Memorize Flashcards
T1 CSE Parameters (TR/TE)
Short TR: 300 to 700ms
Short TE: 10 to 30ms
T2 CSE Parameters
Long TR: 2000ms+
Long TE: 80ms+
PD CSE Parameters
Long TR: 2000ms+
Short TE: 20ms
T1 FSE Parameters
Short TR: 300 to 700ms
Short Effective TE: minimum
T2 FSE Parameters
Long TR: 3000 to 10000ms
Long Effective TE: 80 to 140ms
PD FSE Parameters
Long TR: 3000 to 10000ms
Short Effective TE: minimum
Fat Inversion Time
100 to 175ms
CSF Inversion Time
1700 to 2200ms
T1 CGE Parameters
Short TR: less than 50ms
Short TE: 1 to 5ms
Large Flip angle: 70 to 110 deg
T2 CGE Parameters
Long TR: 200ms+
Long TE: 15 to 25ms+
Small Flip Angle: 5 to 20 degrees
PD CGE Parameters
Long TR: 200ms+
Short TE: 5 to 10ms
Small Flip Angle: 5 to 20 degrees
T1 Incoherent GRE Parameters
TR: 20 to 50ms
TE: 5 to 10ms
Flip Angle: 30 to 45 degrees
T2* Coherent GRE Parameters
TR: 20 to 50ms
Long TE: 15 to 25ms
Flip Angle: 30 to 45 degrees
T2 Steady State Free Precession Parameters
TR: 20 to 50ms
TE: minimum
Flip Angle: 30 to 45 degrees
TOF Parameters
Short TR: 2500ms
TE: minimum
Flip Angle: 45 to 60 degrees
Ideal Temperature for Scanner Room
65 to 75 degrees F
Ideal Humidity for Scanner Room
50 to 70%
FDA Whole Body SAR Limits
4 W/kg /15min
FDA Head SAR Limit
3 W/kg /10min
FDA Torso SAR Limit
8 W/kg /5min
FDA Extremities SAR Limit
12W/ kg / 5min
FDA Static Field Strength Limit Under 1 Month
4T
FDA Static Field Strength Limit Over 1 Month
8T
Precessional Frequency Equation
Wo=Bo x ∆
Precessional Frequency (MHz)= Mag Field Strength (T) x Gyromagnetic ratio of Hydrogen (42.6)
T1 Relaxation Time of Fat
200ms
T1 Relaxation Time of Water
2500ms
T2 Decay Time for Fat
100ms
T2 Decay Time for Water
2500ms
Precessional Frequency Difference Between Fat and Water at 1T
147Hz
Precessional Frequency Difference Between Fat and Water at 1.5T
220Hz
Precessional Frequency Difference Between Fat and Water at 2T
440Hz
Voxel Volume Equation
Pixel Phase Dim x Pixel Freq. Dim x Slice Thickness
Beneficence means
Do no harm
Asepsis types
Medical and Surgical
Medical asepsis
Reduction in the number of pathogens to restrict spread and create a clean environment
Surgical asepsis
The complete elimination of all microorganisms to create a sterile environment
Nosocomial infection
An infection or illness originating from within a hospital
Iatrogenic infection
Infection or illness originating from medical exam or treatment
Adult heart rate
70 to 80 bpm
Child HR
90 to 100 bpm
Blood pressure
110 to 140
60 to 80
Resp rate
12 to 20 bpm
Temperatures per region
Oral: 98.6
Axillary: 97.6
Tymp: 97.6
Rectal: 99.6
Percent of claustrophobic patients
5%
Cpr sequence
CAB
Rate of compressions
80 to 100 per min
CPR Depth for Adults
1.5 to 2 in
Ratio of compressions to breath for 1 and 2 rescuers
1: 30 and 2
2. 30 and 2
Location for compressions
Lower 1/3 of sternum
Gd Contrast agents _____ T1 Relaxation Time
Reduce- brightening them
Gd Contrast agents slightly _____ T2 relaxation times resulting in _____ images
Reduce. Darker
80 percent of Gad is excreted in ____ hrs and 98 percent is excreted in ____ hours
3, 12
Structures that Gd enhances in the brain
Tumors, infection, acute infarct, inflammation and lesions
Super paramagnetic agents are stronger than paramagnetic agents. They ____ T2 Decay times in tissues
Shorten
Most common super paramagnetic agent is
Iron oxide
Iron oxide is the primary contrast agent for imaging the
Liver
Manganese is also used in liver imaging. It causes normal liver cells to
Enhance
Hyperpolarized helium agents are for studies of the
Lungs
Normal GFR
90 or higher
Gd dosing mmol/kg and ml/kg
0.1mmol or 0.2 ml
Level one personnel can be responsible for
Safety of themselves only
Level two personal can be responsible for
Safety of themselves and all others. They are allowed to also screen patients
Temperature of the MR scan room
65 to 75° Fahrenheit
Humidity percentage of the scan room
50 to 70%
Zone 1 are areas that are
Freely accessible to everybody
Zone 2 is accessible to everybody only there is an
MRI gatekeeper between zone 2 and zone 3
Zone 3 contains
The scanner consule
Zone ___ is only suitable for screened patients
4
This type of shielding is accomplished through the use of electromagnetics located at the end of the gantry
Active
This type of shielding is accomplished with steel plates, located within the gantry or the rooms walls, that help to contain the fringe field
Passive
What is the rooms Faraday cage made out of
Copper
Rf pulses can cause reactions in tissue. Name three
Tissue heating, antenna effects and thermal injuries
Which pulse sequence is associated with the highest risk of time varying magnetic field effects
EPI- rapidly switching gradients
Peripheral nerve stimulation includes
Involuntary muscle contractions and cutaneous sensations
The process of seeing stars when sensory receptors in the retina are stimulated by changing magnetic fields
Magnetophosphenes
Decibels exceeding ____ can cause immediate acoustic trauma
130 to 140
This effect increases the amplitude of the T-Wave on the EKG
Magneto hemodynamic effects
Faraday’s law states that for electromagnetic induction to take place, what must be present
a conductor, magnetic field, and motion (between the two) must be present.
Lenz’s Law - The second law of electromagnetism. Lenz’s law states that an electromagnetically induced current within a conductor creates a magnetic field opposing the magnetic field that produced the electromagnetically induced current. These opposing magnetic fields are also
referred to as
Eddy currents
Superconductive magnets are made of what
Niobium and titanium
These magnets have the best magnetic field homogeniety
Superconductive
copper, oxygen, silver, mercury, lead, water, and
graphite have no magnetic moment and are considered
Diamagnetic
tungsten, cesium, lithium, aluminum, magnesium, sodium, platinum, and
gadolinium contrast agents have a small magnetic moment and are considered
Paramagnetic
_________ substances only display a
magnetic moment when grouped. Individualmolecules
have no magnetic moment by themselves. Examples include iron oxide particles and iron oxide contrast agents
Superparamagnetic
__________substances retain their magnetization even
after the removal of the external magnetic field. Examples include; steel, iron, nickel, and cobalt
Ferromagnetic
The ________ coil is the first layer of instrumentation within the gantry of an MRI
machine.
RF
A cylindrical transceiver coil within the circumference of the magnet bore
that acts as the primary RF transmitter in closed-bore MRI systems. This coil provides
a large coverage area, and poor SNR
Body coil
The dephasing of spins due to magnetic field inhomogeneities is
T2 Prime
Pressional frequency is measured in
mHz
What term describes the ratio of a magnetic moment to it’s angular momentum
Gyromagnetic ratio
What constant of proportionality represents the frequency of at element at one Tesla
Gyromagnetic ratio
In the presence of a strong magnetic field, hydrogen nuclei within the body tend to precess _______ during thermal equilibrium
Out of phase
After the application of an RF pulse oscillating at the processional frequency of hydrogen, there are more spins in a high energy state than a low energy state. T or f
True
True or false. Phase coherence occurs when an RF pulse is transmitted at the precessional frequency of hydrogen
True
T or f. Phase coherence occurs at the same time as resonance
True
Phased array coils are also called
Multichannel coils
Transmit bandwidth is indirectly controlled by adjusting
Slice Thickness
Receive bandwidth is directly controlled T or F
T
Decreasing the receiver bandwidth _____ SNR
Increases- Narrower window for noise
Decreasing the receiver bandwidth _____ chemical shift
Increases
Increasing the receiver bandwidth _____ SNR
Decreases
Increasing the receiver bandwidth _____ chemical shift
Decreases
A gap space of _____% the slice Thickness should be selected to prevent sampling of the RF waveforms outer edge
30
The time it takes for a gradient to achieve max gradient amplitude
Gradient Slew Rate
Gradient Slew Rate describes speed and strength and speed and is mesured in
mT/m/s
Typical Slew Rates are between
70 to 200 mT/m/s
Maximum gradient amplitude is the max strength and is measured in
mT/m or G/cm
Gradient rise time is the time it takes for the gradient to turn on, achieve the required strength and turn off. It is measured in
Microseconds
A duty cycle is the time that a gradient is capable of working at max amplitude and is measured in
%
What 2 things occur with resonance
- Spins flip into transverse plane
- Spins precess in phase
FID is the loss off ____ in the transverse plane (T2 Decay) and along the longitudinal axis (T1 Recovery)
Magnetization
The controlling factor of T1 relaxation is ___ in SE sequences and in GE sequences the controlling factor is ____ and _____. Inversion recovery ____ and ______.
SE: TR
GE: TR and Flip Angle
IR: TR and TI
The controlling factor for T2 decay during all pulse sequences is
TE
T2* is a tissue characteristic similar to T2 decay, except that transverse decay occurs ______ due to T2 decay and magnetic field inhomogeneities (T2’)
Faster
T2* Decay is also called
Susceptibility decay
T2’
The dephasing of precessing spins due to magnetic field inhomogeneities
T or F the slice Selection gradient is turned on with the RF pulse
T
The phase Encoding gradient encodes the signal samples along the _____ axis of they anatomy (typically)
Short
The phase Encoding gradient energizes after the application of the ________ and before the ______
Alpha pulse, rephasing pulse
The greater the steepness of the phase Encoding gradient, the _____ the phase shift
Larger
The phase Encoding gradient acts as a rewinder gradient during _______and _______ pulse sequences
Coherent Gradient Echo and Steady State
The frequency Encoding gradient is applied during the collection of the
Echo
The applied ____ and _____ of the phase Encoding gradient determines which line of k space will be filled in
Slope and polarity
The _____ of the phase Encoding gradient determines the degree of _____ between the spins along the slope
Steepness, phase shift
The number of frequencies sampled during the collection of the echo is determined by the
Frequency matrix
The slope of the frequency Encoding gradient is determined by the
Frequency fov
The frequency Encoding gradient is also used for rephasing during ______ pulse sequences
Gradient Echo
K space is rectangular. T or F
T
K space has an X axis for frequency and a Y Axis for
Phase
The ___ half of k space mirrors the ___half of k space
R, L
The ____ half of k space mirrors the ____
Top, bottom
A steep phase Encoding gradient stores
Spatial resolution
Low signal amplitude is stored on the ____ of k space
Outer edge
Low signal amplitude results from a ____ phase Encoding gradient
Steep
A shallow phase Encoding gradient results on ____ signal amplitude
High
High signal amplitude resulting from a shallow phase Encoding gradient is stored in the _____ of k space
Center
K space is located in the
Array processor
A mathematical process that converts data obtained during image acquisition to be stored in kspace
Fast Fourier transform
T or F during a pulse sequence, phase Encoding occurs after frequency Encoding
False
Which of the following parameters would provide the best T1 weighting for CSE pulse
150ms TR, 5ms TE
450ms TR, 20ms TE
900ms TR, 60ms TE
400ms TR, 80m TE
450ms TR, 20ms TE
T or F Increasing the ETL during FSE sequences will cause acquisition time to increase
False
As ETL increases, more T2 weighting occurs T or F
true
What 2 advantages do FSE pulses provide
- Magnetic susceptibility artifact decreases
- Data is acquired faster than with CSE
3 disadvantages of FSE
- Motion artifact decreases
- SNR Decreases
- True image weighting is not possible
Is CSE or FSE better for detection of small hemhorrhages
CSE
What FSE pulse sequence uses a partial Fourier transform to fill all lines of kspace during a single TR period
SSFSE
T or F SSFSE sequence causes increased tissue heated compared to FSE or CSE
T
What FSE pulse sequence uses a reverse flip angle excitation pulse after the applied echo train in order to push the transverse magnetization into the longitudinal plane so that the T1 relaxation can occur quicker?
Dirven equilibrium Fourier transform
What does this pulse sequence represent 90-180-180-90
DRIVE sequence
Which sequence most accurately represents an IR sequence
180-90-180-180
180-90-90
180-90-180-180
The time between the 180° inversion pulse and then 90° alpha pulse is known as the
Inversion Time
Gradient Echo sequences use flip angles less than
90 degrees
Gradient Echo pulse sequences use the _____ to rephase FID
Frequency Encoding gradient
T or F All gradient Echo pulse sequences have some extent of T2*
T
GE pulse sequences are sensitive to ___
Flow
GE sequences are best when demonstrating _____
Brain hemorrhage
What type of gradient echo pulse sequence uses an alpha pulse with a variable flip angle as well as a single application of the frequency encoding gradient for rephasing purposes
Conventional Gradient Echo pulse sequences
How many lines of k space are filled during a single CGE sequence
1
T1 CGE pulse sequences generally require the use of a ___ flip angle
Large
What type of EPI sequence uses a 90° excitation pulse followed by a 180° rephasing pulse and a pulsing phase Encoding ingredient?
Spin Echo EPI pulse sequence
EPA sequences can be performed as either a spin echo EPI or a gradient echo EPA true or false
T
True or false. Distortions and chemical shift artifacts are common problems associated with EPI sequences
T
EPI sequences can be used to prevent
Physiological motion artifacts
True or false. EPI sequences are commonly used to perform physiological studies such as for fusion, diffusion and spectroscopy
T
What type of gradient echo pulse uses constant oscillation of the phase encoding gradient in order to fill all lines of k space during a single TR period
EPI
Balanced gradient echo pulse sequences are useful in providing good SNR and CNR between
Fat, water and surrounding tissue
What type of gradient Echo post sequence uses a significantly shorter TE by only transmitting part of an RF pulse and only sampling a portion of the echo
Fast gradient echo
The flip angles applied during steady state free precession full sequences fall within the range of
30 to 45°
The flip angles applied during coherent gradient echo pulse sequences will fall within the range of
30 to 45 degrees
The flip angles applied during incoherent gradient echo pulse sequences fall within the range of
30 to 45 degrees
For T1 weighted images the ETL needs to be in the range of
2-4
For PD weighted images the ETL needs to be in the range of
6 to 12
For T2 weighted images the ETL needs to be in the range of
12 to 32
Spoilers are gradients that
Dephase
Rewinders are gradients that
Rephase
Coherent (rewound) GRE Creates ___ weighted images and ____ effect
T2*, angiographic
Incoherent (spoiled) GRE Creates ____ and _____ weighted images because residual transverse magnetization is removed prior to the next excitation pulse.
T1, PD
Due to they very short scan times and high ETL, SSFSE are used in ____sequences
MRCP
DRIVE uses a reverse flip angle of
270 degrees
Steep gradients produce a ____ amplitude signal
Low
Sampling time= frequency matrix ÷
rBW
Spin echo time formula
TR X phase matrix X NEX
FSE scan time formula
TR X Phase Matrix X NEX
__________________________
ETL
GRE (2D) Scan Time Formula
TR X Phase Matrix X NEX
GRE (3D) Scan Time Formula
TR X Phase Matrix X NEX X #Slices
Narrow rBW increase _____ artifact
Susceptibility
A Narrow rBW produces a ____ SNR because noise is sampled less
High
A Narrow rBW ____ chemical shift
Increases
A wide rBW reduces susceptibility artifact and chemical _____
Shift
Increasing Phase and frequency matrix _____ SNR due to smaller pixel size
Decreases
To reduce chemical shift _____ the rBW
Increase
To prevent aliasing or wrap _____ the FOV
Increase
Out of phase signal cancellation produces a ring of dark signal where fat and water interface. Select the ____ that matches the periodicity of fat and water to compensate.
TE
Magnetic susceptibility artifact can be reduced by running a _____ sequence and avoiding ______ sequences
FSE, GRE
Truncation or Gibbs artifact can be reduced by increasing the number of ______ Encoding steps
Phase
Cross talk can be reduced by increasing _____ spacing
Slice
Zipper artifact is cause by ____ leakage
RF
Moire artifacts cause black and white banding on the edges of the FOV on _____ sequences. Use a ____sequence instead.
GRE, FSE
Time of flight phenomena are nuclei that are excited and are not rephased produce a signal ____
Void
Doubling the field strength ____ the SAR potential
Quadruples
A spoiled gradient echo sequence removes any residual ____ magnetization
Transverse
Incoherent gradient Echo sequences are also known as ____ gradient Echo
Spoiled
Gradient Echo sequences are influenced by susceptibility, chemical shift and inhomogenities because it does not contain a
180° RF pulse
Steady state occurs when the _____ in a gradient echo is less than the T2 or T2* causing residual transverse magnetization
TR
Incoherent gradient echo sequences have _____contrast due to the removal of residual transverse magnetization before the next excitation
T1
______ sequences are variation of high T2 signal, balance steady state sequences
Fiesta
Fiesta sequences are equipped with sliced, phase and frequency rewinder pulses. These images have mixed _____ contrast
T2/T1
Fiesta sequences are great for the evaluation of______
Cranial nerves
A _____ gradient echo sequence removes any residual transverse magnetization
Spoiled
Steady state refers to residual ______
Transverse magnetization
Spoiled gradient echo sequences spoil away residual transverse magnetization. This creates _____ contrast
T1
Spoiling reduces T2*(transverse magnetization) effect and is achieved by using ____ pulses
RF
A dual contrast spin Echo sequence uses echo times of ____ms and. ____ ms
25, 90
In a dual echo spin Echo sequence, What two types of images are produced
PD (short TE) and T2 (Long TE)
Increasing the echo train lengths can lead to increased______
Blurring
In the fast spin echo pull sequence the number of shots is calculated by the number of _____÷______
Phases, ETL
To calculate the number of shots in an FSE sequence you need to divide the number of _____ by _____
Phase Encoding, ETL
For example: 128 matrix ÷ 128 ETL
=1 Shot
___ sequences are typically used for the evaluation of periventricilar white matter
FLAIR
During a spin Echo pole sequence the application of the slice slut gradient occurs at the same time as the____ and ____ pulses
RF excitation pulse, Rephasing
During a pulse sequence ______ encoding occurs during readout
Frequency
At 1.5T what TI range best suppresses signal from fluid
100-175
2000-3500
400-550
1700-2200
1700-2200
Gradient Echo sequences use flip angles:
Greater than 90 deg
Equal to 90 deg
Less than 90 deg
Equal to 90 deg
Less than 90 deg
Which of the following parameters would produce the best T2 weighting when a GE pulse sequence is applied?
<50ms TR, 15-25ms TE, 90-110 FA
80-100ms TR, 20-50ms TE, 5-20 FA
200+ms TR, 15-25ms TE, 5-20 FA
200+ms TR, 1-5ms TE, 90-110 FA
200+ms TR, 15-25ms TE, 5-20 FA
What sub group of GE pulse sequences use 2 excitation pulses to create a stimulated echo?
Fast gradient echo
Steady state pulse sequences
Balanced gradient echo pulse seq
Echo planar Pulse Sequences
Steady state pulse sequences
What type of pulse sequence maintains partial longitudinal and transverse magnetization at all times
Steady State pulse sequences
During a steady state pulse sequence, if 2 excitation pulses with variable flip angles are applied, a _____ is created
Stimulated echo
If a Steady state pulse sequence uses 2 90 degree excitation pulses, the echo is called a
Hann echo
Steady state pulse sequences typically use flip angles in the range of
30 to 45 degrees
What type of steady state pulse sequence only samples the gradient echo (FID)?
Fast GRE
SSFP
Incoherent GRE
Coherent GRE
Incoherent GRE
Incoherent GE pulse sequences prevent the stimulated echo from contributing to image contrast by using:
RF spoiling
Gradient spoiling
Rewinder gradients
RF spoiling and Gradient Spoiling
RF spoiling and Gradient Spoiling
T or F
RF spoiling can be accomplished through the use of digitized RF pulses
T
T or F
Gradient Spoiling can be accomplished through the application of all 3 gradients
T
Incoherent GE pulse sequences are typically used to obtain _____ and ____ weighted images
T1 and PD
Which of the following parameters would most likely produce T1 weighted images when an incoherent GE pulse sequence is applied
100ms TR, 10ms TE, 45 deg FA
30ms TR, 5ms TE, 35 deg FA
30ms TR, 30ms TE, 90 deg FA
200ms TR, 5ms TE, 90 deg FA
30ms TR, 5ms TE, 35 deg FA
The flip angles applied during incoherent gradient echo pulse sequences fall within a range of
5 to 20
30 to 45
45 to 60
70 to 110
30 to 45
What type of steady state pulse sequence samples both the gradient echo (FID) and the stimulated echo (RTM)?
Fast GRE
SSFP
Incoherent GRE
Coherent GRE
Coherent GRE
Coherent GRE pulse sequences apply _____ to allow both the FID and stimulated echo to contribute to image contrast
Rewinder gradients
Coherent GE pulse sequences are achieved through the application of a rewinder _______ gradient
Phase encoding
Coherent GRE sequence are used to obtain ___ weighted images
T2*
Which set of parameters would provide the best T2* images when a coherent gradient echo pulse sequence is applied
30ms TR, 20ms TE, 35 deg FA
100ms TR, 10ms TE, 45 deg FA
30ms TR, 20ms TE, 65 deg FA
5ms TR, 15ms TE, 35 deg FA
30ms TR, 20ms TE, 35 deg FA
What type of steady state pulse sequence only samples the stimulated echo?
Fast GRE
SSFP
Incoherent GRE
Coherent GRE
SSFP
SSFP pulse sequences apply _____ in order to rephase the stimulated echo (RTM) so it may contribute to image contrast
Rewinder gradients
T or F
Magnetic field inhomogeneities greatly effect image quality when applying a SSFP pulse sequence
F
SSFP typically provide ____ T2 Contrast
Truer
SSFP pulse sequences are achieved through the application of a rewinder _____ gradient
Phase encoding
T or F
SSFP sequences compensate for dephasing caused by magnetic field inhomogeneities
T
Which of the following sets a parameters would likely provide the best T2 image weighting when a SSFP pulse sequence is applied
40ms TR, minimum TE, 40° flip angle
100 MS TR, 10 MS TE, 40° flip angle
40 MS TR, minimum TE, 65° flip angle
5 MS TR, 15 MS TE, 65° flip angle
40ms TR, minimum TE, 40° flip angle
The flip angles applied during SSFP pulse sequences fall within a range of
30 to 45°
What type of gradient Echo pole sequence uses a significantly shorter TE by only transmitting part of a RF pulse and only sampling and portion of the echo
Fast gradient Echo pulse sequence
What term describes the method used when only a portion of the echo is sampled
Partial ecotechnique
What type of gradient Echo pulse sequence uses a balanced gradient system and larger flip angles in order to correct phase errors from flowing blood
Balance gradient Echo pull sequence
Phase mismapping is also referred to as
Phase ghosting or motion artifact
Aliasing is also referred to as
Phase wrap
Aliasing is occurred when ______ occurs along the Phase axis
Undersampling
Truncation or Gibbs artifact appears as ______ occurring at the interface of high and low signal intensities
Black bands
Tunication or Gibbs artifact can be reduced by increasing the _____ to prevent undersampling
NEX
List the precessional frequency differences between fat and water at 1T, 1.5T and 2T
147, 220, 440Hz
Chemical shift occurs at what axis
Frequency encoding
Chemical shift artifacts are caused by the difference between precessional frequencies of ____and____
Fat, water
Chemical shift artifacts appear as ________ at the interface between fat and water along the frequency encoding axis
Dark edges
The larger the pixel size the more chemical shift artifact occurs. T or F
T
Chemical misregistration is also known as _____ artifact
Type 2
Chemical misregistration or type 2 artifact appear as _______ around certain organs were fat and water interface within the same voxel
Rings of dark signal
What body part does chemical misregistration usually occur around
Kidneys
Using an _______ sequence can compensate for chemical misregistration artifact because of their 180° rephasing pulse
SE
What TE interval are fat and n water in phase with each other
4.2ms
Dixon technique is known as _____ of phase imaging
Out
For out of phase or Dixon technique TE of ______is desirable to allow chemical misregistration artifact to occur so a dark outline will appear around structures or fat and water interface
2.1ms
Partial volume averaging is present in all images to some degree. T or F
T
Partial volume averaging is caused by the use of ______ voxels
Large
Cross talk appears as areas of_____ signal
Dark
Cross excitation appears as a reduction in image_____
Contrast - image is darker
To compensate for cross excitation a slice gap of____ is recommended
30%
Interleaving excites every other slice into acquisitions so no gap spaces needed. T or F
T
Moire artifact is only present in_____ pulse sequences
GE
Moire artifact presents as black and white _____ along the edges of the field of view
Banding
Moire artifact is caused by a combination of wrap around artifacts and magnetic field inhomogeneities. T or F
T
To compensate for Moire artifact, switch to a ____ pulse sequence, keep anatomy away from the ____ and Make sure all anatomy is in the ___
SE, bore, FOV
Parallel imaging artifact is only seen when performing parallel imaging and using multichannel _______ coils
Phased array
Parallel imaging artifacts appear as anatomy from the outside of the____ folded onto the end anatomy inside along the_____ encoding axis
FOV, phase
Two compensate for a parallel imaging artifact you may reduce the_____ factor or use a calibration scan
Acceleration
Magic angle artifact can occur around areas where _____are present in the imaging volume
Tendons
Magic angle artifacts appear as an area of _______signal intensity in your areas where collagen is present
High
Magic angle artifacts are caused when collagen-containing structures light at an angle of _____ to the main magnetic field
550 degrees
To compensate for magic angle artifact, alter the angle of the anatomical structure or lengthen the ____
TE
What is the pixel phase dimension when given a FOV of 240 mm and a 256x128 Matrix?
240/256
____ directly controls T1 weighting
TR
The TE is the time between the alpha pulse and the
Peak of the Echo
____ directly controls T2 image weighting
TE
Doubling the NSA, the scan time is ___
Doubled
If the NSA is quadrupled the scantime is
Quadrupled
Doubling the field of view _____the signal
Quadruples
Slice thickness is determined by the _____of the slicelet gradient and the transmitted bandwidth
Slope
A steep slice select gradient and a narrow transmit bandwidth are needed to achieve____ slices
Thin
A shallow slice select gradient slope and a broad transmit bandwidth are needed to achieve _____slices
Thick
Gap is determined by the ____ of the slices as well as the corresponding slice select gradient slope
Thickness
The ETL corresponds to the number of _____ applied
180 degree rephasing pulses
Echoes that represent image contrast get placed in the _____ of k space
Center
Spatial resolution data are put where in case space
Periphery
The transmit bandwidth is influenced by the slice ____
Thickness
If you double the receive bandwidth then ______percent of the signal is lost
40
T2 shine through artifact occurs when areas with a very long ____ decay time remain bright on DWI trace images
T2
Areas with pathology or restricted diffusion appear bright on______ images
DWI Trace
Pathology or areas with restricted diffusion appear _____ on ADC post-processing maps
Dark
Normal tissue or free diffusion has a dark appearance on
DWI Trace images
Normal tissue or free diffusion areas have a bright appearance on
ADC post-processing maps
Lemonar flow is considered_____ order motion
First
Laminar flow has a ____ velocity
Constant
Turbulent flow is considered ____ order motion
3rd
Turbulent flow is the _____ fluctuation of blood through an occlusion
Random
Time of flight phenomenon is only observed using ____ sequences
SE
TOF phenomenon is not observed during GE sequences because the rephasing ingredient is not
Slice selective
TOF effects increase as flow velocity
Inceases
As the ____ increases, more flowing nuclei exit the slice between the excitation pulse and the rephasing pulse
TE
Increasing the ____ thickness decreases TOF effects
Slice
Entry slice phenomenon is also known as the
Inflow effect
The inflow effect explains how spins flowing _____ to a stack of slices enter the stack unsaturated and produce more signal than stationary nuclei that receive repeated excitation
Perpendicular
The further the flow of nuclei enter the stack, they become more saturated which _____ entry slice phenomenon
Decreases
Time of flight imaging uses an _____ GE pulse with gradient moment nulling
Incoherent
Increasing the field of view from 120 mm to 240 mm we’ll have what effect on SNR
Snr increases by a factor of 4
When steep gradient slopes are applied, data gets mapped into the_____ of k space
Periphery
True or false. Imaging coils perform best when positioned perpendicular to the XY plane
T
Which of the following parameters influences SNR the greatest?
Field of view, TR, receive bandwidth, NSA
Field of view
The slope of the ______, along with the transmit bandwidth determines the slice thickness
Slice select gradient
During gradient echo pulse sequences, the controlling factors for T1 relaxation are ____ and _____
TR and Flip Angle
DTI sequences are commonly used to view what in the brain
White matter tracks
The ETL is directly related to the number of_______ during a fast spin echo pulse sequence
Echo sampled and 180° rephasing pulses applied
When scanning a female pelvis what plane best demonstrates the uterus
Sagittal
Both magneto hemodynamic and magneto hydrodynamic effects increase the amplitude of the
T wave
The field of view is the parameter that directly impacts______ the greatest
SNR
What type of flow is gradient moment nulling most efficient at rephasing
Laminar flow
Typically, when GMN is applied during the acquisition of axial images, the _____ gradient is used for flow compensation
Slice select
What term describes the accidental administration of contrast agents into surrounding tissue instead of directly into the vein
Infiltration
A special saturation pulses capable of saturating all tissues within a specified area through the use of an extra 90° RF pulse and a
Broad transmission bandwidth
Areas containing pathology appear _____ on DW Trace images
Bright
Which of the following full sequences most accurately represents an IR pulse sequence
180,90,180,180
180,90,90
90,180,180
180,90,90,180
180, 90, 180,180
Incoherent GE pull sequences are typically used to obtain what weighted images
T1 and PD
In order to increase the SNR by 100% ( double the SNR) The NSA/NEX must be increased by a factor of
4
A _______ is a bipolar gradient used during phase contrast imaging
Velocity gradient
If the number of signal averages is increased by a factor of 2, what happens to the signal to noise ratio
The SNR increases by the root of 2 or by a factor of 1.41 or 41%
Has slice thickness increases, spatial resolution
Decreases
If attempting to obtain T2 images of a patient with a 60 BPM, what is the minimum number of R to R intervals that should be selected
2
In order to more accurately diagnose a syrinx,______ can be used to reduce pulsatile flow artifacts within the spinal canal
Peripheral gating / triggering
Which of the following is an imaging option that applies an extra 90° RF pulse prior to the alpha pulse in order to know the signal from a specified type of tissue throughout the entire imaging volume
Chemical band, spatial saturation, saturation band, chemical suppression
Chemical suppression
Why is cardiac gating useful when imaging patients prone to seizures
It helps reduce pulsatile flow related artifacts within the temporal lobe
A trigger window of ______is commonly used to compensate for heart rate fluctuation
10 to 20%
The T1 relaxation time of fat is
200ms
What is achieved when there are more protons aligned in a low energy state than in the high energy state
Equilibrium magnetization
If the receive bandwidth is doubled approximately what percentage of the SNR is lost
40
Scan time can be reduced using a ____ ETL
Longer
Blurring can be reduced using a ____ etl
Shorter
When a GRE sequence is used during fast breath hold dynamic contrast injections, gradient ____ is used
Spoiling
If the desire is to null specific tissue using an IR sequence, the TI selected should be ___% of then T1 Relaxation Time of that tissue
69
The flip angle is doubled, RF deposition increases by a factor of
4
Reducing the field of view by a factor of two will reduce the voxel Volume by a factor of ____
4
T or F decreasing ETL improves SNR
T
T or F, decreasing RBW improves SNR
T
Decreasing phase matrix____ SNR
Increases
Parallel imaging can be used to _____ magnetic susceptibility artifacts
Decrease
A dual Echo spin sequence generates a proton density image in a T2 weighted image. The t2 weighted image has ____ SNR
Lower
Each train of echoes in a fast-spin echo sequences reduces scan time but also ____ SNR and ____ SAR
Decreases, increases
In a FSE sequence, if the ETL factor is increased by a factor of three, the scan time will be 3 times _____
Faster
In a FSE Sequence, the number of shots is calculated by
phase encodings/ETL
A 3D IR sequence is ____ weighted
T1
In a STIR sequence, the null point of fat in a 1.5 t magnet is approximately ______milliseconds
140 to 160
As the TE is increased, the available number of slices is
Decreased
As the TR is increased, the available number of slices is
Increased
As the TR is increased, SNR is
Increased
Reducing the flip angle yields images with _____ T1 information
Less
Reducing the phase Matrix____ the SNR
Increases
Reducing the receive____SNR
Increases
Reducing the ETL ____ SNR
Increases
A decrease in TR and a reduction in pixel size both____ the SNR
Decrease
Increasing the ETL____ SNR
Decreases
Increasing the NEX increases the SNR by
√Nex increase
Decreasing the bandwidth by a factor of two increases the SNR by
√2
Reducing the field of view decreases the SNR by the
FOV^2
Calculate effective TR in cardiac imaging
60,000 / HR
Calculate available imaging time in a cardiac MR. HR is 80bpm, trigger window 10%, trigger delay 50ms
- Find TR
60,000/80bpm = 750ms - Subtract trigger window
750ms-( 10% of 750)
750ms- 75 = 675 - Subtract delay
675-50
Final answer is 625ms
Signal and contrast are store in the ____ of k space
Center
Data containing ____ resolution information is located in the periphery of k space
High
Low frequency means ____ amplitude signal
High
2D aquisitions require an ____ gap
Interslice
A narrow receiver bandwidth ____ susceptibility artifact
Increases
