University of Twente Student Theses


Force sensing with an acoustically transparent pressure sensor to improve robotic assisted breast biopsy

Nies, S.H.G. (2017) Force sensing with an acoustically transparent pressure sensor to improve robotic assisted breast biopsy.

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Abstract:The purpose of this thesis is investigating the possibilities of using a pad made of flexible acoustically transparent material for determining the elastic properties of a tissue. Furthermore, the possibility to visualize different stiffnesses within a phantom with the use of the pad will be considered. To evaluate these possibilities, four different pads have been made: a small and a large thickness for two different compositions. PVC Plastisol has been used to produce both a phantom and the pads. These compositions are 70% plastisol solution and 100% plastisol solution. Different materials have been placed into the phantom in order to measure different stiffnesses within a material. The basis for this phantom is homogeneous plastisol soft (70% solution) with an eraser, coffee beans, a fish oil capsule and a sphere made of 100% plastisol medium placed in it. This phantom is used to evaluate the deformation of the pad under pressure and the possibility to detect differences in stiffness within a tissue. The designed pads fulfill the most important requirements for this stage of design: it is acoustically transparent, it can be mounted on the ultrasound probe and it deforms under pressure. The deformation of the pads is visible with ultrasound images. For detecting differences in stiffness within a tissue: only the eraser could be detected with the pads. Because the stressstrain relation for this material is not linear, a more accurate measurement has to be done on the behavior. When this behavior is known, it may be possible to determine the applied force on the tissue and to determine the Young’s modulus of the breast. For this to become reality, some improvements have to be made in further research: produce a mold that can be completely fixed, so the pad is reproducible. Furthermore, prevent formation of air bubbles, since this reduces the signal and gives noise in the image. In order to implement it in the MURAB project, real-time analysis of the images would be useful. This real-time analysis should include recognition of the boundary layer.
Item Type:Essay (Bachelor)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Programme:Biomedical Technology BSc (56226)
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