Research into the development and application of ultrasound elastography, a technique for imaging stress-induced tissue strain, has so far taken insufficient account of stiffness anisotropy, either as a source or error or artefact in strain imaging, or as a means of extracting additional useful information. Skin was chosen as a model to investigate anisotropy using elastography, because it is anisotropic and easily accessible. Throughout the project, skin samples were stretched to evaluate stiffness, whilst two different imaging techniques were used to produce the tracking signal for generating strain images. Surface optical elastography was developed, using surface topography as the tracking signal. This novel technique proved feasible, so an optimisation technique was developed to improve the elastograms. High frequency ultrasound elasticity imaging was employed for the first time in combination with uniaxial tensile loading of the skin in the ultrasound scan plane, allowing depth and directional dependence of skin and subcutaneous tissue elasticity to be visualised. A novel ultrasound beam steering method for improving quality of tensile strain images was developed to overcome the problem that tracking across an ultrasound beam produces poor quality strain images. A feasibility study showed that strain image quality improves with the new technique. The techniques were used in two very preliminary clinical trials, for Breast Cancer Related Lymphedema and pigmented skin lesions, establishing that the new techniques were clinically feasible, testing 19 patients and 5 healthy volunteers. Differences in directional mechanical behaviour compared to healthy skin were demonstrated, further studies with larger numbers of cases would be valuable. Finite element modelling was used to provide further insight into the findings. It is concluded that anisotropy is important, as a source of variability in strain images and as a source of diagnostic information, and that the new techniques are clinically feasible, useful and worthy of improvement.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:582604 |
| Date | January 2007 |
| Creators | Coutts, Louise Victoria |
| Publisher | Institute of Cancer Research (University Of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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