Date of Award

2008

Publication Type

Master Thesis

Degree Name

M.Sc.

Department

Physics

Keywords

Applied sciences, Pure sciences

Supervisor

Roman Maev

Rights

info:eu-repo/semantics/openAccess

Abstract

A new method for image reconstruction of a foreign object, i.e. any reflector which somehow could be inserted into the brain tissue, such as a bullet or a piece of shrapnel, is investigated. The method is based on noninvasive transcranial ultrasound propagation through skull bone and brain tissue. A simulation has been developed during the study to process the experimental results and reconstruct an image showing the position of the foreign object. The algorithm is designed for use with a linear array of 128 receivers and a source of ultrasound as the reflector (all at the optimized frequency of 1.7MHz). A simplified simulated skull bone (scattering medium) was also added to the program to distinguish how it affects passing through ultrasonic fields in different circumstances. From an experimental point of view, to check the effectiveness of the algorithm, a simplified skull bone phantom was made and used in data acquisition at the array of receivers. When passed through phantom layer, the ultrasound field (initially generated at the reflector) reaches the array of receivers, and after being saved, the distribution on the array is processed to compensate for the distortion and reconstruct an image which contains data about the reflector's position. Due to high attenuation in scattering medium (which represents skull bone's acoustical properties) and brain tissue, it has been determined that the method can reconstruct the reflector's position roughly at a maximum distance of 15cm from the array of receivers in presence of the phantom which is far enough to cover all inside of a typical skull.

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