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DRG2005 > Mammography - Physics > Flashcards

Mammography - Physics Flashcards

1
Q

What are the equipment features of a Mammography unit?

A
  • Angled tube head
  • C-arm design
  • Fixed focus - detector distance (FDD)
  • Compression Device
  • Fixed Field Size
  • Grids
  • AEC
  • X-Ray Tube
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2
Q

What is the Optimal FDD of a Mammography unit?

A

65 - 66cm

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3
Q

What is the standard compression force of the compression device?

A

100N - 150N

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4
Q

What is the maximum compression force of the compression device?

A

200N

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5
Q

What type of examination is done in Mammography?

A

Breast Only

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6
Q

When do we use Grids?

A

Typical Mammography except for Magnification where air gap is adopted.

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7
Q

What are the types of AEC for mammography unit?

A

SFM - Photo-timer, placed behind the casette
DM - Detector acts as the AEC.

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8
Q

What are the features of a Mammography X-Ray tube?

A
  • Metal tube housing
  • Grounded Mo, Rh anode
  • Anode angle with tube tiled to 24 degrees to minimize Anode Heel effect
  • Vertical Axis of rotation
  • Mo or Rh filters for spectral shaping
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9
Q

Why is single track X-Ray Tube preferred?

A

Single track tube can deliver high current exposure needed for the largest breasts at an acceptable exposure time - reducing motion artifact.

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10
Q

What is operating voltage for cathode and filament circuit?

A

24 - 40 kVp

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11
Q

What is the focal spot size for Mammography?

A

0.3mm
0.1mm for Magnification Mammography

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12
Q

What is the purpose of having a small focal spot in Mammography?

A
  • Minimize geometric blurring
  • Maintains spatial resolution
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13
Q

Why is low kVp preferred in Mammography?

A
  • To minimize Compton Scattering
  • Maximise Photoelectric effect
  • Enhance differential absorption by various breast tissue
  • Reduce radiation dose to breast as Glandular tissues are highly radiosensitive
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14
Q

What is the material of the X-Ray tube window?

A

Beryllium

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15
Q

What is the target-filter & kVp range recommended for fatty breast tissue of up to 4cm thickness?

A

Mo/Mo
24 - 26 kVp

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16
Q

What is the target-filter & kVp range recommended for Glandular breast tissue of 5 - 7cm thickness?

A

Mo/Rh
27 - 31 kVp

17
Q

What is the target-filter & kVp range recommended for dense breast tissue of >7cm thickness?

A

Rh/Rh
27 - 31 kVp

18
Q

What is Half-Value Layer?

A

The thickness of any given material where 50% of the incident energy has been attuenated.

19
Q

What is the Approximate HVL in breast tissue?

A

1 to 2cm - strongly dependent on tissue composition.

20
Q

What is the generator power rating?

A

3 kW

21
Q

What is the voltage supplied to the X-Ray tube?

A

22 - 40 kVp

22
Q

Why is Breast compression necessary?

A
  • Reduces overlapping anatomy
  • Decreases tissue thickness of breast
  • less scatter
  • less geometric blurring
  • more contrast of the anatomic structures
  • Better visualization of tissues near the chest wall
23
Q

What does spot compression entails?

A
  • Better compression over a small area
  • Decreases superimposition of overlying tissues.
24
Q

What are typical interspace materials for the Grid?

A

Carbon Fibre/wood/paper
Al will attenuate too many of the low energy x-ray used in mammography

25
Q

What is the the optimal ambient light intensity?

A

<20 Lux

26
Q

What is the minimum MP of a Diagnostic Display Monitor?

A

5MP - to view fine microcalcifications

27
Q

What is the optimal luminance of a mammography viewbox

A

3000 cd/m square

28
Q

What are the advantages of a Digital Mammography?

A
  • Lower dose
  • Wider dynamic range
  • Higher Contrast Resolution
  • Better Signal Noise Ratio SNR
  • Reduced False Positives
  • Increased Positive Predictive Value PPV
  • Image Manipulative Tools - fewer repeats, minimize patient’s exposure.
  • Eliminate need to leave exam room to process films
  • Eliminates processing issues
  • Faster interventional procedures
  • Faster patient throughput - cost cutting

DRG2005 (7 decks)

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