Brunel University School of Engineering and Design PhD Theses
Abstract
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.Human body scanners used to extract anthropological data have a significant drawback, the
subject is required to undress or wear tight fitting clothing. This thesis demonstrates an
ultrasonic based alternative to the current optical systems, that can potentially operate on a fully
clothed subject. To validate the concept several experiments were performed to determine the
acoustic properties of multiple garments. The results indicated that such an approach was
possible.
Beamforming is introduced as a method by which the ultrasonic scanning area can be increased,
the concept is thoroughly studied and a clear theoretical analysis is performed. Additionally,
Matlab has been used to demonstrate graphically, the results of such analysis, providing an
invaluable tool during the simulation, experimental and results stages of the thesis.
To evaluate beamfoming as a composite part of ultrasonic body imaging, a hardware solution
was necessary. During the concept phase, both FPGA and digital signal processors were
evaluated to determine their suitability for the role. An FPGA approach was finally chosen,
which allows highly parallel operation, essential to the high acquisition speeds required by some
beamforming methodologies. In addition, analogue circuitry was also designed to provide an
interface with the ultrasonic transducers, which, included variable gain amplifiers, charge
amplifiers and signal conditioning. Finally, a digital acquisition card was used to transfer data
between the FPGA and a desktop computer, on which, the sampled data was processed and
displayed in a coherent graphical manner.
The beamforming results clearly demonstrate that imaging multiple layers in air, with
ultrasound, is a viable technique for anthroplogical data collection. Furthermore, a wavelet
based method of improving the axial resolution is also proposed and demonstrated