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CHAPTER 17

CHAPTER 17. Quality Assurance for Full Field Digital Mammography. MAMMOGRAPHY QUALITY STANDARDS ACT ( MQSA ). Designed as guide during reign of film/screen mammography Basic requirements remain unchanged for FFDM No set standards for FFDM

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CHAPTER 17

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  1. CHAPTER 17 Quality Assurance for Full Field Digital Mammography

  2. MAMMOGRAPHY QUALITY STANDARDS ACT (MQSA) • Designed as guide during reign of film/screen mammography • Basic requirements remain unchanged for FFDM • No set standards for FFDM • FDA cedes standard testing must comply with the manufacturers’ recommendations for each unit • Each manufacturer has set testing protocols and schedules for their own equipment • Still need to conform to MQSA regulations

  3. TEST SCHEDULES

  4. TEST SCHEDULES

  5. FFDM TESTING • Secondary erasure of imaging plates (computed radiography only) • Image converted to electronic signal, then image erased

  6. FFDM TESTING • Signal-to-noise ratio • Ratio of signal power to noise power corrupting the signal • Can affect image quality • The higher the signal compared to noise, the better the image

  7. FFDM TESTING • Modulation Transfer Function • Also known as spatial frequency response • Measure of transfer of contrast from subject to image • High spatial frequencies correspond to fine image detail • Only performed on units that use indirect conversion digital detectors

  8. FFDM TESTING • Automatic Optimization of Parameters Mode • Checks system to be sure unit chooses correct technique for each setting • Test using 3 thicknesses of acrylic block using predetermined compression force for each exposure • Each manufacturer has different settings; provide same results • Not all manufacturers require testing by technologist

  9. FFDM TESTING • Uniformity/Artifacts/Flat Field/Interplate Consistency • Images must be uniform in intensity and free of artifacts • Uniformity testing reveals and maps areas of detector no longer operating optimally • Artifacts have many sources • Recommended thickness of block varies between manufacturers

  10. FFDM TESTING

  11. FFDM TESTING

  12. FFDM TESTING • Dead pixels • Consistent black or white spot seen on all images • Calibration procedures for location and removing usually performed by manufacturers’ service; can be performed remotely

  13. FFDM TESTING

  14. FFDM TESTING

  15. FFDM TESTING • Ghosting • Outlines of previous mammogram images • Often seen on flat-field test • Recommend testing by physicist if suspected

  16. FFDM TESTING

  17. FFDM TESTING • Calibration • More a housekeeping chore • Keep images consistent • Weekly program • Unit resets self • Important to perform at correct temperature

  18. FFDM TESTING • Softcopy display: monitors and workstations • Monitors must remain consistent and provide adequate brightness and contrast • Each manufacturer has proprietary workstations • Some facilities prefer workstations from different vendor (ie, PACS vendor) • Acceptable as long as meet FDA requirements and FFDM and PACS are compatible • Use SMPTE test pattern

  19. FFDM TESTING

  20. FFDM TESTING • Compression thickness

  21. FFDM TESTING • Laser printers • Printer uniformity • DICOM Printer Quality Control: SMPTE (Hologic)

  22. TESTS COMMON TO BOTH F/S AND FFDM • All testing required by MQSA • Process of testing will vary by manufacturer • Standards set by manufacturer may be more stringent than MQSA requirement

  23. TESTS COMMON TO BOTH F/S AND FFDM • Phantom Imaging • Compression Force • Repeat/Reject Analysis • Visual Check • Viewbox and Viewing Conditions • Physicist Survey

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