الفهرس 
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Abstract
The aim of this thesis is to use known absorption data in combination with recent theories of transient wave diffraction and ultrasound transducer properties to simulate the [ormation of ultrasound images in medical scanning systems. The re ult of these studies could be used in the future Lo design adaptive or swept coefficient filters thaL correct of these effects in ultrasound scanning systems equipped with radio frequency processing.
Development in ultrasound imaging is reviewed. The effects of the diffraction process on coupling between two coaxial disks are examined. The effect of different absorption mechanisms on a propagation of plane waves are discussed. Piezoelectric transduction during transmission and reception is analysed for times Ie s than one transducer reverberation period using equivalent circuits, adapted by z-transfonn techniques, to fonn a discrete time model of the process. This model can be applied as a recurrence relationship in the manner of a digital filter to detennine the tran ducer response directly in the time domain. Also contained in this thesis is a description of a computer model of a multilayered piezoelectric transducer, and the effects of backing and matching layers are investigated. The overall simulations are analysed for pulse transmission and puJse echo systems. AJso, the signaJ to noise ratio is calculated for a typical pUlse echo rig operating in oft tissue at different depths in frequency domain. Two data sets are examined; one from a wide bandwidth ultrasonic absorption spectrometer which i based 011 short pulse transmission between thick piezoelectric devices. SecondJy, data obtained from a single broad band 3.3 MHz centre frequency compression wave transducer in pulse-echo mode is studied. Simple deconvolution to get the target echo are shown to be adequate in the context of the experiments presented. Hornomorph.ic deconvoJution techniques are applied to the data in order to estimate the reflection equence for some targets. An approximate inverse filter for transducer correction i investigated. FinaJly, the attenuation coefficient correction for liquids to fit the simulation result with recorded data is examined. The thesis concludes that, the correction for the effect of absorption in scanning systems equipped with radio-frequency modules will yield improved images.
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