US Physics Test
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. What would you like to do?
the routine, periodic evaluation of an US system to guarantee optimal image quality
What are some of the requirements of quality assurance?
- assessement of system components
- preventive maintenance
- record keeping
What are some of the goals of quality assurance?
- proper operation of equipment
- detect gradual changes
- minimize downtime
- reduce non-diagnostic exams
- reduce repeat scans
What are the two types of quality assurance devices?
- tissue equivalent phantoms
- test objects
What QA device is a fluid filled tank containing stainless steel pins or plastic strings?
AIUM 100mm Test object
The AIUM 100mm Test object is unable to evaluate?
What does the AIUM 100mm test object evaluate?
accuracy and performance of a system
What does the AIUM 100mm test object determine?
- Axial resolution
- Lateral resolution
- Electrongic caliper accuracy
- Dead zone
What QA device is made of graphite-filled aqueous gel or urethane rubber materials?
Tissue equivalent phantoms
What do tissue equivalent objects assess?
- Detail and Contrast resolution
- Dynamic Range
- Time Gain Compensation Operation
Tissue Equivalent phantoms have features similar to what?
What do Tissue Equivalent Phantoms evaluate?
- tissue texture
- adjustable focus
What are the characteristics that make tissue equivalent phantoms similar to soft tissue?
- speed of sound
- scattering characteristics
This type of QA device will include structures that resemble soft tissue and are imbedded with cysts and solid masses.
tissue equivalent phantom
What type of QA device includes a circulation pump which propels a fluid through vessels embedded in a tissue equivalent phantom?
What do doppler phantoms assess?
- characteristics of all doppler modalities
- continuous wave color
- power mode
Doppler Phantoms may use what as movement?
- vibrating strings
- moving belts
Doppler phantoms can produce what type of movement?
What are the disadvantages of doppler phantoms?
presence of bubbles and non-uniform flow
Dopplar phantoms are helpful in determining what?
accuracy of gate location
What QA device mimics soft tissue and measures the beams geometry perpendicular to the imaging plane?
slice thickness phantom
What are alternative names for slice thickness phantom?
elevational resolution or beam profile
ability of a system to display low-level echoes
assessment of the weakest echo that is accurately displayed determined by setting the TGC flat, then increasing system gain from the minimum value to the gain when a deep rod is displayed
found at a higher gain, all the pins, solid masses, and cystic structures are accurately displayed and adjustments are made to output power, TGC, and amplification
the output power and amplification are set to the highest practical level, the depth of tissue-like texture is determined
results from the transducer ringing and the time it takes for the system to switch from transmit to receive, close to the transducer
Which transducers have a thinner dead zone?
What will help eliminate issues caused by the dead zone?
acoustic standoff pads
ability to place reflections in the proper position while imaging from different orientations
vertical depth calibration places objects correctly parallel to the sound beam
places objects correctly perpendicular to the sound beam
the effects of the sound beam on the body
What instruments measure bioeffects?
- radiation force
Another name for hydrophone
This bioeffects measuring device has a small hypodermic needle with a tiny piece of PZT attached to an oscilloscope with a wire or may contain a very thin membrane of PZT plastic that is placed in the sound beam
What relates to the pressure of the sound beam when using a hydrophone?
What does a hydrophone do?
measures pressure at specific locations
Hydrophone measurements are displayed on an?
What can a hydrophone determine?
- sound beam's shape
- Pulse duration
From lowest to highest, what would the ultrasonic output be?
- songraphic (imaging) low
- M mode and color doppler intermediate
- Pulsed spectral doppler highest
the measurable force on any target caused by a sound beam
radiation force is also referred to as
miniature postal scale
interaction of sound and light
this demonstrates the shape of the sound beam in a medium
Schlieren (shadowing system)
used to measure sound heat, this measures total power through absorption, the beam's total power is calculated by measuring the temperature rise and the time of heating
used to measure sound heat, this tiny electronic thermometer inserted into the sound beam where the temperature is measured. the temperature rise is related to the power at that particular location
used to measure sound heat, this changes color based on the temperature, provided insight into the shape and strength of the sound beam
what is meant by the risk-benefit relationship?
the benefits must outweigh the risks
Is there confirmation of harm resulting from the use of ultrasound at standard intensity?
as low as reasonable achievable
what should techs do to maintain alara
- lowest output power
- lowest scan time possible
the science of identifying and measuring the characteristics of an ultrasound beam that are relevant to its potential for producing biological effects
research performed within the living body
research performed outside the living body in an artificial environment
is it ethical to do all studies in vivo?
searches for a relationship between cause and effect
searches for a relationship between exposure and response
2 mechanisms of bioeffects
bioeffects resulting from tissue temperature elevation
a calculated number useful in predicting max temperature increases under clinically relevant conditions
3 forms of measurement of in vivo tissue temperature changes that are the best
- TIS soft tissue
- TIB bone
- TIC cranial bone
absorption occurs more frequently and at a higher degree in what?
what tissues are less tolerant of tissue heating
how many hours will it take of US exposure to elevate the temperature 2 degrees celcius
Tissue heating is related to what type of intensity
What is worse a focused or unfocused US beam?
interaction of sound waves with microscopic, stabilized gas bubbles in tissues
this type of cavitation occurs at lower MI levels, gaseous nuclei tend to oscillate (expand and contract) bubble don't burst
this type of cavitation occurs at higher MI levels, bubbles burst, and produces highly localized violent effects such as colossal temperatures and shock waves
what is inertial or normal cavitation
related to the likelihood of harmful bioeffects from cavitation, unitless, related to peak negative pressure and frequency, greater likelihood of cavitation bioeffects with additional negative pressure and lower frequencies
exposure-response population studies ultilizing clinical surveys, many dealing with in utero fetal exposure
3 limitations of epidemiology studies
- retrospective studies
- ambiguities may exist in the data
- other risk factors may lead to bad fetal outcomes
what make up the best epidemiologic studies?
prospective and randomized
information is documented as it occurs
creates a control group, takes other risk factors into account
epidemiologic data indicates that ultrasound exposure is not associated with adverse what?
greatest risk in ultrasound is from?
electrical safety (cracked transducer housing)
How should electrical hazards be assessed?
visually check equipment
What would you like to do?
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