Chapter 3 penny Flashcards
the rules that states that it takes 13 microseconds for sound to travel 1 centimeter in soft tissue
13 us rule
the interference pattern caused by scatterers that produces the granular appearance of tissue on a sonographic image
acoustic speckle
the height of the spike on the image is related to the strength (amplitude) of the echo generated by the reflector
A mode
as low as reasonably achievable; the principle that states one should always use the lowest power and shortest scanning time to reduce potential exposure to the patient
ALARA
the part of the receiver that increases or decreases the received echoes equally, regardless of depth
amplification
the maximum or minimum deviation of an acoustic variable from the average of that variable; the strength of the receiver
amplitude
the part of the digital scan converter that converts the analog signals from the receiver to binary for processing by the computer
analog-to-digital converter
without echoes, or black
anechoic
the technique that varies the voltage to the individual elements to reduce grating lobes
apodization
echoes on the screen that are not representative of actual anatomy, or reflectors in the body that are not displayed on the screen
artifacts
a non-Doppler technology that offers real time imaging of blood flow while scanning in grayscale
B-flow imaging
the brightness of the dots is proportional to the strength of the echo generated by the reflector
B mode
the part of the machine that shapes and steers the beam on the transmit end
beam former
the digital language of zeroes and ones
binary system
black and white image
bistable
the smallest unit of memory in a digital device
bit
eight bits of memory
byte
display that uses an electron gun to produce a stream of electrons toward a phosphor-coated screen
Cathode ray tube
a way of processing the pulse to improve contrast resolution and reduce speckle
coded excitation
a type of reverberation artifact caused by small reflectors
comet tail
the function of the receiver that changes the brightness of the echo amplitudes to compensate for attenuation with depth
compensation
the function of the receiver that decreases the range of signal amplitudes present within the machine’s receiver; opposite of dynamic range
compression
the ability to differentiate one shade of gray from another
contrast resolution
the function of the receiver that makes the signal easier to process by performing rectification and smoothing
demodulation
part of the digital scan converter that converts the binary signals from computer memory to analog for display and storage
digital-to-analog converter
the series of echo amplitudes present within the signal
dynamic range
refraction artifact caused by the curved surface of the reflecotr
edge shadowing
arc-like bands that occur when the machine is too close to an unshielded electrical device
electrical interference
an artifact caused by sound passing through an area of lower attenuation
enhancement
places grayscale pixels where there is no signal information based on adjacent scan lines; also referred to as pixel interpolation
fill-in interpolation
one complete ultrasound image
frame
averages the frequencies across the image to improve contrast resolution and reduce speckle
frequency compounding
the operating or resonating frequency emitted by the transducer
fundamental frequency
an artifact caused by extraneous sound that is not located along primary beam paths; occurs with arrays; reduced or eliminated by apodization, subdicing, and tissue harmonics
grating lobes
harmonic signal produced by the patients tissue and that is a multiple of the fundamental frequency; also referred to as native tissue harmonic imaging
harmonics
displayed echoes that are relatively brighter than the surrounding tissue; may also be referred to as echogenic
hyperechoic
displayed echoes that are relatively darker than the surrounding tissue
hypoechoic
display that uses the twisting and untwisting of liquid crystals in front of a light source
liquid crystal display
used to display motion of the reflectors
M mode
the timing component of the ultrasound machine that notes how long it takes for signals to return from reflectors
master synchronizer
an artifact caused by sound bouncing off strong reflectors and causing a structure to appear on both sides of the reflector
mirror image artifact
an artifact caused by the beam bouncing off several reflectors before returning to the transducer
multipath
low-level echoes on the display that do not contribute to useful diagnostic information
noise
strength of the sound entering the patient
output
receiver function that increases or decreases all of the echo amplitudes equally
overall gain
a type of display and storage device commonly used in sonography and other imaging modalities
picture archiving and communications system
the smallest component of a two-dimensional digital image
pixel
occurs at the receiver to the relatively weak signal coming from the transducer; ultimately, the signal has to be increased so the rest of the receiver can analyze it
preamplification
occurs in the A-to-D converter; the image must be live
preprocessing
artifact that occurs because the actual propagation speed of the tissue is greater than or less than 1540 m/s, the machine places the reflector at the wrong location on the display
propagation speed errors
occurs in the D-to-A converter; the image must be frozen
postprocessing
harmonic technology in which the fundamental frequency is flipped 180 degrees and transmitted, which cancels out the fundamental frequency via destructive interference, leaving only the harmonic signal
pulse inversion technology
part of the beam former that controls the amount of energy in the pulse
pulser
equation used to calculate the distance to the reflector; in soft tissue d=0.77t where “d” is the depth of the reflector and “t” is the round trip time of the pulse
range equation
the type of magnification performed in the D-to-A converter (postprocessing) that magnifies the image by enlarging the pixels
read zoom
the component of the machine that processes the signals coming back from the patient
receiver
the part of the receiver that inverts the negative voltages to positives
rectification
function of the receiver that is used to reduce image noise, sets a threshold below which the signal will not be displayed
rejection
an artifact caused by the beam bouncing between two strong reflectors
reverberation
an artifact caused by vibration of air bubbles
ring-down
the part of the ultrasound machine that processes the signals from the receiver; consists of the A-to-D converter, computer memory, and D-to-A converter
scan converter
created when one or more pulses of sound return from the tissue containing information related to the depth and amplitude of the reflectors
scan line
an artifact caused by the failure of sound to pass through a strong attenuator
shadowing
an artifact caused by extraneous sound that is not found along the primary beam path; occurs with single element transducers
side lobes
another name for the receiver
signal processor
artifact that occurs as a result of the beam not being razor thin; thus, unintended echoes may appear in the image as the beam slices through structures adjacent to intended reflectors; also known as elevational plane artifact
slice thickness artifact
part of the demodulation component of the receiver; an “envelope” is wrapped around the signal to eliminate the “humps”
smoothing
technique that eliminates edge shadowing because the object is imaged at different angles
spatial compounding
algorithm used in signal processing to reduce the amount of acoustic speckle
speckle reduction
large, flat, smooth boundaries that cause reflections
specular reflectors
dividing the piezoelectric elements into very small pieces to reduce grating lobes
subdicing
TGC
time-gain compensation
ensures the electrical signals travel in the correct direction
transmit/receive switch
the smallest component of a 3D image
voxel
volume element
voxel
picture element
pixel
the type of magnification performed in the A-to-D converter (preprocessing) that magnifies the image by redrawing it before it is stored in the memory
write zoom
the plane that is perpendicular to the beam path
x-axis
the plane that is parallel to the beam path
y-axis
the brightness, or amplitude, of the dots on the display
z-axis
no image generated, only a set of spikes representing the amplitude of reflectors and their dpeth
A mode
depth along y-axis
time along x-axis
M mode
“ice-pick” imaging
M mode
determines the sequence of the voltage pulses sent to the individual elements in an array transducer
beam former
controls apodization
beam former
works by decreasing the strength of the voltage pulse sent to the outermost elements
apodization
part of the beam former
pulser
the stronger the output power, ______ the beam of sound entering the medium
stronger
controls the amount of power entering the patient
pulser
the higher the output power, the _______ the return echo
stronger
more complicated way of driving the energy pulse
coded excitation
sends a series of encodes pulses to form one scan line instead of the one-pulse-per-scan-line method
coded excitation
allows for multiple focal zones, improved penetration, speckle reduction, B-flow imaging, and improved contrast resolution
coded excitation
controls the timing of the elements to shape the beam for focusing
controls the timing of the elements to steer the beam
controls apodization
beam former
part of the beam former
generates the voltage that drives the transducer
directly controls the amount of power entering the patient
pulser
processes the return echo coming back in this order:
amplification
compensation
compression
demodulation
rejection
receiver
converts analog information from the transducer to digital (binary) form required by scan converter and computer
analog-to-digital converter
ensures the electrical signals travel in the correct direction
ensures that the pulser voltages go to the transducer, and the received voltages from the transducer go to the signal processor
transmit/receive switch
part of the image processor
digital memory
scan converter/ image memory
electron gun shoots a stream of electrons to phosphor coated screen. Beam is steered using magnetic fields. Only seen on older equipment.
Cathode Ray Tube
also called flat panel display
display two polarized filters in front of a light source
sandwiched between the filters are liquid crystals that twist and untwist with the application of electricity to determine if the backlighting gets through or not
liquid crystal display
uses a computer to store images and videos. can transmit images to remote locations. Backed up by RAID array
PACS
high amplitude voltage pulse equals _____ amplitude signal strength
high
tells the pulser to send out a pulse and pays attention to when the echoes come back to determine their range
master synchronizer
ensures that a new pulse is not sent out until the previous pulse has returned
master synchronizer
the deeper a wave travels, the more ______ the wave becomes
deformed
harmonic signal is very narrow, thereby offering improved _________.
lateral resolution
Signals travel from the ______ to the _________ and then to ________ and then to ________.
receiver
analog-to-digital converter
scan converter/image memory
digital-to-analog converter
Number of ______ determines number of shades of grey possible.
bits
The more pixels, the better ________.
spatial resolution
two displays used as ultrasound monitors
cathode ray tube
liquid crystal display
What assumptions does the ultrasound machine make that can result in artifacts?
sound beams travel in a straight line and go directly from the transducer and back
the only propagation speed in the body is 1540 m/s
any reflection that comes back to the transducer must have been along the path of the beam
the slice-thickness beam is razor thin
produces a “step-ladder” appearance of parallel echoes that are equally spaced and decrease in brightness (amplitude) with depth
reverberation
Two types of reverberation
comet-tail
ring-down
caused by small structures like surgical clips or adenomyomatosis within the gallbladder wall
comet tail
caused by sound interacting with small air bubbles, causing the bubbles to vibrate
ring down artifact
occurs when the sound is aimed toward a large specular reflector that acts like a mirror and directs some of the sound in a direction other than back to the transducer
mirror image artifact
causes artifacts as the beam is directed away from the path in which it was originally intended to go
refraction
eliminates edge shadowing because object is imaged from different angles
spatial compounding
improves margin delineation
spatial compounding
reduces speckle artifact and reverberation
spatial compounding
techniques used to reduce or eliminate grating lobes
tissue harmonics
apodization
subdicing
if actual propagation speed through which sound is traveling is less than 1540 m/s, reflectors will be displayed on screen _______.
too far away
If actual propagation speed through which sound is traveling is more than 1540 m/s, reflectors will be displayed on screen _____.
too close
Two potentially useful artifacts
shadowing
acoustic enhancement
also known as elevational plane
slice thickness plane
solution for slice thickness artifact
better focusing in elevational plane
storage in memory corresponding to each pixel on the display
image matrix
if the actual propagation speed of the tissue is greater than or less than 1540 m/s, the machine places the reflector at the wrong location on the display.
propagation speed errors
if the image is too dark, the _________ should always be increased before output power
receiver gain
Present day scan converters are ______ devices.
digital
incoming signals are assigned shades of gray based on their amplitudesw
preprocessing
one-to-one correspondence
physical beam forming is directly coupled with displayed scan lines
Operating principle 1
virtual beam forming does not rely on one-to-one relationship
uses weakly focused or nonfocused transmit beams and computed reception “beams”
images are in focus throughout, improved quality
Operating principle 2
Operating principle 1 is composed of:
beam former
signal processor
image processor
display
where the action originates
beam former
the beam former consists of:
pulser
pulse delays
transmit/receive switch
amplifiers
analong-to-digital converters
echo delays
summer
to avoid _________, all echoes from one pulse must be received before the next pulse is emitted.
echo misplacement
The pulser and pulse delays carry out the following tasks:
sequencing
phase delays
variations in pulse amplitudes
an independent signal path consisting of a transducer element, delay, and possibly other electronic components
channel
an increased number of ______ allow more precise control of beam characteristics
channels
modern sonography systems typically consist of ____, _____, and _____ channels
64, 128, 192
protects the sensitive input components of the amplifiers from the large driving voltages from the pulser
transmit/receive switch
Amplifiers _______ voltage amplitudes
increase
The beam former has _____ amplifier(s) for each channel
one
3dB
x2
10 dB
x10
attenuation and maximum amplifier gain determine the _________.
maximum imaging depth
maximum amplifier gain is determined by ________.
noise
maximum amplifier gain is determined by ________.
noise`
recieves digital signals from the beam former
signal processor
signal processor functions performed in order
bandpass filtering
amplitude detection
compression
sharpens boundaries to make them more detectable and measurements more precise
edge enhancement
reduces noise and smooths image by frame averaging
persistence
acquiring several 2D scans for 3D volume of information in the image memory
3D acquisition
holding and displaying one frame out of a sequence
freeze
storing the last several frames acquired before freezing
cine loop
_______ divides the image into pixels
image memory
Brightness is ________ to echo strength
proportional
if the frame rate increases, temporal resolution _____.
improves
if PRF increass, frame rate ______ increases
increases
presents information regarding contraction and relaxation strain and strain rate information for the myocardium of the beating heart
cardiac strain imagain
a combined presentation of a sonographic anatomic image with another imaging form
fusion imaging
