Quality Control Flashcards
flat field uniformity
an analysis of the homogeneity of the detector field
MTF (modulation transfer function)
measure of image sharpness
CNR (contrast to noise ratio)
measure of the detectors ability to distinguish differences between an objects signal in the image and the image noise corruption
SNR (signal to noise ratio)
compares the level of the desired signal to the level of background noise. high SNR= better image
contrast resolution
ability of an imaging system to distinguish similarities of objects in an image
Purpose of phantom image quality
Assure image quality due to xray imaging system is at optimum level
Frequency of phantom image quality
Weekly for digital manufacturers
Equipment and procedure of phantom image quality
-24x30 cm compression paddle, ACR phantom and 4.0mm thick x 1.0 cm diameter acrylic disk
-make sure filter/kVp selection is done at a thickness of 4.5 cm
-mAs value is determined by a short pre-exposure in AEC mode
Performance criteria of phantom image quality
-mAs plus/minus 15%
-optical density 1.40 and higher
-density difference
-phantom must be scored with 2 fibers, 3 speck groups, and 2 masses
Correction action for phantom image quality
Must pass to do clinical images. Immediate action to fix errors or problems before any clinical images are obtained
Purpose of compression thickness indicator
Make sure the indicated thickness is within tolerance
Frequency of compression thickness indicator
Monthly
Equipment and procedure of compression thickness indicator
-2 1 inch tape rolls 4-6cm thick
-Phantom/spot paddle
-compress about 15 lbs
Performance criteria of compression thickness indicator
Within +/- 0.5 cm of accurate thickness is within tolerance
Corrective action of compression thickness indicator
Failure must be corrected within 30 days
Purpose of visual checklist
Assure that the mammographic xray system indicator lights, displays, and mechanical locks and detents are working properly and that system is mechanically safe
Frequency of visual checklist
Monthly (around same time), after service, and upon instillation
Equipment and procedure of visual checklist
Self assessment of testing and looking at all the parts listed to assess for good condition
Performance criteria of visual checklist
All parts of the machine and performance of machine is in good working order and passes/fails
Correction action of visual checklist
Critical items visualized must be fixed before clinical use, but less critical item fixed within 30 days
What are the critical items in the visual checklist?
-cleaning solution
-all locks work correctly
-paddles and face shields have no cracks
-breast support no cracks or defects
-CR must hold and lock cassettes
-CR IP free of cracks and latches work properly
-CR IP should load into CR reader smooth
Purpose of acquisition and radiologist workstation monitors
Ensure free of any marks that can interfere with clinical information, make sure monitors are calibrated, and meet manufacturers specification
Frequency of acquisition and radiologist workstation monitors
Monthly
Equipment and procedure of acquisition and radiologist workstation monitors
Cleaning lint free cloth and possible monitor cleaning solution and monitor manufacturer automated test
Performance criteria of acquisition and radiologist workstation monitors
SMPTE test pattern
Correction action of acquisition and radiologist workstation monitors
Problems need to be fixed within 30 days, more severe defects problems need to be fixed before any clinical images are performed
Purpose of acquisition and radiologist workstation monitors; monitor cleanliness
Ensure viewing conditions for the radiologist are to the full potential without degrading the images on the monitor
Frequency of acquisition and radiologist workstation monitors; monitor cleanliness
Once a day or when images are going to be read
Equipment and procedure of acquisition and radiologist workstation monitors; monitor cleanliness
-Cleaning agents that do not attack the surface, such as petroleum (mineral) spirits
-do not apply cleaning liquid directly to the monitor housing or screen (dampen cloth sparingly)
Mammographer tests acquisition and radiologist workstation monitors; monitor calibration and test pattern
-SMPTE is performed to check communication between the entities of the detector, printer and monitors. All have to communicate with each other
-task group from American Association of physicist in medicine (AAPM) created a TG-18 SMPTE pattern for a more advanced monitor testing
-TG-task group and 18 stands for the test patterns on the test to check the performance of the monitor’s calibration and visual inspection
Mammographer tests acquisition and radiologist workstation monitors; monitor extra information
-minimum luminance L-min of grayscale monitors @least 250 cd/m^2
-maximum luminance L-max of grayscale monitors @ no more than 420-450 cd/m^2
-reflected ambient light from the display surface should be included in luminance measurement
-min of 8 bit luminance resolution (bit depth) is required
-two monitor portrait set up
-GSDP: gray scale display function
Purpose of repeat analysis test
To determine the number and cause of repeated digital mammograms. Analysis of this data can help identify ways to improve system efficiency and reduce digital retakes and pt exposure
Frequency of repeat analysis test
Performed as much as needed, but needs to have 250 exams or equals a 1000 images
Equipment used for repeat analysis test
Machine computer software and calculator
Performance criteria of repeat analysis test
Is from one quarter to the next, the repeat rate % cannot change more than 2%. If so, must be documented why
Corrective action of repeat analysis test
30 days to correct problems with the department/tech such as remedial positioning, compression, quality education with counseling
Mammographer tests viewing conditions
-each room has a data form that is filled out by the medical physicist for the room configuration
-The medical physicist looks at the normal value of the ambient light in the room and measures it.
-if changes are made in the room, such a small lamp, new doors, room, curtains, blinds
Mammographer tests viewing conditions part 2
-ambient lights should not be turned off completely, nor turned up completely
-20 lux is generally sufficient and is the recommendation for low, 45 to 50 lux is maximum in reading room
Mammographer tests viewing conditions part 3
-Clean view boxes weekly
-general radiography view box luminance level 1,500 candela (nit) so half as strong as mammography
-mammography view box luminance level 3,000 candela (nit)
-change bulbs every 18-24 months
-bulbs increase in brightness about 10% in 2,000 hours. Replace all bulbs
Purpose of compression force test
-assure that the mammography system can provide adequate compression and power driven and manual mode and that the equipment does not allow too much compression to be applied Damaging patient’s breast tissue. Test the mechanism of the equipment.
Frequency of compression force test
-initial installation of machine
-every 6 months/semiannually
Equipment of compression force test
-Analog bathroom scale or dedicated physicist measurement scale
-towels to help to prevent scratches on equipment
Performance criteria of compression force test
-minimum measure of 25lbs and maximum measurement of 45lbs of pressure
Corrective action of compress force test
Source of the problem shall be identified and corrective action shall be taken before any clinical use
Purpose of manufacturer detector calibration
Assure that the system is calibrated properly and to erase artifacts and errors
Frequency of manufacturer detector calibration
Once a week for majority of manufacturers
Equipment of manufacturer detector calibration
Flat field phantom 4 cm thick uniform attenuation block of acrylic large enough to cover FOV
Performance criteria of manufacturer detector calibration
Make multiple exposures with each filter and standard and magnification modes and pass calibration checks
Corrective action of manufacturer detector calibration
If there is any failures must correct errors before any clinical images are performed
