FFDM Quality Control in Canada - a Vendor Neutral Approach Rasika Rajapakshe, PhD, FCCPM BC Cancer Agency-Center for the Southern Interior Kelowna, BC, Canada 2011 Joint AAPM/COMP Meeting August 4, 2011 Vancouver, BC
Outline Background QC Tests Acquisition system Double D SDNR phantom QC Tests Review system Technologist QC Tests Health Canada Draft Safety Code Conclusions
Map of Canada ~ 4.5 Million Population estimate (April 2011) : 34,349,236
Screening Mammography Program of BC (SMPBC) First organized breast screening program in Canada Established in 1988 41 Sites in total 28 Fixed sites include 3 mobiles 13 Ancillary sites 12 Digital sites ~ 300,000 mammograms/year
Digital Transition in SMPBC 2006 - DR mammography implemented in one center 2008-6 more centers implemented DR mammography Currently ~ 20% of SMP centers are digital Mean Glandular Dose (2007) *: 2.8 mgy (Film/Screen) 1.6 mgy (Digital) * R. Rajapakshe, RSNA (2009), SSE22-02
Digital Mammography Process
Digital Mammography QC program goals No international standards in place for digital mammography QC ACR Practice Guidelines recommend following vendor QC Various equipment in place with different recommended QC tests Need a standard in place for the program in order to track, troubleshoot and monitor image quality in a consistent fashion
Where to begin?
Where to begin?
SMPBC QA Tests for Physicist Acquisition System Unit Evaluation AEC / Tracking Resolution Collimation Ghosting Artifacts Noise and Signal Linearity kvp, HVL, Output Dose Evaluation of Site s QC IHE- Mammo profile Review System Monitor Display Quality Monitor Luminous Response View Conditions Measurement Accuracy IHE- Mammo profile
SMPBC QA Tests for Physicist Acquisition System Unit Evaluation AEC / Tracking Resolution Collimation Ghosting Artifacts Noise and Signal Linearity kvp, HVL, Output Dose Evaluation of Site s QC IHE- Mammo profile Review System Monitor Display Quality Monitor Luminous Response View Conditions Measurement Accuracy IHE- Mammo profile
Unit Evaluation 1. Temperature in mammography acquisition room within manufacturer specified tolerances. 2. Free standing unit is mechanically stable. 3. All moving parts move smoothly, without obstructions to motion. 4. All locks and detents work properly. 5. Image receptor is free from vibrations during exposure. 6. Compressed breast thickness scale is accurate to +/- 5 mm, reproducible to +/- 2 mm. 7. Automatic decompression override exists (if applicable) and override status displayed. 8. Manual compression release possible with no power to machine. 9. Patient or operator is not exposed to sharp or rough edges or other hazards. 10. Operator protected during exposure by adequate radiation shielding. 11. Operator technique charts are posted. 12. Indicator lights working properly. 13. Maximum Compression pressure applied under power at least 15 dan and less than 20 dan? 14. Maximum Compression pressure applied manually at least 15 dan and less than 30 dan? 15. Back-up timer functioning correctly 16. Annotation on images correct. 17. DICOM header correctly populated.
SDNR Test Double D Phantom The phantom is a new test object developed for monitoring digital mammography image performance consistency by monitoring weekly variations in the signal difference noise ratio (SDNR), mas and mean pixel value.
AEC / Tracking
Resolution - MTF 1.00 0.90 0.80 0.70 West Edge East Edge North Edge South Edge 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0 1 2 3 4 5 6 7 8 9 10 Effective Frequency (lp/mm)
Ghosting ACR phantom
SMPBC QA Tests for Physicist IHE Mammo Acquisition System Must conform to IHE Mammography Image Integration Profile as an Acquisition Modality Actor
IHE Mammo - Acquisition Modality Actor
SMPBC QA Tests for Physicist Acquisition System Unit Evaluation AEC / Tracking Resolution Collimation Ghosting Artifacts Noise and Signal Linearity kvp, HVL, Output Dose Evaluation of Site s QC IHE- Mammo profile Review System Monitor Display Quality Monitor Luminous Response View Conditions Measurement Accuracy IHE- Mammo profile
Monitor QC Measures two main criteria: Spatial Resolution Luminous Response
Monitor Resolution AAPM TG-18 QC image
Luminous Response AAPM TG-18 NL images Compliance with DICOM GSDF Luminance Response - Left Monitor 0.100 dl/l for a JND 0.010 Normalized Contrast Left Norm. Exp. Contrast Left lower limit Left upper limit Left 0.001 0 200 400 600 800 Average JND
Measurement Accuracy
SMPBC QA Tests for Physicist IHE Mammo Review System Must conform to IHE Mammography Image Integration Profile as an Image Display Actor
IHE Mammo Image Display Actor
IHE Mammo Image Display Actor Image Display Size Same Size True Size 1 : 1 (View actual pixels)
IHE Mammo Image Display Actor Same Size
IHE Mammo Image Display Actor True Size
IHE Mammo Image Display Actor 1 : 1 (100%) Display 3 MegaPixel 1536 x 2048 5 MegaPixel 2048 x 2560
SMPBC QA Tests for Technologist SDNR Test Weekly Artefact Test Weekly Display Monitor QC Weekly RMI Phantom Image Quality Monthly Mechanical Inspection Monthly Compression Test Semi Annual Laser Printer Sensitometry Weekly Laser Printer Artefacts Monthly CR Plate Artefacts Monthly Printed Image Quality Test Monthly Detector Uniformity Test - Monthly
SDNR Test Double D Phantom The phantom is a new test object developed for monitoring digital mammography image performance consistency by monitoring weekly variations in the signal difference noise ratio (SDNR), mas and mean pixel value. Technologists SDNR test is performed on the FOR PRESENTATION images.
Digital Mammography Process
Challenges in image processing Algorithms may differ based on the type of procedure chosen Contact Vs magnification view Therefore proper selection of the procedures is critical for optimal image quality
Challenges in image processing IPPGname=Standard_OV2_hc IPPGparameters=OpView2:_AM(1/1.5 8)_NI(1)_GaL(31)_H(127/0.00)_E(15/ 0.00/0)_AE(3/-0.30)_I(0/0.00010/- 30)_WM(2/130/2.20)_VM(0)_GL((2/4. 00/2048/230))_SB(1)_SEG(1513/0)_S T(0/1513/1.58)_ROI(0/0/0/0)
Changes in image processing 2006 2008
Why FOR PRESENTATION (Processed) images? kv mas Image Pro Signal Bk Std SDNR Processed 29 51 off 2631 2584 12.34 3.81 Processed 29 51 low 2644 2595 20.36 2.41 Processed 29 51 med 2633 2584 28.34 1.73 Processed 29 51 high 2646 2594 40.18 1.29 Raw 29 51 off 698 740 11 3.82 Raw 29 51 low 689 729 11.1 3.60 Raw 29 51 med 698 739 11 3.73 Raw 29 51 high 689 730 11 3.73
mqc Software Automatic SDNR Analysis
mqc Software Reporting for Accreditation
Health Canada Safety Code Current National Consultation: New Safety Code on Mammography You are invited to participate: Consultation - Safety Code Mammography Consumer and Clinical Radiation Protection Bureau Health Canada 775 Brookfield Road, PL 6301A Ottawa, ON K1A 1C1 Tel: 613 954-6699 Fax: 613 941-1734 CCRPB-PCRPCC@HC-SC.GC.CA, Consultation ends October 31, 2011
Health Canada Draft Safety Code - Mammography
Conclusions A unified system of vendor neutral quality control tests have been developed and adopted for digital mammography systems in the provinces of British Columbia and Ontario We are planning on adopting this methodology throughout Canada
Acknowledgements Martin Yaffe Gordon Mawdsley Aili Bloomquist Sam Chen (OBSP)