Lab Final Exam Review Flashcards
(23 cards)
Used to test the accuracy of the kvp settings
Wisconsin test cassette
Used to measure radiation output for mA reciprocity, linearity and reproducibility tests
R-meter
Used to measure the luminance and ambient light output of computer work station monitors as well as radiologists high resolution monitors used for diagnosis
Photometer
Used to determine accuracy of collimation shutters when adjusting light field size
Collimater test tool
Used to determine if primary beam is perpendicular from source to image receptor
Beam alignment test tool (penny test)
Used to check the timer of a 3 phase unit
Motorized synchronous spinning top test tool
What is the formula for the synchronous/electric timer test formula?
360 degrees x Time = degree of arc
What is the variable in the mA reciprocity test?
mA/time is varied to make exposures that will produce the same mAs or quantities of radiation.
How is the mA reciprocity test conducted?
Using an R-meter to measure radiation output. Must be within +or- 10% of each R-meter reading
What does reciprocity allow?
Allows the technologist to vary the mA and time to reduce patient motion or use a breathing technique while still using the same mAs.
What is the CR reproducibility test used for?
- To determine if the same technique will produce a constant radiation output or intensity from one exposure to another.
- To test the calibration of a CR reader.
How is the CR reproducibility test conducted when testing the calibration of a CR reader?
Making 4 exposures using the same KV, mA and time. All 4 images should display the same EI values after being processed in the same CR reader.
What is the percentage of allowance in the reproducibility test?
+or- 5% of each R-meter reading.
Same technique = constant radiation output
What does linearity refer to?
The proportionate accuracy of the radiation output of one mA station in relation to another (typically doubling), but using the same time. Must be within +or- 10% of each R-Meter reading
What can the linearity test he used for?
To test the calibration of a CR reader by making 3 exposures using the same time and doubling the mA, which will double the mAs and radiation output. EI values will increase or decrease proportionately.
Describe the relationships for Konica and Agfa exposure values:
Konica inversely related- double mAs and S number will decrease by half
Agfa directly related- Double mAs and LGM value will increase by 0.3
What is the allowable percentage of error in the collimator test?
\+or- 2% of SID. Approximately 2cm (size of penny)
How much can the KV vary during an exposure? What tool is used to compare exposure densities to determine the correct kvp exposure?
+or- 4 kvp from actual kvp.
Densitometer is used
Explain the dark noise test:
Done on an unexposed and erased plate to asses the level of intrinsic noise present in the CR reader system
How should images look after dark noise and uniformity tests?
Uniform without the presence of any noise or artifacts
What does the AAPM TG 18 test pattern determine?
Spatial resolution, luminance, display noise, and reflection.
Digital display QC test that tests the spatial resolution and quality of the image displayed on the monitor.
What is the half value layer?
The amount of material needed to reduce X-ray beam intensity by half.
- most commonly aluminum
- above 70kvp=2.5 mm AL recommended
What factors does quality control tests test?
Density
Patient dose
Contrast
Repeat rates
