A brief presentation about mammography machine for Radiographers and radiologist

1. Radiographic Equipment
Dr. Umar Abubakar Ciroma

2. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• Mammography techniques require the use of soft radiation
• Such radiation is best produced by a tube operating at low kV
• Preferably with a molybdenum anode in place of the more commonly
used tungsten
• The ka characteristic radiation of Mo is of much lower energy (longer
wavelength than tungsten)
• Therefore forms a useful part of the low energy beam needed for
mammography

3. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• Mammography tube insert

4. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• The cathode end of the beam is limited by means of a diaphragm
• This will minimize radiation dose to the patient's chest wall during the exposure
• The tube has a beryllium window as this is less absorbent than glass, an
important factor with a low energy beam
• Molybdenum filter rather than aluminium is used
• Unlike aluminium, molybdenum is translucent to the characteristic radiation
emitted by the molybdenum target
• This allows the radiation we particularly require to pass through the filter with
minimal absorption
• Mammography tube insert

5. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• A proximal diaphragm reduces the effects of extra focal radiation
• The filament of the mammography tube is set much closer to the
anode than that of the conventional tube
• This means that a given rnA is obtained at a lower filament
temperature
• This is of importance as it results in a reduction in the amount of
tungsten evaporation taking place

6. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• The deposition of such tungsten on the inner surface of the tube
insert is of little importance in the conventional tube
• but is a significant factor in the mammography tube
• Because it produces low energy radiation which would be much more
readily absorbed than the high energy beams produced by
conventional tubes
• Indeed, the absorption of low energy radiation would be an
advantage in the latter case

7. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• The focal spot size of the Siemens tube is 0.6 x 0.6mm,
• and the heat storage capacity of the tube is high enough to allow up
to 60 radiographs per hour to be taken
• The tube is intended for use with the Siemens Mammomat unit in
conjunction with a three-phase (6-pulse) generator giving 300 rnA at
25 k V

8. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• The aim of mammography is early detection of cancer
• Typically, through detection of microcalcifications
• Basic projections: MLO & CC

9. Mammography X-ray Tube
• Some mammography techniques require the use of soft

10. Mammography X-ray Tube
• Some mammography techniques require the use of soft

11. Mammography X-ray Tube
• Some mammography techniques require the use of soft
Cathode
The mammography x-ray tube is configured with dual filament in the focusing cup to produce 0.3-
and 0.1-mm focal spot sizes
• Mammographic x-ray tubes have rotating anode
• Anode angle – 0 to 16 degree
• Source – to – image receptor distance is about 60-65 cm
• Effective anode angle : (the actual anode angle plus the physical tube tilt) is at least 22-24
degrees for coverage of the 24 x 30cm field area

12. Mammography X-ray Tube
• Some mammography techniques require the use of soft

13. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• Beryllium window: is used as it has low atomic number (Z=4)
and lower absorption of less than 5 kVp x-rays, 1mm of Be is
equivalent to 0.1mm AL material (inherent filter)
• HEEL EFFECTS: Positioning the cathode over the chest wall
of the patient and the anode over the anterior portion (nipple)
achieves better uniformity of the transmitted x-rays through the breast
• Orientation of the tube in this way also decreases the equipment
bulk near the patient’s head

14. Mammography X-ray Tube
• Some mammography techniques require the use of soft

15. Mammography X-ray Tube
• Some mammoFOCAL SPOT SIZE
• It is 0.3 to 0.4 mm for contact mammography (breast composed
against the grid and image receptor)
• 0.10 to 0.15 mm for magnification imaging
• If reduce geometric blurring so that micro
calcifications can be resolved

16. Mammography X-ray Tube
uire the use of soft
Target and filter combination
• The filters used in mammography are based on the ‘’ k edge’’ principle and attenuate the
radiation above the k-edge energy of the specific filter material, either molybdenum or rhodium
• Mo target with 0.03mm /Mo filter (42)
• Rh target with 0.025 /Rh filter (45)
• W target with 0.05mm /W filter (74)

17. Mammography X-ray Tube
• Some mammography techniques require the use of soft

18. Mammography X-ray Tube
• Some mammography techniques require the use of soft

19. Mammography X-ray Tube
• Some mammography techniques require the use of soft

20. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• Mo target with Mo filter combination are appropriate for breasts less
than 5 cm thick
• Mo target with rhodium filters or rhodium target with rhodium filters
may be appropriate for breasts greater than 5cm thick

21. Mammography X-ray Tube
• Some mammography techniques require the use of soft
Collimator / Cones
• Cones are required for proper direction of x-ray beam, proper collimation for rejecting scatter
radiation and protection of chest wall and lungs from unnecessary radiation
• THREE DESIGN ARE CURRENTLY USED:
1) Fixed aperture
2) A set of interchangeable cones for various sizes of breast
3) An internal set collimating blades

22. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• For magnification and spot compression studies, manually
Adjusted shutters allow the x-ray field to be more closely matched
To the volume being imaged

23. Mammography X-ray Tube
• Some mammography techniques require the use of soft
Anti scattered grid
• The anti scattered grid must be moving grid
• Carbon fiber is the preferred interspace material
• Focused grid, with a grid ratio of 3:1 or 5:1
• Grid frequencies of 30-40 lines/cm

24. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• Use of such grid does not compromise the spatial resolution but it does increase the patient
dose
• Use of 4:1 ratio grid approximately double the patient dose as compared to non-grid contact
mammography
• A unique grid is developed specially for the mammography called high transmission cellular grid
(HTC) it is a crossed type
• It reduces scattered radiation in 2 direction, HTC grid has a copper as a grid stripe and air as a
interspace, physical dimension grid ratio (3.8:1)

25. Mammography X-ray Tube
• Some mammography techniques require the use of soft
Compression devices
• COMPRESSION PLATE: flat surfaced plate used for uniform compression
1) In conventional compression plate, anterior portion of breast is not compressed properly
2) Newer slanted paddles are now available for equal compression to all areas of the breast

26. Mammography X-ray Tube
• Some mammography techniques require the use of soft
ADVANTAGES
• Provides immobilization of the part during exposure
• Produces radiograph of uniform density
• Reduces geometric unshrpeness due to closer object to IR distance
• Reduces scatter and improves contrast
• Reduces tissue overlap and improves resolution
• Enhancement recognition of architectural distortion produced by tumors
DISADVANTAGE: only patient discomfort
SPOT COMPRESSION: It is used to magnify small area of breast for better visualization

27. Mammography X-ray Tube
• Some mammography techniques require the use of soft

28. Mammography X-ray Tube
• Some mammoIMIIIIIMMgraphy techniques require the use of soft
IMAGE RECEPTOR
FILM-SCREEN COMBINATION
 Single-coated film: screen combination is commonly used today (GADOLINIUM OXYSULPHITE)
provide higher film contrast and require significantly lower radiation exposure as compared to
direct exposure film
 Currently in mammography single emulsion film are used in combination with a single back
screen
 MAMMOGRAPHIC CASSETTE: These are dedicated cassette used mammography only
(18x24/24x30cm)

29. Mammography X-ray Tube
• Some mammography techniques require the use of soft

30. Mammography X-ray Tube
• Some mammography techniques require the use of soft
AUTOMATIC EXPOSURE CONTROL
 Phototimers are design not only to measure x –ray intensity at image receptor but also for x-ray
quality
 Phototimers are also called AEC device
 And it is place after the image receptor
 And consists of a single ionization chamber or an array of three or more semiconductor diodes
 X-rays transmitted through the breast and the image receptor generate a signal in the detector

31. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• The signal is accumulated (integrated)
• When the accumulated signal reaches a preset value, the exposure is terminated
• The preset value corresponds to a specified SNR in digital mammogaphy unity or
• Acceptable optical density (OD) if a film-screen system is used

32. Mammography X-ray Tube
• Some mammography techniques require the use of soft

33. Mammography X-ray Tube
• Some mammography techniques require the use of soft
• DIGITAL MAMMOGRAPHY
Direct conversion
• Amorphous selenium (direct conversion) using the flat panel technology
• 70 microns
• Inirect conversion
• Scintillating phosphor (CsI columns) on an array of amorphous silicon photodiodes
using thin-film transistor (TFT) flat panel technology: 100 micron pixel
• Computed Radiography: 50 micron pixel
• Slot scanning CCD: 27 micron pixel