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FRCR Part 1 Physics > Mammography (Erin) > Flashcards

Mammography (Erin) Flashcards

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1
Q

Why is the breast tissue compressed during image?

A

Decreases the scatter in the image
Reduces required radiation dose

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2
Q

What size is the broad focal spot mammo?

A

0.3mm

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3
Q

What is the size of the fine focus focal spot in mammo?

A

0.1mm

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4
Q

In mammography why is the patient positioned with their chest wall towards the cathode?

A

To reduce the effect of the anode heel effect

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5
Q

What is the typical tube voltage used in mammo?

A

25-35kVp

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6
Q

What is the normal compression forced used in mammo?

A

100-150N

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7
Q

What is the predominant effect utilised in mammography to achieve contrast?

A

Photoelectric effect

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8
Q

What are the two most common anode material targets used in mammo?

A

Molybdenum (Mo)
Rhodium (Rh)

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9
Q

What are the 3 different combinations of target/filter used in mammo?

A

Mo/Mo
Mo/Rh
Rh/Rh

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10
Q

Is Rh/RH (target/filter) used for imaging smaller or larger breasts?

A

Imaging larger breasts

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11
Q

What is the maximum compression force that can be applied to the breast?

A

200N
Standard is 100-150N

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12
Q

What are the characteristic xray energies produced from an Mo target?

A

17.5 and 19.6keV

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13
Q

What is the fixed focus-detector distance used in mammo?

A

65/66cmcm

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14
Q

Should the anode target used in mammo have low or high keV characteristic xrays? And why?

A

Low keV
To promote the photoelectric effect

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15
Q

What are the characteristic energies produced from an Rh target?

A

20.2 and 22.7 keV

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16
Q

Why is a Rh/Mo target/filter combination not used in mammo?

A

Because the Mo filter would attenuate the Rh characteristic xrays

17
Q

What is the typical resolution (in lp/mm) in mammography?

A

10 lp mm

18
Q

What is the mammo filament length?

A

0.3-0.4mm

19
Q

Mammography spatial resolution is limited by…?

A

pixel size

20
Q

T/F: The patient dose will be lower when using a digital mammography unit as compared to an analogue unit

A

True because of the detection efficiency

21
Q

Is Mo/Mo target/filter combination typically used to image larger or smaller/normal sized breasts?

A

Smaller/normal sized breasts

22
Q

What are the characteristic radiation energies released from Mo

A

K alpha - 17.5 keV
K beta - 19.6 keV

23
Q

What are the characteristic radiation energies released from Rh

A

K alpha - 20.2 keV
K beta - 22.7 keV

24
Q

What is the K edge of Mo

A

20 keV

25
Q

What is the K edge of Rh

A

23.3

26
Q

In mammo magnification views how is scatter reduced

A

Breast support table is moved above the film to give magnification views
Large air gap between the breast and the film works to reduce the scatter (so no grid is needed)

27
Q

How are mammo magnification views obtained

A

Breast support table is moved above the film to give magnification views

28
Q

What 3 factors help to improve spatial resolution in mammo?

A

Small focal spot size
Compression of breast tissue
Anti-scatter grid

29
Q

What is the purpose of compression in mammo? (6)

A
  1. Lowers patient radiation dose (lower attenuation)
  2. Reduces scatter
  3. Spreads tissues out so there is less overlaying features
  4. Reduced geometric unsharpness (by moving tissue closer to object)
  5. Reduced movement unsharpness by holding the breast still
  6. Compressed breast is of more uniform attenuation
30
Q

What is the typical average dose per film?

A

1.5-3mGy

31
Q

What is tomosynthesis?

A

Movement of xray tube and detector to obtain different angle shots

32
Q

Why is tomosynthesis useful?

A

To separate structures which lie on top of one another

33
Q

Tomosynthesis dose is much higher than standard mammography- T/F?

A

False
All the angles projections are very lose dose. The sum is no more than 2 mammography doses.

34
Q

Tomosynthesis wider arc angle gives what 2 properties?

A

Improved contrast
Thinner slices

35
Q

Tomosynthesis: 4 uses?

A

Mammography
Lung nodules
Scaphoid imaging
Dental imaging

36
Q

What is the typical pixel size and spatial resolution in mammo?

A

Pixel size = 50 micrometers

Spatial resolution = 10lp/mm

37
Q

What is the population risk of fatal cancers for women undergoing mammography aged 50-65?

A

1 in 50,000

FRCR Part 1 Physics (20 decks)

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