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Huda Facts > Huda Facts2.csv - Huda Facts2.csv > Flashcards

Huda Facts2.csv - Huda Facts2.csv Flashcards

1
Q

Watt

A

Joule/Sec

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2
Q

Lead K-edge

A

88 kev

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3
Q

X-ray wavelength is on the order of:

A

an atom

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4
Q

MR RF wavelength is on the order of:

A

a patient

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5
Q

K shell to outer shell binding energy ratio

A

1000 to 1

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6
Q

Tungsten k-edge

A

70 kev

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7
Q

Extremity radiograph relies mostly of which kind of x-ray interaction with tissue:

A

PE effect due to high z of bone (prob of PE effect increases with z cubed)

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8
Q

KVP for extremity radiograph

A

60 KVP

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9
Q

KVP for abdomen radiogaph

A

80 KVP

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10
Q

KVP for chest radiograph

A

120 KVP

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11
Q

MA for chest radiograph

A

500-1000

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12
Q

MA for CT

A

500-1000

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13
Q

MA for Fluoro

A

5

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14
Q

MAS for a chest xray

A

1

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15
Q

MAS for an abdomen radiograph

A

20

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16
Q

Does energy get transferred with coherent scatter?

A

No

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17
Q

Another name for coherent scatter

A

Raleigh

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18
Q

What percentage of X-rays are absorbed by a patient

A

67%

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19
Q

What percentage of X-rays are scattered by a patient

A

23%

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20
Q

What percentage of X-rays penetrate the patient and hit the detector

A

1%

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21
Q

Which energy is most likely transmitted by an Ag k-edge filter in mammo (25kev k-edge)

A

24 kev

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22
Q

Xray energy where PE = compton in tissue

A

25 kev

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23
Q

What is the half value layer of TISSUE (not aluminum) for x-rays

A

3 cm

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24
Q

What interaction is most likely in a head CT?

A

Compton

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25
Q

Air Kerma for lateral skull radiograph

A

1 mGy

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26
Q

Air Kerma for frontal skull radiograph

A

2 Gy

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27
Q

Air Kerma at the image receptor for all radiographs

A

3 micro Gy

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28
Q

Air Kerma at the receptor is kept constant by the:

A

automatic exposure control (AEC)

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29
Q

Kerma Air Product for a radiograph is about:

A

1 G-square centimeters

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30
Q

KAP for a small bowel follow-through is about:

A

10 G-square centimeters

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31
Q

KAP for a TIPS is about:

A

100 G-sq cm

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32
Q

Air Kerma rate for fluoro

A

10 mGy/min

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33
Q

Cu filter is added for:

A

pediatric radiography

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34
Q

What percentage increased in KAP if a patient gets fatter by 3 cm?

A

100% bc 3 cm of human tissue is one half value layer for radiographs

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35
Q

Which x-ray tube parameter is always increased in fat patients?

A

KVP (not mas)

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36
Q

Skin erythema is technically possible starting at what threshold air kerma?

A

2 Gy

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37
Q

Cataracts are technically possible starting at what threshold air kerma?

A

0.5 Gy

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38
Q

Average glandular dose for a single mammo?

A

3 mGy per view

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39
Q

Dose to the embryo from one abdominal radiograph?

A

1 mGy

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40
Q

Dose to the embryo from one abd/pel CT?

A

10 mGy

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41
Q

Which has highest linear energy transfer among x-rays, gamma rays, and beta particles?

A

All the same.

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42
Q

Effective dose for chest CT, abdomen CT, and pelvis CT?

A

All about 3-5 mSv

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43
Q

Effective dose for head CT?

A

About 2 mSv

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44
Q

Range and examples for very low dose exam?

A

less than 0.1 mSv - examples are extremity radiograph, chest radiograph, and skull radiograph

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45
Q

Range and examples for low dose exam?

A

between 0.1 and 1 mSv. Examples are lateral spine radiograph, abdominal radiograph, and extremity CT.

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46
Q

Range and examples for moderate dose exams?

A

Between 1 and 10 mSv. Examples are CT chest, CT abdomen, CT pelvis, small bowel follow through, and MDP bone scan.

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47
Q

Range and examples for high dose exams?

A

Above 10 mSV. Examples are TIPS, FDG-PET, and triple phase liver protocol CT.

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48
Q

Ubiquitous background radiation per year in the US?

A

1 mSV

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49
Q

Background radiation in the US due to Radon?

A

2 mSV

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50
Q

Average amount of radiation received by a NM tech per year?

A

3 mSv

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51
Q

Average amount of radiation received by both IR fellows and commercial airline pilots every year?

A

5 mSv

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52
Q

Cosmic radiation is higher where?

A

High altitudes

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53
Q

What is the scatter to primary ratio in abdominal x-rays?

A

5 to 1

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54
Q

Name 3 times when you DONT use a grid?

A

peds radiograph, extremity radiopgraphy, and mag mammo

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55
Q

Standard grid ratio for radiography

A

10 to 1

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56
Q

What do the numbers in the grid stand for?

A

first number is height of the septa. Second number is the space BETWEEN the septa.

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57
Q

What percentage of the primary transmission makes it through a grid?

A

70%

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58
Q

What percentage of scatter makes it through a grid?

A

10%

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59
Q

At which patient thickness do you have to start using a grid (in peds)?

A

12 cm

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60
Q

How much more radiation is needed to expose a traditional film without the screen?

A

50 x more

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61
Q

What makes a film “faster?”

A

thicker crystal with increased sensitivity (also increased blur from light dispersion)

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62
Q

Scintillator for FPD

A

CsI

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63
Q

Rank scintillator types by patient dose

A

CsI (lowest), BaFBr (medium), Se (highest)

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64
Q

Rank scintillator types by image sharpness

A

BaFBr (lowest), CsI (moderate), Se (best)

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65
Q

How many shades of gray does one byte code for?

A

256 (2 to the 8th power)

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66
Q

What are the only two imaging modalities that make use of only 1 byte (8bits = 256 shades of gray) per pixel?

A

NM and US (shitty images)

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67
Q

All of modalities make use of 2 bytes (16 bits = 512 shades of gray) per pixel

A

radiography, mammo, CT etc.

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68
Q

How big is a chest Xray file?

A

10 MB

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69
Q

How big is a mammo image file

A

15 MB

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70
Q

How big is a CT image (one slice) image file?

A

0.5 MB

71
Q

How many pixels do you need on a monitor to read mammo?

A

5 MP

72
Q

How man pixels do you need on a monitor to read x-ray?

A

3 MP

73
Q

How many pixels do you need on a monitor to read CT?

A

2 MP

74
Q

Who monitors monitors?

A

Society for Motion Picture and Television Engineers

75
Q

Does analog or digital radiography have more quantum mottle?

A

same

76
Q

How many line pairs can you see if the sampling frequency is 1/6

A
  1. Sampling frequency of 1/6 means 6 pixels for mm. If you divide pixels per mm, you get the number of line pairs visible.
77
Q

What is the y axis of a ROC

A

Sensitivity or true positives

78
Q

What is the x axis of a ROC

A

1-specificity or false positives

79
Q

What is the relationship between geometric magnification and motion blur?

A

independent

80
Q

Rank human cells, bacteria, and viruses in order of least to most susceptible to radiation?

A

human cells most then bacteria then viruses. Viruses are super resistant to radiation.

81
Q

What is the latency period for the onset of radiation induced leukemia?

A

Years

82
Q

What is the latency period for the onset of radiation induced solid cancer?

A

Decades

83
Q

What is the background incidence of cancer in the US without additional exposure to radiation from medical exams?

A

40% of Americans get cancer

84
Q

What is the risk of a 25 year old getting radiation induced cancer from 10 mSV of radiation?

A

0.10%

85
Q

Has there been a study of human offspring having genetic effects of radiation?

A

No. Only animals. not even A bomb survivors.

86
Q

What percent of human births have a genetic defect?

A

4%

87
Q

What is the doubling dose for genetic defects?

A

1Gy (rate goes from 4% of births to 8%)

88
Q

Deterministic effects for an embryo are VERY unlikely below what amount of radiation?

A

100 mGy

89
Q

What is the rate of pediatric cancer in the US?

A

1 in 500

90
Q

What is the doubling dose for pediatric cancers?

A

25 mGy. Rate goes from 1 in 500 to 2 in 500.

91
Q

What is the downside to the ionization chamber method of detecting radiation?

A

Accurate but insensitive (needs billions of photons)

92
Q

Ring radiation detector is what?

A

Thermoluminescent dosimeter (LiF)

93
Q

Who regulates what radiology equipment can be sold in the US?

A

FDA

94
Q

Who regulates dose limits for radiology equipment?

A

States

95
Q

Regulatory dose limits exclude:

A

Medical exposures

96
Q

Regulatory effective dose limits for radiation workers tries to reduce stochastic or deterministic risk?

A

Stochastic (cancer)

97
Q

Eye dose limit

A

150 msv/year

98
Q

Extremity limit

A

500 msv/year

99
Q

Public dose limit

A

1 msv/year

100
Q

Fetal dose limit per month

A

0.5 msv/month

101
Q

Fetal dose limit for whole pregnancy

A

5 Msv after declaring

102
Q

Who regulates radiopharmaceuticals?

A

NRC or agreement states

103
Q

State regulation for required lead thickness in apron?

A

0.25 mm lead

104
Q

How thick is lead usually in apron?

A

0.5 mm

105
Q

How much does 0.5 mm of lead attenuate?

A

90%

106
Q

Which tech gets the most annual radiation?

A

NM

107
Q

Room shielding design?

A

2mm Pb thickness in the wall usually 2 meters high starting at the floor

108
Q

Scattered x-ray intensity at 1 meter from the patient

A

1000 x less

109
Q

What is the average monthly badge reading for radiology residents?

A

< 0.1 mSv per month

110
Q

What does .DAM refer to?

A

Initiative to reduce dose called: “dont order tests that don’t affect management”

111
Q

What is the dose limits for a medical imaging exam?

A

There are no dose limits

112
Q

Average T1 time for human tissue?

A

~500 ms

113
Q

Average T2 time for human tissue?

A

~50 ms

114
Q

Average T2* time for human tissue?

A

~5 ms

115
Q

Which water molecules have longer T1 time in human tissue?

A

Water in solids and free water - both T1 dark.

116
Q

Which water molecules have shorter T1 time in human tissue?

A

Water that is structured such as proteinaceous water.

117
Q

Larmor frequency at 1 T

A

42 MHz

118
Q

What happens to T1 when spin-lattice interactions are increased?

A

Reduced

119
Q

Does T1 change with different flip angles?

A

No, they are independent

120
Q

What kinds of nuclei are used in MRI or NMR?

A

Those with odd mass numbers.

121
Q

How are T1 and Bo related?

A

If you double Bo, T1 increases by root 2.

122
Q

How are T2 and Bo related?

A

Not related.

123
Q

What is the likely T2 value for protons in bone?

A

Very short. (dark)

124
Q

Can T1 be less than T2 for a given tissue?

A

No. It’s impossible.

125
Q

What are the units of magnetic field gradients?

A

Tesla per meter

126
Q

In a 128 x 256 MRI grid, how many phase encoding steps?

A

128

127
Q

In a 128 x 256 MRI grid, what does the 256 refer to?

A

Number of times an individual echo is parsed up or “sampled” by the receiver coil. This is the number of pixels in the frequency encoding direction.

128
Q

Center of an MRI image shows?

A

Low spatial frequency. (contrast)

129
Q

Periphery of an MRI image shows?

A

High spatial frequency. (resolution)

130
Q

How does K space matrix size compare to MR image matrix size?

A

Same.

131
Q

What will most likely reduce T1 weighting in a spin echo image?

A

Increasing TR.

132
Q

What will most likely reduce T2 signal in a spin echo image?

A

Decreasing TE.

133
Q

How does SNR increase with every additional NEX?

A

by root 2

134
Q

What is the upside to GRE?

A

fast. Short TR.

135
Q

What is the downside to GRE?

A

Worse SNR because signal is degraded by T2* effects, which remain present due to lack of 180 refocusing pulse.

136
Q

STIR TI is about?

A

150ms

137
Q

FLAIR TI is about?

A

2400

138
Q

What kind of MRI sequence will produce the strongest echo?

A

SE>GE and shortest TE possible to reduce dephasing.

139
Q

How many pixels would most likely be in a single echo within 128 x 196 SE image?

A
  1. For any given echo (and therefore a single line of K space), the number of pixels is determined by the numbers of samples taken - i.e., the number of data points along the frequency encoding direction.
140
Q

Iron based MR contrast agents are?

A

supra-paramagnetic

141
Q

How does heat dissipate between the focal spot and the anode body?

A

Conduction

142
Q

How does heat dissipate between the anode body and the tube housing?

A

Radiation

143
Q

How does heat dissipate between the tube housing and the atmosphere?

A

Convection

144
Q

What is the usual anode angle?

A

~15 degrees.

145
Q

Three ways to decrease heel effect?

A

Increase anode angle, decrease FOV AKA cassette size, increase SID.

146
Q

Why use a large focal spot of 1.2 mm in PA and lateral chest XR?

A

Increasing focal spot size allows for more power and therefore quicker acquisition which is important to reduce respiratory motion.

147
Q

What increases when KVP increases?

A

Both scatter and penetration.

148
Q

If you increase mAs by 2 how much do you decrease mottle?

A

root 2

149
Q

In fluoro what is the typical SID?

A

100 cm

150
Q

Why keep the II or FPD close to the patient?

A

To reduce dose AND to reduce variable geometric magnification in the patient.

151
Q

Typical SID for PA and lateral CXR?

A

72 inches

152
Q

Use a grid in portable CXR?

A

no

153
Q

Use a grid in portable abdominal XR?

A

yes. Reduce grid ratio from 10:1 to 5:1.

154
Q

What is the problem in a CXR obtained at an exposure index of 100?

A

Way too much mottle. Huda would be furious that yo missed his lung nodule because your contrast to noise ratio would be lower. Not that contrast would not change; only mottle.

155
Q

Why do we see mach band artifact?

A

Lateral inhibition of the retina.

156
Q

If you see an XR and there are parts with fine exposure and parts with shitty exposure, whats the problem?

A

Faulty grid.

157
Q

Tube current in contact mammo?

A

100 MA.

158
Q

Tube current in mag mammo?

A

25 MA.

159
Q

mAs for contact mammo?

A

100 mAs

160
Q

mAs for mag mammo?

A

75 mAs.

161
Q

To change contrast in mammo is it effective to change KVP?

A

Not really. Better to change your target/filter.

162
Q

How does breast compression affect X-ray penetration?

A

Increases penetration because breast tissues is spread apart.

163
Q

Higher/lower/or comparable radiation in digital mammo versus screen film?

A

Comprable.

164
Q

Higher/lower/or comprable radiation in BTS versus FF mammo?

A

Comprable.

165
Q

What should the luminance be for a mammo monitor?

A

600 cd/ sq meter

166
Q

What is the problem with increasing SID to reduce geometric blur?

A

Takes longer resulting in motion artifact.

167
Q

What is the half value layer of normal breast tissue at mammo level xrays?

A

1 cm (compared to 3 cm for diagnostic radiography)

168
Q

What is the HVL of aluminum for mammo?

A

0.5 mm Al (compared to 3 mm Al for diagnostic radiography)

169
Q

What is the angular movement and number of images in BTS?

A

15 degrees, 15 images.

170
Q

What improves in BTS compared to FFDM?

A

Contrast. Resolution and dose DO NOT CHANGE.

171
Q

What are the only machines in radiology that are not regulated at the state level after they have been sold?

A

Mammo machines continue to be regulated at the federal level.

172
Q

What is the MQSA regulation for resolution for SF mammo?

A

12 lp/mm

173
Q

MQSA phantom specs?

A

4.2 cm breast, 50% glandularity.

Huda Facts (5 decks)

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