Ultrasound System Components Flashcards
Amplification(Receiver)
all signals are treated identically
entire image gets brighter or darker
It is adjustable
(Gain/Overall Gain Knob)
Compensation(Receiver)
creates an image of uniform brightness from top to bottom by compensating for the weakening of the soundwave as it travels through the medium
It is adjustable
Compression(Receiver)
performed twice
first-keeps the electrical signal level within the accuracy range of the system’s electronics
second-keeps the image’s grayscale content within the range of detection of the human eye (aprox 20 shades of gray)
It is adjustable
Demodulation(Receiver)
two part process that changes the electrical signals in the receiver into a form more suitable for the monitor
rectification-converts all negative voltages into positive voltages, corrects for, or eliminates, negative voltages
smoothing(enveloping)-places a smooth line around the “bumps” and evens them out
Reject(Receiver)
controls whether low-level signals will be displayed on the image
desirable to display low-level reflections that contain meaningful info
low-level noise should not appear on image
rejection affects all low-level signals on the image, does not affect bright echoes
transducer
transforms electrical energy into acoustic energy
during reception, it converts the returning acoustic energy into electrical energy
display
presents processed data
the display may be a flat screen monitor, a transparency, a spectral plot, or a variety of other formats
display controls
contrast-determines the range of brilliancies within the displayed image
brightness-determines the brilliance of the displayed image
scan converters
store info then display it
grayscale imaging made possible
translates the info from the spoke format into the video format
used analog technology
digital scan converters use computer technology
limitations of analog scan converters
image fade-stored charges on the silicon wafer dissipate over time
image flicker-caused by switching between read and write modes
instability-picture quality depends on many factors, including length of use, room temp, and humidity
deterioration-image degrades as device ages
advantages of digital scan converters
uniformity-consistent grayscale quality throughout the image
stability-does not fade or drift
durability-not affected by age or heavy use
speed-nearly instant processing
accuracy-error free
important elements of digital scan converters
pixel-smallest building block of a digital picture
pixel density-number of picture elements per inch
low pixel density-few pixels/inch, larger pixels, less detailed image, lower spatial resolution
high pixel density-many pixels/inch, smaller pixels, more detailed image, higher spatial resolution
bit-smallest amount of computer memory
fewer bits/pixel-fewer shades of gray, degraded contrast resolution
more bits/pixel-more shades of gray, improved contrast resolution
preprocessing
manipulation of image data before data storage:
time gain compensation
log compression
write magnification
persistence
spatial compounding
edge enhancement
fill-in interpolation
postprocessing
manipulation of image data after storage:
any change after freeze frame
black/white inversion
read magnification
contrast variation
3D rendering
Storage
archives the ultrasound studies
typical storage devices(media):
computer hard drives, CD/DVD, videotape, magneto-optical discs, paper printouts, photographs, USB drives
Pulser
determines amplitude, pulse repetition period(PRP), and pulse repetition frequency(PRF)
pulser is low-image is dark
pulser is high-image is bright
PRP and PRF are reciprocals
master synchronizer
maintains and organizes the proper timing and interaction of the system’s components
beam former
determines the firing delay patterns for phased array systems
it receives the pulser’s single electrical spike and distributes it to the numerous active elements of an array transducer
switch-protects the sensitive electrical components in the receiver from the high voltages created during transmission
during pulse creation-voltages from the system to the transducer are very high
during reception-voltages from the transducer back to the system are very low
receiver
transforms the electrical signals from the transducer(produced by the reflected sound) into a form suitable for display on the system’s monitor
five operations must be performed in the correct order for the system to function properly:
1)amplification 2)compensation 3)compression 4)demodulation 5)reject
