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Imaging > Lecture 8- Mammogram > Flashcards

Lecture 8- Mammogram Flashcards

1
Q

what color is fat on mammogram

A

dark

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2
Q

what color are the glands on mammograms

A

light

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3
Q

what are you looking for in mammogram

A

look for micro calcifications, compare to last two years and subtle differences in the tissue

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4
Q

what is the use of Z in mammogram and what is the usual Z for it

A

adipose, glandular, fibroadenoma, ductal carcinoma, between 5.3 and 5.8- need to maximize the difference between breast tissue to get the best image

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5
Q

which of the 4 x-ray interactions should be maximized for mammography?

A

photoelectric effect

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6
Q

why is the photoelectric effect important to mammography

A

it helps to distinguish different Z so it helps with small differences. You want to vary the energy and low energy X-rays. The interaction probability is proportional to Z3/E3

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7
Q

what is the interaction probability of compote scatter

A

I/E

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8
Q

what is the typical kVP of typical radiography and typical mammography

A

typical radiography is 70-100 and typical mammography is 25-30

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9
Q

draw a mammography Xray beam

A

draw it

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10
Q

what is the difference between a diagnostic and screening mammogram

A

the screening has lower radiation because its a screening test. It needs to image micro calcifications less than 100

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11
Q

draw a mammogram X-ray tube

A

what is different

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12
Q

does mammogram use half filed or full field and draw the breast in it

A

half field

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13
Q

why does it use half-field

A

it uses half field to that it is perpendicular to the chest wall which is important because it gets the better image of the breast

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14
Q

what are the three anode materials for mammography

A

molybdenum, rhodium, tungsten

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15
Q

what is the Z of molybdenium

A

Z=42 and it is the traditional mammography anode material

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16
Q

what is the Z of rhodium

A

Z=45 like Mo

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17
Q

what is the Z of tungsten

A

Z=74 and it is also a typical radiography anode material

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18
Q

what are the spikes on an output to energy spectrum and what is the continuous part called

A

spikes are characteristic Xray

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19
Q

tube filtration- what is it and what does it do

A

an added later of metal at the tube port and it is to selectively remove some x-rays to modify the x-ray beam spectra

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20
Q

what is different about the mammogram filter vs. normal

A

there is an additional ilter

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21
Q

what causes the discontinuity in the attenuation coefficient for Mo, Rh, and Ag

A

K edge absorption

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22
Q

what is the k edge absorption

A

probability of the photoelectric effect increases sharply when incident X-ray energy is just greater than the binding shell energy

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23
Q

what is the use of the mo filter K-edge

A

forms a window to remove low and high energy x=rays leaving Mo characteristic xrays

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24
Q

what is Rh better for

A

higher energy X-rays for more penetration of thicker tissues

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25
Q

what are M anode used for

A

higher energy X-rays and higher tube loading for tomosynthesis.

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26
Q

what filters can be used for mammography

A

Rh, Ag, and Al

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27
Q

what shell is removed with mammography

A

L shell cray are at 10kev remove the L shell

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28
Q

what is a typical HVL for mammography system

A

.3 and .4 mm Al at 30 kvp, 1-2 cm in breast tissues

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29
Q

when is the HVL higher for Z anode and filter

A

Mo/Mo

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30
Q

what are grids used for

A

scatter rejection in contrast imaging. Common grid specifications, Moving bucky to blur grid shadow.

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31
Q

what is the best grid ratio

A

4:1 and 5:1 bucky factor is 2 ro 3

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32
Q

compare mammogram focal spot size to radiography

A

.3/.1 mm and 1.2/.6mm

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33
Q

compare mammogram KVP to radiography

A

25-30 KVP and 50-120KVP

34
Q

compare mammogram mA to radiography

A

LFS:100 and SFS: 30 and 200-800

35
Q

compare mammogram exposure time to radiography

A

1-2 seconds and .1-.5sec

36
Q

compare mammogram grid ratio to radiography

A

4:1-5:1 and 6:1-16.1

37
Q

is magnification used in mammogram and if so, when

A

there is no magnification in screening exams, but if a questionable lesion is found, a diagnostic examination is conducted. Magnification views may be required where investigation or masses or better delineation of calcification is needed

38
Q

what adjustments are made when using geometric maginification

A

magnification factor of 1.5-2 and spot impression paddle with small focal spot size selected (.1mm)-mA reduced to 30 mA. No grid used because air gap reduces scatter that reaches the detector

39
Q

what happens to the penumbra as the geometric magnification increases

A

increases

40
Q

what are the advantages of geometric magnification

A

increases conversion for reduced overlapping tissue, improved

41
Q

what are the disadvantages of geometric magnification

A

smaller imaging field and increased patient motion artifact

42
Q

is screen film for mammography single or double sided

A

single sided

43
Q

what is most commonly used for CR mammogrpahy

A

dual sided CR and imaging pates and dual sided readout. Smaller pixel side.

44
Q

what are the main differences forflat panel detectors for mammography

A

smaller size, smaller izel size, and AEC method

45
Q

AEC in mammography

A

for screen field and CR image receptors, AEC uses a phtootimer sensor and voltage comparator similar to radiography.

46
Q

what changes for flat panel mammography

A

it is a short 50 ms exposure so it is not using a sensor

47
Q

what is a photon counting slit scan system

A

it is single photon detection eliminates electronic noise. Detector arranged as a line that scans across breast. X-ray beam colimated to a slit pre and post patient to minimize the scatter. 3-15 time

48
Q

what is a digital mammography display

A

it is high resolution with 5 Mpixel compared to 2-3 pixel for radiography. there is high luminance of 300-1000 as compared to 200-300 of normal radiography.

49
Q

what is some of the special image processing for digital mammography

A

skin line enhancement and equalized image density

50
Q

what is the formula for the average glandular dose

A

Dg=dgN time Xesak
where Vesak- entrance skin air karma
DgN- average glandular dose conversion factor, which is determined from Monte Carlo simulations of photon interactions within models of breast tissue

51
Q

what causes DgN to increase

A

photon energy

52
Q

what causes DgN to decrease

A

breast thickness

53
Q

who regulates the mammography

A

mammography quality standards act, which is through the american college of radiology or some individual states. Includes personnel requirements and quality control tests and sample clinical images. provided by the FDA after accredidation. Includes annual facility inspection.

54
Q

what aspects are included in physics equipment evaluation

A

collimation, system resolution, AEC performance, artifact evaluation, image quality evaluation, beam quality (HVL), and breast dosimetry.

55
Q

what is the minimum phantom count to pass image quality standards

A

minimum is 4 fibers, 3 speck groups, and 3 masses. Artifacts that look like the object are subtracted from the count

56
Q

what is used to quantify image quality for these tests

A

SNR and CNR

57
Q

what are the qualitites of the breast phantom

A

mimics standard breast attenuation, thickness of 4.2 cm, 50% glandular/50% adipose tissue equivalent

58
Q

what is used to measure breast dosimetry

A

measures entrance skin air karma that is used for 4.2 cm 50% glandular breast for that clinical site. Calculate Dg regulatory upper limit is 3mGy

59
Q

what is breast tomosynthesis

A

it is an X-ray tube and fast detectors that swing at a specific angle

60
Q

what are the imaging equipment requirements for breast tomosynthesis

A

xray tube and gantry automated angled movement, fast readout digital detector, high power and heat loading x-ray tube, and higher beam energy to reduce patient dose

61
Q

is tomosynthesis available on all systems

A

no it depends on the provider

62
Q

how are images reconstructed for tomosynthesis

A

they put the images together from the different angles like a CT scan

63
Q

what is synthesized 2D mammogrpahy

A

it is an mage constructed from tomosynthesis

64
Q

what are the benefits to the 2D synthesized from the tomosynthesis

A

reduces dose, and reduces exposure time in compression.

65
Q

what measure is used is synthesized 2D mammography

A

created as a maximum intensity projection of slice dataset

66
Q

are there differences in sensitivity and specificity for tomosynthesis and 2D images

A

no there are not

67
Q

what happens if the collimator clips at the chest wall

A

colimator blade field extends no more than 2% SID beyond image receptor edges at the chest wall is positioned in too far. Blurred edge indicates obstruction is magnified near the x-ray tube.

68
Q

what are the MQSA requirements for chest clipping

A

no collimator clipping the chest wall. x-ray

69
Q

what happens with grid artifact

A

grid should be moving during he exposure so that the lines can be blurred artifact is subtle if the motion is partial

70
Q

what is cross-hatch grid

A

unitque mammography grid because it is high transmission cellular grid. Grid should be moving during exosure

71
Q

what is a ghost image

A

it is a residual signal from previous image. Direct detector loses sensitivity in areas of high exposure due to retained trapped charge

72
Q

how do you fix issues with ghost image

A

longer wait time between exposures and manufacturers modified detector readout sequence thing to reduce trapped charge

73
Q

what is a tomosunthesis artifact

A

it is artificial low density surrounding high density objects along the scan direction which leads to a halo artifact due to limited angular range in acquisition

74
Q

what is used to fix tomosynthesis artifact

A

various reconstruction algorithm modifications have been proposed to reduce appearance. Based on removing high contrast object from the projection images prior to reconstruction, then adding back into slice images

75
Q

what is the zipper artifact/cause

A

out-of-plane high contrast object is visible as zipper artifact along the scan direction caused by limited angular range in acquisition sweep.

76
Q

how do you resolve the zipper artifact

A

various reconstruction algorithm modifications have been proposed to reduce appearance. Based on removing high contrast object from the projection images prior to reconstruction, then adding back into slice images

77
Q

what is the staircase artifact

A

limited angular range in acquisition sweep results in staircase artifact at edge of field

78
Q

how do you fix the staircase artifact

A

same solutions as halo arifact reduction

79
Q

what causes false calcifications on 2D image slice

A

overlapping dense ligaments in the slice images combine to appear as calcifications

80
Q

how do you resolve false calcifications

A

modifications of the 2D image synthesis algorithm

Imaging (19 decks)

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