Tiffany's SPI Quizlet
While a ___ Measures total heat gain across entire beam length a ____ measures the temperature change at a specific location in the beam
Calorimeter (entire beam) Thermocouple (specific location)
The demodulation of the receiver does what?
Changes the form of the received signal for display
If sound speed is greater than the assumed 1.54 cm/us then the reflector will appear ___ to the transducer than it actually is
Closer!
A sophisticated form of transmission in which the driving voltage pulses have intrapulse variations in amplitude, frequency, and/or phase.
Coded excitation
____ Doppler measures mean velocities ____ Doppler measures peak velocities
Color Doppler = mean Spectral Doppler = peak
'UNIFORM BRIGHTNESS' from top to bottom of image refers to
Compensation/ TGC
Decreases the difference between the smallest and largest amplitudes
Compression
High pressure state of a wave
Compression
The ___ of the receiver changes the gray scale mapping ; allows us to see all gray shades
Compression
____ decreases the dynamic range of the received signal
Compression (Part of Receiver)
____of the system is the inverse of dynamic range
Compression (Decreases the difference in largest and smallest received signal amplitudes; reduces the RANGE)
The hourglass shape of the sound beam is a result of
Constructive and destructive interference (Huygen's principle)
Heart contraction is called ____ Heart relaxing is ____
Contraction = systole Relaxing = diastole
Fewer bits per pixel causes poorer ____ resolution
Contrast
The amount of gray shades in an image defines ____
Contrast resolution
A blunted sector image is seen in which type of transducer
Convex or curvature array
Frequency unit of ultrasound is ____
Cycles per second
Quality assurance evaluation should be performed A) daily B) weekly C) monthly D) routinely
D
The range equation assuming soft tissue is =
D (distance to reflector) = .77 x t (roundtrip time)
Distance to reflector equation
D = c(speed) x t(roundtrip time)/2 Or D = ct/2
In vivo refers to
In living tissue
coded excitation takes place where
In pulser (Long sound pulse with wide range of frequencies)
The PRF will ___ with decreasing depth
Increase
Most common way to improve (increase) signal to noise ratio
Increase output power ***
To improve axial resolution the frequency must ____
Increase! (Causes shorter SPL; this better axial resolution)
Increasing output power has what affect of signal to noice ratio
Increases signal to noise! Better quality image
In Doppler clutter artifact is reduced by ____
Increasing wall filter
Venous flow from the legs in decreased during ____
Inspiration (Review if you miss this, you idiot)
Speed is ____ proportional to density and ____ proportional to stiffness
Inversely proportional to density Directly proportional to stiffness
As compression increases what happens to the dynamic range
It decreases
If the imaging depth increases, what happens to PRF?
It decreases
As the area increases what happens to intensity
It decreases (Intensity = power / area)
If the imaging depth increases, what happens to PRP?
It increases
As power increases what happens to intensity
It increases (Intensity = power / area)
A bit is bistable meaning:
It is either 0 or 1
If the imaging depth is doubled, what happens to the frame rate?
It is halved
When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency?
It stays the same. Maximum imaging depth and frequency are unrelated.
In dynamic aperture more or less elements are used for reception of sound from a DEEP structure
More for deeper structures (Less for shallower structures)
A wide dynamic range means ____ gray shades and ____ contrast
More gray shades, low contrast
Is the SPL adjustable by increasing and decreasing depth?
NO
Does pulse duration change with increasing or decreasing depth
NO (PRP which includes listening time will change with increasing depth)
If the axial resolution is .3 mm can two structures that are .1 mm be resolved?
NO axial resolution must be smaller than the distance
Can refraction occur with a Normal Incidence?
NO - oblique incidence and difference in sound speed is required for refraction
Does the damping material increase or decrease frequency or transducer?
NONE (frequency is only affected by the thickness of the element***)
During compression the smallest amplitudes are increased and the larger amplitudes are decreased to ____
Narrow dynamic range
The area between the face of an ultrasound single-element transducer and the point where the beam starts to diverge is the ____
Near zone
Starting from the same point, the receiver is moving west at 12m/h, the source is moving west at 10 m/h. Is the Doppler shift positive or negative?
Negative because they are moving further apart starting at the same point
A increase of 0 dB =
No change
Does axial resolution change with depth?
No it remains the same as it only depends on SPL
Can pulse duration be changed by the sonographer?
No, pulse duration cannot be changed by the sonographer. Pulse duration is a characteristic of each transducer. It does not change when sonographer alters imaging depth.
Can axial resolution be changed by the sonographer?
No, the sonographer cannot change axial resolution. A new transducer is needed to change axial (LARRD) resolution
Can a transducer with a center frequency of 8 MHz and a bandwidth of 6 MHz image at 3.5 MHz?
No. The range would be between 5 MHz and 11 MHz
Scattering occurs with a specular reflector or non specular reflector?
Non specular reflector
A ____ reflector has a broader smaller than the wavelength of the incident sound beam
Non specular reflector (Causes scattering)
The gain setting where all the pins in the AIUM test object are displayed on the CRT
Normal sensitivity
A ultrasound phantom is a ____
Objective standard
For refraction to occur in ultrasound What two things must happen
Oblique angle of incidence And There must be a difference in impedances between two mediums
____ occurs when the angle of incidence is not perpendicular
Oblique incidence
Which has the lower frame rate? Color Doppler or Power Doppler
Power Doppler has lower frame rate and reduced temporal resolution to color Doppler
Manipulating image data before it is stored in the scan converter
Preprocessing
___ processing assigns a number to the amplitude measured in the system
Preprocessing
write magnification is accomplished pre or post processing?
Preprocessing
Acoustic variables
Pressure, density, and particle vibration; sound wave quantities that vary in space and time.
___ flow relates to changes in waveform due to the cardiac cycle
Pulsatile
The number of pulses that occur in one second.
Pulse repetition frequency
Which is free of range ambiguity continuous wave or pulse wave Doppler
Pulse wave (Able to determine exact location)
Creates the electric signal that excites the PZT
Pulser
If the term has power or output in it, is comes from the ____ of the instrument
Pulser
The ___ of the instrument controls PRF, PRP, and amplitude
Pulser
The ___ produces the electric voltage that drives the transducer
Pulser
The ___ of the instrument controls the power going into the patient
Pulser (Remember output and power think pulser)
___ refers to purity of the beam
Q- factor
___ is the systems accuracy in placing reflectors at correct depths located parallel to the sound beam
Range accuracy or (vertical depth calibration)
Low pressure state of a wave
Rarefaction
units for impedance
Rayls (Z)
____ magnification does not rescan, only reads image in memory
Read magnification
If you magnify an image and the pixels are unchanged, this is an example of ___ magnification
Real magnification (Poorer quality)
affects the brightness by changing the amplification of the electric signals after returning to the receiver
Receiver gain
Step in demodulation that turns negative voltage into positive ones
Rectification
The bigger the mitchmatch at the boundaries or (impedance) the stronger the ____
Reflection.
Edge Shadow Artifact is caused by ____
Refraction
The ___ of the receiver eliminates the smaller amplitude voltages produced by weaker reflection for electronic noise
Rejection
The ____ eliminates low level echos in the receiver
Rejection
Damping material is designed to have few cycles/pulse, therefore reducing the ___
SPL
What happens to the SPL if the frequency is increased
SPL is decreased (Note it's relationship with the wavelength)
Bioeffects intensity limit
SPTA
Which intensity parameter is most closely correlated to tissue heating?
SPTA
the intensity most relevant with respect to tissue heating:
SPTA
Before ____ images were black and white
Scan converter
Translates the ultrasound spoke format into video format
Scan converter
When the sound returning to the transducer is double the fundamental frequency
Second harmonics
Well using a tissue equivalent phantom at a particular depth reflections are no longer observed. what are you evaluating? A) dynamic range B) special positivity C) axial resolution D) Sensitivity
Sensitivity
Dead zone is assessed ____ pin placement in the ultrasound phantoms
Shallow (How shallow can we see)
Which has a higher frame rate, shallow imaging or deep imaging?
Shallow imaging (Higher FR; greater temporal resolution)
Damping material ___ pulse and ___ the durations of the pulse
Shortens pulse and duration
The lower the frequency the ___ the near zone length
Shorter
___ pulses have wider bandwidths
Shorter (Damping material)
Smaller diameter probes (smaller apertures) have ____ near zone lengths and ____ divergence of sound beam
Shorter near zone lengths More divergence
spatial compounding improves ____
Signal to noise ratio (By Fran averaging)
___ transducers are always fixed focused
Single element
Elevation plane refers to ____
Slice thickness 3rd dimension (Slice thickness = elevation plane)
The more elasticity a medium has the ____ the sound speed
Slower (Opposite of stiffness; which increases sound speed)
Persistence is most effective with ___
Slowly moving structures (Ex: helps fill vessel completely)
The ____ the axial resolution the better
Smaller is better!
Step in demodulation that puts envelope around signal to even it out
Smoothing
Which attenuated more blood or soft tissue
Soft tissue
Period of the sound wave is determined by
Sound source (CANNOT be adjusted)
____ tells us the intensity in the center of the beam whereas ___ tells us the average of all the intensities in the beam
Spacial Peak-SP (at center) Spacial average-SA (across beam)
____ resolution is image detail
Spatial
Write magnification can improve ___ and ___ resolution
Spatial And may improve temporal!
In ____ scan lines are steered in different directions so that structures imaged are interrogated by more than one pulse
Spatial compounding
Most effect tool to decrease speckle
Spatial compounding
Averaging of frames that view the anatomy from different angles
Spatial compounding (NOTE: frame averaging)
Visualization detail of an image
Spatial resolution
Spectral analysis is processed by ____ Color Doppler is processed by ___
Spectral = FFT (Fast Fourier Transform) Color Doppler = autocorrelation
In ___ reflectors the wavelength is smaller than the tissue interface
Specular reflectors (Think smooth surfaces; diaphragm, organ walls)
What is the most important factor in determining the FR of the system?
Speed of sound in the medium (Depth can be adjusted; speed cannot)
The fundamental limitation of temporal resolution is ____
Speed through the medium
A ____ can be used to eliminate the dead zone
Standoff pad
To increase propagation speed which do you want to increase Density or stiffness?
Stiffness! (And decrease density as it is inversely proportional)
____ is proportional to propagation speed of a material
Stiffness! (As stiffness increases so does speed)
grating lobe artifact can be reduced by dividing each PZT element into small pieces - a process called _________
Subdicing
Adjusting the ____ on spectral Doppler changes the number of spectral waveforms on the display
Sweep speed
Changing the ___________ changes the number of seconds of activity displayed at one time
Sweep speed
What will you adjust if you can't see reflectors in the far field?
TGC / compensation
What will you adjust if you can't see reflectors in the near field?
TGC / compensation
Compensation of the receiver refers to
TGC! (Compensates for attenuation; creates uniform brightness)
Is the hydrostatic pressure in a patient's foot greater or lower than the patients arm while the patient is in a supine position?
THE SAME (While the patient is lying down hydrostatic pressure is zero across the body)
True or false Power Doppler is not angle dependent
TRUE
True or false Mechanical focusing have a fixed focus that cannot be adjusted
TRUE
True or false Short pulses produce better images
TRUE
True or false CW transducers do not use damping material
TRUE they do not
True or false Beam intensity is important in bioeffects and patient safety
TRUE!
Persistence uses ___ averaging
Temporal
deca (da)
Ten 10^1
PRP can be adjusted by changing____
The PRF (Or depth!)
The received analog signal must be converted into digital form for input into ___
The scan converter
Harmonics are created by
The tissue (Received as twice the frequency)
harmonic frequencies in ultrasound are generated by __
The tissue! Not the transducer (Returning tissue harmonics)
Does Lateral Resolution change with DEPTH?
YES, because the diameter(WIDTH) of the beam varies with depth, therefore the lateral resolution changes with depth
Can amplitude be changed by the operator?
Yes
Can dynamic range be adjusted by sonographer?
Yes (Not the inherent DR but the displayed DR)
Can duty factor be changed by sonographer?
Yes, duty factor can be changed by the sonographer when imaging depth is changed.
Smallest amount of digital storage
a bit
The effects of tissue on sound waves are called:
acoustic propagation properties
the effects of the medium upon the sound wave
acoustic propagation properties
which transducer creates a beam that is focused in all planes at all depths
annular phased array
Define transducer
any device that converts one form of energy into another
Color Doppler reports ____________ or _______ velocities.
average, mean
diffuse reflection is also called
backscatter
The range of frequencies contained in an ultrasound pulse is called
bandwidth
Nano (n)
billionth (10^-9)
Changes in transducer output affect the ______ of the entire image.
brightness
determines the brilliance of the displayed image
brightness
Impedance is ___ not measured
calculated
Area is measured in
cm^2
Volume is measured in
cm^3 and mL
This type of pulser generates a constant electrical signal in the form of a sine wave
continuous wave
determines the range of brilliancies within the displayed image
contrast
fixed focusing is also called?
conventional or mechanical focusing
Damping material reduces the _______ of the transducer and _______ of the diagnostic system.
efficiency, sensitivity
An ultrasound transducer converts ___ into ___
electrical energy into mechanical energy and vice versa
Sound waves carry ___ from one place to another
energy (Not matter; energy transfers from one molecule to the next)
A narrow dynamic range means _______ gray shaded, and ______ contrast
fewer, high
Two types of focusing:
fixed and adjustable
Lateral resolution is best where
focal zone (Narrowest region of the sound beam)
Temporal resolution is determined by?
frame rate
Frame rate is reciprocal to _____
frame time (time to create frame)
number of cycles per second
frequency
Attenuation in lung tissue is [less than, greater than, the same as] attenuation in soft tissue.
greater than (Attenuation is greatest in air)
multiples of the fundamental frequency
harmonics
Bistable images are _____ contrast
high
_____________ Frequency transducers generally have the best range resolution.
high (LARRD)
Hecto (h)
hundred (10^2)
Centi (c)
hundredth 10^-2
As stiffness increases, speed ______.
increases
Damping material ____ the bandwidth
increases
The output gain of the pulser determines the ___ of the acoustic pulse
intensity (Output = POWER)
PRF is _____ related to the maximum imaging depth.
inversely
when adjustments make changes in display or echo brightness from scarcely visible to fully saturated, ____is being assessed
sensitivity
In the far field, axial resolution is best with ____
shortest pulse
Side lobes are produced by ________ crystal transducers
single or mechanical
Axial resolution is determined by
spatial pulse length
Doppler shift is inversely related to
speed of sound in the medium (prop speed)
Bulk modulus is the same as
stiffness. (So when bulk modulus increases, speed increases.)
Deci (d)
tenth 10^-1
The operating frequency is determined by ___
the propagation speed of the element material and the THICKNESS of the transducer element
Eliminating ____ improves the ability to measure the maximum velocity with Doppler
Aliasing
Which parts of the receiver are adjustable by sonographer
All except DEMODULATION (Amplification, compensation, compression, demodulation, rejection)
Power doppler is also called
Amplitude Doppler
True or false The Y axis is B mode imaging is the brightness of the dot!
False (There is NO Y AXIS in B mode imaging
True or false Color in color Doppler display represents velocities
False It represents direction
True or false Longer pulses provide better axial resolution
False!!! (Shorter pulses; remember SPL)
The near zone is aka
Fresnel zone
____ processing pulls the numbers from memory and assigns a shade of gray
Post processing (Then goes to display)
read magnification is accomplished Pre or post processing?
Postprocessing
If sound speed is less than the assumed 1.54 cm/us then the reflector will appear ___ to the transducer than it actually is
Further away
The receiver performs which functions?
- Amplification - compensation - compression - demodulation - rejection (Hint: Alphabetical order)
fixed focusing is done by
- a lens - curved crystal element
Attenutation occurs by ____, ____, and ____
- absorption - reflection - scattering
Lost the following in order from least attenuation to most attenuation -bone - air - fluids -soft tissue
- fluid - soft tissue - bone - air (Do not confuse with propagation speed)
Temporal resolution is determined by 2 factors
- imaging depth (the shallower the better) - miner of pulses per frame (less is better)
How to increase the near zone length
- increase aperture - increase frequency
two steps of demodulation
- rectification - smoothing
Two ways to correct grating lobe
- subdicing - apodization
If we decrease the intensity of a sound beam by 1/2, it is changed by ____ dB
-3 dB Or Minus 3 dB
If the amplitude is halved the power or intensity is changed by ___ dB
-6 dB (Equal to 1/4; p and I are = amplitude squared)
If amplitude is decreased by 50% l, what is the corresponding change in power A) 3 dB B) -6 dB C) -3 dB D) 0 dB
-6 dB (If amplitude is halved, power is decreased by 1/4)
spacial resolution is determined by ____
-Pixel density -lines per frame (The more of each the better)
Tissue harmonic imaging produces a _____ beam and improved ______ resolution.
-Thinner -Improved contrast resolution
Doppler shift is directly related to
-blood cell speed -frequency of the transducer -cosine of the angle between flow and the sound beam
Lost the following in order of increasing propagation speed of sound -liquid -gas -solid
-gas -liquid -solids (Sound travels slowest through gas and fastest in solids)
coded excitation improves
-higher signal-to-noise ratio -improved axial resolution -improved spatial resolution -improved contrast resolution -deeper penetration
Four factors under sonographers control that affect temporal resolution
-imaging depth - # pulses per scan line - sector size - line density
Angle 90 degrees, cosine?
0.0 (NONE)
Two ultrasound systems produce pulses, one is .4 microsecs in duration and the other is .2 microsecs. Which produces the best radial resolution?
0.2 microsecs (Radial = axial resolution; SHORTER PULSES produces best axial resolution)
Angle 60 degrees, cosine?
0.5
The average rate of attenuation in soft tissue
0.5-1 dB/cm/MHz
Angle of 30 degrees, cosine
0.87
In soft tissue every 13 msecs of go-return time means the reflector is ____ away
1 cm
What is the DF of a 7 MHz CW transducer imaging at 10 cm
1 or 100% For CW transducer
If mirror artifact is seen on a Doppler image which two ways could you correct it
1) DECREASE the gain 2) adjust the angle so it is not at 90 degrees
Mirror artifact in Doppler is typically seen because of two reasons
1) gain is TOO HIGH 2) incident angle is 90 degress
If we have 10 bits how many shades of gray are possible
1,024 (2^10)
Reynolds number less than ____ indicates laminar flow
1,500
Soft tissue speed of sound
1,540 meters / sec Or 1.54 mm/us
Five ways to eliminate aliasing
1. Increase Scale/PRF (nyquist limit) 2. lower transducer freq, 3. select new view with a shallower DEPTH 4. use continuous wave Doppler 5. baseline shift
3 factors that determine resistance of flow
1. Radius of lumen (most significant) 2. Length of tube 3. Viscosity
Six basic assumptions of imaging systems
1. Sound travels in a straight line 2. Sound travels directly to a reflector and back 3. Sound travels exactly 1,540m/s 4. reflections arise from structures positioned along the beam's main axis. 5. intensity of the of the reflections is related to the scattering characteristics of the tissue. 6. The imaging plane is extremely thin.
Frame rate is limited by 2 factors
1. The speed of sound in medium 2. Imaging depth
sound beam divergence is determined by what two factors?
1. the transducer aperture or diameter. 2. the frequency of the ultrasound.
Angle 0 degrees, cosine?
1.0
A ____ transducer electronically focuses in the slice thickness or "elevational" plane
1.5D transducer
Axial resolution is =
1/2 SPL
At the focal point of the beam diameter is equal to ____
1/2 the aperture length
The PZT has a thickness equal to_____
1/2 the wavelength
If amplitude is halved, intensity is____
1/4 (quartered)
If amplitude is halved, the power is
1/4 (quartered)
If one frame is created in 1/10th of a second then the frame rate is ____
10/sec or 10 Hz (Reciprocal*)
Intensity limits include ___ for a unfocused beam And ____ for a focused beam (Before bioeffects are seen)
100 mW/cm for unfocused 1 W/cm or 1,000 mW/ cm for focused
The DF of continuous wave sound is _____.
100%
It takes _________ microseconds for ultrasound to travel 1 cm in soft tissue.
13 microseconds
If intensity is 30 mW/cm and the power is reduced by half, what Is the new intensity
15 mW/cm
After analog to digital converters converts signal to digital, the information is in a string of ____
1s and 0s
Any Exam that causes an elevation and temperature of less ___ than may be used without reservation
2 degrees Celsius
Avoiding a local temperature increase exceeding ____ should ensure that there is no thermal induced biological effects
2 degrees Celsius
Bistable imaging refers to
2 shades Black and white
A CW transducer contains what a minimum of ____ crystals
2! One to send One to listen
Reynolds number greater than ____ indicates turbulence
2,000
Impedance of soft tissue is ____
2,000,000 Rayls
Typically the frequency of ultrasound is ___ - ____ MHz
2-15 MHz
Diagnostic ultrasound is typically what range of sound ?
2-20 MHz
In clinical imaging is pulse is composed of ____ cycles
2-4 cycles
The Doppler shift frequency ranges from ___ to ____
20-2,000 Hz (Audible range)
Human range of hearing
20-20,000 Hz
In a linear switched or sequential array approximately ___ rectangular elements are arranged in a line and ___ fire are fired at the same time
200 elements 5-10 fired at a time down the line (to narrow the beam) (This is NOT steered; steering only occurs in phased arrays)
If gain is 30 dB and output power is reduced by one half, the new gain is _____dB
27 dB
The normal propagation speed of the PZT is ____ than that of soft tissue
3-5 times GREATER
How many bits are needed to represent 10 shades of gray?
4 bits (2x2x2x2)
Is the go return time of a sound beam is 52 msecs how far away is the reflector
4 cm
Which assumption does grating lobe arise from 1. Sound travels in a straight line 2. Sound travels directly to a reflector and back 3. Sound travels exactly 1,540m/s 4. reflections arise from structures positioned along the beam's main axis. 5. intensity of the of the reflections is related to the scattering characteristics of the tissue. 6. The imaging plane is extremely thin.
4. reflections arise from structures positioned along the beam's main axis.
Any exam that causes a temperature elevation to greater than ___ is considered potentially harmful to a fetus
41 degrees Celsius
Real time 3D imaging
4D imaging
Half intensity depth equation
6/frequency
What is the reciprocal of 1/8?
8
_____ bits equal 1 byte
8
If two identical Doppler exams are performed with a 4 and an 8 MHz transducer which will yield a Doppler shift that is greater? A) Both the same B) Neither C) 4 D) 8
8 (Directly related!)
How long does it take for sound to reach a reflector at 15mm away?
9.74 microsecs (d = .77t 15mm or 1.5cm = .77 (solve for t) 19.4=t You are only solving for time to reflector not total time so you must divide by 2 So it is 9.74 microsecs to reflector)
A specular reflector is seem best at ___ degree angles
90 degrees
If we triple the amplitude, how many times does the power increase?
9x (Power = Amplitude squared)
The upward deflection of a dot on the screen is a characteristic of ___ mode ultrasound display
A Mode
2 bytes (16 bits) is called
A WORD
A Trapezoid shaped display is displayed by ???
A vector image
Color Doppler __ setting has the greatest effect on jet size
Gain
Which has better lateral resolution, mechanical focus beam or a adjustable focus beam?
Adjustable focus beam has better lateral resolution
With dynamic frequency tuning, what signals are used to create images of superficial structures? a) high freq b) low amplitude c) low freq d) high amplitude
A) higher frequencies
Greatest reflection is seen at which type of boundary?
Air - Tissue interface (99% of US reflected)
A hydrophone measures: A: Acoustic pressure output B: Doppler accuracy C: Penetration D: Contrast resolution E: Measurement accuracy
A: Acoustic pressure output
Spectral analysis is used to: A: Determine the distribution and magnitude of frequency shifts in the reflected Doppler signal B: Eliminate aliasing from the reflected signal C: Color-encode the Doppler frequency shift D: Eliminate low-frequency shifts from the display E: Determine the velocity of the moving reflector
A: Determine the distribution and magnitude of frequency shifts in the reflected Doppler signal
Which attenuated more air or bone
AIR
Which has the greatest impedance ? Bone, air, or fluid
AIR (100% of sound is reflected back; 50% at bone)
____ evaluates research of ultrasound bioeffects
AIUM
In a(n) ___ test object the phantom does NOT have attenuation properties of soft tissue cannot evaluate a gray scale
AIUM 100mm test object
The greatest advantage of pulse wave Doppler is ___
Able to select exact location
The parenchyma of tissue is the product of __ in non specular backscatter
Acoustic Speckle
The ___ inform us which waves are sound waves
Acoustic variables
A-Mode displays ___ over ____
Amplitude over time
"Real world" numbers that are found in every day lives; continuous range value (Ex: your weight or the length of something)
Analog numbers
Signals during reception are converted from ___ to ___
Analog to digital
Grading lobe are produced by ____ crystal transducers
Array
In the circulatory system resistance is highest in the ____
Arterioles
In refraction artifact structures may appear ____
Artifact appears on side of normal anatomy (Think fake twin)
Attenuation per unit length
Attenuation coefficient
Persistence is averaging of ____ used in ____
Averaging of frame rate Used in speckle reduction
The smaller the SPL the better the _____ resolution
Axial
The ability to distinguish two structures lying front to back to the sound beam
Axial resolution
____ Doppler imaging is more susceptible to flash artifact
Power Doppler
Depth calibrations of a machine measure 100 mm spaced wires to be at 90 mm apart. scanning reflectors 50 mm apart, what will the machine calculate the distance to be? A) 40 mm B) 45 mm C) 50 mm D) 60 mm
B) 45 mm (BECAUSE 10% of 50 is 5; thus 10% error = 45 mm)
Which doppler control reduces noice along the baseline? A) scale B) wall filter C) sweep speed D) color gain
B) wall filter
Propagation speed is determined by
Medium only - density and stiffness
PACS stands for: a. Pictures accessed by computers b. Picture archiving and communication system c. Patient access computer system d. Picture access computer system
B. picture archiving and communication system
Areas of dropout seen on an image are due to___
Bad wires Or Bad crystals (Seen as shadows coming from transducer)
___ tells you how uniform the ratio is between SP/SA of the sound beam
Beam Uniformity Ratio (BUR)
The ___ controls the electronic signals sent to the transducer
Beam former
The ___ of the instrument shapes and steers the neam
Beam former and pulser
Why are tissue equivalent phantoms used to interpret grayscale?
Because they ATTENUATE
The higher the PRF the __ the frame rate
Better
The lower the QFactor the ____ the axial resolution
Better
Gigi (G)
Billion 10^9
A group of ___ is assigned to each pixel to store the gray scale color assigned to the pixel
Bits
The more ____ per pixel, the more shades of gray
Bits
As imaging depth increases, PRF___ and PRP ___
Both decrease
between a 6 MHz transducer and a 3 MHz transducer imaging both at the same depth, which has the higher PRF?
Both the same (PRF is determined by depth; not frequency)
SPL is determined by
Both the source and the medium
Which of the following can obtain real time 3D volumes? A) 1D arrays B) 1.5D arrays C) 2D arrays D) CW transducer
C) 2D
With dynamic frequency tuning, what signals are used to create images of deep structures? a) high freq b) low amplitude c) low freq d) high amplitude
C) low frequencies
Which of the following tissues has the higher propagation speed? A) lung B) muscle C) tendon D) kidney E) fluid
C) tendon
Spectral analysis of color flow Doppler is most commonly performed by which of the following techniques? A. zero-crossing detectors B. fast Fourier transforms C. autocorrelation D. Chirp-Z transforms
C. Autocorrelation Autocorrelation is better suited to process the enormous amount of data acquired in a color Doppler study.
Mega (M)
Million 10^6
CW transducers has ___ Q factor And PW transducers have a ___ Q factor
CW = HIGH (No damping material) PW = LOW (Has damping)
higher Q factor is seen in PW or CW?
CW transducer
The best axial resolution is seen is which of the following instruments A) 1.0 MHz, 2 cycle pulse B) 2.5 MHz, 4 cycle pulse C) 4.0 MHz, 4 cycle pulse D) 4.0 MHz, 2 cycle pulse
D) 4.0 MHz, 2 cycle pulse (SPL**)
Which of the following is associated with uniform amplification? A) compensation B) threshold C) overall gain D) receiver gain
D) receiver gain
True or false? The sonographer can alter the period of the ultrasound wave
False
Preprocessing functions may be defined as: A: Any function that can be performed on a frozen image B: A function that takes place in the beam-former and is not controllable by the operator C: A function that allows increased focusing of the sound beam D: A function that is performed before the echo data are stored in memory E: Any function that changes the quality of the ultrasound image
D: A function that is performed before the echo data are stored in memory
The ratio of the largest to the smallest signal that a system can handle is termed: A: Apodization B: Compression C: Threshold D: Dynamic range E: Pulse repetition frequency
D: Dynamic range
What happens to the duty factor when the depth of view is increased
DF Decreases
a standard protocol used for blending a picture archiving and communications system and various imaging modalities
DICOM (digital imaging and communications in medicine)
If the PZT is halved in thickness, the frequency will be ____
DOUBLED
Unit for Dynamic Range?
Db (Note it is a ratio!)
The distance close to the transducer that cannot produce an accurate image on the display
Dead zone
The PRF will ___ with increasing depth
Decease
With increasing depth the frame rate must
Decrease
How to eliminate range ambiguity artifact
Decrease the PRF
To eliminate aliasing ___ the frequency
Decrease!!!
Compression of the receiver refers to
Decreases the difference between the smallest and largest amplitudes
Pulse Inversion Harmonic Imaging ____ temporal resolution (___ FR) and ____ spatial resolution
Degraded temporal resolution (Lower FR) Improves spatial resolution
The process of extracting the Doppler frequency from the transducer frequency (the Doppler shift) is called _____
Demodulation (Performed by demodulator)
How to calculate impedance
Density x Propagation speed
PRF is changed by changing____
Depth
M-mode displays what?
Depth (y axis) Time (x axis)
Backscatter is seen from what type of reflection
Diffuse reflection.
Which type of information Is stored into the scan converter?
Digital
"Computer world" numbers, variable attaining only discrete values (Ex: limited to whole numbers instead of exact number 13.43 would be 13; on or off)
Digital numbers
Doppler shift is ___ related to transducer frequency A) inversely B) not related C) directly
Directly
Once the signal leaves the digital to analog converter it goes to ____
Display
Doppler shift formula KNOW THIS
Doppler shift = 2 x reflector speed x incident frequency x Cos(angle) / propagation speed
Doubling the PRF does what to the frame rate (assuming the line density is unchanged)
Doubles (They are proportional! One up, other goes up)
A form of electronic receive focusing which changes the number of elements used during sound reception
Dynamic aperture
The system changes the number of crystals that are fired to change the width of the beam, this is known as
Dynamic aperture
slide receive frequency from higher to lower with increasing depth, results in good resolution in near field with relatively good penetration in far field
Dynamic frequency tuning
Electronic focusing during reception; completed by time delays
Dynamic receiving focus
A-mode display is most commonly used for what type of ultrasound imaging? A: Small parts B: Abdominal C: Cardiac D: Vascular E: Opthalmologic
E: Opthalmologic
____ is the opposite of stiffness of a medium
Elasticity
The firing pattern that focuses the ultrasound beam relates to ____
Electronic curvature
Adjustable focusing is done by
Electronic focusing (Phased arrays)
The firing pattern that steers the beam up and down relates to ____
Electronic slope
Slice Thickness is aka
Elevation plane
Venous return to the heart decreases during
Expiration
Venous flow from the legs is increased during _____
Exspiration
Panoramic view is aka
Extended field of view imaging
True or false If the amplitude of a wave is increased by 3 times, then the intensity is increased by 6 times
FALSE
True or false A wider beam diameter yields a better lateral resolution
FALSE (A smaller beam diameter is needed to improve later resolution)
True or false the damping material improves lateral resolution
FALSE (Does not affect lateral resolution)
True or false An impedance mismatch is needed for refraction to occur
FALSE (Impedance mismatch is needed for REFLECTION to occur at perpendicular incidence ; refraction occurs when the sound speed is different between two mediums at oblique incidence)
True or false The sonographer can adjust the mechanical focus by changing the sequencing of the phased array
FALSE (Mechanical focusing is fixed focusing and cannot be altered)
True or false The more cycles there are in a pulse, the greater the detail of the image
FALSE (Note axial resolution relationship to more cycles per pulse; less cycles = greater detailed image)
True or false Speed increases as frequency increases
FALSE (Speed is determined by stiffness and density ONLY)
True or false If the frequency of the electrical excitation voltage of a pulses wave transducer is 6 MHz, the main or center frequency of the transducer is 6 MHz
FALSE (pulse wave ultrasound frequency is determined by thickness and prop speed of the element ONLY)
True or false Attenuation coefficient decreases with increasing depth
FALSE Attenuation increases with depth. Not the attenuation coefficient (attenuation per unit length) remains constant
True or false Preprocessing can be reversed
FALSE it cannot
True or false Doppler measures the amplitude of flow
FALSE it measures the frequency shift
A CW will display an image True or false?
FALSE spectral Doppler only
True or false Non specular reflectors are seen best at 90 degree angles
FALSE they are independent of angle ( seen by backscatter)
____ regulates system and transducer output
FDA
A ____ sweep speed displays fewer spectral waveforms on spectral display
Faster
In harmonic nonlinear behavior, sound travels faster in ____ and slower in ____
Faster in compressions Slower in rarefactions
Piezoelectric Materials are aka
Ferroelectric materials
axial resolution (LARRD resolution) is best in a transducer with ____ pulses and ____ frequency
Fewer pulses Higher frequency (Recall SPL; lower is better for axial resolution
Ghosting in ultrasound refers too
Flash artifact or clutter
Variance mode shows flow ___ aswell as ____
Flow direction Presence of TURBULENCE
beam intensity is greatest at which area of the sound beam____
Focal zone of the beam! (Narrower area + same amount of power = greater intensity)
Very low PRFs can adversely affect the ___
Frame rate
temporal resolution refers to
Frame rate
The far zone is aka
Fraunhofer zone
Tissue harmonic imaging reduces ____ artifact
Grating lobe
The beam former and pulser change the excitation voltages of the pulses to minimize ___
Grating lobes
The distance between two reflector most be ___ the axial resolution to be resolved
Greater than or equal too!
Few pulses per scan line creates ____ temporal resolution
Greater! ( the more pulses per scan line the worse the temporal resolution)
The primary disadvantage of pulse wave Doppler is the inaccuracy to measure ___
HIGH VELOCITIES (Aliasing***; note CW Doppler advantage)
the depth at which sound has lost half of its intensity
Half intensity depth (6/frequency)
If the transducer frequency is changed from 5 MHz to 2.5 MHz, what is the effect on the observed Doppler shift frequency from flowing blood?
Halved
____ lime density results in better spatial resolution
High line density (Spatial resolution = detail)
For a high quilt image you want a ___ signal to noice ratio
High signal to noice! (Signal = good; noice = bad)
Range ambiguity artifact is seen when PRF is too ____
High!
The ___ the frame rate the better the temporal resolution
Higher
Thick PZT, low propagation speed will produce ____ frequency
Higher
___ frequencies have increased backscatter
Higher frequencies
Which is better for lateral resolution? Lower or higher frequencies
Higher frequencies (Causes narrower beam and diverges less in the far field)
The compromise of resolution is that higher frequencies provide ____ while lower frequency provide ____
Higher frequency- Greater image detail (better LATA & LARRD resolution) Lower frequency - greater depth! (Deeper penetration)
Highest output intensities are seen with ___ Lowest intensities are seen with ___
Highest with PW Doppler Lowest with gray scale
This principle explains the hourglass shape of the imaging transducer beam
Huygens Principle
As FRAME RATE improves ____ degrades
Image quality! (As temporal resolution improves, image quality may degrade and vice versa**)
The greater the ___, the greater the degree of reflection
Impedance
An echo is only reflected if there is ____
Impedance at tissue interface
Multi focusing will improve ___ resolution and degrade ____ resolution
Improve lateral resolution (More focal zones!) Degrade temporal resolution (Reduces FR)
Increasing the power output ___ the signal to noice ratio
Improves
If the second medium through which the sound wave is traveling through has a slower propagation speed than the first, what will happen to the angle in the second medium?
It will be smaller than the incident angle (and larger if the speed was FASTER in the second medium)
Artifacts are seen when the sound beam is larger or smaller than the reflector?
LARGER
____ resolution varies with depth
LATA (Lateral, Angular, Transverse & Azimuthal)
The more scan lines per frame in a image the ____ the temporal resolution
LESS ( FR= PRF/LPF)
Axial resolution must be ___ than the distance between two structures to resolve them
LESS THAN than distance
Imaging transducers have a ___ Q factor and ____ bandwidth compared to therapeutic and CW Doppler transducers
LOWER Q factor BROADER (wider) bandwidth
What is LATA resolution?
Lateral Angular Transverse Azimuthal (Lateral resolution!!)
___ is the ability to send an ultrasound pulse between two reflectors and not receive and echo
Lateral resolution
Dynamic aperture improves?
Lateral resolution at wide range of depths
Variance Mode: What does the left side color mean & the right side color mean?
Left side = laminar flow Right side = turbulent flow
Vector imaging combines ___ and ___ imaging to create a trapezoid image
Linear sequential and linear phased array
Related to the ability of humans to see gray scale differences in anatomic structures
Log compression
Wider diameter probes (larger apertures) have ____ near zone lengths and ____ divergence of sound beam
Longer near zone lengths Less divergence
Greater frequencies yield ___ near zone lengths
Longer!! (Greater Aperture and frequency Greater NZL)
What is LARRD?
Longitudinal Axial Range Radial Depth (Axial resolution!!)
A ____ Q-factor is seen in PW transducers
Low
A poor quality image is created with a ____ signal to noise ratio
Low signal to noise (Signal is good; noice is bad)
Damping material cause a ___ Q factor
Lower
The deeper you want to image the ___ the PRF
Lower
Thin PZT, high propagation speed will produce ____ frequency
Lower
Which sound waves travel further Higher frequency or lower frequency
Lower frequency sounds travel further
The greater the density of a medium the ____ the propagation speed of the wave
Lower the propagation speed
___ mode scanning is aka "ice-pick" anatomy
M-Mode
With higher frequency transducers ____aliasing is likely to occur (more or less)
MORE
The ultrasound gel has an impedance between ____ and ____
Matching layer and the SKIN
Resistance is measured in
Ohms
Pulse Doppler has a minimum of ___ crystals
One (CW has minimum of 2)
The matching layer is equal to
One quarter of the wavelength
Output is aka
Output gain Acoustic power Pulser power Energy output Transmitter output
____ affects the brightness of the image by adjusting the strength of sound being sent into the body
Output power
Amplification of the receiver refers to
Overall gain! (All amplitudes are increased productivity decreased during reception)
Electronic focusing and steering of the beam is accomplished by
PHASING
Nyquist limit equation
PRF/2
Frame rate is determined by
PRF/LPF (lines per frame)
Time from beginning of one pulse to the beginning of another
PRP
Which includes the listening "dead time" PRP or PD?
PRP
Which includes sound dead time in measurement?
PRP (PD is time of pulse only, no dead time)
Put in order of highest to lowest impedance Matching layer Gel Skin PZT
PZT > matching layer > gel > skin
Axial resolution is ___ to the beam path
Parallel
unit for pressure
Pascal
units for amplitude
Pascals
Lateral resolution is ___ to the beam path
Perpendicular
In a transverse wave, the waves move ____
Perpendicular (Think ripples in pond)
Reflection of ultrasound requires which type of incidence angle?
Perpendicular angle
Occurs when the angle of incidence is at 90 Degrees
Perpendicular incidence (Orthogonal incidence)
Orthogonal incidence is also called
Perpendicular incidence Normal incidence 90 degree incidence
temporal compounding is aka
Persistence
In ____ processing technique, previous image history is added to current image
Persistence/ temporal compounding
____ is used to determine weather flow is toward or away from the transducer (bidirectional Doppler)
Phased Quadrature or quadrature detector
Adjustable focus systems are called what?
Phased array
For ___ systems the pulser is called the "beam former"
Phased arrays
Bi directional color Doppler is accomplished by the ____
Phased quadrature process
___ flow relates to changes in waveform due to the respiration changes
Phasic
The smallest element of a digital picture
Pixel
Two important elements of digital scan converter
Pixel Bits
If the initial intensity of a sound beam is less than the final intensity, then the gain in dB is _____
Positive. The beam's intensity is increasing.
The acoustic impedance of a matching layer in a transducer should have a value between ___ and ____
The element and the skin
At twice the near zone the beam diameter is equal to ___
The equal size of the aperture (Remember it is half the diameter at the end of the near zone; at focal zone)
The transducer output or (power) is determined by ____
The excitation voltage of the pulser
What happens to the length of the pulse of the PD Is decreased?
The length will decrease
Which improves temporal resolution A narrower sector image or a wider sector image
The narrower image has better temporal resolution
The matching layer has an impedance between ___ and ___
The patients SKIN and ACTIVE ELEMENT
The thicker the PZT element of the instrument the ____ the frequency; the thinner the element the ____ the frequency
Thicker element = lower frequency Thinner element = higher frequency (Think about tree size and trying to shake a big tree vs little tree)
Electronic focusing in the transmit mode is accomplished using:
Time delays to excite transducer elements
Three ways to reduce grating love artifact
Tissue harmonic imaging (THI) Apodization Subdicing
harmonic signal produced by the patient during return and is a multiple of the fundamental frequency
Tissue harmonics
Speed error artifact when the propagation speed is less than the assumed propagation speed, reflector will appear too ____
Too deep; too far
If propagation speed is 1.6 mm/us The machines assumes a speed that is too ___ And will display the reflector too ____ to the transducer
Too low Too CLOSE
Speed error artifact when the propagation speed is greater than the assumed propagation speed, reflector will appear too ____
Too shallow; too close
Once a echo is received back from the patient it enters the ____ of the instrument
Transmit/receive switch
A transducer with a spatial pulse length of 4.0 mm encounters two reflectors that are 3.0 mm apart. Will they be resolved as one or two structures?
Two (Axial resolution is = to 1/2 SPL OR 2.0 mm; less than the distance)
Which is more likely to cause temperature elevation in tissues unfocused beams or focused beams?
Unfocused beams ***
PRF is related/unrelated to frequency?
Unrelated. It is only related to depth of view.
The mechanical focusing of the beam is done by
Use of lens or curved element
Trapezoid shaped image is aka
Vector image
Linear probe with the use of virtual convex will have what type of image shape?
Vector image (Trapezoid)
The greatest advantage of a continuous wave Doppler is the ability to accurately measure___
Very high velocities
____ and ___ May be used to evaluate Doppler systems
Vibrating strings moving belt phantoms Pump flow phantoms
units for intensity
W/cm²
unit of power
Watt
Pulse Inversion Harmonic Imaging uses ____ transducers
Wide bandwidth or (broadband)
Damping material does what to the bandwidth
Widens (broader)
Lateral resolution is determined by
Width of the sound beam (narrower beams have better resolution)
Lateral resolution is determined by
Width of the sound beam (narrower beams have better resolution)
The greater the number of scan lines per image the ___ the temporal resolution
Worse
The higher the Q factor the ____ the axial resolution
Worse
____ magnification rescans and acquires new data, discards old image data
Write magnification
Which has better Spatial resolution, an image magnified by read or write magnification
Write magnification (Rescans image; read uses old stored image)
A decrease of 10 dB =
X 1/10 Or Divided by 10 (Can also be -10 dB)
A decrease of 3 dB =
X 1/2 or divided by 2 (Can also be -3 dB)
A decrease of 6 dB =
X 1/4 Or Divided by 4 (Can also be -6 dB)
An increase of 10 dB =
X 10
An increase of 20 dB =
X 100 (Remember for every multiple of 10 add a 0 Ex: 30 dB = x 1,000; 40 dB = X 10,000 and so on)
An increase of 3 dB =
X 2
An increase of 6 dB =
X 4
In A mode imaging the X axis is ____ and the Y axis is ____
X axis = reflector depth Y axis = deflection
In B mode imaging the X axis is ____ and the Y axis is ____
X axis = reflector depth Z axis = brightness of dot (reflector amplitude) (THERE IS NO Y AXIS IN B MODE)
In M mode imaging the X axis is ____ and the Y axis is ____
X axis = time Y axis = depth
The vertical axis is aka the ____ And the horizontal axis is aka _____
Y axis - vertical (up and down) X axis - horizontal (side to side)
Can range ambiguity be seen in CW Doppler scanning
YES Because echoes overlap and depth is unknown
units for attenuation
dB
As density increases, speed ______.
decreases
The dynamic range of information ___ the more it is processed
decreases
when the image is too bright due to high output power, the lateral and longitudinal resolution ____
degrade
In the far field, lateral resolution is best with ____
largest diameter crystal and highest frequency, due to the least divergence
Dynamic aperture optimizes ________ resolution
lateral
refraction artifact degrades ______ resolution
lateral
maintains and organizes the proper timing and interaction of the system's components
master synchronizer
The piezoelectric effect describes the property of certain materials to create a voltage when they are _____
mechanically deformed or when pressure is applied to them
Micro (u)
millionth (10^-6) 0.000001
Tissue harmonic reduces artifact in the __ field
near field
Can spatial pulse length be changed by the sonographer?
no, because a pulse is a pulse is a pulse
Harmonic frequency sound waves arise from
nonlinear behavior
The acoustic parameters are___
period, frequency, amplitude, power, intensity, wavelength, propagation speed
Power and amplitude relationship
power is proportional to amplitude squared
Time it takes for one pulse to occur
pulse duration
If the amplitude is doubled, the intensity is
quadrupled
If the amplitude is doubled, the power is
quadrupled
Two forms of magnification
read and write
Impedance is important in______ at boundaries
reflections
Snell's law relates to
refraction
The operating frequency is dependent on
thickness of the crystal ONLY
Kilo (k)
thousand (10^3)
milli (m)
thousandth (10^-3) 0.001
Doppler shift produces information about
velocity
Can PRF be changed by the sonographer?
yes, with depth of view (Inversely related)
LARRD resolution improves with:
~less ringing (fewer cycles in pulse) ~higher fq sound
focal depth is determined by what two factors?
~transducer diameter ~frequency of the ultrasound