OVERALL REVIEW Flashcards
(144 cards)
1
Q
Unit of all mass
A
Atoms
2
Q
Positive charge particle
A
Proton
3
Q
Negative charged particle
A
Electron
4
Q
Neutral or no charge particle
A
Neutron
5
Q
Ability to attract iron, cobalt, nickel. Creates or induces dipoles
A
Magnetism
6
Q
Magnetic fields characterized by own magnetic north and south poles
A
Dipole
7
Q
Ability to attract or repel magnetic lines of force dependent on magnetic properties of electrons
A
Magnetic susceptibility
8
Q
Paired electrons. Cancel each other out. Weakly attract or repel. Magnetic susceptibility of most human body tissues
A
Diamagnetic
9
Q
Positive susceptibility. Attract and repel substances such as gadolinium, Methameglobin, free radicals. Marked reductions in T1 and T2 relaxation times
A
Paramagnetic
10
Q
Large positive susceptibility. Attract or repel substances such as hemosiderin and super paramagnetic iron oxide. Do not exhibit residual magnetism when external field removed
A
Super paramagnetic
11
Q
Large positive magnetic susceptibility. Attracts iron and cobalt containing metals. Become magnetized and remain magnetized after being removed from magnetic field
A
Ferromagnetic
12
Q
Vector quantity. Symbolized by field or flux lines
A
Magnetic fields
13
Q
Measure flow an area of magnetic field
A
Field or flux lines
14
Q
Flow of energy, magnetic field flowing from north to south poles
A
Flux
15
Q
Ability to create work or change
A
Force
16
Q
Characterized by strength and direction.
A
Vector
17
Q
Homogeneity of MRI magnet
A
20-30 ppm
18
Q
Symbol used to illustrate wavelength and frequency of EM energy
A
Sine wave
19
Q
Distance between two consecutive peaks
A
Wave length
20
Q
Signal height
A
Amplitude
21
Q
A sudden loss of superconductivity with explosive boiling off of cryogen
A
Quench
22
Q
Small electromagnets that are adjusted after installation to correct for inhomogeneities in B0
A
Shim coils
23
Q
Three pairs of small electromagnets that produce GMF. Perform spatial localization
A
Gradient coils
24
Q
Small devices place close to the patient’s body to transmit or receive
A
Radio frequency coils
25
Electromagnetic coils, contain Fringe fields
Active shielding
26
Structural steel within walls of MRI scan room, contain Fringe fields
Passive shielding
27
Spin lattice relaxation, T1 relaxation, regrow the of Mz
Longitudinal relaxation
28
Spin spin relaxation, T2 relaxation, decay of MXY
Transverse relaxation
29
Regrowth of longitudinal magnetization. Time for MZ to recover 63% after 90° RF pulse
T1 curve
30
Decay of transverse magnetization. Time for MXY to fall to 37% after 90° RF pulse
T2 curve
31
A time constant characterizing fast rate of transverse relaxation because of B0 inhomogeneities 
T2 star affects
32
90° RF pulse followed by a 180° RF pulse
Spin echo
33
Less than 90° RF pulse followed by a GMF
Gradient echo
34
180° RF pulse followed by a 90° RF pulse
Inversion recovery
35
To correct for t2* effects
Employ 180° RF pulse
36
Short TR, short TE
T1
37
Long TR, short TE
PD
38
Long TR, long TE
T2
39
Time interval between initial 180° inverting RF pulse and following 90° RF pulse
Ti
40
Large F/A Greater than 45°
T1 weighted
41
Small F/A less than 20°
PD weighted 
42
Medium F/A greater than 20°, less than 45°
T2 weighted
43
Tissues that benefit from proton density image
Air/air containing structures, cortical bone
44
Have very little signal and appear dark, known as flow void
Fast blood flow
45
Have hyperintense signal and appear bright
Slow blood flow
46
Artifact occurs in the Read out/frequency or slice selection axes direction
Chemical shift artifact
47
Effects are more noticeable with longer TE times
Eddy currents
48
How are eddy currents solved
Active gradient shielding
49
Gradient echo pulse sequences are more sensitive to this artifact
Magnetic susceptibility artifact
50
Measured in watts per kilogram
SAR
51
Maximum exposure to head and trunk
3 Tesla
52
Maximum exposure to extremities
5 Tesla
53
Whole body RF no more then
0.4 W/KG
54
Head RF no more than
3.2 W/KG
55
1 g of tissue RF maximum spatial peak of
8W/KG
56
Contains the motor area which directs movement and two areas of speech
Frontal lobe
57
Contains sensory area
Parietal lobe
58
Contains auditory area and all factory lobe concerned with sense of smell
Temporel lobe
59
Contains a visual area
Occipital lobe
60
Conus medullaris location
L1 – L2
61
Aorta bifurcation located
L3 – L4
62
Thecal sac location
S2
63
A collection of many spinal nerves below the conus medullaris resembles a horse tail
Cauda equina
64
Rotator cuff consists of
Supraspinatus, infraspinatus, teres minor, subscapularis
65
Avascular necrosis of lunate of carpal bone. Most common in young adult men
Kienbocks disease
66
Cause muscle contractions, cardiac arrhythmias, Mild cutaneous sensation and visual light flashes
Time varying magnetic fields (gradient)
67
Orientation of the main magnet in a high field, superconducting, short bore magnet
Horizontal
68
Effects of TVMF include
Peripheral nerve stimulation, acoustic damage/hearing loss, magneto phosphines
69
The sequence has more of a detrimental effect on patients with regard to TVMF
EPI/Echo planar imaging
70
The time it takes for the gradient to reach its full amplitude
Gradient rise time
71
Rate of speed of ascent or descent of a gradient from zero to its maximum amplitude
Gradient slew rate
72
The time the gradients are on during a TR period
Duty cycle
73
Strength of a gradient over a specific distance
Slew rate
74
Low energy non-ionizing radiation
Radio frequency
75
Expressed in parts per million
Magnetic field inhomogeneity
76
More of a concern in fast spin Echo sequences due to multiple Echo train lengths. Potential increase in tissue heating
RF heating
77
Technique used to reduce MRI scan time. Requires the use of an array coil
Parallel imaging
78
Applying two gradients simultaneously during slice selection with produce an
Oblique slice
79
Multiple coil elements combined with multiple receiver channels make
Phased array coil
80
Coil construction from innermost to outer
RF coil, gradient coil, shim coil, main magnet (RGSM)
81
Purpose of shimming the magnet is
To make the B0 field as homogenous as possible
82
Intensity limit for static magnetic field in clinical use is
4 Tesla
83
Achieved by lining the scanner room walls with copper
RF shielding
84
Magnetic field of a typical scanner
Horizontal
85
Accomplished by lining the MR room with steel
Passive shielding
86
Super conducting windings within the MR scanner to reduce the Fringe field is defined as
Active shielding
87
Posterior to the vertebral body and consists of two pedicles and two laminae
Vertebral arch
88
In the lower extremity the medial side is the______and the lateral side is the_______
Tibia, fibula (MT, LF)
89
In the upper extremity the medial side is the_______and the lateral side is the_______
Radius, ulna (MR, LU)
90
Optimal view for ovaries
Coronel
91
Optimal view for uterus
Sagittal
92
To correct for Gibbs…
Increase phase encodings
93
Contrast in diffusion waited imaging depends on
Degree of impairment of molecular mobility (water restriction), Brownian motion, direction of water diffusion
94
The corpus callosum consists of
White matter
95
Longer ETL_____scan times
Shorten
96
increasing number of ETL can lead to
Increase in blurring
97
When gradient echo is selected for fast, breath hold dynamic contrast enhanced imaging of abdomen_______is utilized
Spoiling
98
gradient Echo sequences yields_____________
T1 or T2* characteristics
99
To null signal from a specific tissue using an inversion recovery sequence, TI should be
69% of T1 relaxation of tissue
100
Longer TE provides
More T2 contrast, reduced SNR
101
Increased TE _______ # of slices
Decreases
102
Increasing TR, ________ SNR and _______ # of slices
Increase, increase
103
After application of 90° RF pulse, protons begin to
Precess in phase and tip into the transverse plane
104
Increase TR,
Reduce phase matrix,
Increase FOV
Reduce/Narrow receiver bandwidth
Increase NEX/NSA
Reduce ETL
Improve SNR
105
Decrease TR
Reduce pixel size
Decrease FOV
Increase/widen receiver bandwidth
Decrease NEX
Increase ETL
Negatively impact SNR
106
Reducing FOV will
Decrease SNR, but increase spatial resolution
107
Reducing ETL will ________ scan time
Increase
108
Increase in TE will _______ SNR
Decrease
109
Reducing number of lines filled in k-space will
Reduce phase encoding steps
Shorter scan time
Increase SNR
Decrease spatial resolution
110
If phase encodings is increased, SNR
Decreases
111
Narrow receiver band will increase _____________
Susceptibility artifact
Do not use with metal implants
112
Steep slice select slope and narrow bandwidth yield
Thin slice thickness
113
Decrease TR
Increase ETL
Decrease NEX
Enabling half scan
Increasing parallel imaging factor
Shorten scan times
114
Increase TR
Decrease ETL
Increase NEX
Decrease parallel imaging factor
Lengthen scan times
115
Increasing the flip angle
Increases SNR up to the Ernst angle
116
Reducing the flip angle yields images with
Less T1 information
117
Reducing the TE yields images with
Decreased T2 information
118
Transmit bandwidths will affects the_________
Slice thickness; which affects resolution and overall SNR
119
Thin slice thickness is achieved through
Steep, high amplitude slice select gradient
Narrow transmit bandwidth
120
Receiver bandwidth affects the
SNR & chemical shift
121
Decreasing the receiver bandwidth will
Increase chemical shift
122
Collecting low frequency data points in k-space (high amplitude signal) at the start of a scan is known as
Elliptic central K space filling
123
During dynamic enhanced imaging, contest is administered and K space is filled with
Centric K space
124
TOF MRA use 
T1 gradient echoes with TR and FA selections (to suppress signal from tissue and visualize flowing blood)
125
PC MRA use
T2 gradient echoes that rely on velocity induced phase shifts
126
ADC
T1/T2 time
Specific proton density
Flow
Intrinsic parameters
127
TR
TE
FA
TI
ETL/turbo factor
Extrinsic parameters
128
Difference in chemical shift is
3.5 ppm
129
T1 time of fat at 1.5 T
240 with null point of 160ms
130
The biliary tree does not contain what?
Splenic duct
131
Islet cell tumor, scan?
Pancreas
132
Pre-saturation band for intracranial arterial
Superior
133
Velocity of flowing blood
Phase contrast
134
Branches of the abdominal arteries in order from proximal to distal are
Celiac
Superior mesenteric
Renal
Inferior mesenteric
(CSRI)
135
Imaging used for hemangiomas
Delayed imaging
136
Mitral/bicuspid valve lies between
Left atrium and left ventricle
137
Tri cuspid valve separates
Right atrium and right ventricle
138
The fastest vessel is the
Aortic arch
139
The descending aorta is next to
Left atrium
140
Most anterior chamber of the heart
Right ventricle
141
Most posterior chamber of the heart
Left atrium
142
Coronary arteries originate from
Aortic root
143
Collect data continuously during a cardiac cycle
Cine sequences
144
Best to evaluate cardiac infarction
Perfusion cardiac imaging
