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Physical Aspects of Thermotherapy - A study of heat transport with a view to treatment optimisation

Olsrud, Johan LU (1998)
Abstract (Swedish)
Popular Abstract in Swedish

Lokal behandling med målsättning att förstöra kroppsvävnad genom uppvärmning (termoterapi) kan i vissa fall vara ett alternativ eller komplement till kirurgi. I avhandlingen presenteras utrustning och metoder för att, utifrån en fysikalisk synvinkel, göra sådana behandlingar säkrare och effektivare. Genom att beräkna temperaturefördelningen m.h.a. datorsimuleringar kan man i förväg bedöma hur olika applikatorer som används för uppvärmning skall placeras. Man kan t.ex. använda optiska fibrer för att leda laserljus, som sedan absorberas och övergår till värme, in i vävnaden. Hänsyn måste då tas till vävnadens fysikaliska egenskaper, t.ex. värmeledningsförmåga och optiska egenskaper. Även blodflödet... (More)
Popular Abstract in Swedish

Lokal behandling med målsättning att förstöra kroppsvävnad genom uppvärmning (termoterapi) kan i vissa fall vara ett alternativ eller komplement till kirurgi. I avhandlingen presenteras utrustning och metoder för att, utifrån en fysikalisk synvinkel, göra sådana behandlingar säkrare och effektivare. Genom att beräkna temperaturefördelningen m.h.a. datorsimuleringar kan man i förväg bedöma hur olika applikatorer som används för uppvärmning skall placeras. Man kan t.ex. använda optiska fibrer för att leda laserljus, som sedan absorberas och övergår till värme, in i vävnaden. Hänsyn måste då tas till vävnadens fysikaliska egenskaper, t.ex. värmeledningsförmåga och optiska egenskaper. Även blodflödet har stor betydelse för temperaturfördelningen genom sin kylande inverkan och måste tas med i beräkningarna. Under behandling måste temperaturen också kunna mätas för att kontrollera att resultatet blir som man tänkt sig. Vanligtvis används termistorer, som sticks in i vävnaden, för detta ändamål. Man söker emellertid nya metoder för att kunna mäta temperaturen utan att behöva sticka in någon mätprob och för att få information om temperaturen i hela området. En sådan metod bygger på temperaturmätningar m.h.a. s.k. magnetresonanstomografi och har i detta arbetet använts för att studera temperaturfördelningen under bestrålning med laserljus i ett material som liknar vävnad. Utifrån mätresultaten kan man t.ex. kontrollera om beräkningar som gjorts är riktiga. Uppvärmning m.h.a. laserljus kan användas för att döda levertumörer, men har även studerats som en möjlig metod att behandla prostatabesvär, vilket drabbar en mycket stor andel av alla män då de blir äldre. I avhandlingen presenteras, förutom utrustning och beräkningar för behandling av levertumörer, en ny laserapplikator som är avsedd att göra prostatabehandlingar enklare. Vidare har en ny metod för behandling av alltför rikliga bödningar från livmodern studerats genom datorsimulering. Under behandlingen förs en kateter med en expanderbar ballong in i livmoderkaviteten och cirkulerande vätska i ballongen värms upp till en temperatur omkring 75°C. Datorsimuleringar visar hur ballongtemperatur, behandlingstid, blodflöde m.m. påverkar temperaturfördelningen och därmed utsräckningen av det behandlade området. En ökad förståelse av de fysikaliska aspekterna på termoterapi gör att dessa nya behandlingar kan utföras på ett bättre och säkrare sätt. (Less)
Abstract
Local treatment with the aim to destruct tissue by heating (thermotherapy) may in some cases be an alternative or complement to surgical methods, and has gained increased interest during the last decade. The major advantage of these, often minimally-invasive methods, is that the disease can be controlled with reduced treatment trauma and complications. The extent of thermal damage is a complex function of the physical properties of tissue, which influence the temperature distribution, and of the biological response to heat. In this thesis, methods of obtaining a well-controlled treatment have been studied from a physical point of view, with emphasis on interstitial laser-induced heating of tumours in the liver and intracavitary heating as... (More)
Local treatment with the aim to destruct tissue by heating (thermotherapy) may in some cases be an alternative or complement to surgical methods, and has gained increased interest during the last decade. The major advantage of these, often minimally-invasive methods, is that the disease can be controlled with reduced treatment trauma and complications. The extent of thermal damage is a complex function of the physical properties of tissue, which influence the temperature distribution, and of the biological response to heat. In this thesis, methods of obtaining a well-controlled treatment have been studied from a physical point of view, with emphasis on interstitial laser-induced heating of tumours in the liver and intracavitary heating as a treatment for menorrhagia.



Hepatic inflow occlusion, in combination with temperature-feedback control of the output power of the laser, resulted in well defined damaged volumes during interstitial laser thermotherapy in normal porcine liver. In addition, phantom experiments showed that the use of multiple diffusing laser fibres allows heating of clinically relevant tissue volumes in a single session. Methods for numerical simulation of heat transport were used to calculate the temperature distribution and the results agreed well with experiments. It was also found from numerical simulation that the influence of light transport on the damaged volume may be negligible in interstitial laser thermotherapy in human liver. Finite element analysis, disregarding light transport, was therefore proposed as a suitable method for 3D treatment planning. Finite element simulation was also used to model intracavitary heating of the uterus, with the purpose of providing an increased understanding of the influence of various treatment parameters on blood flow and on the depth of tissue damage. The thermal conductivity of human uterine tissue, which was used in these simulations, was measured. Furthermore, magnetic resonance imaging (MRI) was investigated as a method of non-invasive temperature monitoring, and an optically tissue-like phantom material, suitable for MRI, was developed. MRI thermometry in this material was shown to be an excellent method for characterisation of laser applicators and for verification of numerical calculations. Finally, a water-cooled laser applicator for the treatment of benign prostatic hyperplasia, allowing anatomically correct heating, was developed and evaluated ex-vivo. An increased understanding of the physical aspects of thermotherapy, aided by the methods and results presented in this thesis, constitutes a significant contribution to the performance of safe and efficacious treatment. (Less)
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author
opponent
  • Dr van Dijk, van Dijk, Akademiskt Medicinskt Centrum, Universitetet i Amsterdam
organization
publishing date
type
Thesis
publication status
published
subject
keywords
magnetic resonance, non-invasive, temperature, coagulation, prostatic, menorrhagia, liver tumour, finite element method (FEM), thermal conductivity, intracavitary, interstitial, laser, Thermotherapy, hyperthermia, MRI, Medicine (human and vertebrates), Medicin (människa och djur), Physics, Fysik
pages
70 pages
publisher
Department of Radiation Physics, Lund university
defense location
Föreläsningssal F3, Centralblocket, Lunds Universitetssjukhus, Lund
defense date
1998-12-17 10:15
external identifiers
  • Other:LUNFD6/(NFRA-1040)/1-70/1998; LUMEDW/(MERI-1040)/1-70/1998
ISBN
91-628-3235-2
language
English
LU publication?
yes
id
9c2df65b-6685-461e-a7d9-8e670381304f (old id 39177)
date added to LUP
2007-07-31 09:28:37
date last changed
2016-09-19 08:45:11
@misc{9c2df65b-6685-461e-a7d9-8e670381304f,
  abstract     = {Local treatment with the aim to destruct tissue by heating (thermotherapy) may in some cases be an alternative or complement to surgical methods, and has gained increased interest during the last decade. The major advantage of these, often minimally-invasive methods, is that the disease can be controlled with reduced treatment trauma and complications. The extent of thermal damage is a complex function of the physical properties of tissue, which influence the temperature distribution, and of the biological response to heat. In this thesis, methods of obtaining a well-controlled treatment have been studied from a physical point of view, with emphasis on interstitial laser-induced heating of tumours in the liver and intracavitary heating as a treatment for menorrhagia.<br/><br>
<br/><br>
Hepatic inflow occlusion, in combination with temperature-feedback control of the output power of the laser, resulted in well defined damaged volumes during interstitial laser thermotherapy in normal porcine liver. In addition, phantom experiments showed that the use of multiple diffusing laser fibres allows heating of clinically relevant tissue volumes in a single session. Methods for numerical simulation of heat transport were used to calculate the temperature distribution and the results agreed well with experiments. It was also found from numerical simulation that the influence of light transport on the damaged volume may be negligible in interstitial laser thermotherapy in human liver. Finite element analysis, disregarding light transport, was therefore proposed as a suitable method for 3D treatment planning. Finite element simulation was also used to model intracavitary heating of the uterus, with the purpose of providing an increased understanding of the influence of various treatment parameters on blood flow and on the depth of tissue damage. The thermal conductivity of human uterine tissue, which was used in these simulations, was measured. Furthermore, magnetic resonance imaging (MRI) was investigated as a method of non-invasive temperature monitoring, and an optically tissue-like phantom material, suitable for MRI, was developed. MRI thermometry in this material was shown to be an excellent method for characterisation of laser applicators and for verification of numerical calculations. Finally, a water-cooled laser applicator for the treatment of benign prostatic hyperplasia, allowing anatomically correct heating, was developed and evaluated ex-vivo. An increased understanding of the physical aspects of thermotherapy, aided by the methods and results presented in this thesis, constitutes a significant contribution to the performance of safe and efficacious treatment.},
  author       = {Olsrud, Johan},
  isbn         = {91-628-3235-2},
  keyword      = {magnetic resonance,non-invasive,temperature,coagulation,prostatic,menorrhagia,liver tumour,finite element method (FEM),thermal conductivity,intracavitary,interstitial,laser,Thermotherapy,hyperthermia,MRI,Medicine (human and vertebrates),Medicin (människa och djur),Physics,Fysik},
  language     = {eng},
  pages        = {70},
  publisher    = {ARRAY(0x839c3d0)},
  title        = {Physical Aspects of Thermotherapy - A study of heat transport with a view to treatment optimisation},
  year         = {1998},
}