Physics Flashcards
1
Q
100 rad
A
1 Gy
2
Q
1 Gy
A
100 rad
3
Q
SI unit of Exposure
A
R (Roentgen) (C/kg)
4
Q
SI unit of Radiation Dose
A
Gy (J/kg)
5
Q
DLP
A
CTDI vol x scan length
6
Q
DLP units
A
mGy x cm
7
Q
unit of equivalent dose
A
Sv
8
Q
unit of effective dose
A
Sv
9
Q
equation for CTDI vol
A
(CTDI weighted)/(pitch)
10
Q
equation for CTDI weighted
A
1/3 central CTDI + 2/3 peripheral CTDI
11
Q
equation for CT effective dose
A
k x DLP
12
Q
meaning of DQE on film-screen
A
% of x-rays absorbed by screen (% of incident x-rays that interact with screen)
13
Q
DQE (or QDE)
A
Detective quantum efficiency (quantum detective efficiency)
14
Q
conversion efficiency in film-screen
A
% of x-ray photons converted into light photons
15
Q
total efficiency of film-screen (aka intensification factor)
A
DQE x conversion efficiency
16
Q
minimum required resolution of screen film mammo
A
11 lp/mm
17
Q
beam intensity
A
number of x-rays multiplied by energy
18
Q
units of beam intensity
A
R/min
19
Q
3 results of Compton interaction
A
- liberated electron (Compton electron) - scattered photon (deflected incoming photon) - ionized atom
20
Q
3 results of photoelectric effect
A
- characteristic x-ray produced (or Auger electron emitted) - “photo”electron ejected - atom ionized (positive ion)
21
Q
entrance air kerma for fluoro
A
25 mGy/min
22
Q
1 Sv
A
100 rem
23
Q
100 rem
A
1 Sv
24
Q
1 rem
A
10 mSv
25
Heel effect depends on
- field size - anode angle - SID
26
what gets emitted with beta minus decay?
- beta particle - anti-neutrino
27
what kind of process is beta minus decay?
isobaric - mass number doesn't change, proton number increases by 1
28
what decays via electron capture?
Ga-67 In-111 Tl-201 I-123
29
power for plain film radiograph
100 kW
30
typical entrance skin dose for lateral lumbar spine radiograph
15 mGy
31
typical entrance skin dose for PA chest radiograph
0.2 mGy
32
effect of increasing screen thickness on screen speed
INCREASED screen speed
33
ways to improve aliasing in US
- lower frequency probe - increased Doppler angle - reduce distance between US probe and vessel
34
grams of Iodine injected for portal venous abd CT
40 g
35
only iso-osmolal contrast media approved for use in US
iodixanol (Visipaque)
36
how long after cardiac device placement don't perform MRI?
6 weeks
37
disadvantages of STIR
- decreased SNR - can't use post-Gd - longer imaging time (increased TR)
38
US transducer element thickness
1/2 wavelength
39
which Tc-99m chelate doesn't require pre-treatment with stannous ion?
sulfur colloid
40
average power used in x-rays
100 kW
41
size of large focal spot in radiography
1.2 mm
42
power limit on large focal spot in radiography
100 kW
43
size of small focal spot in radiography
0.6 mm
44
power limit on small focal spot in radiography
25 kW
45
mAs for chest radiograph
1 mAs
46
mAs for abdominal radiograph
20 mAs
47
which radiographic exam uses AEC?
skull
48
what change in anode angles increases heel effect?
decreased anode angle
49
what change in SID increases heel effect?
decreased SID
50
which Gd contrast agent has highest risk of NSF?
gadodiamide (Omniscan)
51
which Gd contrast agents are linear (4)
- gadodiamide (Omniscan) - gadopentetate (Magnevist) - gadoversetamide (Optimark) - gadoxetate (Eovist)
52
4 ways to decrease hardware/metallic artifact in CT
- acquire thinner slices - reconstruct thicker slices - increase kVp - use dual-energy
53
definition of CT pitch
(table increment distance during 360-degree rotation of the x-ray tube)/(nominal x-ray beam width)
54
effective mAs
(true) mAs / CT pitch
55
image reconstruction technique used in CT
filtered back projection (FBP)
56
radiation dose with abrupt onset vomiting/diarrhea
10 Gy
57
ideal film density in chest radiograph
1.5
58
dynamic range or radiographic film detectors
10,000 : 1
59
definition of latitude
***_range_*** of radiation intensities that result in satisfactory contrast
60
acute whole-body dose for cerebrovascular syndrome
100 Gy
61
acute dose for permanent sterility in MAN
6 Gy
62
acute dose for permanent sterility in WOMAN
2 Gy
63
0.5 mm lead aprons reduce operator exposure by what %?
90%
64
MRF
mathematical reconstruction filter
65
bone MRF
HIGH noise, HIGH resolution
66
soft tissue MRF
LOW noise, LOW resolution
67
gamma camera uniformity (%)
2-3%
68
PRF (pulse repetition freuquency) is product of what?
line density x frame rate
69
70
in peds, use grid when patient thickness is greater than how much?
10-12 cm
71
72
tube output for CXR
1 mAs
73
computer memory to store AP + lat CXR
10 MB
74
peds 2 view chest dose equivalent
0.02 mSv
75
collimation improves what?
contrast
76
CXR grid primary transmission (%)
70%
77
definition of accuracy
TP (true positive) + TN (true negative)
78
fetal dose for abdominal x ray
1 mGy
79
who has Level 2 MR safety training?
radiologists AND MR techs
80
buzzword - entry slice phenomenon/flow-related enhancement
2D-TOF
81
MC plane for MR venogram
coronal
82
ways to reduce metal-related artifacts in MR
- incr rBW
- lower field strength
- SE/FSE instead of GRE
- thinner voxel (via steeper gradient --\> better in-plane resolution)
83
1 Tesla
10,000 Gauss
84
what *types* of artifacts are greater at higher field strengths?
- susceptibility
- B1 inhomogeneity
85
*range* of energies of Tc-99m tested in linearity
30 uCi - 200 mCi
86
how to reduce CT metal artifact
- incr kVp
- narrow beam
- reconstruct thinner slices
87
CTDIvol of LD CT for attenuation correction
2 mGy
88
CTDIvol/effective dose of diagnostic CT for PET
15 mGy/15 mSv
89
effective dose of PET
8 mSv
90
Gy is SI unit of what?
absorbed dose
91
Sv is SI unit of what?
equivalent and effective dose
92
definition of 1 Gy
1 J of energy aborbed in 1 kg of tissue
93
difference in xray attenuation between gray and white matter
0.5%
94
effective dose of 2 view screening mammo
0.5 mSv
