Podcast
Questions and Answers
The HEIGHT of a peak on an MR spectrum correlates to the _________ of a substance that was detected.
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:
Contrast in Diffusion Weighted Imaging (DWI) depends on:
What is the final result in a perfusion study?
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?
What does the final result in a spectroscopy study represent?
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What is an example of Diffusion Tensor Imaging?
What is an example of Diffusion Tensor Imaging?
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If the TR in a gradient echo sequence is less than the T2 (or T2*), the resulting condition is known as: ______________.
If the TR in a gradient echo sequence is less than the T2 (or T2*), the resulting condition is known as: ______________.
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A gradient echo sequence in which all the remaining residual transverse magnetization is removed prior to the next excitation pulse is known as: ______________.
A gradient echo sequence in which all the remaining residual transverse magnetization is removed prior to the next excitation pulse is known as: ______________.
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What structures comprise the rotator cuff in the shoulder?
What structures comprise the rotator cuff in the shoulder?
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T2 weighted FLAIR sequences are typically used for evaluation of:
T2 weighted FLAIR sequences are typically used for evaluation of:
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If the pulse sequence is a fast spin echo, the number of lines of k-space filled for each TR period would be: ______________.
If the pulse sequence is a fast spin echo, the number of lines of k-space filled for each TR period would be: ______________.
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When a gradient echo sequence is selected for fast, breath-hold dynamic contrast-enhanced imaging of the abdomen, _____________ is utilized.
When a gradient echo sequence is selected for fast, breath-hold dynamic contrast-enhanced imaging of the abdomen, _____________ is utilized.
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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?
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?
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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.
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.
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Which parameter adjustments help to improve SNR in an MR image?
Which parameter adjustments help to improve SNR in an MR image?
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Which of the following parameter adjustments reduce the overall SNR in an MR image?
Which of the following parameter adjustments reduce the overall SNR in an MR image?
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Water has a __________ T1 relaxation time and a ________ T2 relaxation time.
Water has a __________ T1 relaxation time and a ________ T2 relaxation time.
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Which of the following is NOT affected by changing the slice thickness?
Which of the following is NOT affected by changing the slice thickness?
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Which parameter combination will yield the best spatial resolution?
Which parameter combination will yield the best spatial resolution?
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In a fast spin echo sequence, the scan time would be:
In a fast spin echo sequence, the scan time would be:
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Reducing the FOV (field of view) only will result in:
Reducing the FOV (field of view) only will result in:
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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?
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?
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Choose the correct slice thickness to create an isotropic voxel for the following: TR 2000, TE 90, Matrix 272 x 272, FOV 24cm.
Choose the correct slice thickness to create an isotropic voxel for the following: TR 2000, TE 90, Matrix 272 x 272, FOV 24cm.
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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?
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?
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An increase in TE will yield a ______________ in SNR.
An increase in TE will yield a ______________ in SNR.
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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:
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:
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RF energy used in MRI is classified as:
RF energy used in MRI is classified as:
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If the flip angle is doubled, RF deposition increases by a factor of: ______________.
If the flip angle is doubled, RF deposition increases by a factor of: ______________.
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Calculate the voxel volume for the following pulse sequence: TR 2000, TE 85, FOV 24cm, Matrix 272 x 320, 3mm slice thickness, 3 NSA.
Calculate the voxel volume for the following pulse sequence: TR 2000, TE 85, FOV 24cm, Matrix 272 x 320, 3mm slice thickness, 3 NSA.
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Calculate the pixel area for the following sequence: TR 4000, TE 120, FOV 36cm, 408 x 512 matrix, 2 NEX, ETL 12.
Calculate the pixel area for the following sequence: TR 4000, TE 120, FOV 36cm, 408 x 512 matrix, 2 NEX, ETL 12.
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_______ is when only half the views of k-space are filled in the frequency axis.
_______ is when only half the views of k-space are filled in the frequency axis.
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As the number of phase encodings is increased from 256 to 512, SNR (signal to noise ratio): _________________
As the number of phase encodings is increased from 256 to 512, SNR (signal to noise ratio): _________________
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The readout gradient is usually turned on during the sampling or readout of the peak echo and also during which other process?
The readout gradient is usually turned on during the sampling or readout of the peak echo and also during which other process?
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A narrow receiver bandwidth: ______________.
A narrow receiver bandwidth: ______________.
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What effect would using a steep slice select slope and/or narrow bandwidth have on slice thickness? ______________.
What effect would using a steep slice select slope and/or narrow bandwidth have on slice thickness? ______________.
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The process that digitizes the MR signals is known as:
The process that digitizes the MR signals is known as:
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Which of the following parameter adjustments will SHORTEN scan time in an MR pulse sequence?
Which of the following parameter adjustments will SHORTEN scan time in an MR pulse sequence?
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Which of the following parameter adjustments will LENGTHEN scan time in an MR pulse sequence?
Which of the following parameter adjustments will LENGTHEN scan time in an MR pulse sequence?
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If the third ventricle is dilated, but the fourth ventricle is not, there would then be pathology associated with:
If the third ventricle is dilated, but the fourth ventricle is not, there would then be pathology associated with:
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What kind of weighted images are acquired to evaluate the extent of lesion involvement after injection of gadolinium?
What kind of weighted images are acquired to evaluate the extent of lesion involvement after injection of gadolinium?
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In what orientation would a tear of the collateral ligaments of the knee be best visualized?
In what orientation would a tear of the collateral ligaments of the knee be best visualized?
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On a T2 weighted image, edema appears bright because it has a _________ relaxation time.
On a T2 weighted image, edema appears bright because it has a _________ relaxation time.
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The common carotid artery bifurcates into the internal and external carotid artery at the level of the:
The common carotid artery bifurcates into the internal and external carotid artery at the level of the:
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In order to acquire an intracranial arterial blood flow sequence, a presaturation pulse would be applied in which location?
In order to acquire an intracranial arterial blood flow sequence, a presaturation pulse would be applied in which location?
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When imaging a geriatric patient, while performing a PCA MRA sequence, what imaging parameter might the operator adjust?
When imaging a geriatric patient, while performing a PCA MRA sequence, what imaging parameter might the operator adjust?
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The ligamentum flavum can be found in which part of the body?
The ligamentum flavum can be found in which part of the body?
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In a cross-sectional view of the MR magnet design, which coils are closest to the patient?
In a cross-sectional view of the MR magnet design, which coils are closest to the patient?
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Active shielding can be defined as:
Active shielding can be defined as:
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The gradient rise time is defined as the:
The gradient rise time is defined as the:
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A technique utilized to reduce the MRI scan time which requires the use of an array coil is:
A technique utilized to reduce the MRI scan time which requires the use of an array coil is:
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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: ______________.
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: ______________.
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To produce an image based on differences in T1, the time interval between 90° excitation pulses should be:
To produce an image based on differences in T1, the time interval between 90° excitation pulses should be:
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Image 1 is an example of what type of MR image?
Image 1 is an example of what type of MR image?
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Hemangiomas in the liver are typically benign lesions, and are best visualized with:
Hemangiomas in the liver are typically benign lesions, and are best visualized with:
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In an MRA sequence, the removal of signal from vessels is accomplished by:
In an MRA sequence, the removal of signal from vessels is accomplished by:
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Image 2 is what kind of MRI image?
Image 2 is what kind of MRI image?
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Reducing the TE yields images with what change in image contrast?
Reducing the TE yields images with what change in image contrast?
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In a superconducting magnet, the magnetic field strength is increased by increasing the:
In a superconducting magnet, the magnetic field strength is increased by increasing the:
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The transmit bandwidth of the RF pulse affects:
The transmit bandwidth of the RF pulse affects:
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In order to generate thin slices, a ___________ is used.
In order to generate thin slices, a ___________ is used.
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The receiver bandwidth (rBW) affects:
The receiver bandwidth (rBW) affects:
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The B1 magnetic field is produced by a:
The B1 magnetic field is produced by a:
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Shimming in MRI can be performed by:
Shimming in MRI can be performed by:
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The arrows in Image 85 point to what kind of artifact?
The arrows in Image 85 point to what kind of artifact?
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The difference in chemical shift is approximately ______ parts-per-million.
The difference in chemical shift is approximately ______ parts-per-million.
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Which combinations of flip angle (FA) and TR would produce a T2 weighted gradient echo?
Which combinations of flip angle (FA) and TR would produce a T2 weighted gradient echo?
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To produce a high quality reformatted image, the:
To produce a high quality reformatted image, the:
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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.
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.
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________ 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.
________ 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.
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Which of the following best describes an EPI sequence?
Which of the following best describes an EPI sequence?
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Which of the following best describes an IR sequence?
Which of the following best describes an IR sequence?
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Which of the following best describes a FSE sequence?
Which of the following best describes a FSE sequence?
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Calculate the available imaging time for a patient with a heart rate of 90 beats/min, trigger window 15% and trigger delay of 80ms.
Calculate the available imaging time for a patient with a heart rate of 90 beats/min, trigger window 15% and trigger delay of 80ms.
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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.
