Mammo equipment

Question 1

what is key for NHS breast screening programme

Answer 1

mammo using two views of breast

Question 2

what are the technical improvements of mammo

Answer 2

• improved compression cones
• replacement of film with digital shorter exposure times
• improved radiation protection
• improved comfort

Question 3

what are the requirements for optimal mammography

Answer 3

• whole breast must be demonstrated
• reproducible images (comparison)
• equipment and patient must be well supported
• even density across image required
• movement unsharpness needs to be minimised

Question 4

rotation of mammographic units

Answer 4

180 degrees

Question 5

vertical movement of mammographic units

Answer 5

65cm - 135 cm above floor

Question 6

SID

Answer 6

65 cm

Question 7

purpose of compression plate in mammographic unit

Answer 7

to flatten and spread out breast tissue ensuring x ray images are obtained of high quality

Question 8

there are 2 compression plates, what are their dimensions

Answer 8

18x24 cm
24x30cm

Question 9

how is motorized compression initiated

Answer 9

through footswitch

Question 10

what is tube mounting

Answer 10

refers to mechanism by which XR tube is attached and positioned within imaging system
- housing is less bulky
- high tension cables

Question 11

what does shape of breast require

Answer 11

higher intensity of radiation near chest wall to create uniform exposure

Question 12

where is anode positioned

Answer 12

anode is further from patient

Question 13

where is cathode positioned

Answer 13

cathode is closer to chest wall

Question 14

what is the anode heel effect used for

Answer 14

to improve image quality and lower patient dose
- increases intensity of radiation near chest wall (cathode) where greater penetration is needed

Question 15

features of breast support table

Answer 15

• smooth edges and corners
• easy to clean
• power-controlled up and down movements with a brake
• this movement must be disabled when compression applied

Question 16

what does compression do and why do we need it

Answer 16

• reduces superposition of tissues
• contributes to even transmission and scattering over whole breast
• decreases distance from any plane within breast image = reduces geometric sharpness
• provides overall lower attenuation = lower dose
• compressed breast provides more uniform attenuation
• reduces anatomical motion during exposure = reduces image unsharpness

Question 17

features of the compression plate

Answer 17

• radiolucent
• detachable
• transparent
• durable
• can be applied at variable speed
• range of movement
• emergency release control

Question 18

what does beam collimation have to match

Answer 18

the compression plate’s size

Question 19

how do we show small density and atomic number differences between soft tissues in mammo

Answer 19

• using low kVp of 25-35
• at low kVp photoelectric absorption is major attenuation process and proportional to tissue atomic number cubed

Question 20

what good target did we use for mammography

Answer 20

molybdenum (Mo)
- 17 and 19 keV
Rhodium (Rh)
- 20 and 22 keV

Question 21

why do we use Mo and Rh as target materials for mammo

Answer 21

produce characteristic XR that is near optimum energy

Question 22

what do modern XR tubes have

Answer 22

dual material anode target tracks

Question 23

what are filters used to achieve

Answer 23

optimal photon energies that give good tissue contrast

Question 24

why do we use a Mo filter to filter XR beam coming from Mo target

Answer 24

because an element is transparent to its own characteristic radiation so K line energies are let through while other energies are filtered out

Question 25

monoenergetic XR beam

Answer 25

• produced using Mo filter
• gives good image contrast