M1: Quality Assurance Flashcards
what is one of the primary concerns with QA
patient misdiagnosis if the machine is not functioning properly
define QA
program that ensures proper and consistent operation of the imaging systems
list some of the items that QA ensures
equipment operation gradual degradation of performance minimizes repeat exams and machine down time safety cost efficiency maintains standards
list the 3 people responsible for QA
1 physician
2 sonographer
3 service (biomed/manufacturer)
describe the physicians role in QA
Qa director
assess images for overall quality
describe the sonographers role in QA
front line worker
- assess images for quality in the ‘front line’
- may perform routine testing ad record keeping
- will perform routine preventative maintenance (cleaning filters, visual inspections, wiping down machine, etc)
what are the 2 types of service personnel
1 manufacturer
2 biomedical personnel
describe the role of the manufacturer in QA
provides routine preventative maintenance and repairs equipment
describe the role of the biomed in QA
acceptance testing when a machine arrives and before it starts being used… ensures compatibility, imaging performance, power output and safety
in general, what does routine performance testing asses
image performance and changes in quality over time
what is the key component of a good QA program
record keeping…. data must be frequent and be accurately recorded
is it best to have the same person performing the routine performance testing on phantoms each year
yes, for consistency
what is an AIUM 100?
an older test device in a plastic casing w/ 0.75 mm steel rods arranged in grps…. filled w/ water, alcohol and algaecide
what is the downside to an AIUM 100
no grayscale so no attenuation (so cant test sensitivity)
what is an upside to an AIUM 100
inexpensive
what is a tissue equivalent phantom
test object that contains tissue mimicking materials
what are tissue phantoms made of
plastic case w/ a gel mixed w/ graphite powder, rod groups, solid and cystic lesions.
why are tissue phantoms better for testing than AIUM 100s
give a better approximation of clinical perforance, since they allow for grayscale, attenuation, and speed of sound
what is the downside to tissue phantoms
expensive
list the 4 items that an AIUM test object can test for?
dead zone
axial/lateral resolution
depth calibration accuracy
length calibration accuracy
list some of the items that a tissue phantom can test for
all the same things as a test object plus….
elevational resolution TGCs/attenuation/depth penetration uniformity sensitivity dynamic range contrast resolution lesion (cystic/solid) detection
a good phantom must have what 5 characteristics that are similar to soft tissue
attenuation coefficient speed of sound backscatter coefficient/relative contrast elasticity thermal properties
describe the dead zone
area right at the surface of the probe in the near field, also know as the main bang artifact
how do we test the dead zone
imagine the dead zone pins close to the surface of the probe and looking for changes over time
why are the dead zone pins offset in tissue phantoms
to avoid reverberation artifact from the metal pins
how do we test for axial resolution in tissue phantoms
measure the smallest visible separation b/w the axial resolution pins and various depth (size A grp b)
how do we test for lateral resolution in tissue phantoms
measure the lateral resolu. pins…. the results will depend on depth and focal placement since the best lat resolu. is at the focal point (side A, grp c)
how do we test for elevational resolution in tissue phantoms
can test qualitatively or quantitatively…..
- quantitative assessment requires a different type of phantom w/ a ramp… specifically a spherical void phantom or beam profile phantom to get specific measurements
- qualitative assessments can be made w/ the TE phantoms (place focus at structure, if resolved, z axis is probably fine… scan side A, grp e)
how do we test for distance accuracy in tissue phantoms
measure pins at a known distance (vertically and horizon.) and compare the value you get to the true distance
(side A, grp d for horiz.
side A, grp c for verti.)
for distance accuracy, is is more important to measure small or larger distances
why
larger distances, to detect smaller margins of error and enhance the % error
how do we test for TGC accuracy
capture images using different slide pods under different conditions and compare over time
what does image uniformity test
and what does it look for (list some examples)
tests a linear array consistency along the array
looking for inhomogeneous regions/non uniformity… vertical band, reverberations, horizontal band
what does sensitivity test
the ability to detect weak echos
what is a common technique used to test sensitivity
maximum depth of visualization
what is maximum depth of visualization
power and gain are optimized for penetration and the observer records the depth where the brightness starts to fade
what does dynamic range control
contrast resolution
is testing dynamic range a subjective test
yes because you compare images over time and decide if there is a change in the display
why is too little contrast resolution bad
you’ll have poor tissue differentiation because of poor contrast resolution
why is too much contrast resolution bad
you cant tell the similar shades of grey apart and they are grouped together
how is dynamic range tested
compared lesions of similar echogenicities and different sizes, at different depth and see if you can resolve them as separate from surrounding tissue
another name for dynamic range
compression
what does contrast resolution allow us to test
allows us to measure how well we can detect small lesions w/ a variety of appearances (solid, cystic, echogenic) etc.) while varying the settings
what is registration
an old test for static B scanners that ensures the arm positioning is accurate for reconstructing an image
how do we test registration
scan pins from 3 sides and see if the lines intersect at one point
2 types of doppler phantoms
what is the difference b/w them?
- Flow
- String or belt
how the doppler shift is created
which type of doppler phantom matches the clinical experience
what is its downside
flow or TE phantom
expensive
describe a string or belt doppler phantom
what is its upside
they move a string or belt in a water bath
dont match clinical experience but cheap
flow doppler phantoms can be used to measure which factors
maximum depth (how deep can you pick up colour flow) gate position accuracy volume flow and velocity accuracy colour flow penetration Image congruency
all gray scale components since it has tissue mimicking material
how many scan lines does the probe need to send out for colour doppler
minimum 3 scan lines to get a mean… that’s why frame rate goes down so much
how many scan lines does the probe need to send out for 2D imaging
1 scan line
what is an output testing device
a device used by service personnel or manufactures to evaluate the systems power output
3 output testing devices, which is the most common
hydrophone
power (force) balancers
calorimeter
what are 4 features of a hydrophone
plotter
spectrum analyzer
oscillosope
schlieren system (acousitc optical method)
what is plotter
small device the can plot the different intensities found along the beam (SP and SA) and produce a beam profile
what is a hydrophone
small transducer (1mm face) that produces a voltage based on the received acoustic pressure waves from the US beam (placed in the path of the beam) has piezoelectric properties
when a hydrophone is used w/ an oscilloscope, what can it measure
SPL PD PRP PRF DF
when a hydrophone is used w/ a spectrum analyzer, what can it measure
resonant frequency
bandwidth
fractional bandwidth
Q factor
what are power (force) balancers used to measure
how do they work
acoustic power
have a ‘scale’ attached to a sound absorbing block, the more power coming out of the probe, the more the block is pushed down and the more the scale will tip upwards…more tipping = stronger intensity
what is a calorimeter
‘heat meter’ used to measure acoustic power
it contains a sensitive thermocouple the detects temp changes and can determine acoustic power
If calorimeters are measuring heat, this means they are measuring which attenuation process?
Absorption
What does image congruency test
that colour flow is accurately displayed on the screen
Another name for scale
Velocity range
