Cepstral Analysis of Wideband Ultrasound
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Date
2021-03
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Addis Ababa University
Abstract
Ultrasound is a pressure wave with frequency beyond20 ������ . Wideband ultrasound is
ultrasound pulse with mega range of frequency components. Most of the currently available
ultrasound transducers are narrow banded and fail to provide better axially resolved images
for tissues with multiple layers. The methodology used in this thesis models multi-layered
biological medium based on linear acoustics of pulse-echo detection principle, normal
incidence, longitudinal ultrasonic propagation and investigates the feasibility to detect
periodicity. Ultrasound propagation data was generated synthetically and subjected to
cepstral analysis to detect periodicity in a multilayered skin tissue model. Rectangular pulses
with a center frequency of 16-30 MHz and pulse duration of 1.2 × 10−7s and 0.8 × 10−7s were
applied to a 4-layered medium. The output is measured and cepstral analysis was applied to
determine the feasibility of periodicity detection. For layers separated by equal thicknesses,
the cepstral peaks existed at equal intervals where as in the case of different layer
thicknesses, peaks existed at integer multiple of the thinnest layer thickness. In cepstral
analysis, when the cepstral peaks exist at equal intervals or integer multiples of the shortest
time of flight (time of flight to the thinnest layer), periodicity detection is guaranteed. It is
concluded that periodicity is detected with wideband ultrasound pulses and the minimum
and maximum bandwidth are determined based on the duration of the pulse. The possible
limitations with the thesis are the assumption of normal incidence planar waveforms, linear
ultrasound propagation, and parallel surfaces.
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Keywords
Cepstrum, Wideband, Pulse, Ultrasound, Layer, Periodicity