Week #13 Flashcards
What are the 3 main components of QC for fluoro equipment?
Visual inspection
Environmental inspection
Performance testing
According to SC35, how often should collimator operation, locks, table motion, angulation, compression devices, chronometer, protective devices be tested?
Quarterly
According to SC35 how often should collimator operation be evaluated to ensure the dimensions of the xray field do not exceed the area of the II
Annually
According to SC35, what percent should the xray field not exceed the area of the II by the SID?
3%
What lead equivalent should the protective curtain contain?
0.25mm
What percentage should the table angulation and motion be accurate within?
2 degrees
What indicator should be present when inspecting the high level irradiation control?
Ensure that an audible signal is present when in use
According to SC35, what is the limit for reproducibility variance between exposures?
What is the testing frequency?
CV less than or equal to 0.05
Each exposure within 15% of the mean
Annual
At 70 kv, what is the minimum half value layer of aluminum for fluoro?
2.5 mm
How is kvp accuracy tested in fluoro?
Expose a digital kvp meter under fluoro
According to HARP what is the testing frequency and acceptance limit for kvp accuracy?
Semi annual
8%
According to SC35 what is the testing frequency and acceptance limit for kvp accuracy?
Annual
10% for xray tube voltage
20% for xray tube current
Testing involves a series of fluoroscopic exposures, each at double the mA of the previous
mA linearity
What is the required testing frequency for ma linearity according to SC35?
Annual
At what percent of maximum heat should the alarm be activated when exposing a homogenous phantom under fluoro? What is this testing?
When 75% of maximum heat is achieved
Xray tube heat sensor
The ability to resolve objects in a resultant image when the difference in the attenuation between the objects and the background is large compared to noise
Spatial resolution
Ability to resolve small, black and white objects
High contrast resolution
How is testing done for high contrast resolution?
Testing involves imaging a testing tool under fluoro
Depending on the size of the II, a minimum size mesh should be visualized
Follow manufacturer guidelines
Ability to resolve relatively large objects with similar density
Low contrast resolution
What is the minimum source to skin distance for fixed or stationary units?
Not less than 30cm or 15”
What is the minimum source to skin distance for mobile units?
Not less than 30cm or 12”
What is the minimum source to skin distance for specialized units?
Not less than 20cm or 8” for special applications that would be impossible to achieve at a minimum of 30cm or 38cm
Scattered or reflected light in the output phosphor; causes an increase in brightness on the image
Veiling glare
Occurs due to projecting image curved surface to flat surface, such as input phosphor to output phosphor (distortion is greater towards the lateral portion of the image)
Pincushion distortion
Same as pincushion but magnification occurs at the centre
Barrel distortion
A decrease in image brightness at the lateral portions of the image - caused by a combination of pincushion distortion and the coupling of the television camera to the output phosphor
Vignetting
Warping of the image along an S shaped axis and is the result of strong magnetic fields changing the trajectory of the electrons moving across the image intensifier tube
S distortion
What is used for testing of distortion?
Wire mesh tool under fluoro
Can be due to quantum mottle or electronic noise present on fluoro monitor
Image noise
What can be done if quantum mottle is identified on an image?
ma can be increased
How do you test for image noise?
Expose a phantom at lowest mA and 80kvp. Increase mA to maximum value, if noise goes away it is quantum mottle, if it does not it is electronic noise
Ability of imaging system to display events occurring close together in time as separate events
Temporal resolution
Continuation of persistence of image; can blur objects as the II or object is moved
Image lag
- directly influences temporal resolution
What is entrance exposure referred to as?
Air Kerma rate of radioscopic exposure
Max. Air kerma
When equipment is not fitted with an automatic intensity control
50mgy/min
Max. Air kerma
When equipment is fitted with an automatic intensity control
100mgy/min
Max. Air kerma
When equipment is fitted with both an automatic intensity control and a high level irradiation control when the latter is activated
150mgy/min
How do you test the automatic brightness control?
Place a dosimeter between a homogenous phantom and the xray source. Double the phantom thickness and repeat exposure.
**the exposure measurement should be approximately double the first measurement **
According to HARP, what shall every fluoroscopic xray machine be equipped with?
-an audible signal that indicates completion of any preset time of use up to a maximum of 5 minutes
-a shield of at least 0.25mm lead equivalent at 100kvp
What is the exposure rate limit for a machine that uses a zinc cadmium suplphide input phosphor?
-max. Entrance exposure of 12.5R/min
-entrance exposure rate of 5R/min for average patient
What is the exposure rate limit for a machine that has a cesium iodide input phosphor?
-max. Exposure rate of 10R/min
-entrance exposure rate of 2.5R/min for an average patient
According to HARP , what is the testing frequency for:
-max patient entrance exposure rate
-resolution
-limit timer
-automatic brightness control
Every 6 months and upon servicing the machine
