Exam 2 Flashcards
what is screening mammo?
for asymptomatic women (50+ yrs); min of 2 views
what are the 3types of mammo?
screening, diagnostic, & baseline
what is diagnostic mammo?
for pt’s w symptoms or elevated risk factors; 2-3 views
what is baseline mammo?
very FIRST XR of breasts (usually before 40 yrs); used as comparison w ALL FUTURE MAMMOS
80% of breast cancers are?
ductal (mammory duct)
what are the 3 target filter combo’s used in mammo?
Mo/Mo, Mo/Rh, Rh/Rh (Mo = molybdenum, Rh = Rhodium)
Mo targets produce char. XRs w an energy of?
19 keV (good for XRs of smaller breasts)
Rh targets produce char. XRs w an energy of?
23 keV (more penetration for thicker breasts)
what is the best target filter combo for thin breasts?
Mo/Mo
what is the best target filter combo for pt’s w thick breasts?
Rh/Rh
what is the effect of focal spot on spatial res?
(inverse) smaller focal spot –> higher spatial res
what is the purpose of angling the anode and tilting the tube in XR, in mammo?
to obtain smaller focal spot size of 0.3/0.1
how does mammo obtain a focal spot size of 0.3/0.1?
angling anode 23º and tilting tube 6º
what is the anode angle in mammo?
23º
how much is the XR tube tilted in mammo?
6º
what are the advantages of the anode angle and tube tilt in mammo?
smaller effective focal spot –> higher spatial res; CR becomes II to chest wall & no tissue is missed
what is the inherent filtration used in mammo?
0.1 mm of Al equivalent
what is the total filtration used in mammo?
no less than 0.5 mm of Al equivalent
thick dense breasts requires what target filter combo?
Rh/Rh
Mo/Mo for thin fatty breasts
in mammo, to get uniform density, where should you position the anode? the cathode?
anode over nipple
cathode over chest wall
advantages of compression in mammo? (10)
more uniform thickness/OD,
reduce scatter rad,
reduce pt motion,
increase spatial/contrast res,
tissue near chest wall less likely to underexposed,
tissue near nipples less likely to be overexposed,
brings tissue closer to IR –> less focal spot blur,
less pt dose,
less superimposition of tissue (bc spreads it out),
reduces absorption blur
what is the appropriate grid frequency in mammo?
30-50 lines/cm
what is the appropriate grid ratio used in mammo?
4:1 to 5:1 focused grid
in mammo, what happens w use of 4:1 grid?
nearly doubles pt dose, but significantly improves contrast
what is the unique grid specific for mammo?
high transmission cellular grid (HTC)
what is the purpose of an HTC grid?
reduces scatter in TWO directions,
has clean-up char.’s of crossed grid
what is the grid ratio of an HTC grid?
3:8:1
where is the AEC located in a mammo unit?
under the IR (to min. OID & improve spatial res)
in mammo, the effective focal spot should not exceed?
0.1 mm (to help investigate small lesions/micro-calcifications)
how do you place a single emulsion mammo film inside a cassette?
XR film places btw XR tube and rad IS; w emulsion ALWAYS facing IS
what material makes up the CCD in mammo?
a-Si (indirect) or a-Se (direct)
CCD used in mammo converts ______ to _______
vis. light photons to e-‘s
electronic noise in digital mammo can be reduced by?
cooling the detector (which improves contrast res.)
members of a mammo QC team?
radiologist (ultimate responsibility), medical physicist, and mammographer (most hands on)
diff btw QC & QA?
QC - eval./maintain equip., QA - eval. ppl
role of a med physicist in mammo QC?
principally does annual performance eval. of imaging systems/equip.
role of a radiologist in mammo QC?
has ultimate responsibility, supervises entire QA program, oversees/selects team, supervises pt comm. & tracking
4 factors that affect blurring of unwanted structures in tomo?
D of object from focal plane
exposure angle
OID
tube trajectory
how does exposure angle in tomo affect blurring of unwanted structures?
increase exposure angle –> increase blurring
how does OID in tomo affect blurring of unwanted structures?
increase OID –> increase blurring
how does tube trajectory in tomo affect blurring of unwanted structures?
linear trajectory has least blurring, whereas spiral/hypocycloidal has the most blurring
what is the relationship btw tomo angle & slice thickness
inverse (larger angle gives thinner slices)
what is the focal plane in tomo?
(aka objective plane) plane in which object is clear & in focus; where the img is the most sharp
what is zonography?
uses tomo angle LESS than 10º to get very large section thickness
when is zonography used?
when subject contrast is so low that thin section tomo will not give clear img
what are most common exams performed for zonography?
chest and renal
what are the advantages of tomo?
(principally) to improve rad. contrast, & to blur overlying/underlying tissue structures
what is the disadvantage of tomo?
increased pt dose
what is the rad dose of a single tomo exposure of the kidneys?
1000 mrad
what is panoramic tomo?
XR tube & IR move around the head to img curved bony structures (mandible)
what is the most common use for panoramic tomo?
dental survey
2 formulas for magnification factor?
MF = img size/object size MF = SID/SOD
2 daily tasks in mammo QC
darkroom cleanliness, processor QC
3 weekly tasks in mammo QC
viewboxes/viewing conditions, phantom imgs, & screen cleanliness (screens should be allowed to air dry VERTICALLY)
3 semiannual tasks in mammo QC
darkroom fog, screen-film contact, compression
how much luminance is required for mammo viewboxes?
3000 nit (candela per square meter)
when should phantom img’s be taken?
after equipment installation/maintenance
how often should a repeat analysis be performed?
quarterly
what is an acceptable repeat rate?
2%
what is the min. mammo’s to be included during a repeat anal.?
at least 250 mammo’s
what is the formula to determine the repeat rate?
repeat rate (%) = (# of repeated XRs/total # of XRs) x 100
how is screen film-contact checked?
perform wire mesh test and view it from a distance of 3 ft. dark areas indicate poor screen-film contact
how often should you perform a wire mesh test
semiannually
how much compression is required in mammo?
25-40 lbs held for at least 15 seconds
in tomo, what is the net effect of increased blurring?
a thinner focal plane
what is fulcrum?
a pivot point along the connecting rod btw XR tube & film in a tomographic system; only anatomic structures in this plane are seen clearly (area of interest)
fulcrum types?
adjustable & fixed
what is trajectory (tomo)?
type of movement (5 types)
what are the 5 trajectories in tomo?
linear (least blurring), elliptical, circular, spiral, & hypocycloidal (most blurring)
DICOM?
digital imaging & communications in medicine
SMPTE stands for?
society of motion pictures & television engineers
what is an SMPTE pattern?
measures the res. of a display system, to point out any gross deviations in luminance adjustment (5% on black, 95% on white)
GSDF?
“gray scale display f(x)”, ensures consistent gray scale appearance in img transfers
DIN?
(Deutaches Instiitut fur Normung) acceptance testing standard to address requirements for digital display
AAPM TG 18?
(American Assoc. of Physicists in Medicine, developed test patterns/procedures in Task Group Report 18)
what does a photometer do?
measures the amount of light
2 types of photometers?
near range & telescopic (1m away from monitor)
in regards to photometers, the National Institute of Standards & Technology (NIST) recommends…..?
better than 5% response at 50º angulations
2 types of geometric distortions?
pincushion & barrel-like distortions
geometric distortions affect what?
relative size/shape of image features
what are the 2 types of reflection?
diffuse & specular
what is diffusion reflection
seen at all points
what is specular reflection
a reflection only seen at one vantage point
what is used to evaluate display res?
TG 18 CX & TG 18 QC
what is used to eval. res. uniformity?
TG 18 PX
what is used to eval. display noise on a digital system?
TG 18 AFC pattern
the max non-uniformity of a display device should be
LESS THAN 30%
in mammo, low kVp produces ____ _________ & ____ ________, which gives better contrast
less Compton Scatter & more photoelectric absorption
how many lp’s in mammo? what is the result?
15 lp’s for better spatial res. (v. digi’s 10 lp’s)
how many total lobes in the breast?
30-40
(tomo) more movement/trajectory produces what?
a sharper image
VESA
video electronic standard assoc
does acceptance testing for the requirements for digi. display systems
DIN
ea breast is made up of how many lobes
15-20
do we use magnification in mammo?
not routinely (doubles dose)
what is the dose density relationship displayed in digi rad?
response of a CCD is linear, not curvilinear like screen film
Ex. pt’s femur is XRed w grid ratio of 8:1 at an SID of 40”. The femur was 4” away from the IR. what is the actual size of the femur if the img size was 24 cm?
21.62 cm
In digital mammo, the repeat rate should not exceed?
1%
how many women get breast cancer?
1/8
in digi mammo, spatial res. is _________ bc of XR tube focal spot size
superior
what is spatial res. limited by in digi mammo?
pixel size
