Pulsed Echo Instrumentation Flashcards
highly sophisticated machine that creates and receives sound pulses to present audio and visual information for interpretation
ultrasound machine
6 major components of an ultrasound machine
transducer pulser and beam former receiver display storage master synchronizer
what creates and controls the electrical signals sent to the transducer that generate sound pulses
pulser and beam former
what does the pulser determine
amplitude, PRP, PRF
what does the pulser do
excites the crystal and creates the sound beam
does the pulser operate during transmission or reception
transmission
can we adjust the pulser voltage?
yes, by changing the output power
attempts to standardize output have resulted in these two measurements on modern systems
thermal and mechanical index
thermal index
mechanical index
what determines firing delay patterns for phased array systems
beam former
is the beam former part of transmission or reception
considered part of transmitter but functions during both
what does the beam former do
coordinates electrical signals to optimize the sound beam being transmitted
adjusts electrical spike voltages to reduce lobe artifacts
establishes correct time delays used for dynamic receive focusing in reception
controls dynamic aperture by varying the number of PZT crystals used during reception and transmission
what are the advantages of using a modern, digital beam former
has system updates, software updates, rapid product improvement, rapid development, stable (no mechanical parts to wear out), and versatile because they can use transducers of wide frequencies
what is the beam former switch
a transmit/receive switch that protects receiver components from powerful signals during transmission
also directs signals from transducer to appropriate electronic processing components within the US system
function of the receiver
to transform electrical signals from transducer into a form suitable for display
order of operations of a receiver
amplification compensation compression demodulation reject
what is the process of improving quality of signal before it is amplified
preamplification
what are the 2 parts of demodulation and their purpose
rectification - convert negative voltages to positive ones
smoothing / enveloping - smoothing line around bumps
purpose of US display
to display data
storage devices
hard drive, CD, DVD, videotape, magneto-optical discs, paper printouts, photos, USB drive
what is the purpose of the master synchronizer
to maintain and organize proper timing and interaction of system components
random disturbance that reduces a signal’s clarity and contaminates an image
noise
comparison of signal to noise
signal to noise ratio
when the signal to noise ratio is high, the signal is (higher or lower) than the noise
higher
signal to noise ratio has what relationship with power
direct
what is another name for PRP
depth of view
the time between a voltage spike and the next (or time from the start of one pulse to the start of the next pulse)
PRP
can we adjust the PRP?
yes, by changing the depth
DIRECTLY related to depth
what is the number of pulses that an US system transmits per second
PRF
can we adjust the PRF?
yes, by adjusting the depth of view
INVERSELY related to depth
what is a channel made of
made of a single PZT element, beam former / pulser, and the wire connecting them
amplification
also called receiver gain,
treats all signals identically
amplitude brightens the entire image
we CAN adjust it
compensation
TGC, DGC, swept gain
treats all signals differently based on depth because of attenuation
uniformly bright, with proper compensation images become increasingly darker with depth
we can adjust it
compression
log compression, dynamic range
signals treated differently based on strength
changes in grayscale mapping, strong signals appear bright white
we CAN adjust
demodulation
prepares electrical signals to be suitable for display
we CANNOT adjust this
reject
threshold, suppression
only weak signals affected
weak echoes appear or are eliminated from image
we CAN adjust
near gain
constant amount of compensation
delay
varying compensation
slope
compensation corrects for attenuation
knee
reflections are at max compensation
far gain
max compensation that receiver can provide
if a TGC curve attenuates at a shallow depth, it has a (high or low frequency)
high
dynamic frequency tuning
dampening of high frequency pulses to create a good axial resolution
ALARA
as low as reasonable achievable
used to minimize bio effects on patient
what do output power and receiver gain have in common
they both change the brightness of the entire image
output power
changes brightness of entire image alters signal to noise ratio alters bio effects bioeffect concerns decrease this FIRST if image is too bright
receiver gain
changes brightness of entire image does not alter signal to noise ratio no exposure no bioeffect concerns increase first if image is too dark
