Test 1 Flashcards
Atoms with odd mass number is considered ___
MR active
What two components must a vector have?
A. Energy and speed
B. Mass and charge
C. Magnitude and direction
D. Phase and frequency
C
opposing vectors with the same magnitude will ___
a. cancel out
b. double
A
vectors with the same magnitude and direction___
a. cancel out
b. double
B
Electric charge is measured in ___
a. Coulombs (C)
b. Amps (A)
c. Ohms
d. Volts (V)
A
Resistance is measured in __
a. Coulombs (C)
b. Amps (A)
c. Ohms
d. Volts (V)
C
Electric current is measured in ____
a. Coulombs (C)
b. Amps (A)
c. Ohms
d. Volts (V)
B
Voltage is measured in ____
a. Coulombs (C)
b. Amps (A)
c. Ohms
d. Volts (V)
D
___ is the friction that impedes flow of electrons
a. resistance
b. electric current
c. electric charge
d. voltage
A
___ is electric potential
a. resistance
b. electric current
c. electric charge
d. voltage
D
____ is the movement of electric charge
a. resistance
b. electric current
c. electric charge
d. voltage
B
Ohm’s law is used to calculate relationship between ___ , ____ and ____
voltage, current, resistance
Ohm’s Law equation
V = IR
Power is the measurement of ____ per ___
work
time
what are 4 electrical states of matter
insulator
conductor
superconductor
semiconductor
which electrical state of matter resist flow of electron?
a. insulator
b. conductor
c. superconductor
d. semiconductor
A
which electrical state of matter allows flow of electron with some difficulty?
a. insulator
b. conductor
c. superconductor
d. semiconductor
B
which electrical state of matter can behave as an insulator or conductor
a. insulator
b. conductor
c. superconductor
d. semiconductor
D
which electrical state of matter freely allows flow of electrons with zero resistance?
a. insulator
b. conductor
c. superconductor
d. semiconductor
C
every magnet contains a north and south pole called ____
dipole
Like poles ___
Unlike poles ___
repel
attract
magnetic flux lines leaves the ___ pole and returns the ___ pole
north
south
magnetic field is measured in ____
Tesla (T) & Gauss (S)
what is magnetic susceptibility
the degree a material is magnetized by a magnetic field
what determine magnetic susceptibility
electron configuration
what are 3 types of magnetic susceptibility
Diamagnetism
Paramagnetism
Ferromagnetism
___ is slightly repelled by external magnetic field
a. Diamagnetism
b. Paramagnetism
c. Ferromagnetism
A
___ is slightly attracted by external magnetic field
a. Diamagnetism
b. Paramagnetism
c. Ferromagnetism
B
___ is strongly attracted to external magnetic field
a. Diamagnetism
b. Paramagnetism
c. Ferromagnetism
C
which type of magnetic susceptibility retains magnetism when removed from external field?
a. Diamagnetism
b. Paramagnetism
c. Ferromagnetism
C
Determine magnetic susceptibility of
a. Diamagnetism ____
b. Paramagnetism ____
c. Ferromagnetism ____
a. low negative
b. low positive
c. high positive
Iron & Steel are examples of ____
a. Diamagnetism
b. Paramagnetism
c. Ferromagnetism
C
Copper, Lead, and Water are examples of ___
a. Diamagnetism
b. Paramagnetism
c. Ferromagnetism
A
Gadolinium, aluminum, tungsten are examples of ____
a. Diamagnetism
b. Paramagnetism
c. Ferromagnetism
B
An electron in motion has both ___ & ____
electric and magnetic field
As current increases = strength of magnetic field ___ (increase/decrease)
increase
If a wire is bent to form loops, what is formed?
solenoid
what is created when there is a rod of ferromagnetic material placed inside the solenoid
electromagnet
If a rod of ferromagnetic material placed inside a solenoid, would the intensity of magnetic field increase or decrease
increase
what is Faraday’s Law
describe how a moving magnet can induce charge in a coil of wire
3 main components of Faraday’ Law
motion
charge
magnetism
A moving electric charge will ____
induce magnetic field
A moving magnet will ___
induce charge in wire
When a moving charge slows down or speed up, photon is emitted - what kind of photon is this?
a. Bremss
b. Characteristic
A
high frequency = ___wavelength
short
90 degree to external magnetic field is ____
a. longitudinal plane
b. transverse plane
B
direction of magnetic field is ____
a. longitudinal plane
b. transverse plane
A
what are 2 components of MRI instrumentation
RF transmit coil
RF receiver coil
Function of RF transmit coil ____
a. manipulate hydrogen
b. detect signal from patient
A
Function of RF receiver coil ____
a. manipulate hydrogen
b. detect signal from patient
B
Which of the following is not a characteristic of MR Active nuclei?
a. spins do not cancel out
b. odd mass number
c. angular momentum
d. even mass number
D
protons and neutrons spin cancel each other out when there are the same number of ____ & ___
protons
neutrons
2 main components of MR Active Nuclei
- electrical charge
- spinning (motion)
MR active nuclei automatically acquire a ____
magnetic field
The magnetic field acquired by MR active nuclei is called___
magnetic moment
The isotope of hydrogen is called __
protium
what happened to MR active nuclei when there is no external magnetic field applied
randomly oriented and cancel each other out
What happened to MR active nuclei when there is an external magnetic field applied
align with B0
what are 2 ways that MR active nuclei align with external magnetic field
- spin up
- spin down
if MR nuclei spin up, the energy is ___
a. low
b. high
A
if MR nuclei spin down, the energy is ____
a. low
b. high
B
There are always more ____ energy aka ____ at equilibrium
a. low - parallel
b. high - antiparallel
c. low - antiparallel
d. high -parallel
A
more magnetic moments spin ____
up
As B0 increases, ___ hydrogen have the energy to oppose B0 (less/more)
less
As B0 increases, more H spin ___
up
the MR nuclei wobble around ___
B0 (external magnetic field)
What is the gyromagnetic ratio of hydrogen?
a. 21.28 MHz/T
b. 63.86 MHz/T
c. 127.71 MHz/T
c. 42.57 MHz/T
c. 42.57 MHz/T
At equilibrium, there are always more _________ nuclei when aligned in a magnetic field.
I. Low energy
II. High Energy
III. Spin up
a. I and II
b. I and III
c. I, II, and III
d. III
B
What is the larmor equation?
a. Precessional frequency = gyromagnetic ratio * field strength
b. MHz = MHz/T * T
c. ω0 = γ * B0
d. All the above
D
What is precessional phase
position of each magnetic moment on its precessional path
at equilibrium, spins will be ___ (out of phase/ inphase)
out of phase
what is precessional frequency
time it takes one revolution around precessional path
unit for frequency
Hz
What does lamor equation determine
speed at which H precess
In the larmor equation - ω0 = γ * B0 ,
what does each component stand for and its unit
ω0 = larmor frequency (Hz)
γ = gyromagnetic ratio of H - 42.57 MHz/T
B0 = external mag field (T)
Resonance in MRI is achieved when ___
EM pulse emitted at the larmor frequency of H
another name for EM pulse
RF excitation pulse (B1)
B1 (RF pulse ) is 90 degree to ____
a. B0 - longitudinal
b B0 - transverse
B
MR active nuclei only resonates when ____
its precessional frequency matches the frequency of RF pulse
Excitation causes H to gain more energy resulting in more _____
a. spin down ( high E, antiparallel)
b. spin up ( low E , parallel)
A
Excitation moves ____ away from ___ plane into ___ plane
NMV
longitudinal
transverse
The NMV can only be measured by flipping magnetization:
a. in the +Z direction axis
b. 90º to the transverse plane
c. in the transverse plane
d. in the longitudinal plane
C
When there is excitation, MR nuclei become ____
a. inphase
b. dephase
A
after a 90 degree excitation pulse, H are ____ and precess fully in __ plane
a. dephase - longitudinal
b. inphase - transverse
B
How is a MR signal is detected
- H is coherent in transverse plane
- Place coil near it
- electric current produced
- voltage produced is MR signal
signal frequency of MR depends on ___
rotation of NMV
signal magnitude of MR depends on ___
amount of coherent magnetization on transverse plane
For a MR nuclei to resonate what are needed? (3)
strong B0
H precess fast
high frequency RF pulse
More signal = ___ NMV = _____ energy H
large
low
Resonance results in ___ & ___
excitation & coherence
If NMV only can be measured when they move toward transverse plane, then RF pulse needed to be ___ and the flip angle need to be____
a. strong or longer
b. larger
______ magnetization produce MR signal
a. coherent transverse
b. incoherent transverse
c. coherent longitudinal
d. Incoherent transverse
A
FID ( free induction decay) is produced when ___
a. excited and inphase
b. relax and dephase
B
what form part pulse sequences
magnitude
timing of RF pulse
what are the cons of MRI (3)
long scan time
expensive
complex
pros of MRI (4) - which is the main pros
no ionizing radiation
multiplanar
multiparametric
contrast resolution ***
why contrast resolution is a primary advantage for MRI
visualize soft tissue
THe ability to distinguish between two points as separate and distinct is ____
a. spatial resolution
b. contrast resolution
A
The ability to distinguish adjacent soft tissues from one another is ___
a. spatial resolution
b. contrast resolution
b
what are two main factors that can determine image contrast
intrinsic or extrinsic contrast parameter
which contrast parameter can be controlled by technologist
extrinsic
density of bone will be considered ____
a. extrinsic contrast
b. intrinsic contrast
B
T1 time, T2 time, PD, flow, ADC will be considered ____
a. extrinsic contrast
b. intrinsic contrast
B
TR, TE, Flip angle, TI, ETL, b value will be considered ____
a. extrinsic contrast
b. intrinsic contrast
A
which of the following is NOT intrinsic contrast parameter?
a. T1 time
b. TR
c. PD
d. ADC
B
which of the following is NOT extrinsic contrast parameter
a. TR
b. TE
c. T2 time
d. b value
C
what happened when RF pulse is turned off ? (2)
- H realign with B0
- magnetic moment dephase
T1 recovery in ___ plane
longitudinal
T2 decay in ___ plane
transverse
T1 recovery is caused by ____
a. nuclei giving up energy to surrounding env
b. nuclei’s magnetic field bumps into each other
A
T2 decay is caused by ____
a. nuclei giving up energy to surrounding env
b. nuclei’s magnetic field bumps into each other
B
Spin-lattice relaxation refers to ____
T1
Spin-spin relaxation refers to ____
T2
would T1 recovery or T2 decay also cause the nuclei to dephase?
T2
T1 recovery is the time it takes a tissue to ____
recover 63% of its longitudinal magnetizaton
T2 decay is the time it takes a tissue to ___
decay/ dephase 63% of its transverse magnetization
Amount of T1 is controlled by ____
Amount of T2 is controlled by ____
TR
TE
Which process is faster ? T1 recovery or T2 decay
T2 decay
A tissue has a high signal if ____
it has a large transverse component of coherent mag at TE.
high signal = ____ bright/dark
BRIGHT
images produced constantly mainly thru which 2 factors
1/ proton density
2/ T1 recovery - T2 decay
3 primary mechanisms of T1/T2 to produce contrast in different tissue
- inherent energy of tissue
- how close molecules are
- matching larmor frequency
In T1, which mechanism is important in how contrast is generated?
1. inherent energy of tissue
2. how close molecules are
3. matching larmor frequency
1
In T2, which mechanism is important in how contrast is generated?
1. inherent energy of tissue
2. how close molecules are
3. matching larmor frequency
2
a better contrast is generated in T1 if the tissue has ____ inherent energy (low/high)
low
a better contrast is generated in T2 if the tissue has molecules that are ___ (close, far away)
close
Tissues with short T1 time appears___ on ___ image
bright
T1-weight
Tissues with short T2 time appears ___ on ___
bright
T2-weight
In T1,
fat will have _____ T1 time
water will have___ T1 time
short
long
why fat has a short T1 time
inherent energy of H is low and larmor frequency matches with its longitudinal magnetization
why water has a long T1 time
inherent energy of H is high and larmor frequency is slightly faster than its longitudinal magnetization
Fat in T1 look ___ (bright/dark)
BRIGHT
Water in T1 look ___ (bright/dark)
DARK
Fat in T2 look ___ (bright/dark)
dark
Water in T2 look ___ (bright/dark)
bright
A good contrast for T1 need a ____
a. short TR
b. short TE
c. long TR
d. long TE
A & B
A good contrast for T2 need a ____
a. short TR
b. short TE
c. long TR
d. long TE
C & D
A good contrast for PD need a ____
a. short TR
b. short TE
c. long TR
d. long TE
B & C
If water/fluid looks white, the image is __
T2
if water/fluid looks dark, the image is ___
T1
Magnetization of XY PLANE is ____ plane
TRANSVERSE
T2 time of fat is ___
short
T2 time of water is ____
long
Why do we need a short TR for T1 images
short TR so there will be differences in tissue relaxation. if TR is too long, all tissues will fully recover
Fat has __ (low/high) signal on T1
high
Why do we need a long TE for T2 contrast
to measure difference in T2 decay and to allow enough time to pass so different tissues can dephase before signal is read.
Tissues with a high PD are ____ (bright/dark)
bright
Tissues with low PD are ____ (bright/dark)
DARK
By altering ___ contrast parameters we can alter the type of contrast present
a. extrinsic
b. intrinsic
A
T1 weighting requires ____ ____ to capture T1 effects before vectors are allowed to fully recover
a. short - TE
b. short - TR
c. long - TE
d. long TR
B
T1 weighting requires ___ ___ to reduce T2 effects
a. short - TE
b. short - TR
c. long - TE
d. long TR
A
T2 weighting requires ___ ____ to give time for vectors in different tissues to dephase
a. short - TE
b. short - TR
c. long - TE
d. long TR
C
T2 weighting requires ___ ___ to reduce T1 effects
a. short - TE
b. short - TR
c. long - TE
d. long TR
D
which of the following is needed to make a PD-w image?
a. long TR
b. short TR
c. long TE
d. short TE
e. B & D
f. A & C
g. A & D
E - short TE & long TR
●Short TR = 300ms-700ms
● Long TR = ≥2000ms
● Short TE = 10ms-30ms
● Long TE = 80ms
What would be the weighting of an image with:
- TR of 2000ms and a TE of 80ms?
T2
●Short TR = 300ms-700ms
● Long TR = ≥2000ms
● Short TE = 10ms-30ms
● Long TE = 80ms
What would be the weighting of an image with
-TR of 2000ms and a TE of 20ms?
PD
●Short TR = 300ms-700ms
● Long TR = ≥2000ms
● Short TE = 10ms-30ms
● Long TE = 80ms
What would be the weighting of an image with
- TR of 500ms and a TE of 80 ms?
Poor Contrast
●Short TR = 300ms-700ms
● Long TR = ≥2000ms
● Short TE = 10ms-30ms
● Long TE = 80ms
What would be the weighting of an image with
- TR of 500ms and a TE of 20ms?
T1
The recovery of longitudinal magnetization due to spin-lattice relaxation is ___
a. T1
b. T2
T1
The decay of coherent transverse magnetization due to spin-spin relaxation is ____
a. T1
b. T2
T2
___ is the movement of molecules in the
extracellular space due to random thermal motion
Diffusion
tissues have ADC which is ____
a. extrinsic contrast parameter
b. intrinsic contrast parameter
B
what does ADC stand for
apparent diffusion coefficient
what is ADC
net displacement of molecules across an area of tissues per sec
DWI or diffusion -weighted imaging measures ____
the differences in ADC
what does b value determine
amount of diffusion weighting
MRI use ____ to measure ADC
2 gradients ( one to rephase, another dephase)
High ADC = dephase ___ (more/less)= ___ signal (high/low)
more - low
Low ADC = dephase ___ (more/less)= ___ signal (high/low)
less - high
stronger diffusion gradients = ____ b value (high/low)
high
TO acquire a DWI, how many directions must be measured
3 (AP, RL, SI)
b-value of 0 = ___-weighted
T2
T2 shine through is when __
pathology with hyperintense T2 signal appear white on DWI can be mistaken for acute stroke.
ADC map can be created using ___ & ___
B0
DWI images
if ADC is high, water will appear ___ on DWI
DARK
if ADC is low, water will appear __ on DWI
BRIGHT
what is the purpose of SWI
highlight differences between magnetic susceptibility of tissues
____ is helpful in imaging brain bleed
a. DWI
b. T1-w
C. SWI
d. fMRI
SWI
___ is used to measure brain activity
a. DWI
b. T1-w
C. SWI
d. fMRI
D
fMRI use ____ to create contrast
BOLD (blood oxygenation level dependent)
___ blood causes more dephasing
a. deoxygenated
b. oxygenated
A
less dephasing = ___ signal (increase/decrease)
increased
relaxivity is the ability to ___
change the relaxation times of tissues
The higher the relaxivity, the ___ it appear on image (brighter/darker)
brIghter
what is the most common contrast agent?
Gadolinium - T1 agents
what is the purpose of pulse sequences
rephase magnetic moment to produce an echo of the FID
what are the 2 types of pulse sequence
spin-echo
gradient-echo
___-echo pulse sequence use 180 RF
a. spin
b. gradient
A
Pulse sequence uses ___ & ___, and they are timed to control the weighting
RF pulse
gradients
The ___ nuclei needed to be ___ to create a signal
transverse coherent
rephase
what is the command to turn around for spin-echo pulse sequence
180 RF rephasing pulse
spin-echo occurs at time ___
TE
In SE, TR is the time between ___
a. 90 degree excitation pulses
b. 90 degree excitation pulse and peak of the echo
A
In SE, TE is the time between ___
a. 90 degree excitation pulses
b. 90 degree excitation pulse and peak of the echo
B
what is TAU
time between 90 degree excitation pulse and 180 RF pulse
in CSE,how many rephasing pulses are used to get a T1 image?
1
in CSE, how many rephasing pulses are used to get a PD & T2 image?
2
pros & cons of CSR
pro: true T2 weighting
con: long time scan
