Quality Assurance Flashcards
What is the attenuation coefficient?
1/2 frequency x path length
Expensive and closely matches the clinical experience vs string/belt in a water bath that dont match the clinical experience but are more affordable
Flow vs String/belt Doppler phantoms
The ability to distinguish between 2 objects perpendicular to the beams path
Lateral resolution
Elevational resolution
Looks for areas of non-uniformity in a linear array
Image uniformity
The ability to distinguish 2 objects perpendicular to the beam’s path
Elevational resolution
SPL =
Wavelength x RD
1/2 SPL
Axial resolution
3 other uses for phantoms that are not QA
- Demonstration
- Training
- Research & development
A structure that contains one or more materials that simulate body tissues
Tissue equivalent phantom
Who are the 3 people responsible for QA?
- Physician
- Sonographer
- Service (biomedical and manufacturer)
Dead zone measurement, detailed resolution, distance accuracy, image uniformity, depth of penetration, cyst imaging capabilities
The things phantoms can test for
Dead Zone
PZT Curie temp
350 celsius
Image uniformity
A test for older static B scanners to ensure the positioning is accurate for the reconstructed image
Registration
Testing the system’s ability to detect weak echoes
Sensitivity tests
A form of radiotherapy where a sealed radiation source is placed inside or next to the area requiring treatment
Brachytherapy
A small transducer that produces a voltage proportional to the received acoustic pressure wave for the purposes of measuring output power or intensity
Hydrophone
AIUM 100 benefits
Quite inexpensive but have no grayscale and therefore no attenuation
Responsible for acceptance testing when a machine arrives on site to ensure patient and employee safety
Measuring pins at known distances with calipers and comparing the numbers
Distance accuracy
1540 m/s
Speed of sound in soft tissue
Another name for dead zone
Main bang artifact
What are the 5 things doppler phantoms test
- Maximum depth
- Gate position accuracy
- Volume flow and velocity accuracy
- Colour flow penetration
- Image congruency test
Number of shades of grey
Dynamic range
The systems ability to detect weak echoes
Sensitivity
The ability to differentiate between two separate objects along the beam path
Axial resolution
Lateral resolution
Older testing device in which a plastic case contains steel rods and is filled with water
AIUM 100
1/2 Frequency
Attenuation coefficient
Axial resolution
Why is it important to measure over larger distances when testing distance accuracy?
Detects smaller margins of error
Distance = go return time x speed of sound /2
Range equation?
The director of the quality assurance program
Radiologist/physician
Sensitivity
5 mechanisms of attenuation
- absorption
- reflection
- refraction
- wavefront divergence
- scatter
The use of extreme cold produced by liquid nitrogen (or argon gas) to destroy abnormal tissue
Cryosurgery
Name 4 reasons for quality assurance
- Ensure the equipment is working properly
- Detects gradual degradation that would otherwise be missed in daily use
- Minimize machine downtime
- Minimize misdiagnosis
Contrast resolution
Flow and String or Belt
The two types of doppler phantoms
The display filling in the missing gaps with estimated data points
Interpolation
Why are phantoms better than AIUM? Why are they worse?
They give a more realistic approximation of performance because they allow for grayscale, attenuation and speed of sound in soft tissues
They are also more expensive
Plastic case that contains gel, graphite powder and can mimic solid and cystic lesions
Phantoms
How does a hydrophone produce a voltage?
From the received acoustic power
What does a plotter do for a hydrophone?
Can be moved throughout the sound field to test the power output at different areas
What does a hydrophone with an oscilloscope do?
Measures SPL, PD, PRP, PRF, DF
What does a hydrophone with a spectrum analyzer do?
Measures resonant frequency, bandwidth, fractional bandwidth, and Q factor
