MEDRAD QUIZ 4 MAMMO Flashcards
What target is best for dense breast tissue and why?
Rhodium, because it’s a higher atomic number, so able to penetrate the dense tissue better and provide clear image
SID for mammography?
60-80cm
What window glass is used? why?
beryllium windowm, because it allows low E photons to pass
Does mammography use high or low atomic number materials?
low
High or low kvp with mammography?
low kvp
What target material is used in mammography? (other than dense tissue)
molybdenum
Beam energy magic number for photon E (best for imaging breast)
17-24 kev
Molybdenum k-shell BE
20 kev
How often is mammography screening? ages?
every 2 years ages 40-74
Breast cancer is the
most common cancer amongst women
List breast cancer risk factors
age (older), family history, genetics, early mensuration, menopause after 55, no children or having children late, prolonged estrogen use, rad therapy at young age, more dense breast, more education, more socio-economic
Explain digital tomosynthesis
tube moves during exam, takes many images at a time, can see different “slices”, only done if needed, blurs out different parts
Pros of digital tomosynthesis
decreases movement during exam, increased contrast resolution
Con of digital tomosynthesis
Increased patient dose
What kvp do you use in mammography
30 kvp
What is the magic number for photon E in mammography good at, regarding the image?
Good at showing the difference in tissues
Why do we use a heavy element filter in mammography?
Because you just want the narrow range of photon E in the beam, so it absorbs the low E and the high E photons (lets through JUST the ones just below the BE)
What is the filter made of in mammography?
Molybdenum
Why do we screen?
Since screening, there’s been a huge decrease in deaths from breast cancer
Why do we use low kvp with mammography?
breast has no bone / air - there’s fat / tissue which are similar density / Z. Low kvp is for more absorption
Which type of breast are at higher risk for breast cancer?
dense breast
Why do we use molybdenum?
because with MO you get a large spike at 17-19kev (which works with MO magic number of 17-24)
Why don’t we want photons below 17 and above 24?
Because the low E photons (below 17) will get absorbed by the breast (not useful), and high E doesn’t play a role because they don’t highlight details in the breast tissue
What do you use to get rid of the low and high E photons we don’t need?
k-edge filter
What is the k-edge filter made of?
molybdenum
What is the k-edge # for molybdenum
20 (lets through mostly 17-19 photons)
What does the k-edge allow?
to get rid of photons not needed (ones that are too low so will just get absorbed, and ones too high that won’t provide anything useful for the photo)
What resolution is important for mammography?
Spatial resolution because of the fine details needed
What decreases the anode heel effect in mammography?
tube tilt
Downside to short SID used?
anode heel effect, higher dose, diverging beam
Plus side to short SID used?
shorter exposure time, sharpness (SR), technique (mAs)
What does compression help with?
even out breast tissue, OID, CR/SR, measures thickness
Weight of compression?
20 kg
Spike occurs at 17-19, why?
k-edge filter
Same target and filter produces?
char rad
Mixed target and filter produces mostly?
brems rad
Digital tomosynthesis produces what resolution?
contrast resolution
What factors improve SR in mammography?
Small FS, compression, grounded metal tube, AEC location, IR design (direct)
AEC is located where for mammography?
AFTER IR
Grounded metal tube helps with?
reducing off focus radiation
Digital produces better ______ than film
CR
Factors influencing CR in mammography?
compression, beam energy, grid, tube tilt, tube orientation
Why is the tube tilted in mammography?
reduces anode-heel effect while maintaining spatial resolution and contrast resolution-improves image quality
Angle of tube tilt?
20-24 degrees, anode side higher
What is at cathode and anode end?
chest wall at cathode end, breast tissue at anode end
What effect does magnification have on the image in mammography?
uses small FS and increased OID. Outer area will have more divergence and middle area will be sharper. Image will have more pixels per area of tissue and more photons per area of tissue, reduce mAs
Grid used in mammography?
crossed grid - helps reduce / absorb scatter (more line pairs)
Beam energy in mammography?
low
Grid not used during?
magnification mode
Decreased SOD in magnification mode causes?
increased dose
What shape focal spot?
circular
increase or decrease patient dose: compression
decrease
increase or decrease patient dose: beam energy
increase
increase or decrease patient dose: grid
increase
Most of mammography beam is what kind of radiation?
char rad
Best filter combo in mammo?
mo + mo
What should the mammo filter, filter out?
all but 17-19 photons
What size FS?
small
Small FS helps with?
beter SR, see more details
Most photons that make it through k-edge filter?
17-19kev (they’ll show most detail)
The distance between cathode and anode are _______ in mammo
closer together (have a shorter distance)
AEC will ______ after enough rad exposure
shut down
Purpose of having AEC after IR in mammo?
to get breast closer to IR (decrease OID = better SR)
