What is quality assurance?
routine, periodic evaluation of an ultrasound system to guarantee optimal image quality
When should quality assurance be performed?
periodically and routinely
What are the 4 requirements for a quality assurance program?
assessment of system components
repairs
preventative maintenance
record keeping
What are the goals of a quality assurance program?
guarantee proper position of the system
detect gradual changes
minimize downtime
reduce # of non diagnostic exams
reduce # of repeat scans
What devices are helpful to perform quality assurance?
tissue equivalent phantom
doppler phantom
beam profile/slice thickness phantom
What methods are necessary to perform proper quality assurance?
test under known, defined conditions
use constant instrument settings
use a phantom with measurable characteristics
image in an identical environment
What is an objective statement?
completely unbiased
What is a subjective statemtent?
one that is influenced by an individual's experience or beliefs
What is evaluated with a tissue equivalent phantom?
gray scale
What is assessed with a doppler phantom?
pulsed, continous wave, color and power doppler
What is assessed with the slice thickness phantom?
slice thickness
What is sensitivity?
the ability of a system to display low level echoes
What are the 2 forms of sensitivity?
normal and maximum
What is normal sensitivity?
settings where all the pins, solid masses and cystic structures in a test phantom are accurately displayed
What is adjusted to establish normal sensitivity?
output power, TGC and amplification
What is maximum sensitivity?
evaluated with the output power and amplification of a system set to maximum levels
What is the dead zone?
the region close to the transducer where images are inaccurate
Where is the dead zone located?
from the transducer to the shallowest depth from which meaningful reflections appear
How does one work on minimizing the dead zone?
standoff pad
What is registration accuracy?
the ability of a system to place reflection sin the proper positions while imaging from different orientations
What is range accuracy?
describes systems accuracy in placing reflectors at correct depths parallel to the sound beam
What is another term for range accuracy?
vertical depth calibration
What is horizontal calibration?
systems ability to place echoes in their correct position when the reflectors are perpendicular to the sound beam
What is the focal zone?
area around the focus
What is the focus?
area where the sound beam is the narrowest
What is axial resolution?
smallest distance at which 2 pins can be placed parallel to the sound beam and be displayed as 2 separate echoes
What is lateral resolution?
minimum distance at which 2 side by side pins are displayed as two distinct images
What is uniformity?
the systems ability to display similar reflectors in the phantom with echoes of equal brightness