Quality assurance

11 Quality assurance

Definition of quality assurance

	A method of testing digital imaging systems to ensure consistency of results within the computer network. (See also Appendix F: Quality Assurance and Tests.)
Equipment Required	• 1 mm copper filter • 1 straight edge metal strip • Leeds Tor 18 test tool • Leeds test object N3 • Leeds test object GS2 • Leeds test object T010

Test for low contrast sensitivity and resolution

Equipment Required	• Leeds Tor 18 test object • 1 mm copper filter • 24 × 30 cm cassette • X-ray tube
Equipment Tested	• Viewing stations • Laser printers
Testing Frequency	Weekly
Testing Method	• Test tool is placed in the centre of the cassette • X-ray tube centred to the cassette • Collimators are fully opened • Copper filter placed next to the tube • Expose plate using:

100 cm, 55 kVp, 45 mAs

• Process the film

Results

• View the image on the main workstation monitor

• The monitor should not be adjusted

• 18 discs around the inside edge of the circular image should be seen

This gives the grey scale of contrast

• The line pairs in the middle of the pattern are counted

Note if the lines appear to merge they are not counted

This gives the resolution of the system

• The test is repeated on the other monitors by the same person

• The test is sent to the laser printers and evaluated by the same person

Evaluation

• Using the table for testing fluoroscopic equipment

• Acceptable results are:

16 discs seen, 14 line pairs

2.24 spatial frequency cycles per millimetre

A difference of 3 or more discs or 3 or more line pairs indicates a problem, but note that a difference of one could be due to the eyesight of the person doing the test

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