11 April 2007 Ultrasonic imaging in extinction and velocity contrast by time selective first arrival line tomography in transmission
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Abstract
Narrowband excitation at 86 MHz with vector detection and wideband excitation in the range of 2 to 20 MHz have both been used for tomographic imaging in transmission. A line-shaped point spread function has been realized by temporal apodization selecting from a pulsed signal observed in transmission only the contribution traveling the path connecting the transducer foci. By this method a pair of scanned focusing transducers mounted in a defocused arrangement was employed for tomographic imaging. The technique relates to shadowing of a point source in transmission as used in X-ray tomography, but, in addition, variations of the time-of-flight are measured else by phase contrast or a cross-correlation procedure with high resolution. From these data an image with velocity contrast can be derived in addition to the conventional image representing the extinction in the samples under investigation. Examples presented include resolution test samples and biomedically relevant materials. It is also demonstrated that the coherent detection scheme can be used to enhance the resolution by the synthesis of an enlarged aperture. Respective procedures are implemented for image reconstruction.
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Andre Schwagmann, Dimo Ivanov, Evgeny Twerdowski, Mieczyslaw Pluta, Wolfgang Grill, "Ultrasonic imaging in extinction and velocity contrast by time selective first arrival line tomography in transmission", Proc. SPIE 6532, Health Monitoring of Structural and Biological Systems 2007, 65321N (11 April 2007); doi: 10.1117/12.715414; https://doi.org/10.1117/12.715414
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