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mammo > physics > Flashcards

physics Flashcards

1
Q

mammo equipment uses what 3 target (anode) materials

A

molybdenum Mo
Rhodium Rh
tungsten W

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2
Q

system will choose ____ that is best for tissue type and thickness

A

the best target material

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3
Q

_____ will be automatically selected by your machine based on the thickness of the breast

A

filter type

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4
Q

filters are most often made of… (4)

A

molybdenum Mo
Rhodium Rh
aluminum Al
silver Ag

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5
Q

_____ material is inserted into the xray beam to enhance contrast

A

filter

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6
Q

2 types of filtration

A

inherent and added

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7
Q

composed of parts of the xray tube and tube housing

A

inherent filtration

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8
Q

thin sheets of metal inserted in the xray beam

A

added filtration

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9
Q

what is exit window of tube housing made of

A

beryllium

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10
Q

2 important roles of added filtration

A

removes soft energy photons which add dose
removes higher energy photons which reduce contrast

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11
Q

used to absorb scatter and improve contrast

A

grid

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12
Q

grids absorb ___% of scatter

A

75-85

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13
Q

the ratio of the height of the lead strips to the distance between the lead strips

A

grid ratio

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14
Q

high grid ratio= ______ image contrast and _____ patient dose

A

better,higher

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15
Q

grid ratio in mammo

A

3:1-5:1

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16
Q

2 types of grids used in mammo

A

linear/focused
honeycomb/HTC

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17
Q

3 benefits from good compression

A

uniform breast thickness
reduce blurring
reduce scatter; improves contrast

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18
Q

the compression paddle should not extend beyond the chest wall edge of the IR by more than __% when compressed on the average breast

A

1

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19
Q

the mammo light field is controlled by

A

paddle size

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20
Q

the light field will come all the way to the chest wall and not exceed any edge by more than __%

A

2

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21
Q

the radiation shield must have the equivalent attenuation of at least ____ mm lead at __ kVp to limit the operator’s exposure to below __ mSv a week

A

0.08
35
1

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22
Q

the area of the anode (target) bombarded by electrons. this spot never changes

A

actual focal spot

23
Q

downward projection of the actual focal spot; dependent on the steepness of the anode angle

A

effective focal spot

24
Q

the steeper the angle the _____ the effective focal spot and the ____ the detail

A

smaller, better

25
Q

mammo tubes have 2 focal spots

A

large- 0.3mm
small- 0.1mm

26
Q

refers to the intensity of the xray beam which is not uniform in all portions of the beam

A

anode heel effect

27
Q

in the anode heel effect, the anode acts as a filter- we call this

A

self filtration

28
Q

the xrays toward the ____ end of the tube have more intensity because they have less of the anode to travel through. the dose will be more at this end.

A

cathode

29
Q

the xrays toward the ____ end are less intense because they have more of the anode to travel and are more absorbed. there is less dose at this end

A

anode

30
Q

in mammo the tube is moved anteriorly in the tube head (closer to the patient). lead is used to block half of the beam from the lungs

A

half field geometry

31
Q

controls the wavelength of the xray beam

A

kvp

32
Q

penetrating power

A

kvp

33
Q

influences contrast and exposure latitude

A

kvp

34
Q

average kvp in mammo

A

25-35

35
Q

a unit of radiographic exposure equal to the product of the mA and the exposure time in seconds

A

mas

36
Q

used to control the image blackening

A

ma

37
Q

typical mA selection

A

20-100

38
Q

typical time selection

A

.4-1 second

39
Q

2 types of radiation are produced when electrons hit the anode

A

characteristic, bremsstrahling

40
Q

xrays produced are confined to 2 energy spikes. the energy spikes will be determined by the anode material. this radiation is most important for determining xray beam penetration and giving up optimal contrast

A

characteristic radiation

41
Q

xrays produced with multiple energies. this is the most common type of radiation produced

A

bremsstrahling radiation

42
Q

the max permissible dose for one view of an average breast is ___mRad or __mGy

A

300
3

43
Q

the distance between the xray source and the image receptor

A

source to image distance SID

44
Q

average mammo SID

A

65-66cm

45
Q

the distance between the object to the imaging receptor

A

object to image distance OID

46
Q

an increase in OID will result in what

A

mag

47
Q

mag increases the possibility of unsharpness so we use the small focal spot to gain detail; this ____ the dose

A

increases

48
Q

3 most common mag factors

A

1.5x
2.0x
1.8x

49
Q

purpose is to ensure that mammo equipment meets FDA

A

mammography equipment evaluation MEE

50
Q

purpose is to ensure that the xray field aligns with the light field; to ensure it allows for full coverage of the IR by the xray field but does not allow significant radiation beyond its edges; to ensure that the chest wall edge of the paddle aligns with the edge of the IR.

A

collimation assessment

51
Q

how often is collimation assessment done

A

done for new units, relevant service and annually

52
Q

how often is mammography equipment evaluation MEE done

A

completed after installation of new units and relevant service

53
Q

purpose- a more detailed eval to monitor contrast delivered by detector

A

system resolution tests-modulation transfer function MTF

54
Q

to ensure that the image acquisition chain is consistently producing adequate image quality, that artifacts are not clinically significant, and that the SNR and CNR are adequate

A

artifact evaluation

mammo (13 decks)

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