Midterm Flashcards
(61 cards)
Most state regulations require QC programs. A good one involves what 3 people?
Coordinator
Liscensed Medical physicist
Service engineer
What are the 3 steps of QC for x-ray generating equipment?
Acceptance of new equipment
-done by physicist. Check for current or get updated inspection.
Performance evaluation
-annual evaluation and routine maintenance
Correction protocol should begin whenever any problems are detected
-report to service engineer
How do you report equipment problems?
Document exactly what happened and when
Write down any error messages on console as they appear
Guidelines for testing equipment: 7 tests
filtration collimation focal spot size kVp calibration exposure timer accuracy exposure linearity exposure reproducibility
WHen does a medical physicist perform testing of equipment?
- newly installed machine
- at leats once a year
- if a major component ir replaced or recalibrated
WHo conducts performance evaluations?
Physicist
What does the generator do?
Generator provides electrical power for the tube, other parts of the machine and other functions
Powers x-ray tube to produce x-rays
Control panel allows radiographer to select:
mA - and the appropriate focal spot size for exam
time (mA x time = mAs: total number of x-rays)
kVp (the energy of the x-rays in the beam)
in some cases: manual or automatic exposure timing
What are the 3 types of generators commonly used in chiro offices?
- single phase (half or full wave rectification) - old
- Three phase (6 pulse 12 pulse)
- high frequency or constant potential - newest
-same components
-differ in:
complexity
cost (high frequency : approx. $4,000 - 5,000)
efficiency in producing x-rays (high frequency higher energy)
exposure to the patient: (high frequency less exposure)
Annual generator & x-ray production test
kVp delivered during exposure must be within ± __% of the selected kVp. A variation of __-__ kVp affects patient dose and image density
5
2-3
Exposure timer – __ __ test must be tested annually
patient dose is directly affected by exposure time - very important
accuracy must be within ± __% for times greater than 10 milliseconds
below 10 milliseconds ± __ % is acceptable
spinning top
5
20
What is x-ray unit’s ability to produce a constant radiation output for the same mAs using different combinations of mA and time?
Linearity
Linearity test must be performed annually.
a dosimeter is used to measure radiation intensity which should be within ± __%
10
What is the same combination of kVp, mA and exposure time producing the same density and contrast every time called?
Reproducibility
should be within +-5%/ performed annualy
What tools can be used to test the focal spot?
Pinhole camera
Slit camera
star pattern
What are some ways to prolong tube life?
- avoid excessive exposure
- use a warm up procedure- 3 exposures, 5 sec apart, start low with large focal spot
- avoid unnecessary long exposure times
- use tube rating and cooling curve charts
- avoid high mA
What are 3 types of filtration?
inherent- from machine design i.e. glass tube
Added (aluminum between x ray and collimator)
COmpensation
Gonad shield face tube side is made of ___ and __ side is against patient
copper
aluminum
What is minimal acceptable filtration?
2.5mm Al (HVL) equivalent
What isan example of an x-ray and light beam alignment test?
If out of alignment +-__% of the SID additional anatomy is exposed.
9 penny test
2%
**Should be performed twice a year
WHat is the inverse square law?
Intensity of teh radiation is inversely proportional to the square of the distance
WHat is the anode heel effect?
Variation of x-ray intensity
- Anode less intense, cathode more
- can be used to balance body part density
- anode-cervical
- cathode-lumbar
What is best veiw to see z joints in C spine?
Lateral
What is best view to see IVF in C spine?
45 degree post. oblique
What is best view to see Z joints in T spine?
70 degree post. oblique
