1. Basic Aspects of Full Field Digital Mammography (FFDM)

2. FDA Approved FFDM Units

3. FFDM Units and Facilities

4. FFDM Differences Image acquisition and display are separated
Wide dynamic range (versus H&D curve)
Lower Dose (~20%)
Same dose limits as for film-screen
Higher kVp (+3 kVp)
Better for dense breasts
Imaging detector can be used as AEC detector
Automated AEC sensor adjustment (under some AEC modes)
Use of Mo/Mo, Mo/Rh, Rh/Rh, W/Rh and W/Ag targets

5. FFDM Differences Digital images Require workstations
Post-processing image enhancement
Computer aided diagnosis
Archival issues (>9 Mbyte/image)

6. Good Digital Mammo Resource
© Report 05037: Comparative Specifications of Full Field Digital Mammography Systems 2005

7. AEC
Done with the image detector rather than discrete radiation detectors:
Amorphous silicon
PIN diodes (with scintillator)
PM tube (with scintillator)
Ion chamber
System can automatically select the densest aspect of the breast for AEC “cell” positioning or the technologist can manually select the AEC “cell” position

8. Prep Delay Can be quite long Up to 7 seconds Especially in AEC mode
Very brief for film-screen mammography

9. Breast Dose Systems display breast dose with image
Dose recorded in DICOM image header
Entrance skin exposure and/or average glandular dose
Vendors use different dose calculation algorithms
Dance
Wu & Barnes
U.S. Method

10. Siemens Mammomat Novation
Focal Spot Size
GE Senographe 2000 D
GE Senographe DS
Hologic Selenia
Siemens Mammomat Novation
Detector material
Caesium iodide /TFT array
Amorphous selenium /TFT array
Detector type
Indirect
Direct
Focal spot sizes (mm)
.3 and .1
Target materials
Mo and Rh Mo OR W
Mo and W
Filter materials
Rh and Ag
© Report 05037: Comparative Specifications of Full Field Digital Mammography Systems 2005

11. Fuji Digital Mammography
ClearView-CSM
Reads image plate from both sides
50 micron resolution
10 lp/mm

12. FFDM Detectors
Scintillating phosphor (CsI columns) on an array of amorphous silicon photodiodes using thin-film transistor (TFT) flat panel technology (GE)
~100 micron pixels
Mo/Mo. Mo/Rh, Rh/Rh
Amorphous selenium (direct conversion) using (TFT) flat panel technology (Siemens, Hologic)
~70 micron pixels
Mo/Mo, Mo/Rh OR W/Rh, W/Ag for Hologic
Mo/Mo, Mo/Rh, W/Rh for Siemens
Computed radiography (Fuji)
~50 micron pixels
Slot scanning CCD (Fischer? Fischer Medical Technologies?)
~27 micron pixels

13. Digital Mammography: X-ray Source
Target Material and Characteristic X-ray Emission
Mo (kα=17.4 keV; kβ =19.6 keV)
Rh (kα=20.2 keV; kβ =22.7 keV)
W (kα=58.6 keV; kβ =67.4 keV)
Filter Material and K-edge (Absorption Edge)
Mo (K edge = 20.0 keV)
Rh (K edge = 23.3 keV)
Ag (K edge = 25.5 keV) 13

14. X-ray spectral distribution is determined by:
anode target material
filter material and thickness
kVp.
Screen-film mammography emphasizes characteristic X-rays rather than Bremmstrahlung photons.

15. Spectra of Mo/Mo and Mo/Rh at 28 kVp
Slide courtesy of Hologic 15

16. Mo & Rh
targets
Mo/Rh
©1994 Williams & Wilkins

17. Mo/Mo
Rh/Rh
©1994 Williams & Wilkins

18. Spectra of W/Rh and W/Ag at 28 kVp
Slide courtesy of Hologic 18

19. X-Ray Spectra

20. Siemens Mammomat Novation
Focal Spot Size
GE Senographe 2000 D
GE Senographe DS
Hologic Selenia
Siemens Mammomat Novation
Grid technology
Linear
Cellular (HTC)
Grid interspcae filler
Paper
Air
Maximum field size (cm)
19 x 23
24 x 29
23 x 29
Maximum image matrix (pixels)
1914 x 2294
3328 x 4096
Pixel pitch (microns)
100 70
Hich contrast limiting resolution (lp/mm) 5
> 7
© Report 05037: Comparative Specifications of Full Field Digital Mammography Systems 2005

21. System MTF
©1994 Williams & Wilkins

22. Scattered Radiation Control
Only 40-75% of the possible contrast is imaged in mammography unless scatter is controlled.

23. Scattered Radiation Control
Linear Grids
Grids preferentially remove scattered photons.
Lead laminae separated by radiolucent spacers.
Grid ratio (height of lamina/distance between laminae): 4:1 or 5:1 w/ lines/cm.
Conventional grids are 8:1 to 12:1 (up to 43 lines/cm).

24. Scattered Radiation Control
Linear Grids
Grids move (linearly or oscillatory L<-->R) during an exposure (20 or more grid line spacings) to blur out grid lines.
Short exposures can cause gridline artifacts that result from insufficient motion.
Mammography grids transmit 60-70% of primary X-rays and absorb 75-85% of the scattered X-rays.

25. Scattered Radiation Control
Linear Grids
Breast dose is increased by grids (Bucky Factor: x2 to x3) w/40% improvement in contrast.
Laminae are focused to the focal spot to prevent grid cut off.

26. Scattered Radiation Control
High Transmission Cellular (HTC) Grids
Focused
Increased 2D absorption of scattered radiation
Increase contrast
Must move the grid a very precise distance during exposure regardless of exposure duration
Essentially same grid ratio and dose as conventional linear grids

27. HTC Grid

28. HTC Grid

29. HTC Grid

30. HTC Grid

31. Siemens Mammomat Novation
Focal Spot Size
GE Senographe 2000 D
GE Senographe DS
Hologic Selenia
Siemens Mammomat Novation
Acquisition bit depth (bits) 14
Image bit depth (bits) 8
Workstation bit depth 10 12
Maximum image size (Mbyte) 9 27
Time to display image on acquisition workstation (s)
<15
10 to 15
40 to 50
Reject analysis No
Yes
Stereotactic biopsy devices
© Report 05037: Comparative Specifications of Full Field Digital Mammography Systems 2005

32. Future of Digital Mammography (as of 2005)
GE Medical Systems:
tomosynthesis.
Hologic:
tomosynthesis
dual energy imaging
imaging with contrast media.
Siemens Medical Solutions:
increased post processing capabilities at the review workstation
improved reporting workstation with image fusion (ultrasound, MRI, etc)
2nd generation CAD.
© Report 05037: Comparative Specifications of Full Field Digital Mammography Systems 2005

33. Tomosynthesis
3:00 -7:00

34. Breast Tomosynthesis (Hologic)
Data acquisition
15 discrete views
Limited arc (~50 degrees?)
7 frames/sec
5 second exposure
Reconstruction
50 slices
1 mm thick
Back projection

35. Tomosynthesis

36. Breast CT
U C Davis

37. Breast CT
U C Davis

38. Cone Beam Breast CT
University of Rochester
300 views
10 seconds

39. Cone Beam Breast CT
University of Rochester

40. Cone Beam Breast CT

41. References ©NCRP 2006 ©1994 Williams & Wilkins ©1993 RSNA ©1992 RSNA
NCRP Report 149, “A Guide to Mammography and Other Breast Imaging Procedures” National Council on Radiation Protection and Measurements, 2004
©1994 Williams & Wilkins
Bushberg, JT, Seibert, JA, Leidholdt, EM Jr., Boone, JM, ”The Essential Physics of Medical Imaging” Williams & Wilkins, Baltimore, Maryland, 1994
©1993 RSNA
Haus, AG, Yaffe, MJ, Eds., “Syllabus: A Categorical Course in Physics Technical Aspects of Breast Imaging”, 2nd Edition, RSNA, 1993
©1992 RSNA
Haus, AG, Yaffe, MJ, Eds., “Syllabus: A Categorical Course in Physics Technical Aspects of Breast Imaging”, RSNA, 1992
©1987 IOP Publishing
Johns, PC, Yaffe, MJ, “X-Ray characterisation
of normal and neoplastic breast tissues”, Phys Med Biol, 1987, 32,