Application of coded transmission technique to Ultrasonic Computed Tomography of soft tissues
Résumé
Ultrasonic Computed Tomography (UCT) is an ultrasonic imaging modality of soft tissues. The main performance of the UCT is to improve the image resolution by eliminating unwanted noise, and/or wave interference such as speckle. When an acoustical properties contrast exists between the material and the mean medium, such as micro-calcification under soft tissues for example, the presence of some physical phenomena generates complex signals consisting of several packets with different signatures, which it is often difficult to interpret in terms of wave path, in terms of depth-dependencies, or in terms of reflectivity, velocity or attenuation. To improve the quality of the tomogram, several approaches have been used so far; such as filtering or deconvolution, which may be sophisticated and unstable. An alternative methods is to consider the waveform generated by the array, and propagating in the reference medium before the scatterer, and in particular methods based on a coded waveforms, which make it possible to process the local, and much more global information available in terms of frequency and time parameters. In this work, the Golay coded excitations are performed as processing tools, before tomographic image reconstruction to increase the signal-to-noise ratio and the depth inspection of soft tissues.
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