sec of exposure time) to 728.2 ºC (for a power setting of 3.4 watt and a 365 sec exposure time). At 6 mm from the fiber tip the max. temperature was measured to be 86.4 ºC for  a power setting of 4 watt and 325 sec exposure time. For each power a non linear  regression  analysis  was  performed  during  the  heating  and  cooling  down  for  the  dependent (temperature) and independent (time) parameters. The max. value for the cubic equation is shown to be R = 0.99 during the heating and for the exponential equation to be R = 0.89 during the cooling down. A p value of 0.01 is considered significant. The diameter of the necrotic liver tissue increases from 12.95  mm  at  600  joules  to  16.15  mm  at  1200  joules  of  energy.  When  the  total  applied  energy  is increased  from  600  to  1200  joules,  the  thermal  ablation  increased  by  25  while  there  was  a  56 increase  in  the  carbonization  area.   Increasing  the  carbonization  area  caused  a  decreases  in  the penetrability of the laser beam.  Discussion and Conclusion: A useful treatment planning based on a non-linear regression analysis could  be  prepared  for  the  treatment  of  hepatocellular  carcinoma.  In  this  analysis,  the  temperature changes in the necrotic area are monitored as a function of power setting in the range of 2-4 watts in LITT.Â

Item Type: Article
Subjects: WN Radiology . Diagnostic Imaging
Divisions: Journals > Iranian J Medical Physics
Depositing User: ijmp ijmp
Date Deposited: 21 Jan 2018 15:37
Last Modified: 21 Jan 2018 15:37
URI: http://eprints.mums.ac.ir/id/eprint/9004

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