Huda Facts2.csv - Huda Facts2.csv Flashcards
1
Q
Watt
A
Joule/Sec
2
Q
Lead K-edge
A
88 kev
3
Q
X-ray wavelength is on the order of:
A
an atom
4
Q
MR RF wavelength is on the order of:
A
a patient
5
Q
K shell to outer shell binding energy ratio
A
1000 to 1
6
Q
Tungsten k-edge
A
70 kev
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)
8
Q
KVP for extremity radiograph
A
60 KVP
9
Q
KVP for abdomen radiogaph
A
80 KVP
10
Q
KVP for chest radiograph
A
120 KVP
11
Q
MA for chest radiograph
A
500-1000
12
Q
MA for CT
A
500-1000
13
Q
MA for Fluoro
A
5
14
Q
MAS for a chest xray
A
1
15
Q
MAS for an abdomen radiograph
A
20
16
Q
Does energy get transferred with coherent scatter?
A
No
17
Q
Another name for coherent scatter
A
Raleigh
18
Q
What percentage of X-rays are absorbed by a patient
A
67%
19
Q
What percentage of X-rays are scattered by a patient
A
23%
20
Q
What percentage of X-rays penetrate the patient and hit the detector
A
1%
21
Q
Which energy is most likely transmitted by an Ag k-edge filter in mammo (25kev k-edge)
A
24 kev
22
Q
Xray energy where PE = compton in tissue
A
25 kev
23
Q
What is the half value layer of TISSUE (not aluminum) for x-rays
A
3 cm
24
Q
What interaction is most likely in a head CT?
A
Compton
25
Air Kerma for lateral skull radiograph
1 mGy
26
Air Kerma for frontal skull radiograph
2 Gy
27
Air Kerma at the image receptor for all radiographs
3 micro Gy
28
Air Kerma at the receptor is kept constant by the:
automatic exposure control (AEC)
29
Kerma Air Product for a radiograph is about:
1 G-square centimeters
30
KAP for a small bowel follow-through is about:
10 G-square centimeters
31
KAP for a TIPS is about:
100 G-sq cm
32
Air Kerma rate for fluoro
10 mGy/min
33
Cu filter is added for:
pediatric radiography
34
What percentage increased in KAP if a patient gets fatter by 3 cm?
100% bc 3 cm of human tissue is one half value layer for radiographs
35
Which x-ray tube parameter is always increased in fat patients?
KVP (not mas)
36
Skin erythema is technically possible starting at what threshold air kerma?
2 Gy
37
Cataracts are technically possible starting at what threshold air kerma?
0.5 Gy
38
Average glandular dose for a single mammo?
3 mGy per view
39
Dose to the embryo from one abdominal radiograph?
1 mGy
40
Dose to the embryo from one abd/pel CT?
10 mGy
41
Which has highest linear energy transfer among x-rays, gamma rays, and beta particles?
All the same.
42
Effective dose for chest CT, abdomen CT, and pelvis CT?
All about 3-5 mSv
43
Effective dose for head CT?
About 2 mSv
44
Range and examples for very low dose exam?
less than 0.1 mSv - examples are extremity radiograph, chest radiograph, and skull radiograph
45
Range and examples for low dose exam?
between 0.1 and 1 mSv. Examples are lateral spine radiograph, abdominal radiograph, and extremity CT.
46
Range and examples for moderate dose exams?
Between 1 and 10 mSv. Examples are CT chest, CT abdomen, CT pelvis, small bowel follow through, and MDP bone scan.
47
Range and examples for high dose exams?
Above 10 mSV. Examples are TIPS, FDG-PET, and triple phase liver protocol CT.
48
Ubiquitous background radiation per year in the US?
1 mSV
49
Background radiation in the US due to Radon?
2 mSV
50
Average amount of radiation received by a NM tech per year?
3 mSv
51
Average amount of radiation received by both IR fellows and commercial airline pilots every year?
5 mSv
52
Cosmic radiation is higher where?
High altitudes
53
What is the scatter to primary ratio in abdominal x-rays?
5 to 1
54
Name 3 times when you DONT use a grid?
peds radiograph, extremity radiopgraphy, and mag mammo
55
Standard grid ratio for radiography
10 to 1
56
What do the numbers in the grid stand for?
first number is height of the septa. Second number is the space BETWEEN the septa.
57
What percentage of the primary transmission makes it through a grid?
70%
58
What percentage of scatter makes it through a grid?
10%
59
At which patient thickness do you have to start using a grid (in peds)?
12 cm
60
How much more radiation is needed to expose a traditional film without the screen?
50 x more
61
What makes a film “faster?”
thicker crystal with increased sensitivity (also increased blur from light dispersion)
62
Scintillator for FPD
CsI
63
Rank scintillator types by patient dose
CsI (lowest), BaFBr (medium), Se (highest)
64
Rank scintillator types by image sharpness
BaFBr (lowest), CsI (moderate), Se (best)
65
How many shades of gray does one byte code for?
256 (2 to the 8th power)
66
What are the only two imaging modalities that make use of only 1 byte (8bits = 256 shades of gray) per pixel?
NM and US (shitty images)
67
All of modalities make use of 2 bytes (16 bits = 512 shades of gray) per pixel
radiography, mammo, CT etc.
68
How big is a chest Xray file?
10 MB
69
How big is a mammo image file
15 MB
70
How big is a CT image (one slice) image file?
0.5 MB
71
How many pixels do you need on a monitor to read mammo?
5 MP
72
How man pixels do you need on a monitor to read x-ray?
3 MP
73
How many pixels do you need on a monitor to read CT?
2 MP
74
Who monitors monitors?
Society for Motion Picture and Television Engineers
75
Does analog or digital radiography have more quantum mottle?
same
76
How many line pairs can you see if the sampling frequency is 1/6
3. 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
What is the y axis of a ROC
Sensitivity or true positives
78
What is the x axis of a ROC
1-specificity or false positives
79
What is the relationship between geometric magnification and motion blur?
independent
80
Rank human cells, bacteria, and viruses in order of least to most susceptible to radiation?
human cells most then bacteria then viruses. Viruses are super resistant to radiation.
81
What is the latency period for the onset of radiation induced leukemia?
Years
82
What is the latency period for the onset of radiation induced solid cancer?
Decades
83
What is the background incidence of cancer in the US without additional exposure to radiation from medical exams?
40% of Americans get cancer
84
What is the risk of a 25 year old getting radiation induced cancer from 10 mSV of radiation?
0.10%
85
Has there been a study of human offspring having genetic effects of radiation?
No. Only animals. not even A bomb survivors.
86
What percent of human births have a genetic defect?
4%
87
What is the doubling dose for genetic defects?
1Gy (rate goes from 4% of births to 8%)
88
Deterministic effects for an embryo are VERY unlikely below what amount of radiation?
100 mGy
89
What is the rate of pediatric cancer in the US?
1 in 500
90
What is the doubling dose for pediatric cancers?
25 mGy. Rate goes from 1 in 500 to 2 in 500.
91
What is the downside to the ionization chamber method of detecting radiation?
Accurate but insensitive (needs billions of photons)
92
Ring radiation detector is what?
Thermoluminescent dosimeter (LiF)
93
Who regulates what radiology equipment can be sold in the US?
FDA
94
Who regulates dose limits for radiology equipment?
States
95
Regulatory dose limits exclude:
Medical exposures
96
Regulatory effective dose limits for radiation workers tries to reduce stochastic or deterministic risk?
Stochastic (cancer)
97
Eye dose limit
150 msv/year
98
Extremity limit
500 msv/year
99
Public dose limit
1 msv/year
100
Fetal dose limit per month
0.5 msv/month
101
Fetal dose limit for whole pregnancy
5 Msv after declaring
102
Who regulates radiopharmaceuticals?
NRC or agreement states
103
State regulation for required lead thickness in apron?
0.25 mm lead
104
How thick is lead usually in apron?
0.5 mm
105
How much does 0.5 mm of lead attenuate?
90%
106
Which tech gets the most annual radiation?
NM
107
Room shielding design?
2mm Pb thickness in the wall usually 2 meters high starting at the floor
108
Scattered x-ray intensity at 1 meter from the patient
1000 x less
109
What is the average monthly badge reading for radiology residents?
< 0.1 mSv per month
110
What does .DAM refer to?
Initiative to reduce dose called: “dont order tests that don’t affect management”
111
What is the dose limits for a medical imaging exam?
There are no dose limits
112
Average T1 time for human tissue?
~500 ms
113
Average T2 time for human tissue?
~50 ms
114
Average T2* time for human tissue?
~5 ms
115
Which water molecules have longer T1 time in human tissue?
Water in solids and free water - both T1 dark.
116
Which water molecules have shorter T1 time in human tissue?
Water that is structured such as proteinaceous water.
117
Larmor frequency at 1 T
42 MHz
118
What happens to T1 when spin-lattice interactions are increased?
Reduced
119
Does T1 change with different flip angles?
No, they are independent
120
What kinds of nuclei are used in MRI or NMR?
Those with odd mass numbers.
121
How are T1 and Bo related?
If you double Bo, T1 increases by root 2.
122
How are T2 and Bo related?
Not related.
123
What is the likely T2 value for protons in bone?
Very short. (dark)
124
Can T1 be less than T2 for a given tissue?
No. It’s impossible.
125
What are the units of magnetic field gradients?
Tesla per meter
126
In a 128 x 256 MRI grid, how many phase encoding steps?
128
127
In a 128 x 256 MRI grid, what does the 256 refer to?
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
Center of an MRI image shows?
Low spatial frequency. (contrast)
129
Periphery of an MRI image shows?
High spatial frequency. (resolution)
130
How does K space matrix size compare to MR image matrix size?
Same.
131
What will most likely reduce T1 weighting in a spin echo image?
Increasing TR.
132
What will most likely reduce T2 signal in a spin echo image?
Decreasing TE.
133
How does SNR increase with every additional NEX?
by root 2
134
What is the upside to GRE?
fast. Short TR.
135
What is the downside to GRE?
Worse SNR because signal is degraded by T2* effects, which remain present due to lack of 180 refocusing pulse.
136
STIR TI is about?
150ms
137
FLAIR TI is about?
2400
138
What kind of MRI sequence will produce the strongest echo?
SE>GE and shortest TE possible to reduce dephasing.
139
How many pixels would most likely be in a single echo within 128 x 196 SE image?
196. 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
Iron based MR contrast agents are?
supra-paramagnetic
141
How does heat dissipate between the focal spot and the anode body?
Conduction
142
How does heat dissipate between the anode body and the tube housing?
Radiation
143
How does heat dissipate between the tube housing and the atmosphere?
Convection
144
What is the usual anode angle?
~15 degrees.
145
Three ways to decrease heel effect?
Increase anode angle, decrease FOV AKA cassette size, increase SID.
146
Why use a large focal spot of 1.2 mm in PA and lateral chest XR?
Increasing focal spot size allows for more power and therefore quicker acquisition which is important to reduce respiratory motion.
147
What increases when KVP increases?
Both scatter and penetration.
148
If you increase mAs by 2 how much do you decrease mottle?
root 2
149
In fluoro what is the typical SID?
100 cm
150
Why keep the II or FPD close to the patient?
To reduce dose AND to reduce variable geometric magnification in the patient.
151
Typical SID for PA and lateral CXR?
72 inches
152
Use a grid in portable CXR?
no
153
Use a grid in portable abdominal XR?
yes. Reduce grid ratio from 10:1 to 5:1.
154
What is the problem in a CXR obtained at an exposure index of 100?
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
Why do we see mach band artifact?
Lateral inhibition of the retina.
156
If you see an XR and there are parts with fine exposure and parts with shitty exposure, whats the problem?
Faulty grid.
157
Tube current in contact mammo?
100 MA.
158
Tube current in mag mammo?
25 MA.
159
mAs for contact mammo?
100 mAs
160
mAs for mag mammo?
75 mAs.
161
To change contrast in mammo is it effective to change KVP?
Not really. Better to change your target/filter.
162
How does breast compression affect X-ray penetration?
Increases penetration because breast tissues is spread apart.
163
Higher/lower/or comparable radiation in digital mammo versus screen film?
Comprable.
164
Higher/lower/or comprable radiation in BTS versus FF mammo?
Comprable.
165
What should the luminance be for a mammo monitor?
600 cd/ sq meter
166
What is the problem with increasing SID to reduce geometric blur?
Takes longer resulting in motion artifact.
167
What is the half value layer of normal breast tissue at mammo level xrays?
1 cm (compared to 3 cm for diagnostic radiography)
168
What is the HVL of aluminum for mammo?
0.5 mm Al (compared to 3 mm Al for diagnostic radiography)
169
What is the angular movement and number of images in BTS?
15 degrees, 15 images.
170
What improves in BTS compared to FFDM?
Contrast. Resolution and dose DO NOT CHANGE.
171
What are the only machines in radiology that are not regulated at the state level after they have been sold?
Mammo machines continue to be regulated at the federal level.
172
What is the MQSA regulation for resolution for SF mammo?
12 lp/mm
173
MQSA phantom specs?
4.2 cm breast, 50% glandularity.
