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RADT 412 QC
Quality Control
Question | Answer |
---|---|
QC deals with _______ | EQUIPMENT Routine checks reduces need for maintenance |
QA deals with _______ | PEOPLE How techs are performing |
CQI (Continuous Quality Improvement) | Combination of both QA & QC; ensures quality patient care is being given! (Regulated by government) |
3 parts of QC Program | *Checks overall quality of equipment 1) Visual inspection 2) Environmental Inspection 3) Performance Testing |
Visual Inspections should happen ______ | DAILY |
Visual Inspection checks (list 5) | 1. Control panel 2. Overhead tube crane (no exposed wires, broken ties, etc) 3. Table 4. Lead aprons/shields (check aprons when new then every 6 months) 5. Ancillary equipment: sponges, calipers, filters, grids, etc. |
Environmental Inspections checks ______ | High tension cables (visible wires for fraying, discoloration, sparking) Room temperature (equipment can get too hot) |
Performance testing levels include | - Acceptance testing - Baseline performance parameters: est. baseline 1 or 2 months of use - Preventative maintenance & Routine testing: service engineer/medical physicist; checks after major component replaced - Daily, weekly, monthly checks |
Exposure (mA) Linearity | Definition: accuracy of mA station relative to another used ANNUAL + or - 10% of adjacent station *Least reliable technique factor |
Exposure Reproducibility | Definition: ability of equipment to repeat the same overall technique settings to get same results in exposure + or - 5% ANNUAL |
filtration & Half Value Layer (HVL) | Definition: thickness of absorber material required to reduce the intensity of the xray beam to 1/2 its original value ANNUAL |
HVL is the most _________ and the most ________ quality | accurate measurement of beam penetration; important |
High HVL = _________ penetrating beam | HIGH |
kVp Accuracy | use kVp meter, ion chambers/photodiodes ANNUAL + or - 5% |
Timer Accuracy | Measures accuracy of exposure timer selected ANNUAL + or - 5% |
Beam Alignment | Checks the crosshairs of collimator light using metal screw & BB SEMI-ANNUAL + or - 2 degrees off vertical |
Collimator Accuracy | Checks projected xray field vs. the actual xray field (penny test) SEMI-ANNUAL + or - 2% of SID (0.8") |
Distance | Measure SID to see if indicator reads the same SEMI-ANNUAL + or - 2% of SID |
Focal Spot Size & Condition | Checks for last resolved line pair (LP/mm) ANNUALLY + or - 50% of stated size of focal spot |
AEC | Looking for repeatability; making sure back up timer shuts off when it should ANNUAL + or - 10% same unit |
IR calibration is done ______ | daily |
IR maintenance is done _________ | semi-annual |
IR tests done for (list 4) | Intrinsic (dark noise) Erasure thoroughness Plate/ Field Uniformity Spatial Resolution |
Intrinsic (dark noise) comes from ___________ ___________ so we must erase CR detectors every _________ | background radiation; 48 hours |
Erasure thoroughness is known as | Ghosting or Image Lag |
Determine ghosting with | 2 exposures (1 with high attenuator object 1 without object) |
Plate / Field Uniformity | Use long SID (don't change contrast) and check similarity of contrast boxes DAILY or SEMI-ANNUALLY |
Spatial Resolution | Uses wire mesh, line pair took, or digital test test should look uniform in shade and crosses |
KNOW TABLE 37.1 | :) so sorry |
3 main parts of the fluoro unit | 1. x-ray tube 2. generator 3. image intensifier (I.I.) |
Image intensifier parts | Glass envelope (vacuum), input phosphor, photocathode, electrostatic focusing lenses, anode, output screen/phosphor |
Minification Gain | input diameter squared / output diameter squared |
Flux Gain "Flow" | Acceleration of electrons increases kinetic energy so more light is released |
Brightness Gain | minification gain x flux gain |
Image is magnified in an I.I by _________ | moving the focal point closer to input phosphor |
Unique feature of fluoroscopy = meter that detects _______ | Air Kerma/ DAP meters or the radiation interactions occurring in the air when x-rays sent toward patient |
2 examples of phantom tests | Spatial resolution & uniformity AND contrast linearity |
Exposure rate (fluoro) should not exceed _________ | 100 mGy/min or 10R/min |
_______ kVp and ______ mA is desired | High; low |
Source-to-skin distance (SSD) needs to be ________ for mobile c-arm | 12 inches |
SSD needs to be ______ for standard stationary/fixed | 15 inches |
Collimator Accuracy (fluoro) | shutters should be visible on monitor field within 4% of SID |
Visible/Audible Monitors for fluoro exposure time | Cumulative timer: every 5 min Visible indicator: beam on light |
Automatic Brightness Systems (ABS) are used to _________ | maintain a constant image brightness |
The exposure switch is a _________ switch, meaning if exposure button is released, then it will stop | Deadman switch aka if you die, the exposure will stop x.x |
Veiling Glare | light reflected "glare" shows up white |
Pincushion distortion | input phosphor curve compared to flat output phosphor shape creates distortion around periphery |
Barrel distortion | opposite to pincushion (looks like barrel) |
Vignette | lateral borders are darker |
S-distortion | strong magnetic field creating s-shape distortion |
Protective Apparel QC checked | ANNUALLY Includes lead gloves, aprons, and protective curtains |
Primary Display Devices are used by _________ | radiologists! Interpretation & diagnosis larger matrix and smaller pixel size |
Secondary Display Devices are used by ______ | technologists/PACS used for everything else |
Interpolation definition | mapping of image of one matrix to a display of another size; ex. small artifacts to a tech can look HUGE to a radiologist monitor |
Aspect ratio definition | ratio of width to height of display |
Refresh rate definition | how many times each second the monitor rewrites the image on the display |
2 main types of electronic display devices | 1. Liquid Crystal Diodes (LCD) displays 2. Light emitting diodes (LED) displays |
Disadvantages of LCDs | viewing angle is best head on (glare), lack of true black color, time/temperature dependency for brightness |
LEDs are | NOT used in radiologic imaging |
QC of electronic display devices | clean front screen MONTHLY |
Luminance definition | intensity of light emitted |
Resolution definition | ability to differentiate between things |
Grayscale standard display function (GSDF) | use photometer to check consistency/intensity of gray scale appearance on screen regardless of monitor device |
Dead Pixels appear as _____ | a dot! 12 pt font will appear as a white spot on black background |
Stuck pixels appear as ____ | a black dot on a white background it is any signal not refreshed or "stuck" from previous image |
QC benefits (list them) | Patient Safety (#1 benefit! All about the pt) Reduced radiation Exposure Efficacy of Patient care Departmental efficiency Consistent image quality Cost-effectiveness |