Phyrev ch.6 - Demodulation amplitude detection envelope detection(pre-processing changes the signals form to one more suitable for tv display fixed

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Demodulation - amplitude detection, envelope detection (pre-processing) - changes the signals form to one more suitable for tv display, fixed by manufacturer - Rectification – turns all negative voltages into positive ones. Eliminates negative voltages - Smoothing ( enveloping) – putting an envelope aroung the bumps to even them out Rejection – Suppression , threshold, filtering (dynamic range) - affects all low level signals everywhere on the image but does not affect bright echoes Harmonic Imaging – creating an image from sound reflections at twice the transmitted frequency. Are multiples of the transducer frequency. Output power vs. Receiver Gain: - output power – affects brightness by adjusting the strength of the sound pulse sent to the body by the transducer. When image too bright due to out power, lateral and axial resolution degrade When pulse is more powerful, returning echoes are stronger, and image is brighter. - Receiver Gain – affects brightness by changing the amplification of signal after returning to the receiver. When amplification is increased, signals in receiver are boosted, image will be brighter. ALARA – as low as reasonably achievable – minimize patient exposure Ch. 14 Displays CRT (Cathode-Ray tube) – the phosphors glow and turn electron into light to see on
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This note was uploaded on 11/22/2010 for the course ULTRASOUND 729 taught by Professor Barnes during the Spring '10 term at El Centro College.

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Phyrev ch.6 - Demodulation amplitude detection envelope detection(pre-processing changes the signals form to one more suitable for tv display fixed

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