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QC & QA Radiography
Covering Quality Control and Quality Assurance for Diagnostic Imaging
| Question | Answer |
|---|---|
| The invisible image on an unprocessed radiograph formed during exposure of the receptor | latent image |
| Marks, spurious objects, motion, or unwanted optical density on the image that do not represent the anatomic structure | artifact |
| A reduction in image contrast resulting from x-ray exposure of the detector by other than the useful beam; usually occurs during storage | radiation fog |
| The ability to image small, high contrast objects | spatial resolution |
| Appears on a radiograph as a speckled background; occurs most often when high-kVp and low mAs techniques are used in cases of high DQE | image noise/quantum mottle |
| The visible light emitted | luminance |
| visible light only emitted while x-ray beam is on | fluorescence |
| another name for afterglow; undesirable continued emission of light after exposure of the phosphor terminates | phosphorescence |
| Causes of image fog | Heat, radiation |
| The splotchy appearance of a radiograph that has been exposed by a limited number of x-ray photons | quantum mottle |
| An image artifact produced during processing of the image | processing artifact |
| examples of exposure artifact | foreign objects, double exposure, grid cutoff, patient motion |
| a type of processing artifact | histogram analysis error, bad DELS |
| concerns people; Monitoring of the patient, technologist, radiologist and interpretation of images | quality assurance |
| concerns equipment; That part of quality assurance that deals with the performance of imaging systems | quality control |
| minimum amount of filtration required for general purpose radiographic units | 2.5 mm Al |
| the follow up of patient reports to make sure the diagnosis was correct; looking at consistency amongst radiologists' readings and ultimate patient diagnosis | outcome analysis/outcome assessment |
| continuous quality improvement - an ongoing process that involves QA and QC; never ends | CQI |
| If 50 mAs produces x-ray intensity of 100 mR then an exposure at 100 mAs should produce an x-ray intensity of 200 mR - this is an example of what? May also be expressed as EI number tracking in a linear fashion as a function of increasing exposure | exposure linearity |
| If 50 mA @ 1 sec produces 50 mAs (100 mR output intensity), then 100 mA @ 0.5 sec should also yield 50 mAs with a 100 mR intensity | reciprocity |
| Three steps of quality control for radiographic equipment | acceptance testing; routine testing; preventative maintenance |
| Reason why TJC (the Joint Commission) QA program is used in hospitals? | higher patient care, accreditation, reimbursement |
| three people on the diagnostic imaging QC team | supervising radiologist, QC technologist, medical physicist |
| Why are proper x-ray beam alignment and collimation important? | To ensure that only the anatomy of interest is imaged. |
| kVp should be within what range | +/-5% (most states); +/-10% federal |
| three QC tools to measure focal-spot size? | Pinhole camera, star pattern, slit camera |
| What is the permitted variation of radiographic reproducibility? | +/- 5% |
| What test is performed to check for geometric distortion/spatial accuracy in digital? | wire mesh |
| How often should lead apparel be checked for integrity? | annually |
| how do we check kV accuracy? | dedicated kV meter |
| Unit of luminance on a viewbox or monitor | candela per meter squared or lumens |
| What is the importance of preventative maintenance and a good QC program on a processor? | Preventive maintenance reduces the probability of unscheduled maintenance |
| What is the permitted radiographic collimator field misalignment? | 2% of the SID |
| Also known as the true negative fraction – ability to be given a negative diagnosis when no disease is present; How well are we able to rule out or eliminate the possibility of the disease not being there; has a low false positive rate | specificity |
| Also referred to as the true positive fraction; indicates the likelihood of obtaining a positive diagnosis in a patient with the disease (ability to detect disease); How well can the exams pick things up; has a low false negative rate | sensitivity |
| True positive plus the true negative divided by the total number of exams; How accurate are the exams; How many true positive and true negatives do we get when we look at all exams – how many are read correctly? | accuracy |
| If a radiologist determines something on a film to be a disease and further lab tests confirm it is that disease | true positive |
| If a radiologist dictates the presence of a disease on an image and further tests determine that a disease (or the disease dictated) is not present | false positive |
| If a radiologist dictates no disease present and further testing results in demonstrating no disease present | true negative |
| If a radiologist dictates no disease present and further testing determines that a disease is present | false negative |
| dark bands at the interfaces of structures have differing brightness levels (contrast and surrounding tissue, hardware) | halo artifact |
| can result from unerased IR or severely over exposed IR that didn’t get completely cleared | Phantom image artifact /ghosting |
| Poor collimation leads to this error in CR and DR image processing | histogram analysis |
| scratches or dust/dirt on the PSP plate will appear ____ on the image | white |
| dust in the path of the laser beam in the CR reader may cause this type of artifact | line |
| When an erasure lamp is not working properly in PSP imaging, this artifact may result | phantom image/ghosting |
| When grid lines are parallel to the direction of laser beam travel in a CR reader, this artifact can result | Moire or Aliasing |
| how often should image receptors be cleaned as part of a QC program in digital imaging? | weekly |
| how often should CR cassettes be erased? | daily |
| who is responsible for acceptance testing of radiologic equipment? | medical physicist |
| who is responsible for routine maintenance of radiologic equipment? | technologist |
| who is responsible for preventative maintenance/system adjustments of radiologic equipment? | vendor service personnel |
| skin exposure rate that should not be exceeded during fluoroscopy with ABS | 10R/min |
| minimum SSD for mobile fluoroscopy units | 12" |
| minimum SSD for fixed fluoroscopy units | 15" |
| matrix is composed of _____ | pixels |
| TFT arrays are composed of _____ | DELS |
| white lines of this tool can be used to check for image distortion on a display screen | SMPTE test pattern |
| display monitor: has a greater viewing angle | CRT |
| display monitor: has better contrast resolution | LCD |
| light being reflected from the window of output phosphor that decreases contrast, happens when you are moving II over body parts of differing densities. (chest to abd) | Veiling or flare |
| projection of image from a curved surface (such as the input phosphor) onto a flat surface (output phosphor) Distortion is greater on the lateral side of image. The magnification increased towards the middle of the image | Pincushion distortion |
| opposite of pincushion, but the mag is higher in the middle | Barrel distortion |
| decrease in image brightness at the lateral portions of the image, due to a combo of pincushion and the coupling of the TV camera | Vignetting |
| image is warped in an s shape, caused by a magnetic field interfering with electrons as they flow across the II | S distortion |
| steps of CR image creation | radiation strikes IP, electrons of phosphors raised and trapped in higher energy state, IP exposed to laser light to release electrons, PMT detects light emission of electrons as they return to their stable state, IP exposed to intense white light |
| detector quantum efficiency | ability of a screen to absorb x-rays |
| conversion efficiency | ability to give off light in proportion to amount of radiation absorbed |
| type 1 histogram | chest or extremities; will have direct exposure spike at far right side of histogram |
| type 2 histogram | abdomen; anatomy fills the IR |
| type 3 histogram | contrast, prosthesis, or other high attenuating material expected in the region of interest (ROI) |
| left side of histogram represents this type of anatomy | radiopaque |
| right side of histogram represents this type of anatomy | radiolucent |
| where is EI measured from? | half way point between S1 and S2 of a histogram |
| scatter radiation has what effect on histogram production? | widens the histogram |
| used to evaluate collimation/beam restriction and central ray alignment | 8 or 9 penny test, collimator test tool |
| used to evaluate and check voltage waveform | oscilloscope |
| Used to check/evaluate the timer | digital timer or electronic ion chamber |
| used to chek luminance of a monitor | photometer |
| in this fluoroscopic mode, only a portion of the input phosphor is being used which results in increased patient dose due to mA adjustments to maintain brightness | image magnification |
| in this fluoroscopy mode, the entire input phosphor is being used resulting in decreased patient dose | image minification |
| visible image | manifest image |
| the progressive increase in dose to patients as technologists rely on automatic rescaling to compensate for overexposure | dose creep |
| Individual DELs _______ be replaced when they fail | CANNOT |
| _____ and ______ can be adjusted for most digital images reducing the need for repeats and allowing optimal patient dose techniques to be utilized. | brightness, contrast |
| True or False: Electronic markers are acceptable to use in the event that a technologist's markers do not display within the final image | FALSE |
| Digital imaging software can compensate for some under and over exposures in the range of ______ under and _____% overexposure | 60,120 |
| Most common bit depth for digital imaging systems | 14 |
| TFT | thin film transistor |
| DEL | detector element |
| PSP | photostimulable phosphor |
| LUT | look up table |
| PMT | photomultiplier tube |
| ADC | analog to digital converter |
| IP | imaging plate |
| VOI | volume of interest |
| ROI | region of interest |
| DAP | dose area product |
| matrix size of typical technologist workstation | 1024x1280 to 1200x1600 |
| matrix size of typical radiologist workstation | 2048x2560 to 4096x6144(mammo) |
| another name for technologist workstation | secondary display or class II |
| another name for radiologist workstation | primary display or class I |
| test tool utilized for general monitor evaluation including spatial resolution, geometric distortion, and contrast resolution | SMPTE or TG18-QC |
| test tool for evaluating the effect of ambient lighting on viewing conditions for a monitor | TG18-AD |
| test tool for evaluating display luminance and visibility of contrast resolution compared with other monitors | TG18-CT |
| test tool for evaluating spatial lumninance response of the system requiring the use of a photometer to measure and ensure luminance values are greater than 171cd/m2 | TG18-LN |
| Besides the SMPTE or TG18-QC test pattern, this pattern can also be used to check for spatial resolution | TG18-CX |
| three levels of QC and system maintenance | routine, full inspection, system adjustment |
| QC test used to evaluate the ability of a system to completely remove previous exam data | erasure thoroughness |
| QC test to evaluate brightness across an image | uniformity/shading test |
| degree of angulation for the spatial resolution test pattern phantom to the laser scan or TFT detector array | 45 |
| three parts of a QC program on equipment | visual inspection, environmental inspection, performance testing |
| What organization released an advisory opinion statement on electronic cropping? | ASRT |
| Deviation Index level of +3.0 or greater means this | over 100% greater exposure of the target range |
| Deviation index level of -3.0 or greater means this | less than 50% exposure of the target range |
| disadvantages of an LCD monitor compared to a CRT monitor | No true black, Less viewing angle, brightness can diminish with room temperature extremes, |
| what is the permitted variance of the central ray | +/-1% of SID or 2 degrees |
| how do you check for a dead pixel on a display monitor | use a solid black background to look for a white dot |
| how do you check for a stuck pixel on a display monitor | use a solid white background to look for a black dot |
| AAPM standard for class 1 (primary) monitors used for diagnosis to "pass" inspection for defective pixels | 15 or fewer bad pixels across entire screen, 3 or fewer bad pixels within any circle of 1cm diameter, 3 or fewer bad adjacent pixels |
| common causes of x-ray field and collimation field misalignment | collimator gears/belts slipping & crooked mirrors |
Created by:
hschmuck1
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