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

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

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

3. Recall film-screen-mammography…

5. Constancy in film-screenmammography • AEC: long termreproducibility • AEC: object thickness and tube voltage compensation • sensitometry: base and fog • sensitometry: speed • Sensitometry: Contrast & Gradient • Imgequality: artefacts • Image quality: spatial resolution, reference ROI • Image quality: thresholdcontrastvisibility

6. Centrallysupervised performance tests

7. Centrally supervised performance tests

9. Digital imaging: 10th birthday • It isanother world, withother challenges • Westayedwithcentrallysupervised QC • Long termreproducibility • Detector homogeneity • UncorrecteddefectiveDELs (DR) • UncorrecteddefectiveDELs (DR) • Display & printer: Geometricaldistortion (CRT) • Display & printer: Contrastvisibility • Display & printer: Displayingartefacts

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

11. Screenshot of ourplatform Automated constancy check in digital mammography: implementation and first results of a multi-center studyJ. Jacobs, K. Lemmens, F. Shannoun, G. Marchaland H. Bosmans, RSNA 2007

12. Centrally supervised performance tests

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; colorcoded if %-value • Automatic artefact detection & pixel value copying

15. Example: Siemens system

16. Data from the images • Mean PV; SNR; Std. Dev. • calculate values from small ROIs Mean PV; SNR; Std. Dev.; Variance; Min PV; Max PV; Median PV; Kurtosis; Skewness 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)  THUMBNAILS

17. Data from the images

18. Type 1 DR: find out the service techniciancamealong

19. Type 1

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

21. Type 2 GE system: normal situation, be happy

22. Type 2

23. Type 2

24. Type 3 • CR system: Scan line artefact Mean pixel value SNR Deviation SNR

25. Type 3

26. Type 3

27. Type 4 CR: inhomogeneities

28. Type 4

29. Type 4 Agfa DM1000 DR

30. Latestexample: artefact in the Ag filter • Acquisition with 4cm of PMMA • Acquisition with7cm of PMMA, using Ag filter

31. Type 5 DR: calibration tooquicklyafter a patient scan (ghost)

32. Type 5 • A suboptimalstart….

33. Type 5 DR: Ghost artefact & smallfieldused at calibration

34. Type 5

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

36. Type 5: latestexample

37. Suggestions for improvedmammo DQC • CR: include all CR cassettes systematically in the DQC procedure • CR: Enforcecompletelyfilled in DICOM headers • CR&DR: Include all clinicallyused anode/filtercombinations in the DQC procedure • CR&DR: Workwith NPS data, usingaveraging • Applybig data analysis techniques • Include QC (quality and dose) of the clinical image • Extra analysis of local variance ‘variations’ Unchanged: 2 homogenous acquisitions eachday, withphantomrotated over 180° !!!!

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;

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.

41. Part 2

42. Daily QC of monitors • Obligation • To bedonewith a variable pattern

43. MoniQA - pattern 1 2 3 4 5 J. Jacobs, J Kotre, … , Med Phys. 2007 Jul;34(7):2744-58 43

44. Resolution check General artefacts Geometric check Luminance check

49. It can all bepoor.. Yetwedon’tseedeviations in halfyearly test. Is it a readingtest for operators?

50. Resultsfrom data analysis