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Digital Breast Tomosynthesis
Digital Breast Tomosynthesis
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Digital Breast Tomosynthesis with Minimal Compression

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Breast compression is utilized in mammography to improve image quality and reduce radiation dose. Lesion conspicuity is improved by reducing scatter effects on contrast and by reducing the superposition of tissue structures. However, patient discomfort due to breast compression has been cited as a potential cause of noncompliance with recommended screening practices. Further, compression may also occlude blood flow in the breast, complicating imaging with intravenous contrast agents and preventing accurate quantification of contrast enhancement and kinetics. Previous studies have investigated reducing breast compression in planar mammography and digital breast tomosynthesis (DBT), though this typically comes at the expense of degradation in image quality or increase in mean glandular dose (MGD). We propose to optimize the image acquisition technique for reduced compression in DBT without compromising image quality or increasing MGD. A zero-frequency signal-difference-to-noise ratio model is employed to investigate the relationship between tube potential, SDNR and MGD. Phantom and patient images are acquired on a prototype DBT system using the optimized imaging parameters and are assessed for image quality and lesion conspicuity. A preliminary assessment of patient motion during DBT with minimal compression is presented.

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Digital Breast Tomosynthesis with Minimal Compression

  1. 1. Digital Radiological Imaging Laboratory Digital Breast Tomosynthesis with Minimal Compression David A. Scaduto, Min Yang, Wei Zhao DEPARTMENT OF RADIOLOGY
  2. 2. Breast Compression
  3. 3. Breast Compression • Image Quality  Attenuation equalization  Structure superposition  Contrast resolution  Geometric unsharpness  Motion artifacts • Dose reduction
  4. 4. Reduced Breast Compression • Patient comfort/compliance • Tomosynthesis  Reduced superposition of tissue structures • Contrast-enhanced imaging  Significant reductions in blood flow (~88%) observed in forces of up to 10 daN  2 daN resulted in 50% blood flow reduction 1 G. Marshall, J. Public Health Medicine. 16(1), 79–86 (1994). 2 A.R. Aro, H.J. de Koning, P. Absetz, and M. Schreck, J. Med. Screen. 6(2), 82–88 (1999). 3 D.R. Busch et al., Acad. Radiol. 21(2), 151–61 (2014).
  5. 5. Reduced Breast Compression • Increased breast thickness  Increased mean glandular dose (MGD)  Increased scatter radiation (reduced contrast) • Increased patient motion
  6. 6. Previous Work: DBT • Saunders et al.: Monte Carlo simulation; 12.5% increase in breast thickness  Comparable image quality when maintained detector signal  Poorer lesion conspicuity when maintaining MGD  Constant tube potential R.S. Saunders, E. Samei, J.Y. Lo, and J.A. Baker, Radiology 251(3), 673–682 (2009).
  7. 7. Previous Work: DBT • Förnvik et al.: Observer study; compression reduced by 50%  Constant kVp, mAs for both scans  Comparable image quality D. Förnvik, I. Andersson, T. Svahn, P. Timberg, S. Zackrisson, and A. Tingberg, Radiat. Prot. Dosimetry 139(1-3), 118–23 (2010).
  8. 8. Technique Optimization • Optimize technique to  Reduce breast compression  Maintain image quality / lesion conspicuity  Minimize dose increase • Lesion conspicuity may be maintained by increasing effective beam energy (kVp) while maintaining comparable MGD (< 10% increase)
  9. 9. Methods • Theoretical optimization study  Zero frequency SDNR analysis • Image quality study  Phantom study  Clinical study W target 50 μm Rh filtration
  10. 10. Zero Frequency SDNR Model , , 2 2 2 , , SDNR P B P L P B S B a         T tμLμB Φ0 ΦB ΦL W. Zhao, R. Deych, and E. Dolazza, Proc. SPIE 5745, 1272–1281 (2005). 26 28 30 32 34 36 0 2 4 6 8 10 12 14 4 cm 6 cm 8 cm SDNR kVp
  11. 11. Effect of kVp on SDNR 26 28 30 32 34 36 0 2 4 6 8 10 12 14SDNR kVp 4.0 cm 4.5 cm
  12. 12. Effect of kVp on MGD 26 28 30 32 34 36 0 2 4 6 8 10 12 14SDNR kVp 4.0 cm 4.5 cm 1.0 1.2 1.4 1.6 1.8 2.0 MGD[mGy] 6.8% 26 28 30 32 34 36 0 2 4 6 8 10 12 14SDNR kVp 4.0 cm 4.5 cm 1.0 1.2 1.4 1.6 1.8 2.0 MGD[mGy] -11.8%
  13. 13. AEC Dose Study 28 29 30 31 kVp + 0 kVp + 1 kVp + 2 kVp + 3 5 10 15 20 25 4.5 cm (4.0 cm) %ChangeinMGD kVp
  14. 14. AEC Dose Study
  15. 15. Technique Chart Full Compression Minimal Compression Breast Thickness (mm) kVp Breast Thickness (mm) kVp 20-29 26 20-29 28 30-39 27 30-39 30 40-49 28 40-49 31 50-59 29 50-59 32 60-69 30 60-69 32 70-79 31 70-79 33 80-89 33 80+ 35 90+ 35
  16. 16. Image Quality: Phantom Assessment 4.5 cm 28 kVp 5.0 cm 28 kVp 5.0 cm 31 kVp 1.63 mGy 1.96 mGy 1.66 mGy Full Compression Minimal Compression
  17. 17. Thickness (fully compressed) kVp Masses Calcifications 2 Full Compression 26 5 6 Minimal Compression 28 5 6 3 27 5 5 30 5 5 4 28 4 5 31 4 6 5 29 5 5 32 5 5 6 30 4 5 33 4 5 7 31 4 5 33 4 6 8 33 4 5 35 3 5
  18. 18. Clinical Observer Study • IRB approved protocol • Two DBT scans  Full Compression (8-10 daN)  Minimal Compression (2-4 daN) • Endpoints:  Lesion conspicuity (radiologist assessment)  Mean glandular dose  Motion assessment
  19. 19. Patient 1 6.4 daN 36 mm 26 kVp 1.9 mGy 2.3 daN 42 mm 28 kVp 2.0 mGy
  20. 20. Patient 2 7.7 daN 51 mm 29 kVp 2.64 mGy 3.1 daN 58 mm 32 kVp 2.54 mGy
  21. 21. Patient 3 8.2 daN 52 mm 29 kVp 1.3 mGy 3.2 daN 59 mm 32 kVp 1.3 mGy
  22. 22. Dose and Patient Comfort Patient Mean Glandular Dose (mGy) % Change Full Compression Minimal Compression 1 1.95 2.05 5.1 2 1.62 1.49 -8.0 3 1.95 1.64 -15.8 4 2.64 2.54 -3.8 5 1.34 1.35 0.7 • All patients report minimal compression to be “much more comfortable” than full compression
  23. 23. Motion Assessment Tube Travel
  24. 24. Motion Assessment
  25. 25. Motion Assessment
  26. 26. Motion Assessment 0 5 10 15 20 25 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 DifferentialMarkerPosition[mm] Projection Number Stationary Phantom (A) Stationary Phantom (B) Full Compression (A) Full Compression (B) Minimal Compression (A) Minimal Compression (B) 0 5 10 15 20 25 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 DifferentialMarkerPosition[mm] Projection Number Stationary Phantom (A) Stationary Phantom (B) Full Compression (A) Full Compression (B) Minimal Compression (A) Minimal Compression (B) 0 5 10 15 20 25 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 DifferentialMarkerPosition[mm] Projection Number Stationary Phantom (A) Stationary Phantom (B) Full Compression (A) Full Compression (B) Minimal Compression (A) Minimal Compression (B)
  27. 27. Discussion and Future Work • Image quality comparable; lesion conspicuity maintained • Increase in quantum noise evident • Compensation schemes  Effect of different reconstruction algorithms  Non-uniform dose distributions  Synthetic mammograms Y.-H. Hu and W. Zhao, “The effect of angular dose distribution on the detection of microcalcifications in digital breast tomosynthesis,” Med. Phys. 38(5), 2455 (2011).
  28. 28. Conclusions • Zero-frequency SDNR model implemented to optimize imaging technique • Increasing kVp for minimally compressed breasts minimizes MGD increase without significantly sacrificing SDNR • Increased scatter increases quantum noise • Lesion conspicuity may be maintained • Initial clinical results suggest breast compression may be reduced in DBT
  29. 29. Acknowledgements We gratefully acknowledge • NIH 1 R01 CA148053 • Siemens Healthcare

Notizen

  • Improvement in contrast resolution by decreasing scatter
    Also allows us to use less penetrating beam, maximize inherent contrast
    Reduces superposition of tissue structures in planar mammography
    Reduce dose by decreasing effective thickness of breast
  • UK study: 41% of non-reattenders cite pain

    50% reduction observed for forces of just 2 daN
  • Reduced contrast
  • Spatial resolution: geometric unsharpness
    Contrast resolution: scatter radiation
  • Measure mAs delivered to phantom of nominal and increased breast thickness at manufacturer specified kVp and increased kVp
  • Some motion, but not gross patient motion
  • Despite decreased SDNR and potential of patient motion
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