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The potential for using combined electrical impedance and ultrasound measurements for the non-invasive determination of temperature in deep body tumours during mild hyperthermia
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Islam, Naimul (2012) The potential for using combined electrical impedance and ultrasound measurements for the non-invasive determination of temperature in deep body tumours during mild hyperthermia. PhD thesis, University of Warwick.
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WRAP_THESIS_Islam_2012.pdf - Submitted Version Download (5Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b2681925~S1
Abstract
The effectiveness of mild hyperthermia in improving the outcome of radiotherapy and chemotherapy
treatment is well established for surface tumours (e.g. an average improvement of 20% in the 5 years survival
rate using mild hyperthermia in conjunction with radiotherapy). However, to apply this technique to deep body
solid tumours clinically, a non-invasive thermometry method is needed. Several approaches have been
proposed for non-invasive thermometry in the past but none were capable of providing 3D temperature
distributions in-vivo with the required accuracy. In this thesis, the potential for determining the temperature in
a deep body solid tumour during mild hyperthermia by combining ultrasound propagation velocity and
electrical impedance measurement techniques has been investigated.
Simultaneous ultrasound propagation velocity and electrical impedance measurements were made in-vitro on
liver, fat and layered fat-liver samples as the temperature was increased to mild hyperthermia levels (45°C
max.). From the ultrasound measurements a linear correlation was found between the percentage of fat in the
sample and the change in ultrasound propagation velocity with temperature (-0.12ms-1°C-1%-1, r2 = 0.93).
Analysis of the data from the multi-frequency electrical impedance measurements showed that the magnitude
of the electrical impedance measured at 256kHz normalised to the magnitude of the electrical impedance
measured at 8kHz gave a linear correlation with the percentage of fat in the sample (0.003 %-1, r2 = 0.72) but no
statistically significant correlation between the fat content and the temperature coefficient at 256kHz (r2 =
0.007, p >0.05). These results support an approach of using high to low frequency impedance ratios to
determine the percentage of fat in the tissue and then this together with an ultrasound propagation velocity
measure to detect the change in the temperature of the tissue. Application of this technique is limited by the
variation in the change in ultrasound propagation velocity with temperature between tissue samples found in
this study but the origins of this are unclear. In addition, further improvements in the spatial sensitivity of the
tetrapolar impedance measurements are necessary to ensure an adequate spatial determination of fat content.
Item Type: | Thesis (PhD) | ||||
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Subjects: | R Medicine > R Medicine (General) | ||||
Library of Congress Subject Headings (LCSH): | Fever, Impedance (Electricity), Ultrasonics in medicine | ||||
Official Date: | May 2012 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Wilson, Adrian J. | ||||
Sponsors: | Commonwealth Scholarship Commission in the United Kingdom | ||||
Extent: | xvi, 183 leaves : illustrations. | ||||
Language: | eng |
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