Ch 14 Pulsed Echo Instrumentation
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38 Terms
2 System Functions
Preparation and transmisson
Reception of electrical signals
6 major components of ultrasound systems
transducer, pulser and beam former, receiver, display, storage, master synchronizer
when does the transducer function
transmission and reception
What is the function of the pulser
determines amplitude, PRF, PRP
when does the pulser function
transmission
what is the function of the beam former
determines firing delay patterns for phased array systems
when does the beam former function
transmission and reception
what does the pulser do
creates electrical signal that excites the PZT
when does the pulser function
transmission
what does the pulser determine
amplitude of sound beam
higher voltage means ______ amplitude
higher
low voltage means the pzt vibrates _____
gently
low voltage = ____ sound beams
weak
weak amplitude = entire image is _____
dark
output power is measured and displayed using _____
Mechanical Index and Thermal Index
noise
undesirable information
signal
meaningful information
signal-to-noise ratio
compares meaningful info to contamination
high signal-to-noise ratio
high quality image, signal is stronger than noise
low signal-to-noise ratio
lower quality image, signal is close to noise strength
what kind of signals are suseptible to noise
weaker signals
how to improve signal-to-noise ratio
increase output power
the _____ optimizes steering and focusing during transmission
beam former
why is the switch necessary
to protect weak signals being received
when does the receiver function
reception
what 3 processes contribute to attenuation
absorption, scattering, reflection
whats the order of receiver functions
amplification
compensation
compression
demodulation
reject
how are signals amplified
equally
does amplification increase signal-to-noise ratio
no
higher frequency = ______ attenuation
higher
2 occurences of compression
keep electrical signals in systems range
keeps gray scale to be within human eye range
fewer shades of gray = _____ contrast
higher
what is demodulation
changes electrical signals to usable form for display
2 parts of demodulation
rectification
smoothing
demodulation (rectification)
negative voltages made positive
demodulation (smoothing)
smooths all voltages into one big voltage
rejection function
decides what level of low level echoes to trash
high frequency = ____ axial resolution
better
Note 
Flashcards (46)