In-Depth Overview: Quality Assurance in Mammography

1. CHAPTER 13 Quality Assurance in Film/Screen Mammography

2. PURPOSE OF QUALITY ASSURANCE … to attempt to improve and stabilize the entire process of patient care, to avoid, or at least minimize, issues that may occur

3. PURPOSE OF QUALITY ASSURANCE • Quality assurance • Quality images • Qualified reader • Excellent quality of equipment and supplies • Provide top-quality results to the patient and her physician • Quality control – highlight inconsistencies, diagnose problems, resolve quickly

4. HISTORY OF QA IN MAMMOGRAPHY • Before 1992, at discretion of each facility • 1987, effort to standardize by ACR • ACR MAP – included examination of equipment, films and processing, image quality, and facility personnel • 1992, ACR published guidelines • Updated several times with change in technology • SBBAP • BUAP • BICOE

5. MQSA AND FDA • Major breakthrough in standardizing the quality of mammography • FDA – all facilities must first be certified by FDA to perform mammograms • Approved accreditation bodies: ACR, SAR, SIA, STX • Annual inspections • Final regulations are national quality standards; based on MQSA of 1992 and MQSA Reauthorization of 1998

6. ESTABLISHING A QA PROGRAM Must address certain standards: • Equipment • Compatibility • Purchase specifications • Monitoring and maintenance • Standards for image quality • Technical evaluation procedures

7. ESTABLISHING A QA PROGRAM • Personnel • Assignment of responsibility • Training • Policy and corrective measures • Record keeping • Manuals • Communication channels • Review

8. DOCUMENTATION SCHEDULE

9. BI-RADS ASSESSMENT CATEGORIES • Category 0: Need additional imaging evaluation and/or prior mammogram • Category 1: Negative • Category 2: Benign finding(s) • Category 3: Benign finding – Initial short-interval follow-up suggested

10. BI-RADS ASSESSMENT CATEGORIES • Category 4: Suspicious abnormality – Biopsy should be considered • Category 5: Highly suggestive of malignancy – Appropriate action should be taken • Category 6: Known biopsy-proven malignancy– Appropriate action should be taken

11. COMPONENTS OF A QA PROGRAM • Standards of performance • Equipment testing • Documentation of personnel training and continuing education • Review of the facility’s quality

12. TESTING SCHEDULE

13. EQUIPMENT TESTING • Most time consuming • All QC tests performed by physicist and the technologist • Reviewed quarterly by radiologist • Some equipment requires more frequent testing • The larger the facility, the more time involved • Each test has a purpose

14. TECHNOLOGIST’S TESTS • Sensitometry • Darkroom cleanliness • Viewboxes • Phantom imaging • Visual checklist • Fixer retention • Repeat/reject analysis • Compression check • Screen/film contact • Darkroom integrity and fog test

15. SENSITOMETRY • Processor QC • Ensures that delicate chemical balance used for processing remains consistent

16. SENSITOMETRY

17. SENSITOMETRY

18. DARKROOM CLEANLINESS • Not mandatory “test” but should be performed and documented daily • Cleanliness will reduce artifacts • Use black lights to help identify problematic areas • Thoroughly clean darkroom weekly

19. VIEWBOXES • Clean weekly to remove smudges, dust, grease pencil marks, etc. • Test bulbs with light meter • Use same type of bulb throughout facility • Vacuum inside box to remove dust

20. PHANTOM IMAGING • The Phantom – square acrylic block with wax insert containing simulated masses, fibrils, and calcium specks of varying sizes, approximately 4.5 cm thick

21. PHANTOM IMAGING • Radiographic image obtained of phantom • Scored according to what is “seen” • The higher the scores of the phantom image, the better the imaging system • 4-mm thick disk included to determine density difference

22. PHANTOM IMAGING

23. PHANTOM IMAGING • Technique • Always use same cassette and photocell placement • Always use same technique used for patients • Document consistency of unit • Manufacturer service personnel can use data to determine problem

24. PHANTOM IMAGING • Analysis • As per MQSA, reading at center must be at least 1.20 OD • OD should not vary by more than ± 0.20 OD • Must achieve the minimum score established by facility’s accrediting body and the FDA • Compare readings with previous scores

25. VISUAL CHECKLIST • Indicator lights • Locks • Detents • Ensure mechanically stable • Properly working • Report any malfunctioning equipment immediately

26. FIXER RETENTION • Quantity of fixer indicates how long film will keep its image quality • Performed on clear or unexposed area of processed film • MQSA – no more than 5 µg/cm2 of fixer should remain • Ensure recommended rates are used

27. FIXER RETENTION

28. REPEAT/REJECT ANALYSIS • Evaluate the reason films are repeated or thrown out • Log number of rejected films by categories • Determine length of time • Can help to pinpoint problem areas in department • Once area of inefficiency is located, take steps to correct • May be equipment or personnel

29. COMPRESSION CHECK • Image QA test • Safety test • Check pressure applied to breast during compression

30. SCREEN/FILM CONTACT • Very critical in mammography • Obtain image of fine-mesh test-object

31. SCREEN/FILM CONTACT

32. DARKROOM INTEGRITY AND FOG TEST • Need to assure fogging not occurring from white light • Turn off all lights • Look for leaks in ceiling, around doors, seals around equipment • Personnel wearing clothing, jewelry, Band-Aids with luminescent or phosphorescent qualities • Often due to deteriorated safelight filter or position of safelight

33. PHYSICIST’S TESTS • Automatic Exposure Control Performance • Kilovolt peak Accuracy and Reproducibility • Focal Spot Condition • Beam Quality Assessment (Half-Value Layer) • AEC Reproducibility and Breast Entrance Air Kerma • Dosimetry (Average Glandular Dose) • X-ray Field/Light Field/Image Receptor/Compression Paddle Alignment • Uniformity of Screen Speed • System Artifacts • Radiation Output • Decompression

34. AUTOMATIC EXPOSURE CONTROL PERFORMANCE • Ensures exposures have consistently reproducible quality at varied breast thicknesses and kilovolt peaks • Determines percentage of density change between density control settings • Physicist takes a number of exposures using phantom material, compare OD

35. KILOVOLT PEAK, ACCURACY AND REPRODUCIBILITY • To determine if kilovolt peak indicated on unit is the kilovolt peak produced by the unit • Needs to be consistently reproducible • Kilovolt peak meter • Must be accurate within ±5% of set value • Cannot vary more than the standards set by MQSA

36. FOCAL SPOT CONDITION • Determined by obtaining a bar-pattern image on film/screen combination that is used clinically • Bar pattern placed in certain position relative to anode-cathode axis • Must meet specified standards set by MQSA

37. BEAM QUALITY ASSESSMENT (HALF-VALUE LAYER) • Determines beam quality • Must be adequate to minimize the dose of radiation given to the patient • Determined by making x-ray exposure with and without an attenuator in the path of x-ray beam • Each kilovolt peak measured must be ≥kVp/100

38. AEC REPRODUCIBILITY AND BREAST ENTRANCE AIR KERMA • Measures breast-entrance exposure or entrance skin exposure, in exposures taken with AEC on average patient • Represents amount of energy deposited per unit mass or air • Determines if unit consistently and reproducibly delivers the same dose over several exposures • Variations must measure less than 0.05

39. DOSIMETRY (AVERAGE GLANDULAR DOSE) • Calculation derived from measured HVL and breast-entrance exposure obtained from two preceding tests • Represents amount of energy absorbed by glandular tissue in breast of average size and tissue composition from single x-ray exposure • MQSA specifies may not exceed 3.0 mGy, 0.3 rad, or 300 mrad per exposure

40. X-RAY FIELD/LIGHT FIELD/IMAGE RECEPTOR/COMPRESSION PADDLE ALIGNMENT • Verifies: • That as much breast tissue as possible is shown on each patient’s films • That technologist can accurately determine location of radiation field • That the field of radiation is aligned with image receptor • That the patient does not receive unnecessary radiation exposure • Components must be aligned to each other • MSQA allows little tolerance in deviation of alignment

41. UNIFORMITY OF SCREEN SPEED • Ensures all screens in cassettes provide same amount of density to all images • Obtain identical exposures on all cassettes • Calculate density to determine optical density range • MQSA states optical density range cannot exceed 0.30 OD

42. SYSTEM ARTIFACTS • Use same cassettes as used for patients • Obtain 2 images of homogenous density • Feed films into processor, one length-wise, one width-wise • Analyze all films • Once it is determined that artifacts exist, identify cause and correct problem

43. RADIATION OUTPUT • Measurement of x-ray tube’s efficiency • Ensures unit produces consistent, homogenous, uniform beam and has enough energy to produce quality image • MQSA requires minimum output of 7.00 mGy per second (800 mR/sec) • Must be able to maintain the minimum output averaged during a 3-second long exposure

44. DECOMPRESSION • Mechanical safety check • Ensure automatic decompression device will engage after each exposure or when power is interrupted • Test to confirm override is operational • Confirm manual override is operational • Equipment without decompression system is not acceptable for obtaining patient examinations

45. RADIOLOGIST INVOLVEMENT • Not responsible for performing equipment testing • Responsible for reviewing QA program • Rely on technologists and physicists • Responsible for: • Reviewing Medical Outcomes Audit annually • Documenting dates and results of audit • Informing other radiologists in facility of results • Documenting follow-up to audit

46. MEDICAL OUTCOMES AUDIT

47. MEDICAL OUTCOMES AUDIT

48. MEDICAL OUTCOMES AUDIT

49. MEDICAL OUTCOMES AUDIT

50. MEDICAL OUTCOMES AUDIT