US Physics Chapter 14 Flashcards
What does beam former do
takes single elecgtrtical input and optimizes transmitted ultrasound beam. Splits it to the elements, apodization, etc.
What does switch do in ultrasound machine
Its allows for high voltage used in transmission and much lower voltage when received. It also directs things to the appropriate circuitry for transmission or input
5 steps an ultrasound receiver does
in order (also alphabetical). Amplification, compensation, compression, demodulation reject
What does amplifier do?
It makes all elements of input brighter and doesn’t improve signal to noise ratio
What does preampfification do?
It improves the quality of the signal by preventing electronic noise from contaminating signals
What does compensation do?
It corrects for the attenuation of a signal that would occur the deeper you look because of signal attenuation.
Some other names for compensation
time-gain compensation, depth gain compensation, and swept gain
What has greater attenuation - high or low frequency probes?
high frequency probes
What does ultrasound compression do?
It compresses signal without changing ranking making it suitable to electrical system and also to the human eye since we can only distinguish 20 shades of grey
Can compression be adjusted
Yes.
why is compression performed on a logarithmic basis?
because signals are very weak and the most meaningful signals between soft tissues are slight differences in weak signals.
What is demodulation? Adjustable?
Rectification of signal and smoothing so its more suitable to system display. Not adjustable.
What is rejection?
Consists of user modified and built in. Allows the user to filter out some clinically meaningless low level signals.
What is dynamic frequency tuning
Higher frequency sound used for superficial depth while lower frequency is used fro deeper reflectors
Does adjusting output power improve the signal to noise ratio?
Yes if there are too many bright reflectors turning down the power can improve the quality of th image.
