MRI Quiz & Flashcards: Gradient Echo & Inversion Recovery

Questions and Answers

The HEIGHT of a peak on an MR spectrum correlates to the _________ of a substance that was detected.

amount

Contrast in Diffusion Weighted Imaging (DWI) depends on:

The sensitivity of the sequence to Brownian motion (correct)

The degree to which molecular mobility is impaired (water restriction) (correct)

T1 relaxation time

T2 relaxation time

The direction of water diffusion (correct)

What is the final result in a perfusion study?

A set of calculated images which indicate various flow characteristics

What does the final result in a spectroscopy study represent?

A spectrum of specific detected metabolites Signup and view all the answers

What is an example of Diffusion Tensor Imaging?

Diffusion Tensor Imaging (tractography) Signup and view all the answers

If the TR in a gradient echo sequence is less than the T2 (or T2*), the resulting condition is known as: ______________.

Steady state Signup and view all the answers

A gradient echo sequence in which all the remaining residual transverse magnetization is removed prior to the next excitation pulse is known as: ______________.

Incoherent or spoiled Signup and view all the answers

What structures comprise the rotator cuff in the shoulder?

Infraspinatus muscle and tendon Signup and view all the answers

T2 weighted FLAIR sequences are typically used for evaluation of:

White matter disease Signup and view all the answers

If the pulse sequence is a fast spin echo, the number of lines of k-space filled for each TR period would be: ______________.

2 Signup and view all the answers

When a gradient echo sequence is selected for fast, breath-hold dynamic contrast-enhanced imaging of the abdomen, _____________ is utilized.

Spoiling Signup and view all the answers

Which field strength would require the shortest TI time to suppress the signal from fat when performing a STIR sequence in an MRI of the ankle?

0.5T Signup and view all the answers

If the desire is to null the signal from a specific tissue using an inversion recovery sequence, the inversion time (TI) selected should be ______ of the T1 relaxation time of that tissue.

69% Signup and view all the answers

Which parameter adjustments help to improve SNR in an MR image?

Reduce Phase Matrix Signup and view all the answers

Which of the following parameter adjustments reduce the overall SNR in an MR image?

Decrease NEX Signup and view all the answers

Water has a __ T1 relaxation time and a T2 relaxation time.

long; long Signup and view all the answers

Which of the following is NOT affected by changing the slice thickness?

The T2 contrast Signup and view all the answers

Which parameter combination will yield the best spatial resolution?

Thinner slices yield improved spatial resolution (detail), in addition to smaller pixel size (higher phase matrix). Signup and view all the answers

In a fast spin echo sequence, the scan time would be:

3 minutes 7 seconds Signup and view all the answers

Reducing the FOV (field of view) only will result in:

Decreased signal-to-noise Signup and view all the answers

What would the scan time be in a 3D volume acquisition as follows: TR 24 ms, TE 7 ms, Flip Angle 15°, FOV 20cm, 2mm slice thickness, 76 slices, 176 x 256 matrix, 1 NEX?

5 minutes 21 seconds Signup and view all the answers

Choose the correct slice thickness to create an isotropic voxel for the following: TR 2000, TE 90, Matrix 272 x 272, FOV 24cm.

0.88 mm Signup and view all the answers

What is the pixel size of the images which result from a 3D acquisition using a 260 mm FOV, a 320 x 320 matrix, 32 slices and a volume of 64 mm?

0.81 x 0.81 mm Signup and view all the answers

An increase in TE will yield a ______________ in SNR.

decrease Signup and view all the answers

Acquiring a bit more than half the phase k-space samples, then interpolating the data with zeroes for the remaining half is a technique known as:

Half Fourier, or Zero Fill Signup and view all the answers

RF energy used in MRI is classified as:

Low energy, nonionizing radiation Signup and view all the answers

If the flip angle is doubled, RF deposition increases by a factor of: ______________.

4 Signup and view all the answers

Calculate the voxel volume for the following pulse sequence: TR 2000, TE 85, FOV 24cm, Matrix 272 x 320, 3mm slice thickness, 3 NSA.

1.98 mm3 Signup and view all the answers

Calculate the pixel area for the following sequence: TR 4000, TE 120, FOV 36cm, 408 x 512 matrix, 2 NEX, ETL 12.

0.62 mm2 Signup and view all the answers

_______ is when only half the views of k-space are filled in the frequency axis.

Partial or fractional echo Signup and view all the answers

As the number of phase encodings is increased from 256 to 512, SNR (signal to noise ratio): _________________

Decreases Signup and view all the answers

The readout gradient is usually turned on during the sampling or readout of the peak echo and also during which other process?

Frequency encoding Signup and view all the answers

A narrow receiver bandwidth: ______________.

Increases susceptibility artifact Signup and view all the answers

What effect would using a steep slice select slope and/or narrow bandwidth have on slice thickness? ______________.

Slices will be thin Signup and view all the answers

The process that digitizes the MR signals is known as:

Fourier transform Signup and view all the answers

Which of the following parameter adjustments will SHORTEN scan time in an MR pulse sequence?

Increase NSA Signup and view all the answers

Which of the following parameter adjustments will LENGTHEN scan time in an MR pulse sequence?

Increase Phase Matrix Signup and view all the answers

If the third ventricle is dilated, but the fourth ventricle is not, there would then be pathology associated with:

Aqueduct of Sylvius Signup and view all the answers

What kind of weighted images are acquired to evaluate the extent of lesion involvement after injection of gadolinium?

T1 weighted Signup and view all the answers

In what orientation would a tear of the collateral ligaments of the knee be best visualized?

Coronal Signup and view all the answers

On a T2 weighted image, edema appears bright because it has a _________ relaxation time.

long T2 Signup and view all the answers

The common carotid artery bifurcates into the internal and external carotid artery at the level of the:

C3-4 disc space Signup and view all the answers

In order to acquire an intracranial arterial blood flow sequence, a presaturation pulse would be applied in which location?

Superior to slice group Signup and view all the answers

When imaging a geriatric patient, while performing a PCA MRA sequence, what imaging parameter might the operator adjust?

VENC (velocity encodings) Signup and view all the answers

The ligamentum flavum can be found in which part of the body?

Spine Signup and view all the answers

In a cross-sectional view of the MR magnet design, which coils are closest to the patient?

Radiofrequency coils Signup and view all the answers

Active shielding can be defined as:

Superconducting windings within the MR scanner, reducing the fringe magnetic field Signup and view all the answers

The gradient rise time is defined as the:

Time it takes for the gradient to reach its full amplitude Signup and view all the answers

A technique utilized to reduce the MRI scan time which requires the use of an array coil is:

Parallel imaging Signup and view all the answers

Calculate the dose of contrast (0.2 mL/kg) that should be administered to a patient weighing 176 lbs with normal kidney function in a routine MR examination. The dose is: ______________.

16 mL Signup and view all the answers

To produce an image based on differences in T1, the time interval between 90° excitation pulses should be:

Short Signup and view all the answers

Image 1 is an example of what type of MR image?

T2 weighted with fat suppression Signup and view all the answers

Hemangiomas in the liver are typically benign lesions, and are best visualized with:

Delayed images Signup and view all the answers

In an MRA sequence, the removal of signal from vessels is accomplished by:

Spatial presaturation Signup and view all the answers

Image 2 is what kind of MRI image?

T2 weighted with no suppression Signup and view all the answers

Reducing the TE yields images with what change in image contrast?

Decreased T2 information Signup and view all the answers

In a superconducting magnet, the magnetic field strength is increased by increasing the:

Turns of wire Signup and view all the answers

The transmit bandwidth of the RF pulse affects:

Slice thickness, which has an effect on resolution and the overall SNR in the MR image. Signup and view all the answers

In order to generate thin slices, a ___________ is used.

Steep slice selection gradient Signup and view all the answers

The receiver bandwidth (rBW) affects:

Signal-to-noise ratio (SNR) Signup and view all the answers

The B1 magnetic field is produced by a:

Radiofrequency coil Signup and view all the answers

Shimming in MRI can be performed by:

-adding current to the gradient coils (gradient shimming), -adding metal to different coils within the shim coil (passive shimming) -and/or changing the current in the shim coil (active shimming) Signup and view all the answers

The arrows in Image 85 point to what kind of artifact?

Gibbs truncation Signup and view all the answers

The difference in chemical shift is approximately ______ parts-per-million.

3.5 Signup and view all the answers

Which combinations of flip angle (FA) and TR would produce a T2 weighted gradient echo?

450 TR; 30º flip angle Signup and view all the answers

To produce a high quality reformatted image, the:

Acquisition voxel should be isotropic Signup and view all the answers

During dynamic enhanced imaging for vasculature or visceral structures, contrast is administered and k-space is filled with __________ to ensure that the contrast enhancement is well visualized.

Centric Signup and view all the answers

sequences use T1 gradient echoes with TR and FA selections to suppress signal from stationary tissues, visualizing flowing blood by flow-related enhancement, whereas __ sequences use T2 gradient echoes with parameter selections that suppress stationary tissue and rely on velocity-induced phase shifts for vascular signal.

TOF MRA; PC MRA Signup and view all the answers

Which of the following best describes an EPI sequence?

A train of gradient echoes Signup and view all the answers

Which of the following best describes an IR sequence?

A 180° pulse followed by a 90°/180° combination Signup and view all the answers

Which of the following best describes a FSE sequence?

A train of spin echoes Signup and view all the answers

Calculate the available imaging time for a patient with a heart rate of 90 beats/min, trigger window 15% and trigger delay of 80ms.

487 ms Signup and view all the answers

Study Notes

MRI Concepts and Definitions

Amount: Peak height on an MR spectrum indicates the concentration of a detected substance.
Diffusion Weighted Imaging (DWI): Contrast is influenced by molecular mobility impairment, sensitivity to Brownian motion, T1 relaxation time, and water diffusion direction.
Perfusion Study Output: Results in a set of calculated images showing various flow characteristics.
Spectroscopy Study Output: Produces a spectrum depicting specific detected metabolites.
Diffusion Tensor Imaging (Tractography): Example depicted in Image 94.
Steady State: Occurs when TR in a gradient echo sequence is less than T2 or T2*.
Incoherent or Spoiled Sequence: A gradient echo sequence that removes residual transverse magnetization before the next excitation pulse.

Shoulder Anatomy

Rotator Cuff Structures: Includes subscapularis, infraspinatus, teres minor, and supraspinatus muscles and tendons.

Imaging Techniques

T2 Weighted FLAIR Sequences: Primarily used to assess white matter diseases.
Fast Spin Echo Sequence: Uses multiple echoes to fill k-space, reducing scan time by the number of echoes (e.g., by 2).
Spoiling: Technique used for fast, breath-hold dynamic contrast-enhanced imaging of the abdomen.
Incoherent Gradient Echo: Utilized for dynamic MRA sequences of mesenteric arteries.
STIR Sequence: Requires a shorter TI time at a 0.5T field strength to suppress fat signal.

MRI Parameters Impact

Inversion Time (TI): Should be approximately 69% of the T1 relaxation time to null a specific tissue signal in inversion recovery sequences.
Fast Spin Echo Parameter Adjustments: SNR can be improved by increasing TR, reducing phase matrix, increasing FOV, or reducing receiver bandwidth.

Safety and Personnel Training

Level 2 Personnel: Individuals with extensive MRI safety training regarding magnetic, gradient, and RF fields.
Level 1 Personnel: Individuals with limited MRI safety training.

Isolation and Contrast Use

Isolation Precautions for HIV: Standard (universal) precautions are recommended in MRI suites.
Contrast Administration: Dose calculated at 0.2 mL/kg requires adjustment based on patient weight (176 lbs translates to 16 mL).

Image Quality Factors

SNR Considerations: Increased TE leads to decreased SNR; thicker slices generally yield poorer spatial resolution, while thinner slices improve detail.
Receiver Bandwidth (rBW): Impacts signal-to-noise ratio (SNR) and chemical shift artifacts.

Gradient, Frequency, and Voxel Calculations

Gradient Rise Time: Defines the time to reach full amplitude.
Voxel Volume Calculation: Involves pixel area derived from FOV and matrix dimensions and multiplies by slice thickness.
Slice Thickness & Isotropic Voxels: Achieved by dividing the FOV by the matrix to maintain equal dimensions in three directions.

Artifact Identification

Gibbs Truncation: A specific artifact identified in MRI images.

Clinical Applications

Hemangiomas in Liver: Best visualized with delayed images.
Flow Sequences: TOF MRA emphasizes flow-related enhancement using T1 gradient echoes, while PC MRA relies on velocity-induced phase shifts.

MRI Sequences

EPI Sequence: Described as a train of gradient echoes.
IR Sequence: Consists of a 180° pulse followed by a combination of 90° and 180° pulses.
FSE Sequence: Defined as a train of spin echoes.

Vascular Imaging

Spatial Presaturation: Used in MRA sequences to remove vessel signals effectively.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge with these flashcards designed for MRI mock registry preparation. Each card contains key terms and definitions essential for understanding MR imaging concepts, including diffusion-weighted imaging and spectral analysis.

MRI Quiz: Mock Registry Flashcards