| 2. |
- Olsrud, Johan, et al.
(author)
-
MRI thermometry in phantoms by use of the proton resonance frequency shift method: application to interstitial laser thermotherapy
- 1998
-
In: Physics in Medicine and Biology. - 1361-6560. ; 43:9, s. 2597-2613
-
Journal article (peer-reviewed)abstract
- In this work the temperature dependence of the proton resonance frequency was assessed in agarose gel with a high melting temperature (95 degrees C) and in porcine liver in vitro at temperatures relevant to thermotherapy (25-80 degrees C). Furthermore, an optically tissue-like agarose gel phantom was developed and evaluated for use in MRI. The phantom was used to visualize temperature distributions from a diffusing laser fibre by means of the proton resonance frequency shift method. An approximately linear relationship (0.0085 ppm degrees C(-1)) between proton resonance frequency shift and temperature change was found for agarose gel, whereas deviations from a linear relationship were observed for porcine liver. The optically tissue-like agarose gel allowed reliable MRI temperature monitoring, and the MR relaxation times (T1 and T2) and the optical properties were found to be independently alterable. Temperature distributions around a diffusing laser fibre, during irradiation and subsequent cooling, were assessed with high spatial resolution (voxel size = 4.3 mm3) and with random uncertainties ranging from 0.3 degrees C to 1.4 degrees C (1 SD) with a 40 s scan time.
|
|
| 3. |
- Persson, Bertil R.R., et al.
(author)
-
Numerical calculations of temperature distribution resulting from intracavitary heating of the uterus
- 1998
-
In: Gynaecological Endoscopy. - 0962-1091. ; 7:4, s. 203-209
-
Journal article (peer-reviewed)abstract
- Objective To estimate, using numerical calculations, the depth of tissue damage in the uterus following balloon thermal endometrial destruction. Design A parameter, therapeutic depth, was defined. This was the maximum depth into the uterine myometrium, from the uterine cavity, at which a predefined temperature was reached after a certain time and with a constant intracavitary temperature. Setting Departments of radiation physics and gynaecology at a university hospital. Results After 30 min of treatment with an intracavitary temperature of 75°C, the maximum depth into the myometrium at which the tissue had been exposed to a temperature of 55°C, when blood flow was neglected, was 8.9 mm. Taking into account blood flow the depth was 3.4 mm, and including the pressure because of the balloon it was 5.6 mm. With the inclusion of a local increase in blood flow because of elevated tissue temperature the depth was 4.4mm. Finally when damage to blood vessels due to coagulation was also accounted for, the depth was 5.2mm. The therapeutic depth decreased only slightly when the treatment time was shortened to 15 min. Conclusions Numerical calculations provide a basis for estimation of the optimal intracavitary temperature and treatment time when performing thermal endometrial destruction by means of a balloon catheter.
|
|
