final quizzes
Which area of k-space has a high contrast signal amplitude and low resolution?
Central portion
The appearance of magnetic susceptibility artifact is:
Distortion of the image and signal voids
A technique used to visualize the morphology of the heart and great vessels is:
Double IR
When does slice selection occur in a gradient echo sequence?
During RF excitation pulse
When is the frequency gradient turned on during a pulse sequence?
During rephasing/dephasing part of the echo and the peak
FSE uses _________, to fill multiple lines of ___________ per TR.
ETL, k-space
The time from the application of the RF pulse to the peak of the signal induced in the coil is termed the:
Echo time (TE)
The application of an RF pulse that causes resonance to occur is termed:
Excitation
The cause of cross excitation/cross talk is:
Excitation of nuclei in adjacent slices
All wheelchairs, IV poles, and gurneys are allowed in the MRI room.
False
Doubling the NEX doubles the SNR.
False
In net magnetization at thermal equilibrium, there are equal amounts of hydrogen alignment in the low and high energy states (spin-up and spin-down).
False
Phase encoding gradient is turned on after application of excitation pulse.
False
The type and size of a receiver coil does not affect the quality of the MR signal.
False
to achieve thick slices, the machine uses a steep slice gradient slope and/or a narrow transmit bandwidth.
False
Whose law states that "a moving magnetic field induces a voltage in a conductor coil"?
Faraday
An advantage to using gradient echo sequences is:
Faster scan times
In STIR sequences, which tissue is being suppressed?
Fat
The cause of chemical shift artifact is:
Fat and water precessing at different frequencies
Which statement is not true about FSE pulse sequences?
Fat is darker on T2 weighted FSE pulse sequences
The greatest hazard of the main magnetic field is:
Ferromagnetic projectiles
An object that has a strong magnetic attraction is known to have:
Ferromagnetism
Which of the following modes of MR scanning should a technologist consider patient's dissipation of heat before using?
First-level controlled operating mode
STIR sequences can suppress the signal from all of the following EXCEPT:
Fluid (CSF)
The technique by which signal data is transformed from a plot of signal intensity over time to a plot of signal intensity over frequency is known as:
Fourier transformation
The "readout" gradient is also known as the:
Frequency
The gradient that is on during the production of the echo is the:
Frequency
What function do the gradients perform?
Frequency encoding Slice selection Phase encoding
The field of view is related to the slope of the:
Frequency encoding gradient
In entry slice phenomena, nuclei that are flowing and have not received repeated RF pulses are said to be:
Fresh
The stray magnetic field that extends outside the bore of the magnet is known as the:
Fringe field
Increasing the FOV:
Increases the SNR
Raymond Damadian's first human-sized maching is named:
Indomitable
The appearance of truncation is:
Interfaces of bright and dark "ringing"
What is the principle advantage of a superconducting magnet?
Low power requirements
Precessional frequency in MRI is measured in:
MHz
Who is the last person in the line of defense and in charge of the safety of the MR room and environment?
MR technologist
The person responsible for the safety of everyone in and around the MRI environment is the:
MRI technologist
A technique that involves the fast exchange of energy between bound and free nuclei is:
MTC
The cause of magnetic susceptibility artifact is:
Metal objects within the imaging volume
A 1.5T magnet produces higher SNR than a 0.7T magnet due to:
More H protons contributing to the NMV
The _________ is the number of times each line of k-space is filled with data.
NEX
Which factor below does not control the size of the voxel?
NEX
One way to improve the SNR without affecting the resolution is by changing the:
NEX NSA Naq
The remedy for aliasing artifact is:
No phase wrap, reposition anatomy or enlarge FOV
The original names for the technology, NMR, stood for what?
Nuclear Magnetic Resonance
The point in a tissue's longitudinal recovery where there is no component of magnetization and therefore no signal created on an IR pulse sequence is called:
Null point
Which of the following is not one of the extrinsic parameters?
PD
An object that has a small magnetic moment is known to have:
Paramagnetism
A technique that fills only a proportion of k-space with data and putting zeros in the remainder is known as:
Partial averaging
A technique that samples only a part of the echo and extrapolating the remainder in k-space is known as:
Partial echo
Who must be screened before entering MR area?
Patients Visitors Ancillary personnel
Fluid attenuated inversion recovery (FLAIR) sequences are typically used for the evaluation of:
Periventricular white matter disease
Which is not one of the principle flow phenomena?
Phase contrast
Which gradient changes its slope from one TR period to the next to encode the next line of k-space?
Phase encoding gradient
An RF coil that uses several small surface coils linked together to provide improved SNR and a larger area of coverage is called a:
Phased array coil
Which of the following determines whether the line of k-space is filled left to right?
Polarity of the frequency encoding gradient
Which of the following determines whether the line of k-space is filled at the top or bottom?
Polarity of the phase encoding gradient
What is the basic assessment done before scanning pregnant patients?
Risk vs benefit
The ratio of the signal received to the average of the noise is called:
SNR
Which of the following is defined as the speed and strength of a gradient measured in mT/m/s?
Slew rate
The remedy for cross excitation/cross talk is:
Slice spacing, interleaving, or concatenation
What affects time of flight phenomena?
Slice thickness Velocity of flow TE
Which of the following contributes to image resolution?
Slice thickness FOV Matrix
Imaging parameters in GRE PD-weighted sequences should have:
Small flip angle, long TR, short TE
Imaging parameters in GRE T2*-weighted sequences should have:
Small flip angle, long, TR, long TE
A pulse sequence with a 90⁰ RF excitation pulse followed by a 180⁰ RF rephasing pulse is known as a(an):
Spin echo
When a gradient echo sequence is acquired for dynamic contrast-enhanced imaging of the liver, _______________ is performed.
Spoiling
The ability to distinguish between two points in an image as separate points is known as:
Spatial resolution
SAR stands for:
Specific absorption rate
A condition where the TR is less than T1 and T2 relaxation times of tissues, where energy in equals energy out is known as:
Steady state
To achieve a small FOV in the frequency direction, a ___________ frequency encoding gradient is applied.
Steep
In order to obtain thin slices, a ________ slice-select slope and /or a _________ bandwidth is applied.
Steep, narrow
Surface coils are used for:
To improve the SNR
What is the purpose of cryogens?
To supercool the coils of wire in a superconducting magnet
Which of the following force(s) is responsible for ferromagnetic materials becoming attracted to the static magnetic field?
Translational force
Aliasing is caused when sampling is less than once per cycle representing incorrect frequency.
True
Data in the top half of k-space are identical to those in the bottom half.
True
Gradient echo pulse sequences are much more susceptible to artifacts than spin echo sequences.
True
Gradient echo sequences can yield either T1 or T2* characteristics.
True
The 180⁰ RF pulse is the rephasing pulse that creates the spin echo.
True
The cables connected to coils must never be looped or frayed.
True
The outer portion of k-space contains signal data that have low signal amplitude and high resolution.
True
The steady state is equal amounts of longitudinal and transverse magnetization.
True
There are no known irreversible biological effects of the static magnetic field at clinical levels.
True
Time of flight phenomena can produce flow-related enhancement or signal void.
True
The type of flow where the velocity difference across the vessel changes erratically is:
Turbulent flow
The cause of truncation artifact is:
Undersampling of data inside FOV from too low matrix
The cause of aliasing artifact is:
Undersampling of data outside the FOV
Contrast to noise ratio can be increased by:
Use of T1-weighting imaging You Answered Use of T2-weighting imaging Contrast enhanced sequences Correct Answer b and c
The remedy for Moire "Zebra Stripe" pattern is:
Use spin echo, keep patient arms within or out of the FOV
Active shielding of the main magnetic field uses:
Uses solenoid electromagnets located around the outside of the main magnet
A method of reducing motion artifact due to phase mismapping from heart motion is:
cardiac gating
The hydrogen proton induces a strong magnetic field because it is:
charged and spinning
The frequency difference between fat and water is called:
chemical shift
The early NMR machines studied _____________ using a technique called __________________.
chemicals spectroscopy
What are the two branches of physics used to describe the basic principles of MRI?
classical and quantum theories
What imaging technique can be used to overcome artifacts and the problem with loss of signal due to in-plane flow?
contrast-enhanced MRA
One of the most important safety concern associated with MRI is:
ferromagnetic attraction
A common name for gradient moment rephasing (nulling) is:
flow compensation
Artifacts on MR images reduce:
image quality
What is TOF MRA?
imaging technique that relies on flow-related enhancement
Under what circumstances should a superconducting magnet be turned off?
in certain emergencies
What has MRA helped to reduce in patients?
invasive conventional angiography
One reasons that the hydrogen atom is used in clinical MR imaging are its abundance in the body and:
its solitary proton creates a large magnetic moment
What combination of TE and TR create a T2-weighted image?
long TE, long TR
The remedy for zipper artifact is:
Call the engineer
In FLAIR sequences, which tissue is being suppressed?
CSF
A ___________ sequence is acquired in slices, whereas a _________ sequence is acquired in a volume or slab.
2D, 3D
TOF MRA can be performed using what methods?
2D, 3D
1 Tesla
10,000 gauss
In what year did the physicists win the Nobel Prize?
1952
In what year did MRI receive its FDA approval?
1985
In the multi-echo spin-echo sequence shown below, the number of images PER SLICE LOCATION created will be:
2
In the multi-echo spin-echo sequence shown below, the number of LONG TE images created with a 20-slice sequence will be:
20
In the multi-echo spin-echo sequence shown below, the number of SHORT TE images created with a 20-slice sequence will be:
20
If a phase resolution of 256 is desired, then the TR must be repeated (for one NSA):
256 times
What is the modern SAR limit by the FDA for the whole body?
4.0
In the multi-echo spin-echo sequence shown below, the TOTAL images created with a 20-slice sequence will be:
40
At what fringe field strength must the public be protected from?
5G
T1 relaxation time is defined as when:
63% of the longitundinal magnetization has recovered
T2 relaxation time is defined as when:
63% of the transverse magnetization has decayed
The Larmor precessional frequency of hydrogen in a 1.5T magnet is:
63.86MHZ
Which of the following best describes an EPI sequence?
A "train" of gradient echoes
IR pulse sequences are characterized by:
A 180⁰ inversion RF pulse followed by a 90⁰ excitation RF pulse
GRE T2*-weighted sequences use:
A gradient rewinder
The cause of shading artifact is:
Abnormal loading of the receiver coil
Applying electromagnetic fields to adjust the uniformity of the magnetic field, especially over body parts in certain pulse sequences is called:
Active shimming
The appearance of cross excitation/cross talk is:
Adjacent slices with different image contrast
A designated "Zone 1" in a MRI facility includes:
All areas that are freely accessible to the general public
Which of the following determines how far left and right of a line of k-space is filled?
Amplitude of the frequency encoding gradient
Which of the following determines how for up and down a line of k-space is filled?
Amplitude of the phase encoding gradient
The cause of phase mismapping is:
Anatomy moving in the phase direction
The appearance of aliasing is:
Anatomy wrapping into the FOV
The Z-gradient allows selection of what plane of anatomical slices?
Axial
A technique that uses the differences in magnetic susceptibility between oxyhemoglobin and deoxyhemoglobin to image areas of activated cerebral cortex is:
BOLD
The appearance of Moire is:
Black and white banding on the edges of the FOV
The appearance of chemical shift is:
Black and white borders on opposite sides of an organ
Who is considered to be the father of MRI with their development of the T1 and T2 equations?
Bloch
Which two physicists first won a Nobel Prize for their development of nuclear induction?
Bloch and Purcell
The top portion of K space is a mirror image of the:
Bottom
The appearance of zipper artifact is:
Bright and dark line across the image
T1 weighted images are characterized by:
Bright fat and dark water
Flow related enhancement results in:
Bright, high signal from moving nuclei
The best method to get claustrophobic patients through an MRI exam is:
Communication by the technologist
The Y-gradient allows selection of what plane of anatomical slices?
Coronal
Who is credited with the first human body image under NMR in 1977?
Damadian
T2 weighted images are characterized by:
Dark fat and bright water
Decrease flip angle from 45 degrees → 20 degrees
Decrease SNR
Increase TE from 10ms → 30ms
Decrease SNR
Increase the receive bandwidth from 16kHz → 32kMz
Decrease SNR
Decrease TR from 4000ms → 2000ms
Decrease scan time
An object with no magnetic moment is known to have:
Diamagnetism
Magnetic field strength is measured in which units?
Gauss, Tesla
The appearance of phase mismapping is:
Ghosting replications of anatomy
The steepness of a gradient is known as:
Gradient amplitude
Which of the following is defined as the strength of a gradient measured in mT/m or G/cm?
Gradient amplitude
The pulse sequence consisting of a variable flip angle RF excitation pulse followed by a pulse of the magnetic field gradients is called:
Gradient echo
Which of the following is defined as the time for a gradient to reach maximum strength in µs?
Gradient rise time
Gradient echo T1-weighted sequences use:
Gradient spoiling
What is the main cause of acoustic noise in the scan room?
Gradients
Spin echo sequences
Have a 90-degree excitation pulse followed by 180-degree rephasing pulse
An example of a volume RF coil is the:
Head coil Body coil Quadrature knee coil
The cryogen used in modern superconducting systems is liquid:
Helium
Small voxels produce:
High resolution
Thicker slices yield __________ SNR.
Higher
An advantage of a 3DTOF over a 2DTOF is:
Higher resolution
The uniformity of a magnetic field is also known as:
Homogeneity
TR, TE, TI and flip angle determine what in a pulse sequence?
Image contrast weighting and pulse timing
SNR, CNR, spatial resolution and scan time are all considerations for:
Image quality
Dynamic enhanced MRA sequences of the renal arteries are performed with the use of:
Incoherent gradient echoes
Gradient echo sequences acquired for high signal from fluid are known as all of the following EXCEPT:
Incoherent gradient echoes
A gradient echo sequence in which any residual transverse magnetization is removed prior to the next excitation pulse is known as:
Incoherent/spoiled
Decrease matrix from 512x512 → 256x256
Increase SNR
Increase NEX from 1→ 2
Increase SNR
Increase FOV from 32cm → 40cm
Increase SNR Decrease SNR Decrease spatial resolution Correct! A and C
Which of the following interventions can be made to reduce RF depostition?
Increase TR Reduce flip angle Remove presaturation pulses
Increase TR from 400ms → 700ms
Increase scan time
Decrease SNR
Increase scan time Decrease slice thic
Increase slice spacing from 1mm → 2mm
Increase special resolution
The remedy for truncation artifact is:
Increase the number of phase encoding steps
The remedy for shading artifact is:
Increase the number of phase encoding steps Don't allow patient to touch the coil
Entry slice phenomena increases as the velocity of the flow:
Increases
The time between 180⁰ inversion pulse and the 90⁰ excitation pulse is known as:
Inversion time
Items that are "unsafe" to go into the MRI scan room have a label that:
Is a red circle with a diagonal line and "MR" inside of it
Who was the first person to demonstrate a radio signal from the nucleus of an atom?
Isidor Rabi, Ph.D.
1. Which statement(s) below is(are) true about k-space?
It is the raw scanned signal data that must be mathematically transformed into the image
When using terms for MRI safety, "MR conditional" means:
Item demonstrated to pose no known hazards in a specified MR environment with specific conditions of use
The storage for spatial frequency data before image reconstruction is called:
K-space
The type of flow where the velocity is greater in the center of the lumen of the vessel and slower at the walls is:
Laminar flow
Imaging parameters in GRE T1-weighted sequences should have:
Large flip angle, short TR, short TE
The time constant of the precessional frequency of a specific MR active nucleus at 1 Tesla in MHz/T is called:
Larmor frequency
In reference to MRI safety training, as an MRI technologist, which level are you according to the ACR levels of personnel?
Level 2
Which combination of TE and TR creates a T2-weighted image?
Long TE, long TR
Which combination of TE and TR create a T1-weighted image?
Long TE, short TR
Which would not be an advantage of a permanent magnet?
Low SNR
Phase encoding is performed:
Prior to frequency encoding
What is shimming?
Process where the homogeneity of the magnetic field is even
The part of the system that controls the order and timing of the RF and gradient pulses is the:
Pulse generator module
Sudden loss of cryogens is called a:
Quench
The cause of zipper artifact is:
RF leak in scan room
Energy can be transmitted in a short burst of RF by the:
RF transmitter Body coil within the magnet bore Head coil
Spiral and propeller are methods of:
Rapid k-space filling
Another name for frequency encoding is:
Readout
The range of frequencies of the signal that is read and digitized and the speed at which this happens is controlled by the:
Receive bandwidth
The range of frequencies that are sampled during the application of the readout gradient is called the:
Receive bandwidth
The remedy for magnetic susceptibility artifact is:
Remove all metal objects
The time from the application to one RF pulse to the application of the next RF pulse is called the:
Repetition time (TR)
Energy is most effectively transferred from one system to another when the systems are at:
Resonance
A technique that uses differences in magnetic susceptibility between tissues to generate image contrast is:
SWI
The X-gradient allows selection of what plane of anatomical slices?
Sagittal
The process by which the scanner reads and digitizes the signal is called:
Sampling
The remedy for chemical shift artifact is:
Select a TE when fat and water are in phase
Which combination of TE and TR creates a T1-weighted image?
Short TE, short TR
The phase encoding direction of the image is normally the:
Short axis of the anatomy
A technique that allows k-space to fill from a single echo train is known as:
Single shot imaging
A designated "Zone 4" in a MRI facility includes:
Suitable for screened patients under direct supervision of MRI staff
Which is the most common type of magnet used in current clinical MR imagers?
Superconducting
Which of the following describes how passive shielding is accomplished?
Surrounds the magnet room with steel plates
Gradient echo sequences acquired for the evaluation of hemorrhagic lesions rely on:
Susceptibility
The remedy for phase mismapping is:
Swap phase/frequency, saturation bands, gating or FC
In IR sequences, the resultant contrast depends primarily on the
T1
Incoherent GRE sequences are:
T1-weighted
Coherent GRE sequences are typically:
T2*-weighted
Short tau inversion recovery images are:
T2-weighted, fat saturated images
Which combination of TR and TE creates a T1-weighted image?
TE 15ms, TR 400ms
Which combination of TR and TE create a T2-weighted image?
TE 90ms, TR 4000ms
Which of the following is not one of the intrinsic contrast parameters?
TR
For a conventional pulse sequence, the scan time equals:
TR x NEX x phase matrix
When using a receive-only surface coil, which coil transmits the RF pulse to the patient's body?
The body coil
Magnetic isocenter refers to:
The center of the magnet in all planes
The contrast information of the image is encoded into what part of k-space?
The central lines
The resolution of the image is encoded into what part of k-space?
The outer lines
Why do large voxels produce a higher SNR than small voxels?
They contain more H nuclei
The flow phenomenon where a nucleus may have only received an 90-degree excitation or a rephasing 180-degree pulse because it is moving is called:
Time of flight
Which MR component can cause cutaneous sensations and muscle contractions?
Time varying gradient magnetic fields
The main biological effect of RF is:
Tissue heating
The tissue most often saturated with chemical pre-sat is:
fat
The appearance of shading artifact is:
Varying signal intensity across an image
SAR is measured in:
W/kg
In a balanced GRE acquisition, the contrast weighting is:
Weighted for the ratio of T2/T1
The cause of Moire "Zebra Stripes" pattern is:
Wrap and field inhomogeneities on GREs
The ______ gradient selects sagittal slices, whereas the _____ gradient selects axial slices.
X, Z
Which gradient performs the frequency encoding when acquiring coronal images of the brain?
Y-gradient
Below critical temperature, superconducting magnet coils have _______ resistance.
Zero
Phase is:
a position at a given time
What tissue is bright on diffusion weighted imaging?
abnormal tissue
Free induction decay occurs:
after 90-degree RF excitation pulse
What does ADC stand for?
apparent diffusion coefficient
The number of protons in a nucleus is termed:
atomic number
Slice thickness is controlled by:
b. Bandwidth a. Steepness of slope
Which factors determine pixel size?
b. Field of view a. Image matrix
Spatial pre-saturation is effective in reducing flow artifact provided that the saturation pulse is placed ________ the flow and the imaging stack.
between
T2 weighted images are characterized by:
bright fat and bright water
T1 weighted images are characterized by:
bright fat and dark water
The term used to describe the movement of molecules due to random thermal motion is:
diffusion
The time from the application of the RF pulse to the peak of the signal induced in the coil is termed the:
echo time (TE)
What conditions are necessary for resonance?
energy applied at the precise frequency and at a right angle
The application of an RF pulse that causes resonance to occur is termed:
excitation
Gradient moment rephasing is more effective on fast, turbulent arterial flow.
false
T1 agents lengthen T1 recovery times in order to be seen on post contrast images.
false
The direction of frequency encoding can always be determined on the image because mismapping and aliasing is always in that direction.
false
Chemical pre-saturation saturates a particular tissue by targeting its specific:
frequency
What is the name of the advanced technique that images brain activity?
functional
In bright blood imaging, flowing spins in blood vessels are hyper-intense to stationary tissue and are based on:
gradient echo sequences
Which is not an advantage of 3D TOF MRA?
high SNR
Frequency is:
how fast
Which of the following is the most abundant atom in the human body
hydrogen
With regard to energy, protons in parallel alignment are in the ____________ state, whereas protons in an anti-parallel alignment are in the ____________ state.
low, high
The tiny magnetic field of the hydrogen proton that is induced by spin and charge and has a north and south pole is called:
magnetic moment
The method used for reformatting TOF MRA data is known as:
maximum intensity projection
T1 and T2 relaxation depends on the molecular tumbling rate matching the Larmor frequency of hydrogen and
molecules that are closely packed together
In MR imaging, the term "spin" refers specifically to the spinning:
nuclei
The nucleus of a hydrogen atom contains:
one proton
Who should be screened before entering the MRI environment? Check all that apply.
patients, & patients fam
What type of magnet cannot be turned off?
permanent
What are the three basic types of magnets used to construct MRI scanners?
permanent, resistive, superconducting
TOF MRA is most sensitive to flow that is _____________ to the FOV, the slices, and/or the slab
perpendicular
What can be used on spin echo and gradient echo sequences to enhance the signal from flowing blood and suppress the signal from stationary tissue?
pre-saturation pulses, flow comp, and magnetization transfer
What is the Larmor equation used to calculate?
precessional frequency
The number of mobile hydrogen protons per unit volume of the tissue is known as:
proton density
Artifacts can be:
reduced or eliminated avoided irreversible
The time from the application to one RF pulse to the application of the next RF pulse is the:
repetition time (TR)
Energy is most effectively transferred from one system to another when the systems are at:
resonance
A _____________ is applied above or below the imaging slices or slab to saturate unwanted in-flowing spins.
saturation pulse
What combination of TE and TR create a PD-weighted image?
short TE, long TR
Black blood acquisitions produce images where blood flow is dark and are based on:
spin echo sequences
T1 recovery is caused by:
spin-lattice relaxation
T2 decay is caused by:
spin-spin relaxation
What happens to the hydrogen protons when they are placed in a magnetic field?
they align parallel and anti-parallel
Why was the name changed from NMR to MRI prior to FDA approval?
to prevent patients from thinking it was radiation
Fat has a shorter T1 recovery time that of water.
true
Spatial pre-saturation can be used inside as well as outside the FOV.
true
Water has a longer T2 decay time than fat.
true
The magnitude of intra-voxel dephasing depends on the degree of:
turbulent flow
Phase contrast MRA uses __________________ to provide image contrast in flowing blood.
velocity differences
VENC stands for the:
velocity encoding gradient