Physics Ch 5 Mammo Flashcards
mammo XR vs gen XR –> differences? (3)
- kVp
- beam spectrum
- anode
- lower kVp
- use nearly monoenergetic beam
- anode: molybdenum or rhodium
which anode target & filter combination should never be used?
Rh/Mo
what anode target & filter combination is used for denser breasts?
Rh/Rh –> higher energy than Mo/Mo
some digital systems –> use anode target & filter combination for inc penetration/lower dose? (2) Con? (1)
- Tungsten/Rho
- Tungsten/Silver
dec contrast –> but can improve contrast w post-processing
mammo filter –> inc k-edge energy –> what happen to beam avg energy? contrast?
- avg energy inc
- contrast dec
focal spot size?
- mammo
- gen XR
- mammo: 0.1 & 0.3 mm
- gen XR: 0.6 & 1.2 mm
mammo vs gen XR –> difference in…
- focal spot size
- mA
- exposure time
- focal spot size –> smaller
- mA –> lower
- exposure time –> longer
what factor is changed to maximize detection of solid breast mass in the background of normal breast parenchyma?
- mAs
- inc kVp
- dec kVp
dec kVp
what factor is changed to maximize detection of low grade ductal malig (no assoc mass) on background of normal breast parenchyma?
- mAs
- inc kVp
- dec focal spot size
dec focal spot size
XR tube –> window material?
- gen XR
- mammo XR
- gen XR –> pyrex glass
- mammo XR –> beryllium
mammo –> compress breast tissue –> #1 advantage?
dec dose & scatter
grid –> pro? con?
- remv scatter –> improve contrast
- inc dose
mammo vs gen XR –> difference in grid ratio?
mammo –> lower grid ratio
mammo XR –> magnification –> goal?
improve detection of calcifications
mammo XR –> how magnified?
- dec source to obj distance
- inc obj to detector distance
mammo XR –> mag view –> use grid? why?
no grid –> air gap act as grid
mammo XR –> mag view –> change in…
- focal spot?
- mA?
- exposure time?
- focal spot –> smaller
- mA –> dec
- exposure time –> inc
what is air kerma?
XR density –> #XRs per unit of space
mammo XR vs gen XR –> difference?
- optical density
- receptor air kerma
mammo XR:
- optical density –> higher
- receptor air kerma –> higher
digital mammo –> what detector type has best spatial resolution?
photoconductors (selenium)
digital mammo –> MQSA requirement for line pair?
digital –> no specific line pair requirements
dark noise –> caused by?
electronic fluctuations w/in detector element
digital mammo –> artifacts? (2)
- ghosting
- pixels gone bad
what is ghosting artifact?
high attenuating obj –> ie lead –> placed in beam –> burned into detector –> residual image from prior exposure
digital breast tomosynthesis –> advantage over conventional mammo?
dec effects of tissue superimposition –> inc sens & spec –> reduce false positives
digital breast tomosynthesis vs conventional mammo –> difference?
- mass margin & shape
- mass density
- fat mass
tomo:
- margin & shape –> improved
- density –> dec
- fat mass –> on tomo, cancer may be shown to engulf fat –> intralesional fat –> still recommend bx
what is positive predictive value?
positive study –> actually have breast cancer
positive predictive value –> formula?
positive exam w CA / (positive exam w CA + positive exam w/out CA)
what is PPV1?
screening mammo –> positive
what is PPV2?
recommend bx
what is PPV3?
bx –> positive
mammo workstation –> minimum #megapixels?
3 MP
MQSA –> processor QC –> how often?
daily
MQSA –> darkroom cleanliness –> how often?
daily
MQSA –> viewbox conditions –> how often?
wkly
MQSA –> phantom eval –> how often?
wkly
MQSA –> repeat analysis –> how often?
qtrly
MQSA –> compression test –> how often?
semi-annual
MQSA –> darkroom fog –> how often?
semi-annual
MQSA –> screen film contrast –> how often?
semi-annual
breast phantom –> dose limit w grid? without grid?
- grid –> 3 mGy
- no grid –> 1 mGy
MQSA: last 2 yrs of training –> required to read how many mammo exams to be able to read mammos?
240
