QA alternative tests mechanical safety and collimation test tool Flashcards
what to check for?
- check for physical damage
- ensure interlocks work
- check automatic collimator
- check safety devices
- check radiation leakage
- wiring
two major test tools to test collimation
- collimator test tool
- LBD alignment tool
what is the collimator test tool
- copper plate with radiopaque markings
- measures light field and radiation field congruency
what is the LBD alignment tool
resign with radiopaque ball-bearings/ markers
- checks if the x ray beam is exactly perpendicular to image receptor
what happens in the LBD central ray is misaligned
image distortion can occur
what is the aim of the collimation and LBD alignment test tool
aim is to minimise unnecessary exposure by checking the accuracy of LBD
what is collimator measured in
cm
what is LBD alignment measured in
degrees (%)
the frequency of checking collimator and LBD alignment
1-2 months
- checked by radiography or MPE
how does LBD alignment work
- the longitudinal body dimension is the vertical axis of the body and alignment involves orienting the axis in relation to the XR beam, detector plate/ imaging equipment
- central ray should be perpendicular to LBD for optimal imaging
how to set up for the collimator test
- tube and table level
- collimator test tool placed on image receptor
- ensure the dot on the lower left-hand side of the tool is placed on the anode side to help with orientation
the set up for the LBD collimator test
- same set up for collimator test
- place LBD alignment test tool directly in centre of collimator test tool and collimate rectangular area of test tool
- exposure 50kVp and 4mAs on fine focus
- repeat on broad focus
how much is acceptable to be exposed when testing for collimation
1cm within or outside
