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1. Medical Radiation Sciences > Mammography > Flashcards

Mammography Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the types of tissues in the breast and what simularities does it have?

A
  1. Adipose
  2. Glandular
  3. Fibrous
  4. Tumours

Simular densities and atomic numbers, but Z# is main factor

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2
Q

With mammography, what energy do you use and what type of the material is the target?

A

-Use low E
-Use molybdenum target

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3
Q

What type of radiation do we ussually get when in mammography?

A

-We ussually get charecteristic radiation (because Z# is lower, and kVp is at 30 kVp)

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4
Q

What percentage of the beam is k-charecteristic in mammography?

A

20-30%

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5
Q

For breast imaging, what is the average energy?

A

17-24 kEV

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6
Q

What are ways that we can control beam quality in mammography?

A
  1. Filtration
  2. Anode to Cathode distancce
  3. Equipment composition
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7
Q

What type of filters/target do we use in mammography?

A

-We would use k-edge filters
-Specifically using a molybdenum filter with a molybdenum target

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8
Q

What benefits do we have in the image when we add filtration?

A

It narrows the range of energy to increase subject contrast

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9
Q

When is a Rhodium filter used?

A

When you have a patient with thicker breast tissue

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10
Q

What is the K-edge for Rhodium?

A

24

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11
Q

What type of radiation would you have when you use a Rhodium filter? What changes would occur?

A

-You would have mostly Bremms radiation
-An increase in charecteristic radiation

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12
Q

What is the difference in average energy when you use a rhodium filter vs a molybdenum filter?

A

The average energy is the same, although you would have more Bremms radiation with a rhodeium filter

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13
Q

With a lower kVp, will the space charge be larger or smaller?

A

The space charge would be larger because youre not pulling e- across as effectively

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14
Q

What are the effects of having a very low kVp regarding space charge?

A

-Filament gets hotter, so it could cause vaporization
-Attenuation of the beam before hitting the target

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15
Q

Why does mammography have shorter cathode to anode distance?

A

-Less attenuation of the beam before it hits the target
-Less vaporization

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16
Q

What does the pyrex glass in the tube do regarding attenuation?

A

Filters out low energy photons

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17
Q

In mammography, what is the window made out of?

A

Beryllium

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18
Q

What pieces of eqipment are modifed in mammography?

A
  1. Window
  2. Mirror
  3. Glass tube
  4. Anode angle
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19
Q

What type of radiation is produced with a molybdenum filter and a molybdenum target? What is the expected keV after filtration?

A

-All radiation but more charecteristic
-17-19 keV

20
Q

What type of radiation is made with a molybdenum filter and a tungsten target? What is the expected keV after filtration?

A

-Bremms
-17-19 keV

21
Q

What type of radiation is made with a rehnium filter and a molybdenum target? What is the expected keV after filtration?

A

-Bremms
-20-23

22
Q

What type of radiaiton is made with a rehnium filter and a rehnium target?

A

Charecteristic

23
Q

What type of anode angle does is used in a mamography machine? Why?

A

-A very small anode ange
-For better spatial resolution

24
Q

What are the cons of a small anode angle?

A

-Anode heel effect
-Smaller uniform field size

25
Q

Why do we use a low output in mammography?

A

-Because we have a llow mA and a low fluxence, both of these combine for a longer exposure time

26
Q

What are the pros of having a shorter SID in mammography?

A
  1. Increase in mGy/mAs
  2. Shorter exposure time
27
Q

What are the cons of having a shorter SID in mammography?

A
  1. Higher dose
  2. Less sharpness
  3. Greater anode heel effect
28
Q

How do we compensate for the anode heel affect in mammography?

A

Tilt the x-ray tube so that the anode is higher than the cathode

29
Q

What are the pros of having a tube tilt to compensate for the anode heel effect in mammography?

three

A
  1. Increase in mAs/mGy
  2. More uniform beam
  3. Larger field size
30
Q

What are the cons of having a tube tilt in mammography?

Why?

A

Less spatial resolution because the field size is larger and the anode is not as bent

31
Q

What 2 systems work together so that AEC can function?

A
  1. AEC
  2. Compression device
32
Q

Where are the AEC detectors located in mammography? Why?

A

After the IR, because with low energies, we would see the detectors on the image

33
Q

What selection is made after the AEC is set up in mammography?

A

Both AEC and compression device combine to select optimal technique and target material

34
Q

How does the AEC work in mammography?

A

Sends out a 100ms burst of radiaiton before the exposure to tell how much radiation is needed

35
Q

What factors increase spatial resolution in mammography?

Five

A
  1. Compresssion
  2. AEC location
  3. Grounded metal tube
  4. Image receptor design
  5. Small focal spot/anodeangle
36
Q

Would an increased SOD cause more or less dose?

A

Less dose

37
Q

How do we calculate the end result of dose in mammography?

A

Mag dose=contact dose

38
Q

What affect does magnification have on spatial resolution? Why?

A

Increases SR-there is more pixels per area of tissue

39
Q

What are the pros of magnification in mammography?

A
  1. Increased SR
  2. Increased contrast resolution
  3. More photons per area of tissue
40
Q

What are the cons of magnification in mammography?

A
  1. Increased skin dose

However we lower our technique to compensate bc of air gap technique increasing spatial resolution

41
Q

How do we improve contrast resolution in mammography?

A
  1. Compression
  2. Beam E
  3. Grid
  4. Tube tilt
  5. Tube orientation
  6. Digital tomosynthesis
  7. Magnification
  8. Filtration
42
Q

What is digital tomosynthesis?

A

-When the tube moves during the exam to create many images “slices”

43
Q

What are the effects of digital tomosythesis?

A
  1. Increased dose
  2. Increased contrast resolution
44
Q

What are the pros of film screen mammography?

A

Pros: HIgher spatial resolution and Low attenuation cassetes

45
Q

What are the benefits of digital mammography?

A

-Higher contrast resolution
-No phosphor

1. Medical Radiation Sciences (18 decks)

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