Physics

Question 1

Target (anode) material

Answer 1

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

Question 2

Filter material is inserted into xray beam to

Answer 2

Enhance contrast

Question 3

Filters are most ofter made of

Answer 3

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

Question 4

Exit window of tube housing made of

Answer 4

Beryllium

Question 5

Roles of added filtration

Answer 5

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

Question 6

Grids

Answer 6

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

Question 7

Grid ratio in mammography

Answer 7

3:1 to 5:1

Question 8

Linear/focused grid

Answer 8

-reduce scatter from 1 direction
-interspace material is carbon

Question 9

Honeycomb/HTC grid

Answer 9

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

Question 10

How far will light field come?

Answer 10

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

Question 11

Radiation shield must have the equivalent attenuation of at least

Answer 11

0.08 mm lead at 35 kVp

Question 12

Line focus principle

Answer 12

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

Question 13

Large focal spot measures

Answer 13

0.3 mm and is used for standard imaging

Question 14

Small focal spot measures

Answer 14

0.1 mm and is used for magnification imaging

Question 15

The anode acts as a what

Answer 15

A filter; called self-filtration

Question 16

The xrays towards the cathode end of tube have

Answer 16

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

Question 17

The xrays toward the anode side are

Answer 17

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

Question 18

Half field geometry

Answer 18

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

Question 19

kVp

Answer 19

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

Question 20

mAs

Answer 20

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

Question 21

Typical mA selection

Answer 21

20-100 mA

Question 22

Typical time in sections

Answer 22

0.4 to over 1 second

Question 23

Backup timers

Answer 23

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

Question 24

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

Answer 24

1) characteristic radiation
2) bremsstrahlung radiation

Question 25

Characteristic radiation

Answer 25

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

Question 26

Bremsstrahlung radiation

Answer 26

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

Question 27

Anode material molybdenum (characteristic radiation)

Answer 27

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

Question 28

Anode material rhodium (characteristic radiation)

Answer 28

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

Question 29

Molybdenum filter (bremsstrahlung radiation)

Answer 29

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

Question 30

Rhodium filter (bremsstrahlung radiation)

Answer 30

-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

Question 31

Pt dose with and without grid (one view)

Answer 31

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

Question 32

What is average breast made of?

Answer 32

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

Question 33

Average SID in mammography machine

Answer 33

65-66 cm

Question 34

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

Answer 34

Small focal spot

Question 35

Common magnification factors

Answer 35

1.5x or 2x, some units offer 1.8x