Mammo equipment Flashcards
what is key for NHS breast screening programme
mammo using two views of breast
what are the technical improvements of mammo
- improved compression cones
- replacement of film with digital shorter exposure times
- improved radiation protection
- improved comfort
what are the requirements for optimal mammography
- 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
rotation of mammographic units
180 degrees
vertical movement of mammographic units
65cm - 135 cm above floor
SID
65 cm
purpose of compression plate in mammographic unit
to flatten and spread out breast tissue ensuring x ray images are obtained of high quality
there are 2 compression plates, what are their dimensions
18x24 cm
24x30cm
how is motorized compression initiated
through footswitch
what is tube mounting
refers to mechanism by which XR tube is attached and positioned within imaging system
- housing is less bulky
- high tension cables
what does shape of breast require
higher intensity of radiation near chest wall to create uniform exposure
where is anode positioned
anode is further from patient
where is cathode positioned
cathode is closer to chest wall
what is the anode heel effect used for
to improve image quality and lower patient dose
- increases intensity of radiation near chest wall (cathode) where greater penetration is needed
features of breast support table
- smooth edges and corners
- easy to clean
- power-controlled up and down movements with a brake
- this movement must be disabled when compression applied
what does compression do and why do we need it
- 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
features of the compression plate
- radiolucent
- detachable
- transparent
- durable
- can be applied at variable speed
- range of movement
- emergency release control
what does beam collimation have to match
the compression plate’s size
how do we show small density and atomic number differences between soft tissues in mammo
- using low kVp of 25-35
- at low kVp photoelectric absorption is major attenuation process and proportional to tissue atomic number cubed
what good target did we use for mammography
molybdenum (Mo)
- 17 and 19 keV
Rhodium (Rh)
- 20 and 22 keV
why do we use Mo and Rh as target materials for mammo
produce characteristic XR that is near optimum energy
what do modern XR tubes have
dual material anode target tracks
what are filters used to achieve
optimal photon energies that give good tissue contrast
why do we use a Mo filter to filter XR beam coming from Mo target
because an element is transparent to its own characteristic radiation so K line energies are let through while other energies are filtered out
monoenergetic XR beam
- produced using Mo filter
- gives good image contrast
