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1 November 1982 Overview Of Ultrasonic Imaging
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The speed of ultrasound in soft tissues is about 1 500 m s-1, and different soft tissues have similar characteristic impedances. Reflexion and scattering occur as ultrasound travels through tissues, and the received frequency may be shifted by the Doppler effect if the target is moving. The attenuation is about 1 dB cm-1 MHz-1. Ultrasound is generated and detected by piezoelectric transducers. Pulse-echo techniques, giving resolution cells of the order of a few wavelengths in size, are used for A-scan, B-scan and time-position (M-mode) displays. Real-time scanners are based on mechanical or electronic beam steering, and arrays are often used. Tissue-equivalent phantoms have been developed. Doppler techniques, continuous wave and pulsed, are used for the detection of, structure motion and for blood flow studies. Pure Doppler and duplex pulse-echo/pulsed Doppler systems are very useful clinically. Transmission techniques have limited applicability. Ultrasonic diagnostic methods appear to be safe.
© (1982) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
P. N.T. Wells "Overview Of Ultrasonic Imaging", Proc. SPIE 0372, Physics and Engineering in Medical Imaging, (1 November 1982);

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