Date of Award

2012

Degree Type

Thesis

Degree Name

M.Sc.

Department

Physics

First Advisor

Roman Maev

Rights

CC-BY-NC-ND 4.0

Abstract

The main goal of this study is to develop a new image reconstruction approach for the ultrasonic detection of foreign objects inside the human brain through a simplified skull model. The proposed solution is based on the "Harmonic Phase Conjugation" technique. A source of ultrasound (transducer), small reflecting and scattering objects, a simplified skull layer, and a linear array of ultrasonic receivers are the main components of the test setup. The algorithm starts with the forward propagation step, when the phase and amplitude distributions of the ultrasonic field from the source transducer are recorded with an array of receivers. These distributions are also calculated in presence of a skull layer and small reflecting objects. The recorded phase and amplitude information is then used in the back propagation step, when the phase-conjugated scattered field is numerically propagated through the same medium in the reverse direction. As this field naturally focuses at the locations of the reflecting objects, their image can be reconstructed. After testing the algorithm using a numerical model, a set of laboratory experiments was conducted to verify the accuracy of the developed simulation. The results of these tests are presented, and the main advantages and drawbacks of the approach are discussed.

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