ultra sound first set of questions made by class Flashcards
Why do we use phased array?
a) To minimise heat
b) To steer the beam of sound
c) To change AC – DC
d) To reduce artifacts
b) To steer the beam of sound
How do you control the shape of the beam being produced?
Change the focus of the beam
What does TCG stand for?
Time gain compensation
What does A stand for?
Amplitude
What does focus control?
a) Penetration depth
b) Region of best resolution
c) Enlarges ROI
d) Pulse repetition frequency
b) Region of best resolution
When does refraction occur?
Deviation is in the path of a beam, it occurs when the beam passes through interfaces between tissues of differing speeds of sound, when the angle of incidence to an interface is not 90o
As the pulse travels through the body it loses energy due to what?
Backing material
What are the 6 steps for processing?
- Detection
- Preamplification
- Time gain compensation
- compression
- rectification and envelope detection
- rejection
What will too much preamplification produce?
introduce excessive noise into the subsequent analysis
The machine is calibrated so that the speed of sound is what?
1540 m/s which is the speed of sound in soft tissue
What does the speed in which the pulse travels through the body depend on?
The tissue type e.g. fat muscle blood and bone
If rejection threshold is too low what happens?
leads to many echoes which don’t represent anatomy
We look at data through a what?
window
Name 2 advantages of A mode:
Very quick as only 1 pulse needs to be sent out
Can give a clear picture on the anatomical boundaries
Name 2 disadvantages of A mode:
Small amount of data means less to interpret
Only 1 dimensional
What takes longer to produce A or M mode?
M Mode
What type of pulse will produce a wide range of frequency’s?
Narrower pulses
Define the term axial resolution:
The ability to display small targets along the path of the beam as separate entities
Define pulse length and wave length:
- Pulse length is determined by number of cycles in one pulse and length of each cycle (ie: wavelength)
- inversely proportional to frequency (c=fλ) so higher frequencies generate shorter wavelengths and therefore shorter pulse lengths
What is a backing material made from?
epoxy resin with rubber powder embedded in the epoxy
What is a phased array used for?
a) Increase frequency
b) Steer the bandwidth
c) Decrease the signal
d) Steer the sound beam
d) Steer the sound beam
What is a transducer and what is its purpose?
transducer in an ultrasound instrument
changes electrical energy into sound energy, and it can change sound energy into electrical energy.
What do piezoelectric crystals respond to?
to an electric field by producing pressure
basic transducer consists of 3 main parts
- The case
- The crystal
- The damping material – more on that soon
The input to a transducer is called what?
Signal
Electrical signal coming in to the transducer produces?
a) Sound at a different frequency
b) Stays at an electrical signal
c) Sound at the same frequency
d) Returning echos
d) Returning echos
Explain the superposition principal:
When more than one wave is present at a given point we can simply add the value of the waves together at that point
Why is coupling gel needed in USS examinations?
a) Decrease noise
b) Remove impedance difference
c) Lubrication to reduce friction
d) Increase impedance difference
b) Remove impedance difference
What is the chosen wavelength difference for the matching layer?
¼ wavelength
The longer the pulse the ……………… the bandwidth.
Narrower
The ALARA principle is still relevant is USS:
a) True
b) False
a) True
What is not a type of interaction in USS?
a) Thermal
b) Mechanical
c) Photoelectric
c) Photoelectric
Give settings that will affect heating:
- Output power
- Frequency
- Duration
- Mode (scanned or unscanned)
- Focal zone position
- Field of view
Which one isn’t a form of recording method?
a) Static imager
b) Reverberation
c) Cine loop
d) Pacs storage
b) Reverberation
Give USS assumptions:
- Sound travels in strait lines
- Echos originate only from objects along the beams axis
- The intensity of the echos relates directly to the reflecting or scattering properties of distant objects
- Sound travels at a fixed speed in the body
- The attenuation is the same for all tissues being imaged
- Tissue that should look the same does look the same
The USS machine assumes sound travels at what speed?
1540 m/s-1
What is one of the main biological effects of USS?
a) Nausea
b) Heating
c) Radiation dose
d) None of the above
b) Heating
Gives examples of in vivo biological effects:
- Foetal weight loss
- Foetal death
- Blood flow anomalies
- Lung haemorrhage
Give examples of in vitro biological effects:
1) Mitosis rates altered
2) Cell membranes ruptured
3) Change in cell motility
4) Cell death
5) Degradation
How does edge shadowing appear?
a) A line that appears brighter
b) A darker line is shown tangential to edge
c) 3 or more lines shown perpendicular to each other
d) A brightened area
b) A darker line is shown tangential to edge
Depth artefacts include:
a) Reverberation
b) Side lobes
c) Side width
d) Comet tail
e) A & D
e) A & D
Describe the appearance of comet tail artefact:
Loss of energy with reverberation cycle which results in a rapid brightness of the artefact.
When does refraction occur?
a) Where the echoes are presumed to have come from along the original beam path and are therefore place in an incorrect position on the ultrasound image.
b) When the lobe are circumferential around the main lobe
c) Where there is misregisistration by half the band width
d) When there is a short range of reverberation effect
a) Where the echoes are presumed to have come from along the original beam path and are therefore
What is an artefact?
An appearance in an ultrasound image that does not accurately represent the anatomy or structure of the section in the path of the beam.
What is not a cause of artefact?
a) Violation of assumtions (acoustic artefact)
b) Faulty equipment
c) Electrical interference
d) Bandwidth
d) Bandwidth
Define shadowing:
Caused by a high degree of attenuation of the beam at an interface.
How does shadowing appear?
Darkened line cast behind a region of greater attenuation than surrounding tissue.
Enhancement is?
a) Brightened line behind a region of low attenuation than surrounding tissue.
b) Darkened line behind a region of high attenuation than surrounding tissue.
a) Brightened line behind a region of low attenuation than surrounding tissue.
How does edge shadowing appear?
a) A line that appears brighter
b) A darker line is shown tangential to the edge
c) 3 or more lines shown perpendicular to eachother
d) A brightened area
b) A darker line is shown tangential to the edge
What does colour Doppler flow indicate?
Flow direction and speed
What are the four ways blood can flow in a vessle?
1) Plug flow
2) Lamina flow
3) Disturbed flow
4) Turbulent flow
What are the 5 stages the system goes through when receiving Doppler information?
1) Amplification
2) Compensation
3) Compression
4) Demodulation
5) Rejection
What is used in pulse wave Doppler to select a window in time during which echoes are allowed to pass to the receiver?
1) Window
2) Gate
3) Tunnel
4) Channel
1) Window
The shorter the pulse the better the ……………. Resolution
a) Longitudinal
b) Lateral
c) Transverse
d) Axial
a) Longitudinal
What is aliasing?
The rate at which we sample the signal can cause the sonographer to miscalculate the rate of motion in the body.
What is half the Doppler PRF?
Nyquist limit
