Chapter 22 Quality Assurance Flashcards
What is quality assurance?
routine, periodic evaluation of an ultrasound system to guarantee optimal image quality
Who is responsible for implementing a quality assurance plan?
the sonographer
What are the 4 requirements of a quality assurance program?
- assessment of system components
- repairs
- preventive maintenance
- record keeping
What are the goals of a quality assurance program?
- guarantee proper operation of the system
- detect gradual changes
- minimize downtime
- reduce the number of non-diagnostic exams
- reduce the number of repeat scans
what are the three Quality assurance devices?
- tissue equivalent phantom
- doppler phantom
- beam profile/ slice thickness phantom
What are the methods of quality assurance?
- test under known, defined conditions
- use constant instrument settings
- use phantom with measurable characteristics]
- image in an identical environment
What type of information is unbiased, factual, repeatable, and able to be counted; information will be the same even from different people?
Objective standards
What type of information is affected by opinion, belief, or assumption and will vary from person to person?
Subjective standards
All Quality assurance programs should be based on what standards?
Objective standard
What has features similar to soft tissue, is used to evaluate characteristics such as gray scale, tissue texture, multi-focus and adjustable- focus phased array transducers?
tissue equivalent phantom
How are tissue equivalent phantoms similar to soft tissue?
- speed of sound (1,540 m/s)
- attenuation
- scattering characteristics
- echogenicity
How is the gray scale evaluated in a tissue equivalent phantom?
the phantom contains structures that mimic hollow cysts and solid masses
What is the device of choice to evaluate Doppler systems?
Flow Phantoms
name the types of Doppler phantoms
- Vibrating strings
- moving belt
- flow phantom
What modalities are assessed by a Doppler phantom?
- pulsed wave doppler
- Continuous wave
- Color
- Power mode
Slice thickness determines______
Elevational resolution
What assesses the slice thickness and its effect on image accuracy, contains a diffuse scattering plane and measures the beam perpendicular to imaging plane?
Slice thickness phantom
What slices diminish spatial resolution and reduce the ability to visualilze small, low contrast reflectors and cystic structures may appear filled?
Thicker slices
What is the ability of the system to display low level echoes?
Sensitivity
What are the two forms of sensitivity?
- normal
- maximum
What is normal sensitivity?
All pins, solid masses, and cystic structures are accurately displayed
TGC and gain are adjusted to establish normal sensitivity
Under what sensitivity should Quality Assurance assessments be made?
Normal sensitivity
What is maximum sensitivity?
Evaluated with output power and amplification:
Set to max practical levels
Maximum visualization depth is used to assess sensitivity
How can sensitivity be adjusted?
Adjust the brightness
What is the dead zone?
Region close to the transducer where images are inaccurate
What does the dead zone result from?
Transducer ringing and the time is takes the system to switch from the transmit to the receive mode
what transducers have a thinner dead zone?
Higher frequency transducers
What should be used to accurately image important superficial structures?
gel or standoff pad
What do increasingly deeper dead zones indicate?
A cracked crystal, detached backing material or a longer pulse duration
What is the ability of the system to place reflections in proper positions while imaging from different orientations?
Registration accuracy
What describes the system’s accuracy in placing reflectors at the correct depths located parallel to the sound beams main axis?
Range accuracy (vertical depth calibration)
What may be the cause of range accuracy?
- system malfunctions
- the speed of sound in the phantom is different than 1,540 m/s
Depth calibration is__________
the accuracy of reflector depth positioning in A-mode, M-mode, B-mode and 2-D imaging
What is the system’s ability to place echoes in their correct position when the reflectors are perpendicular to the beam?
Horizontal calibration
What is the assessment of the measurement capability of a system?
Distance measurement accuracy
in what direction should digital calipers be measured?
Vertical and horizontal
The depth at which the intensity is the highest and the beam is the narrowest
Focus
What surrounds the focus
Focal zone
______________ resolution is excellent at the focal zone because the beam is narrow
Lateral
______ resolution uses pins that are parallel to the sound beam
Axial
the minimum distance at which two side-by-side pins are displayed as two distinct images
lateral resolution
What describes the ability of a system to display similar reflectors with echoes of similar brightness?
Compensation operation or uniformity
What is the tissue equivalent phantom used to evaluate?
dimensions, texture, and fillin of cysts
True or False
Adjusting the system’s output power and amplification should produce changes in the gray scale display
True
What standard is best is used in a quality assurance program?
Objective
All of the following are characteristics of a tissue equivalent phantom except?
A. speed of sound similar to that in soft tissue
B. attenuation properties similar to that of tissue
C. scattering characteristics similar to that of soft tissue
D. density similar to that of soft tissue
D. density similar to that of soft tissue
What form of resolution is evaluated by measuring the width of reflections arising from small point targets?
Lateral resolution
What form of resolution is evaluated by visualizing closely spaced pins that are parallel to the sound beam’s main axis?
Axial resolution
At what interval should quality assurance evaluations be preformed?
routinely
True or False
Quality assurance evaluations of ultrasound systems can only be performed by biomedical engineers or physical scientists?
False
True or False
Proper QA programs require the assessment of every transducer used in the clinical laboratory?
True
Which of the following statements are true of a tissue equivalent phantom?
A. it has the same propagation speed as that of soft tissue
B. it attenuates ultrasound at a rate similar to soft tissue
C. embedded in it are solid masses and cystic structures
D. it is the device of choice for quality assurance studies
all are true
All of the following may be used to evaluate Doppler systems except? A. tissue equivalent phantom B. moving belt phantom C. vibrating string phantom D. Doppler phantom
A. tissue equivalent phantom
systems with dynamic receive focusing should produce ___________ reflections over a wide range of depth
narrow
