ultrasound physics 22
Card Set Information
ultrasound physics 22
What are the four requirements for a quality assurance program?
1.) assessment of system components
3.) preventive maintainance
4.) record keeping
What are five goals of a quality assurance program are?
1.) guarantee proper operation of the system
2.) detect gradual changes
3.) minimize downtime
4.) reduce the number of non-diagnostic exams
5.) reduce the number of repeat scans
What are the three devices that enable the sonographer to perform quality assurance?
1.) tissue equivalent phantom
2.) Doppler phantom
3.) beam profile/slice thickness phantom
What are the four proper methods for quality assurance programs?
1.) test under known, defined conditions
2.) use constant instrument settings
3.) use a phantom with measurable characteristics
4.) image in an identical environment
What are objective statements? (4)
1.) completely unbiased.
2.) not affected by an individual's previous experience, preference, or taste.
3.) objective information is factual, repeatable, and able to be counted.
4.) is the same, even when obtained from different people.
What are subjective statements? (3)
1.) is one that is influenced by an individual's experience or beliefs.
2.) It cannot be verified using concrete facts and figures.
3.) Is affected by opinion, belief, or assumption and frequently varies from person to person.
Tissue equivalent phantoms are used to evaluate characteristics such as...(3)
1.) gray scale
2.) tissue texture
3.) multi-focus and adjustable-focus phased array transducers
Tissue equivalent phantoms are similar to soft tissue in the following ways: (4)
1.) speed of sound (1,540 m/s)
3.) scattering characteristics
How does the tissue equivalent phantom work to evaluate gray scale?
It contains small scatterers that act like soft tissue. Structures that mimic hollow cysts (hypoechoic) and solid masses (hyperechoic) are also embedded in the phantom.
What are Doppler phantoms? (2)
1.) are the devices of choice for evaluating Doppler systems.
2.) modern Doppler phantoms include a circulation pump which propels fluid through vessels embedded in a tissue equivalent phantom.
What is slice thickness phantom?
determines elevational resolution
What does sensitivity refer to?
the ability of a system to display low-level echoes.
What are two forms of sensitivity?
Normal sensitivity settings are those at which..
all the pins, solid masses, and cystic structures in the test phantom are accurately displayed.
What three things are adjusted to establish normal sensitivity?
1.) output power
All subsequent quality assurance and performance measurements are made at what sensitivity?
Maximum sensitivity is evaluated with...
the output power and amplification of the system set to the maximum practical levels.
What is the dead zone?
the region close to the transducer where images are inaccurate. Information within the dead zone is unreliable and may not be used in the diagnostic setting.
What is the dead zone caused from?
From the transducer ringing and the time it takes the system to switch from the transmit to the receive mode.
What transducers (higher or lower) have thinner dead zones?
higher frequency transducers have thinner dead zones.
What can help image important superficial structures?
an acoustic standoff, or gel pad, positioned between the transducer and the patient allows accurate imaging of important superficial structures.
A 50 cc bag of IV fluid may also be used.
What does a increasingly deeper dead zone mean or indicate?
a cracked crystal, detached backing material, or a longer pulse duration.
What do use to identify the dead zone?
a tissue equivalent phantom.
What is depth calibration?
the accuracy of reflector depth positioning in A-mode, M-mode, B-mode and 2-d imaging.
What is Registration Accuracy?
is the ability of the system to place reflections in proper positions while imaging from different orientations.
What is Range Accuracy?
Describes the system's accuracy in placing reflectors at correct depths located parallel to the sound beam.
What can range accuracy also be called?
vertical depth calibration
What is horizontal calibration?
the systems ability to place echoes in their correct position when the reflectors are perpendicular to the sound beam.