1. QA in digital mammography: local activities and remote control H. Bosmans et al.

2. Belgium, 1996 Role of radiographers in QC minimal Enthusiasm of radiologists for QC: minimal No physicists working in X-ray imaging EC-guided screening made the difference 2

3. Recall film-screen-mammography… 3

4. 4

5. Constancy in film-screen mammography AEC: long term reproducibility AEC: object thickness and tube voltage compensation sensitometry: base and fog sensitometry: speed Sensitometry: Contrast & Gradient Imge quality: artefacts Image quality: spatial resolution, reference ROI Image quality: threshold contrast visibility 5

6. Centrally supervised performance tests 6

7. 7

8. 8

9. Digital imaging: 10th birthday It is another world, with other challenges We stayed with centrally supervised QC – Long term reproducibility – Detector homogeneity – Uncorrected defective DELs (DR) – Display & printer: Geometrical distortion (CRT) – Display & printer: Contrast visibility – Display & printer: Displaying artefacts 9

10. Data from DICOM header & global score From 2 ‘FOR PROCESSING’ flood images: DICOM header is scrutinized for kV, mAs, anode/filter, detector temperature, detector ID, thickness & compr force, MGD, detector calibration date, … Follow up in time Comparison between DICOM headers possible Limiting values set 10

11. Screenshot of our platform Automated constancy check in digital mammography: implementation and first results of a multi-center study J. Jacobs, K. Lemmens, F. Shannoun, G. Marchal and H. Bosmans, RSNA 2007 11

12. 12 Centrally supervised performance tests

13. 13 Data from DICOM header & global score

14. Data from the images From 2 ‘FOR PROCESSIING’ flood images: In homogenous segment: Noise power spectrum (1D, radial or 2D NPS) In reference ROI: Pixel value, SNR, st dev, variance Global image analysis: Thumbnail images of PV, SNR and variance; color coded if %-value Automatic artefact detection & pixel value copying 14

15. Example: Siemens system 15

16. »Mean PV; SNR; Std. Dev. »calculate values from small ROIs 2 mm * 100 µm  20 x 20px (GE DR) * 70 µm  28 x 28px (Siemens DR, Hologic DR) * 50 µm  40 x 40px (Fuji CR, Agfa CR) Mean PV; SNR; Std. Dev.; Variance; Min PV; Max PV; Median PV; Kurtosis; Skewness  THUMBNAILS Data from the images

17. 17 Data from the images

18. Type 1 DR: find out the service technician came along

19. Type 1

20. Scanning system (Philips Microdose) : normal situation 20 Type 2

21. GE system: normal situation, be happy 21

22. Type 2 22

23. Type 2 23

24. CR system: Scan line artefact 24 Mean pixel valueSNRDeviation SNR Type 3

25. 25

26. Type 3 26

27. CR: inhomogeneities 27 Type 4

28. 28

29. Agfa DM1000 DR Type 4

30. Latest example: artefact in the Ag filter Acquisition with 4cm of PMMA Acquisition with 7cm of PMMA, using Ag filter 30

31. DR: calibration too quickly after a patient scan (ghost) 31 Type 5

32. A suboptimal start…. 32 Type 5

33. DR: Ghost artefact & small field used at calibration 33 Type 5

35. Calibration phantom artefact Calibration needs 4 x rotation / flipping of phantom Type 5

36. 36 Type 5: latest example

37. Suggestions for improved mammo DQC CR: include all CR cassettes systematically in the DQC procedure CR: Enforce completely filled in DICOM headers CR&DR: Include all clinically used anode/filter combinations in the DQC procedure CR&DR: Work with NPS data, using averaging Apply big data analysis techniques Include QC (quality and dose) of the clinical image Extra analysis of local variance ‘variations’ Unchanged: 2 homogenous acquisitions each day, with phantom rotated over 180° !!!! 37

38. Daily QC could help prioritize the work! (IWDM 2010, K. Michielsen) Hypothesis: “systems that show little or no deviation during DQC show basically unchanged results in the half-yearly quality control” For 50 systems of 6 vendors (CR and DR) 129 events: 2 half yearly tests and DQC 74 events: 2 half yearly tests and DQC and same CDMAM phantom Data: the mean glandular dose (MGD) and signal- difference to noise ratio (SDNR) for 2, 3, 4, 5, 6 and 7 cm of PMMA and small aluminum disk of 0.2 mm; 38

39. Declared unchanged if both SDNR & MGD did not change by more than 10% A system was declared as unchanged between two half- yearly QC tests if the contrast threshold did not increase by more than 15%. The DQC results were declared as ‘unchanged’ between these two points if the following criteria were met: – no change in anode/filter combination, – a maximum change of the average nominal kVp of 1.0, – less than 5% change in SNR, – less than 10% change in mAs – no change of detector ID. 39

40. 40

41. Part 2 41

42. Daily QC of monitors Obligation To be done with a variable pattern 42

43. 12345 43 MoniQA - pattern J. Jacobs, J Kotre, …, Med Phys. 2007 Jul;34(7):2744-58

44. Luminance check Geometric check Resolution check General artefacts

45. 45

46. 46

47. 47

48. 48

49. It can all be poor.. Yet we don’t see deviations in half yearly test. Is it a reading test for operators? 49

50. Results from data analysis 50

51. Mean score of all monitors: 51

52. Half yearly tests and daily QC tests are hardly correlating. ρ(652) = 0.107, p < 0.01. These tests may be testing other aspects of the imaging chain. 52

53. Suggestions for improved monitor DQC Make a very simple daily QC test Keep present test on weekly basis – Not acceptable in euref protocol – Therefore not acceptable for application in Belgium 53

54. Conclusion It is possible to organize quality Quality control is not necessarily very time consuming !

55. Acknowledgement The Leuven QA team & all our students The Leuven mammography and LUCK J Jacobs, Qaelum NV (www.qaelum.com) The OPTIMAM project The EUREF team