final quizzes

अब Quizwiz के साथ अपने होमवर्क और परीक्षाओं को एस करें!

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


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