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Mammo > Physics > Flashcards

Physics Flashcards

1
Q

Target (anode) material

A

-molybdenum (Mo)
-rhodium (Rh)
-tungsten (W)

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2
Q

Filter material is inserted into xray beam to

A

Enhance contrast

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3
Q

Filters are most ofter made of

A

-molybdenum (Mo)
-rhodium (Rh)
-silver (Ag)
-aluminum (Al)
Filter type will be selected by machine based on breast thickness

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4
Q

Exit window of tube housing made of

A

Beryllium

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5
Q

Roles of added filtration

A

1) removes soft energy photons which add dose
2) removes high energy photons which reduces contrast

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6
Q

Grids

A

-used to absorb scatter and improve contrast
-absorb 75-85% of scatter

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7
Q

Grid ratio in mammography

A

3:1 to 5:1

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8
Q

Linear/focused grid

A

-reduce scatter from 1 direction
-interspace material is carbon

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9
Q

Honeycomb/HTC grid

A

-reduces scatter in 2 directions
-better contrast
-interspace material is air

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10
Q

How far will light field come?

A

All the way to chest wall and not exceed any edge by more than 2%

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11
Q

Radiation shield must have the equivalent attenuation of at least

A

0.08 mm lead at 35 kVp

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12
Q

Line focus principle

A

The steeper the angle the smaller the effective focal spot and the better the detail

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13
Q

Large focal spot measures

A

0.3 mm and is used for standard imaging

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14
Q

Small focal spot measures

A

0.1 mm and is used for magnification imaging

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15
Q

The anode acts as a what

A

A filter; called self-filtration

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16
Q

The xrays towards the cathode end of tube have

A

-More intensity (less of anode to travel through)
-dose is more at cathode end

17
Q

The xrays toward the anode side are

A

-less intense (more of the anode to travel and more absorbed)
-less dose at anode end

18
Q

Half field geometry

A

Lead is used to block “half” of the beam from and prevent it from going into lungs

19
Q

kVp

A

-controls wavelength of xray beam
-penetrating power
-influences contrast and exposure latitude
-average range in mammo is 25-35

20
Q

mAs

A

-will control xray beam intensity
-used to control image blackening

21
Q

Typical mA selection

A

20-100 mA

22
Q

Typical time in sections

A

0.4 to over 1 second

23
Q

Backup timers

A

-600 mAs for grid techniques
-300 mAs for non-grid work

24
Q

What are the two types of radiation produced in mammo xray spectrum?

A

1) characteristic radiation
2) bremsstrahlung radiation

25
Q

Characteristic radiation

A

-2 energy spikes (determined by anode material)
-important for determining xray beam penetration and giving optimal constant

26
Q

Bremsstrahlung radiation

A

-xray produced with multiple energies (keV)
-det. by selected kVp

27
Q

Anode material molybdenum (characteristic radiation)

A

-produces the characteristic rad ,2 strikes, optimal to penetrate breast
-moly anode prod. char. rad. spikes of 17.6 kaV & 19.7 keV

28
Q

Anode material rhodium (characteristic radiation)

A

-Rh prod. char. rad. spike of 20.3 and 22.7 keV

29
Q

Molybdenum filter (bremsstrahlung radiation)

A

-Mo’s k-edge is 20 keV
-it will filter (slow down) xrays with energies above 20 keV, which decreases contrast

30
Q

Rhodium filter (bremsstrahlung radiation)

A

-Rh has k-edge of 23 keV
-it will filter (slow down) xrays with energies about 23 and get them closer down to 23
-good for thicker breast

31
Q

Pt dose with and without grid (one view)

A

-with grid: 3mGy
-w/out grid: 1mGy

32
Q

What is average breast made of?

A

-50% glandular 50% fat
-compress to 4.2 cm

33
Q

Average SID in mammography machine

A

65-66 cm

34
Q

Magnification increases possibility of unsharpness, so what do you used to help gain detail?

A

Small focal spot

35
Q

Common magnification factors

A

1.5x or 2x, some units offer 1.8x

Mammo (16 decks)

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