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QC/QA
| Question | Answer |
|---|---|
| quality assurance involves | people |
| repeat anaylsis | techs side/why things went wrong |
| accuracy | radiologist side/diagnostic performance evaluation |
| sensitivity | ability to detect disease |
| what is the most common cause for repeat imaging | positioning errors |
| casual repeat rate equation | # of repeats for specific cause/total # of repeats (multiply by 100) |
| total repeat rate equation | # of repeats/total # of views taken (multiply by 100) |
| total repeat rate for department or mammo | 3-5% for regular department and less than 2% for mammo |
| Performance measurement: 1) true positive 2) false positive 3) true negative 4) false negative | 1) radiologist diagnosis disease 2) RAD gives positive diagnosis but pt does not have disease 3) RAD reads exam as negative and additional exams confirm 4) RAD missed a diagnosis |
| what is image retention | previous image is not completely erased (lead marker from first image shows on second image) |
| dropped/dead pixels | caused by monitor artifact |
| digital receptor sensitivity | how sensitive detector is to picking up small artifact (collar on shirt showing, folded sheet, etc) |
| backscatter | scatter hits a device and goes back to detector |
| corduroy artifcat | processing error- AMA reading rate not matching |
| tiling | room temp changes/affects callibration |
| double exposure | (sharper than ghosting) exposes anatomy on top of anatomy just exposed |
| honeycomb | detector is upside down |
| what are the three parts of QC? | visual inspection, environmental inspection, performance testing |
| visual inspections | should happen daily (control panel, overhead tube crane, table,etc) lead aprons should be checked when new then every 6 months |
| SDM meaning | Calculate percentage- Solving Dumb Math( Subtract the difference, Divide by the lesser, Multiply by 100) |
| what is exposure (mA) linearity ,its acceptable range, how often it is checked | accuracy of Ma and exposure; + or - 10% of adjacent station, LEAST RELIABLE TECH FACTOR, checked annualy |
| exposure reproducibility, acceptable range, how often checked | repeat same overall tech setting and achieve same results, done with 10 exposure, + or - 5% annualy |
| filtration/half value layer, range, checked | thickness of absorber material required to reduce intensity of beam to half its original value, MOST accurate measurement of beam penetration, MOST important, checked annual |
| kVp acuracy, range, checked when | done by physicist annually, + or - 5% |
| timer accuracy, range, checked when | physicist checks annually; is exposure time accurate/too long/too short? ; + or - 5% |
| beam aligment | checks vertical beam alignment of CR, SEMI-ANNUAL, + or - 2 degrees of vertical; rough handling and age cause misalignment of beam |
| collimator acuracy | check projected xray field vs actual field; penny test; SEMI-ANNUAL, + or - 2% of SID |
| distance | simply measuring SID and seeing if indicator is the same; + or - 2% of SID |
| focal spot size/condition | annual; + or - 50% of stated size of focal spot |
| AEC | looking for repeatability (5 exposures); + or - same unit, annual |
| intrinsic (dark noise) | geared more towards CR ; erase CR detector EVERY 48 hours |
| plate/field uniformity | LONG SID(anode heel is minimized use 72 inches); can be repeated daily or semi-annually ; + or - 10% |
| minification gain | input diameter squared / output diameter squared |
| flux gain (flow) | acceleration of electrons increases kinetic energy so when they hit the output phosphor more light is released |
| brightness gain | minification gain X flux gain |
| how is an image magnified? | focal point moves closer to photocathode resulting in the lose of peripheral |
| what is Air Kerma 'AKA' DAP meters? | monitors radiation passing through air, required on all machines |
| exposure rate | shall NOT exceed 10R/min (checked with dosimeter) high KVP and low mA is desired |
| how far does a c-arm need to be kept from patients skin? | 12 inches |
| how far does a standard stationary machine need to be kept from pts skin? | at least 15 inches |
| Collimator accuracy | shutters should be visible on monitor ; field should be withing 4% of SID |
| when does the cumulative timer sound? | every 5 minutes |
| who/what is primary displace devices ued for? | Radiologist use for interpenetration and diagnosis |
| who/what is secondary display devices used for? | Technologists PACs, used for everything but interpretation and diagnosis |
| what is interpolation? | mapping of image of one matrix size to a display of another size (small artifacts to a tech can look massive to a radiologist monitor) |
| what is aspect ratio? | ratio of width of display to the height of display |
| what is refresh rate? | how many times each second the monitor rewrites the image on the display |
| how often is the front screen cleaned? | monthly, it is commonly neglected |
| how big are dead pixels? | period in 12 font |
| how are dead pixels tested and what do they look like? | tested with black background and appear as a white spot |
| how are stuck pixels tested and what do they look llke? | tested with white background and appear as a black dot |
Created by:
ashhbre
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