Exam 2 Flashcards by Bree Reppy

what is screening mammo?

for asymptomatic women (50+ yrs); min of 2 views

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what are the 3types of mammo?

screening, diagnostic, & baseline

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what is diagnostic mammo?

for pt’s w symptoms or elevated risk factors; 2-3 views

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what is baseline mammo?

very FIRST XR of breasts (usually before 40 yrs); used as comparison w ALL FUTURE MAMMOS

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80% of breast cancers are?

ductal (mammory duct)

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what are the 3 target filter combo’s used in mammo?

Mo/Mo, Mo/Rh, Rh/Rh (Mo = molybdenum, Rh = Rhodium)

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Mo targets produce char. XRs w an energy of?

19 keV (good for XRs of smaller breasts)

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Rh targets produce char. XRs w an energy of?

23 keV (more penetration for thicker breasts)

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what is the best target filter combo for thin breasts?

Mo/Mo

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what is the best target filter combo for pt’s w thick breasts?

Rh/Rh

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what is the effect of focal spot on spatial res?

(inverse) smaller focal spot –> higher spatial res

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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

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how does mammo obtain a focal spot size of 0.3/0.1?

angling anode 23º and tilting tube 6º

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what is the anode angle in mammo?

23º

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how much is the XR tube tilted in mammo?

6º

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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

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what is the inherent filtration used in mammo?

0.1 mm of Al equivalent

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what is the total filtration used in mammo?

no less than 0.5 mm of Al equivalent

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thick dense breasts requires what target filter combo?

Rh/Rh

Mo/Mo for thin fatty breasts

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in mammo, to get uniform density, where should you position the anode? the cathode?

anode over nipple

cathode over chest wall

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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

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what is the appropriate grid frequency in mammo?

30-50 lines/cm

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what is the appropriate grid ratio used in mammo?

4:1 to 5:1 focused grid

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in mammo, what happens w use of 4:1 grid?

nearly doubles pt dose, but significantly improves contrast

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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?

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?

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

Exam 2 Flashcards

(101 cards)