Physics CORE Review Flashcards
What is acoustic propagation?
Refers to the effects tissues causes on sounds
What are bio effects?
Effects of U/S on tissue
What are acoustic variables?
When sounds travel through a medium certain variables apply
What are four examples of acoustic variables?
- Pressure
- Density
- Particle motion
- Temperature
What are two types of density?
- Rarefactions
- Compressions
What is rarefactions?
Low density
What is compressions?
High density
What does this waveform represent in terms of pressure?
Pressure variations
Label the image
In terms of Particle motion what does this mean?
Particles vibrate back and forth
What are two thing that can be said about temperature and energy in ultrasound?
- Sound is an energy
- Energy creates heat
What are sound waves?
Mechanical waves
Sound waves require what to travel?
Medium through which to travel
Can sound waves travel through a vacuum?
No
What can sound waves carry? What can they not carry?
- Energy
- Matter
What states can Longitudinal waves support? 3
- Solids
- Liquids
- Gases
What transverse waves support?
Solids
What is mode conversion? Where can it occur?
- When one wave is converted to another wave
- May occur at a tissue bone interface
What are parameters of sound? 6
- Period
- Wavelength
- Frequency
- Propagation speed
- Amplitude
- Intensity
What is a period cycle?
One complete variation
What is period?
The time for 1 cycle to occur
What is the formula for Period?
P = 1/f
What does this image represent in terms of period?
One period
What is wavelength?
Distance for 1 complete cycle
What does this image represent in terms of wavelength?
One wavelength
What is the units for period?
microsecond
What is the units for wavelength?
mm
What is the formula for wavelength?
What is the formula and the units for frequency?
What is frequency?
The rate of complete cycles per second
What does propagation speed mean?
The speed with which a wave moves through a medium
What is the propagation speed of sound in soft tissue?
1.54 mm/us or 1540 m/s
What determines propagation speed?
Medium
What is the common units for propagation speed?
Mm/us
What is the relationship between wavelength and frequency?
Inverse relationship because
Wavelength = propagation speed / frequency
What does higher frequency mean in terms of detail and penetration?
Better detail, but less penetration
What are two variables for wave strength?
- Amplitude
- Intensity
What is amplitude in terms of waves?
Maximum variation of an acoustic variable
What is the formula for intensity?
I = P/A
What is power?
Total energy over the entire cross sectional area
What does amplitude mean? (in terms of a sound wave)
Strength of the sound wave
Amplitude is determined by what? What happens as it moves through the body?
- The sound source
- Changes as energy travels through the body
What is intensity? How does it interact with the body?
- Concentration of energy in a sound beam
- Varies as ultrasound travels through the body
What does this image represent?
Amplitude
How should we think of intensity in terms of a flashlight?
Think of a flashlight and how the mean spreads with distances but decreases with intensity.
What is the units for intensity?
mW/cm^2
What is intensity proportionate to?
1 = amplitude^2
Is intensity constant? Why?
- No
- Beam intensity is not uniform in time or space
What do we need to know where intensity is? What do we refer to?
- Need terminology to know where intensity is.
- We refer to space and temporal intensity
What are three variables of intensity?
- Space
- Time
- Within a pulse
What do we need to remember about space and intensity?
Intensity is greatest at the center and falls off near the periphery
What is intensity like in terms of listening time?
No intensity during listening phase
What is intensity like within a pulse?
Intensity starts off high at the beginning of pulse, then falls off
What do we need to consider to assess the dose of the patient?
Several intensities
What is spatial peak? Where is it normally?
- The greatest intensity across the beam
- Usually at the center
What is spatial average?
Average intensity measured over the entire beam
What is SP and SA related to? (Ratio)
Beam uniformity ratio (BUR)
What is the formula for BUR?
BUR = SP/SA
Label
What is temporal peak?
Greatest intensity found in the pulse as it passes by
What is pulse averege?
Average for all values found in a pulse
What is temporal average?
Includes the dead time between pulses where there is no intensity
What is TP and TA related by?
Duty factor?
What is Duty factor?
Time sound is ON (no units)
Label the TP and the TA?
What are three examples of intensity of pulse u/s? What are the in order of highest to lowest and biological considerations?
- SPTP: Highest
- SPTA: Biological considerations
- SATA: Lowest
What is the low to high grades of SPTA in terms of intensity? 4
- M mode
- Real time B mode
- Doppler
- Continuous wave (No dead time SPTP)
All of these depend on the depth
What propagation speed is u/s machines calibrated to? why?
- 1540 m/s or 1.54 mm/us
- Average speed in soft tissue
Label the speed?
What is the assumed speed of soft tissues? What happens because of this?
- 1540 m/s
- Artifacts occur because of this assumption, especially through fat
What is the ranged equation used to calculate? (Position)
Position of a reflector
What is the average speed of sound in the range equation?
1.54 mm/us
What is the range equation formula?
D = (1/2)(C)(T)
D = distance
C = Speed (usually sound)
T = Time (1/2 because time is there and back)
What is the 1cm rule?
1 cm (there and back) requires 13 microseconds (us)
The 1cm rule only applies in what tissue?
Soft tissue only
How can we prove the 1cm rule?
- Substitute 1.54 mm/us into the range equation
- (2)(1)/ (0.154cm/us) = 13 us
- Result is 13 us/cm round trip time
What is Pulsed repetition frequency (PRF)?
The number of pulses occurring in 1 sec
Diagnostic probes emit how many pulses/sec?
A few thousand
In terms of PRF, common units are what?
KHz
What does this image represent?
PRF
What does Pulsed repetition period (PRP) stand for?
The time from the beginning of one pulse to the beginning of the next (in seconds)
What does this image represent?
Label the image
What does Duty factor mean?
The fraction of time that pulsed ultrasound is on
Duty facto is usually expressed how?
Percentage
What is the duty factor of CW?
100% of the time
Higher PRF increase duty factor why?
There is less dead time between pulses
What does Duty factor increase with?
Increased pulse duration and PRF
What is the formula for Duty factor?(In terms of pulses, not beams)
Duty factor = Pulsed duration/ pulsed repetition period
What is spatial pulse length?
The length of a pulse from front to back
What is the formula for spatial pulse length?
Label this waveform
What would increase SPL?
Decreased frequency and increased wavelength
What decreases SPL?
Decreasing the number of cycles
Why is SPL important?
SPL is important to our image resolution
What does decreasing SPL mean?
Increases resolution
What is the formula for PRF?
What is pulse duration?
The time interval for one pulse
What is the formula for pulse duration?
PD = (# of cycles)(period)
In terms of acoustic velocity, sound velocity is determined by what?
Medium, which depends on the density and compressibility of the medium
What is density?
The mass of an medium per unit volume or concentration of matter
If all other factors remain constant, an increase in density will do what?
Impede the rate at which sound travels (More mass requires more energy for particle motion)
What does compressibility indicate?
Fractional decrease in volume when pressure is applied to the material
What is the compressibility of slower velocities?
Easy compressible materials
What does dense material mean in terms of compressibility and velocity?
Low compressibility (bone) and increased velocity
What is bulk modulus?
The reciprocal of compressibility
What is the negative ratio of stress and strain?
Bulk modulus
As bulk modulus increases, compressibility and velocity does what?
- Compressibility decreases
- Velocity increases
What is bulk modulus usually referred to?
Stiffness
What is elasticity?
Ability of an object to return to its original shape and volume after a force is no longer acting on it
How doe U/S waves cause elastic deformation?
By separation and compression of molecules
Increased density affects velocity how?
Decreases velocity
Increased stiffness does what to velocity?
Increases it
A change in density is usually coupled with a larger change in what?
Compressibility
Between compressibility and density which one is the dominating factor?
Compressibility
As temperature increases, what happens to the velocity of sound?
It increases
What is the variation of temperature in the human body?
Little variation.
Phantoms must be kept in what temperature conditions? Why?
Room temperatures, change will alter sound velocity
What is attenuation?
Weakening of the sound beam as it travels
What is three reasons that attenuation is important?
- Limits our imaging depth
- Need to compensate for it
- Can be useful in diagnosis
Attenuation varies with what three things?
- Nature of the tissue
- Frequency of the ultrasound
- Depth
What is the rule of thumb for dB in terms of dB drops and intensity? 2
- 3dB drop = 1/2 original intensity
- 10dB drop = 0.1 original intensity
What is the definition of attenuation coefficient?
The amount of attenuation that occurs with each one centimetre travelled
What is the attenuation coefficient units?
DB/CM
In soft tissue there are 0.5 dB of attenuation in one centimetre for for every what?
1 MHz
Attenuation coefficient = what?
1/2 frequency
What is the formula for total attenuation?
Total attenuation coefficient x path length (CM)
Or soft tissue
1/2 MHZ x Path length (cm)
How is frequency and attenuation related?
They are proportional
As frequency increases what happens to attenuation?
It increase and depth of penetration decreases
What is a half valve layer?
Thickness of material that will reduce the intensity to half its original value
3dB rule
Mechanisms of attenuation include what? 5
- Absorption
- Scatter
- Beam divergence
- Reflection
- Refraction
What happens to sound in absorption?
Conversion of sound energy into heat energy
What is the most dominant factor in attenuation?
Absorption
What are three factors that influence absorption? 3
- Frequency
- Viscosity
- Relaxation time on molecules
How does viscosity affect absorption?
Increased viscosity provides greater resistance and increased attenuation
How does relaxation time affect absorption?
If molecules can’t get back to their original position before the next compression phase, then more energy is required to stop the molecule and reverse its direction again. This produces more heat.
In terms of frequency and absorption, if frequency increases what happens? 2
- The molecules must move more often, creating more heat from drag
- Decreased time available for molecules to recover during relaxation process
In terms of frequency and absorption, what happens as the number of cycles per second increases? What does this mean?
- The time between rarefactions decrease and absorption increases
- If frequency increase, absorption increases
What is impedance?
Relationship between acoustic pressure and the speed of particle vibrations in a sound wave (sound propagation)
What is the formula and the units for impedance?
Impedance = density x velocity (p x c)
Units are rayls = z
What is acoustic impedance referred to as?
Characteristic impedance
In terms of acoustic impedance, What does impedance(z) increase with?
- Density
- Velocity
What is acoustic impedance?
The difference in density and stiffness from one tissue to another
In terms of acoustic impedance, the difference in density and stiffness changes what?
The propagation speed
Acoustic impedance does not depend on what variable?
Frequency
In terms of acoustic impedance, what doe we need to get our acoustic information (image)?
Reflection
In terms of acoustic impedance, the larger the difference at the interface of the two media, what happens?
The bigger the reflection
What are two variables that affect reflection?
- Perpendicular incidence
- Direction of sound
What does this diagram represent?
Reflection
What does this image represent?
Impedance
What is the intensity reflection coefficien
As impedance differences goes up, what happens to the intensity reflection coefficient?
It goes up
What is transmission coefficient?
How much is transmitted into the medium
What is the formula for Transmission coefficient? What does this mean in terms of IRC?
- ITC = 1- IRC
- ITC increases as IRC decreases
What happens to reflection if the media impedance is equal?
If media impedance is equal, there is no reflected sound
What happens to total reflection if the impedance mismatch is large?
Almost total reflection occurs
What does this image represent?
Total reflection due to large impedance mismatch
What is the impedance values for bone? What is it for average soft tissue? What is it for air?
What is the air - soft tissue impedance%? What does this mean?
How many types of reflectors are there? What are they?
- Two
- Specular and non Specular
What are Specular reflectors? Reflections from interfaces contribute to what?
- Large smooth surfaces
- Reflections from interfaces contributes to the majority of our image
What is considered a large smooth surface?
Anything greater than 1 wavelength
What is a example of a good Specular reflector in the body?
Diaphragm
In terms of Specular reflection, the intensity of the reflected sound will depend on what two things?
- Angle of incidence (angel at which the sound hits the interface)
- Acoustic impedance of two media
What does intensity of reflection depend on?
Perpendicular incidence
In terms of reflection, what is the relationship of angle of incidence and angle of reflection?
They are equal
What does this image represent?
How the angle of incidence and the angle of reflection is equal. Even for oblique incidence as well
What is refraction?
The bending of the sound beam at an interface due to a difference in media velocity
What law does refraction obey?
Snells law of optics
What is snell’s law (formula)?
Refraction does not occur if what happens?
The velocities are the same
V of medium 1 = V of medium 2
What does this image demonstrate?
Velocity medium 1 < Velocity of medium 2
What does this image represent?
Velocity of medium 1 > Velocity of medium 2
What are two criteria for circle angle refraction?
- Medium 1 velocity < Medium 2 velocity
- The angle of incidence is beyond the critical angle for that medium
What happens with a critical angle in terms of the beam?
The beam can’t enter the second medium and is instead refracted angling the interface surface
What does this image represent?
Critical angle refraction
Refraction will not occur when what two things occur?
- Velocities are equal
- Perpendicular incidence
What does this image represent?
Bending of sound
Scatter is independent of what?
Sound direction
Scatter is determined by what?
Tissue characteristics
How much bigger is scatter than the wavelength?
It is a causal way smaller
In terms of non-Specular reflectors, what doe we see scatter from?
Heterogenous medium (From cells or suspended particles)
What is scatter of non-Specular reflectors responsible for?
Internal texture of organs
What is Rayleigh scattering?
Scattering by small particles in which the linear dimensions are smaller than the wavelength
Rayleigh scattering is most commonly from what?
Red blood cells
What does this image represent?
Scatter specifically Rayleigh scatter
What is an example of non-Specular reflectors?
Tissue parenchyma
Backscatter depends on what? Why? 2
Frequency and reflector size.
1. Higher the frequency, the greater the scatter
2. Smaller the reflector, the greater the scatter
What happens to sound in backscatter?
Sound is directed back to the origin
What is acoustic speckle?
Brightness non-uniformities
Acoustic speckle results from what?
Interface patterns from echoes that have undergone multi-path scattering
What does acoustic speckle look like?
Dot pattern of black and white
Acoustic speckle inhibits detection of what?
Low contrast structures
What kind of reflectors result in acoustic speckle?
Interference and multi- path reflectors
What does this image represent?
Acoustic speckle
What does this image represent?
Diffraction
Who proposed the theory of doppler?
Christian Andreas doppler, to explain the observed differences of the colour of some starts
Besides ultrasound, what are some uses of doppler?
Radar and sonar
What is the Doppler effect?
A change in pitch resulting from relative motion of the source of the sound
In the case of doppler, what happens to the wave crests as the sources is moving towards you and further fro you?
- When the sound sources is moving towards you, the wave crests are closer together and the pitch is higher.
- If moving away from you,n the crests are further apart and the pitch sounds lower
What is the ultrasound application of doppler?
The doppler effect is used by bouncing sound waves off moving blood cells
In terms of ultrasound application of doppler, what happens to the reflected sound off the moving blood?
The reflected sound from moving blood is changed. The amount of change is related to the direction and speed of the blood. The change is within our range of hearing
What does this image represent?
Doppler effects with ultrasound
Intensity of scattered sound is proportion to what? What does this indicate? (In terms of u/s)
The number of RBCs, and thus indicates the quantity of blood in the sample.
What is beat frequency?
Doppler shift is based on principe of wave interference
How do we get beat frequency?
A reflected wave varies slightly in frequency from transmitted wave; the result is beat frequency
What is the formula for doppler shift frequency?
Doppler shift Frequency = received f - transmitted f
What is duplex scanning?
Combination of imaging and doppler
Not all test involve imaging
What is the doppler shift formula? (Detailed)
What are some factors that affect doppler shift?
- Operating frequency
- Blood flow velocities
- Angle of insonation
- Speed of sound in tissue
(Think doppler shift formula)
Doppler shift is directly proportional to what? What does this mean?
- Operating frequency and Blood flow velocity
- An increase in the operating frequency and blood flow velocity will increase the doppler shift
Doppler shift is inversely related to what? What does this mean?
- Doppler angle
- Therefore, if you increase the angle between the probe and the vessel, the doppler shift will decrease
Cos(90) = 0, therefore the doppler shift will = 0
What happens with a doppler angle of 90?
Cosine of 90 degrees is 0, so if U/S beam is perpendicular to vessel, no doppler shift will be picked up
Angle of insonation should be less than what? Why?
- 60
- Cosine function has a steeper curve above 60 errors are magnified
What is the Cosine of 0?
1
What is the Cosine of 60?
0.5
What do we need to remember in terms of angle correction? Why?
- Angle correction <60 degrees
- If angle correction >60 degrees, the flow velocities produced will have significant error
What is the angle correction in relation to the percent error for 60, 70, and 80 degrees?
- 3%
- 5%
- 10%
When can angle correction be done? What does this mean?
- Post processing
- Can be applied to a frozen image
Does angle correction effect the doppler shift waveform?
No
What does angle correction affect?
The velocity scale that is displayed
What is the Nyquist limitation?
PW can only send out pulses as fast as they can be returned by the speed of sound in tissue. Therefore, there is a limit to recording velocities/ frequency shifts
What is the formula for Nyquist limit?
1/2 PRF
Where does the Nyquist limitation usually fall?
Between 5-30 kHz
What happens if the Nyquist limitation is exceeded?
Aliasing
Why is there aliasing with the Nyquist limitation?
The blood cells are not being sampled fast enough so a false reading occurring- parts of the signal are wrapped around the baseline
What does this image represent?
Aliasing with doppler waveforms
What are some ways we can correct for aliasing?
- Move baseline
- Increase PRF
- Increase doppler angle (heel or toe probe)
- Lower operating frequency
- Change to continuous wave
- Change depth*
What are some characteristics of pulsed doppler samples? (How its used) 2
- Sample volume or gate
- Positioned in vessel in the middle or where the highest flow occurs
In terms of PW, multigating allows for what?
Several depths to be sampled simultaneously
What is the normal gate sizes for PW?
1-10mm
What can be noted about PW sample volume? 2
- Samples at certain time intervals represent depth
- Range gating (Recall 13us/cm rule)
In terms of PW sample volume, Sample volume is determined by what? 3
- Beam width
- Receiver gate
- Emitted pulse (number of cycles in pulse)
What is PD sample volume equal to? What does this mean?
- 1/2 the pulse length + gate length
- As gate length is reduced, pulse length is also reduced
The typical number of cycles in a pulse for PW is what?
5-30 cycles/ pulse
What happens to doppler shift the longer the pulse?
The more accurate the Doppler shift
What does smaller gate length do?
Increases spectral display (clearer window)
How do we get CW?
At the intersection of transmitting and receiving beam
What is the angle needed for correct CW Sample volumes? What does this mean?
- No angle correct
- Direction of moving reflector must be parallel to beam
The sample volumes for CW tends to be how large? (Actual measurement)
Between 5-6 cm
How complex are CW waves? And why?
Very complex waves from from many depths
What is the CW sample volume usually referred to?
Zone of sensitivity
What does this image represent?
CW probe with two crystals
What is spectral analysis? 2
- Spectrum is an array of the components of a wave arranged in order of increasing frequency
- Analysis means to take apart
How does spectral analysis work? 2
- The ultrasound beam interests flow and echoes are produced
- Many different doppler shifts are received from the vessel
In terms of spectral analysis, the range of generated doppler shift frequencies depends on what?
The character of flow (if it was laminar or disturbed)
What can a spectrum analyzer do?
Separate the complex doppler shifted signals into their separate frequencies for each moment in time and display these signals onto a doppler spectral display
In terms of a spectrum analyzer, for every 20 milliseconds of time, the system provides what? 2 (d/s)
- Magnitude of all doppler shifts
- Amplitudes of all doppler shifts
What does spectral displays show? 2 (in terms of Doppler shift)
- Magnitude of the doppler shifts
- Amplitude of the doppler shift
What is the definition of magnitude of a spectral display?
Size and quantity
What can be said about the magnitude of a +4kHz doppler shift and a -4kHz doppler shift?
They have the same magnitude
What is the definition of amplitude of doppler shift signal in terms of spectral display?
Strength
What are some things that affects Mangitude? 3
- Blood volume
- Angle of insulation
- Operating frequency
What are some things that affect amplitude of doppler shifts? 3
- RBC density
- Attenuation
- Power output and gain
What is Fast Fourier transform?
Mathematical algorithm used to dissect the frequencies in a doppler shift
What does FFT separate?
A waveform into a series of single frequency sine waves components
How often does FFT happen?
Every 20 milliseconds (50/second)
FFT transforms the signal (RF) into what?
A digital (Mathematical) spectrum
What does this image represent?
FFT
What does the X,Y, and Z values represent on the doppler spectrum?
- x-axis (horizontal) represents time
- y-axis (vertical) represents velocities or doppler shift
- Z-axis represents brightness of pixels related to strength (amplitude) of returning echoes
What are some things that can be viewed with waveform analysis? 5
- Peak systolic
- Envelope (white)
- Window (clear black)
- Diacritic notch
- End diastole
In terms of spectrum what are two things that can both be on the y axis?
Frequency and velocity
In terms of spectrum what is preferred to be on the Y axis? Why?
- Velocity
- Doppler shift is linked to frequency of probe; velocity is not
- Velocity measurements compensate for variations in vessel alignment relative to surface
How can we discern the direction of flow? (Relative to what?)
Relative to transducer
What does antegrade mean?
Towards or above baseline
What does retrograde mean?
Away or below baseline
Why is flow direction arbitrary?
Because it can be altered by the user or inverted on machine
What is a wall filter used for?
To reject the low frequencies from wall motion
What does wall filters effect?
The display at the baseline
Doppler information can be presented in different ways such as what? 4
- Audible sound
- Strip chart recording
- Spectral display
- Colour display
What information can doppler give us? 4
- Presence of flow
- Direction of flow
- Speed of flow
- Characteristic of flow
Most accurate colour flow imaging (CFI) occurs when?
Beam is parallel to flow
What happens to the estimate of the frequency shift the closer to perpendicular the beam is?
The lower the estimate
What does colour doppler provide?
Complete blood flow analysis over a wide field of view
Colour doppler combines what?
Anatomical detail and physiological hemodynamics
What are four synonyms for colour doppler?
- Colour doppler imaging
- Colour flow imaging
- Colour flow mapping
- Colour doppler
How do we see the colour display? (What is it)
IT is a pulsed, multi gated technique which displays both doppler data with the greyscale image
How many processes are involved with colour doppler? What are they?
- Two
- Doppler and non- doppler processing
What is the doppler processing part of colour doppler? (What does it do, where we see it, what is measured and displayed?) 3
- Analyzes signals at various depths
- Throughout the imaged field
- Reflector velocities at each depth are measured and displayed
What process helps us determine colour doppler?
A mathematical technique called autocorrelation
What is the non doppler processing portion of colour doppler?
This is conventional gray scale processing
What is processed doppler? 2
- Extension of pulsed-echo gray scale imaging
- Additional pulses (pulse trains) are used
How many scan lines are seen with processed doppler?
3-32 pulses per scan line
What is the definition of ensemble length?
Number of pulses used for each colour scan line
In terms of ensemble length, to create a black and white image (various shades of grey) what is used?
One scan line is used
In terms of ensemble length, to image colour, the u/s system uses what?
Multiple scan lines
Ensemble length of 5 equals what?
5 pulse s
What is the size of ensemble length?
Ranges of sizes
The larger the ensemble length, what happens to mean velocities?
The more accurate the mean velocities
The smaller the ensemble length, what happens to mean velocities?
Less accurate
Ensemble length does what to frame rate?
Significantly impacts frame rate
What does autocorrelation do?
A means of rapidly determining the sign, mean, power, and variance of the returning signal
What yields the information autocorrelation?
Mathematical processes yields this information each sample time
In terms of autocorrelation, there are how many doppler samples per scan line?
100 to 400
Autocorrelation allows for how many frames per second? What does this depend on?
- 5-50 frames per second.
- Depends on sample box size
In gray scale we use how many pulses per scan line?
1
Multiple focuses means what in terms of pulses?
Multiple pulses
In terms of autocorrelation, how many pulses are needed to get accurate information? What does more pulses mean?
- At least 3 pulses
- More pulses mean more phase shifts
What are components of colour? 4
- Hue
- Saturation
- Luminance
- Variance
What is hue?
The colour that your see
What is saturation generally?
The amount of colour in a mix with white
What doe an increase of white mean with saturation?
Then there is a decrease in the amount of saturation
Decrease saturation means what in terms of velocity?
Higher velocity
What does luminance mean?
Brightness of the hue and saturation presented
Various combinations of hue, saturation and luminance indicate what?
The sign, magnitude of the mean and sometimes the power of variance
What does variance mean?
The amount velocities differs from the mean
What are some examples of colour control? 11
- Window
- Gain
- Steering
- Inversion
- Wall filter
- Priority
- Baseline shift
- Scale
- Colour map
- Smoothing
- Ensemble length
What is power doppler also known as?
Energy mode
What are two advantages of power doppler?
- Less affected by angle and free of aliasing
- More sensitive to low flow states
How does power doppler work?
Uses the amplitude of the reflectors rather than the frequency shift
What is a major disadvantage of power doppler?
No flow characteristics or speed info
What does new technology mean for power doppler?
Some allows for some directional display
A sonographer with sonography Canada generalist and vascular certification is performing an abdominal u/s in the ICU. The referring physician asks the sonographer to investigate the heart for LV hypertrophy. How should the sonographer proceed?
- Angle the transducer towards the heart, and tell the referring physician that the heart looks fine
- Explain to the referring physician that they are not credentialed in cardiac sonography but they will “take a look” and make an educated guess
- Angle the transducer towards the heart, compare the size of the right and the left ventricles and record their findings on their technical impressions
- Explain to the referring physician that they are not credentialed in cardiac sonography and they suggest they contact the echocardiography department.
4
What is the cause of the indicated artifact?
- Reverberation
- Refraction of sound
- Increased absorption
- Perpendicular angle of incidence
2
Which of the following scenarios would cause a sonographer to be in violation of the sonography Canada code of ethics?
- Obtaining the required continuing medical education credits
- Ensuring patient is adequately covered during an endovanginal examination
- Discussing their personal beliefs with a patient considering termination of a pregnancy
- STopping an exam because the patient indicates they no longer want to have the u/s
3
What is the Nyquist limit for PRF of 10,000 Hz?
- 4000 Hz
- 5000 Hz
- 6000 Hz
- 7000 Hz
5000 Hz
Which of the following is NOT an example of a sonographer applying universal precautions?
- Gloves should be removed and discard between patients
- Needles and sharps should be promptly disposed of in the garbage
- Protective equipment should be worn if exposure to bodily fluids is anticipated
- Hand washing should be completed before and after each interaction with patients.
2
Which of the following changes could a sonographer make to optimally assess the dynamic changes occurring in a rapidly moving structure?
- Reduce sector width
- Change multiple foci
- Increase scan line density
- Decrease the operating frequency
1
Which of the following actions should eliminate side lobe artifacts?
- Increase gain
- Lower frequency
- Adjust post processing
- Reorient scan plate
D
Which of the following is the most reasonable action for a sonographer take when the image on the ultrasound system displays only those reflectors in the near field but not reflectors in the far field
- Decrease the power output
- Adjust the systems compression
- Use a higher frequency transducer
- Adjust the systems time gain compression
D
Based on the following images, which parameter should be adjusted to best improve the diagnostic quality?
- Pre-set
- Harmonics
- Transducer frequency
- Transducer orientation.
A
During a sonographer examination, a 72 year old patient experiences chest pain, shortness of breath and loses consciousness. What should be the response of the sonographer?
- Begin CPR
- Call a code
- Administer oxygen
- Assess systolic function
B
Which one of the following may contribute to a temperature rise in tissue when exposed to diagnostic ultrasound?
- A increased transducer frequency
- Decreased dynamic range
- Decreased overall gain
- Increased persistence
1
A patient arrives for an ultrasound and tells the sonographer: I am very nervous because I don’t know what having a ultrasound feels like. What should the sonographer do before starting the exam?
- Start the scan without further delay
- Review the patients medical history
- Acknowledge the patients feelings and explain the procedure
- Rebook the patient for another day when they are feeling less anxious
3
Which of the following information must be indicated on a standard imaging requisition in order to proceed with a requested diagnostic procedure?
- Requesting physicians name, home address, and contact information
- Patients name, address, and pertinent clinical information
- Reference to previous diagnostic procedure and results
- Medical registration number and accession number
2
When performing a scan on a patient who is under enteric precautions, which one of the following is not required?
- Wear gloves
- Wear a gown
- Wear a mask
- Dispose of contaminated articles in specially provided bags
3
Interaction with patients sometimes results in exposure to blood and body fluids. Which one of the following groups of patients required the sonographer to adhere to infection-control measures?
- All patients
- Hepatitis B/ C patients
- Patients that are visibly ill
- Patients with open wounds
A
After getting the patient from the waiting room, the sonographer enters the scanning room and asks the patient to sit on the stretcher. The sonographer makes sure to close the scanning room door before proceeding to explain the examination to patient. Which principle is the sonographer fulfilling by closing the door?
- Reducing extrinsic noise
- Obtaining patient consent
- Maintaining patient confidentiality
- Generating a positive environment with staff
3
Which one of the following best describes the characteristics of a modern transducer?
- Narrow bandwidth, short pulse duration, High Q factor
- Narrow bandwidth, Long pulse duration, Low Q factor
- Wide bandwidth, short pulse duration, Low Q factor
- Wide bandwidth, Long pulse duration, High Q factor
C
Bulk modulus refers to which of the following?
- Mass
- Density
- Stiffness
- Frequency
3
Which of the following sonographer controlled instrumentation is least likely to improve the contrast resultion of an image?
- Read zoom
- Chroma maps
- Dynamic range
- Output power levels
1
Which imaging instrumentation change would best reduce the artifact demonstrated in either of the following images, as indicated by the white arrow?
- Use tissue harmonic images
- Alter position on the focus
- Increase the 2D B mode dynamic range
- Utilize the 2D B-mode Colour or chroma map
1
Which of the following instrumentation controls is related to overcoming the affects of the attenuation and measured as dB?
- Multi-focus function
- Time gain compensation
- Tissue harmonic images
- Dynamic range/ compression control.
B
Failure to maintain appropriate personal boundaries in order to put a patient at ease conflicts with which on of the following guidelines?
- Scope of practice
- Health profession ace
- Sonography canada code of ethics
- Health Canada Privacy act.
C
While scanning an obese patient, which of the following most effectively improves image quality?
- Apply read zoom
- Apply power doppler
- Decreased frequency
- Increase log compression
3
Which of the following factors does not cause an increase in the duty factor?
- Increased damping
- Longer pulse duration
- Decreased transducer frequency
- Higher pulse repetition frequency
A
Which area within the image is displaying the lowest mean doppler shifts?
C
Which of the following operating modes is at the highest risk for thermal bio effects?
- M-mode
- Colour doppler
- Pulsed doppler
- CW doppler
4
If a patient adamantly refuses the sonographic examination, which one of the following actions should the sonographer take?
- Continue with the examination
- Persuade the patient to have the examination
- Respect the patients decision, and document refusal
- Bring in another sonographer to explain the examination
3
Which of the following criteria is found on a supplier label for any hazardous product used at a workplace?
- Employer information
- Recommended use
- Quantity of product
- Identification number
B
What aspect of blood flow is NOT appreciated when looking at a pulsed wave doppler spectral trace?
- Turbulence
- Direction
- Velocity
- Viscosity
D
Which of the following transducer bandwidths is the best for harmonic imaging?
- 3-1 MHZ
- 6-3 MHz
- 6-1 MHz
- 12- 8 MHz
3
Which of the following tissues is at the highest risk for thermal bio effects?
- Fat
- Bone
- Liver
- Muscle
B
Thermal bio effects can be explained by which component of attenuation?
- Reflection
- Absorption
- Refraction
- Scattering
B
Which one of the following is an advantage of applying B-colour (2D colour maps)?
- Improved contrast resolution
- Improved temporal resolution
- Information on moving structures
- Increased digital memory capacity
1
Which of the following questions is appropriate to ask when obtaining information about a patients medical history and condition?
- How old are you
- What is your martial status
- Do you consider yourself healthy
- Have you had any past surgical procedures
D
Which one of the following instrumentation controls would the sonographer adjust to optimize the colour display?
- Wall filter
- Colour gain
- Velocity range
- Ensemble length
C
