Huda Facts 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.
