Parameters 2 Flashcards
Increasing TR will:
a) Decrease scan time
b) Increase T1 weighting
c) Increase scan time
d) Decrease SNR
c) Increase scan time
A short TE primarily enhances:
a) T2 weighting
b) Proton density weighting
c) SNR
d) Motion artifacts
b) Proton density weighting
What happens if TE is increased?
a) T1 contrast increases
b) Scan time decreases
c) SNR decreases
d) Image resolution improves
c) SNR decreases
Longer TE means waiting longer for the signal, which leads to more decay and lower signal-to-noise ratio (SNR)
Which TR and TE combination is best for T1-weighted imaging?
a) Long TR, long TE
b) Short TR, long TE
c) Long TR, short TE
d) Short TR, short TE
d) Short TR, short TE
What does a long TR help reduce?
a) T1 contrast
b) T2 contrast
c) Spatial resolution
d) Motion artifacts
a) T1 contrast
What happens if phase matrix is increased?
a) SNR increases
b) Scan time decreases
c) Spatial resolution increases
d) Motion artifacts increase
c) Spatial resolution increases
Increasing FOV will:
a) Increase spatial resolution
b) Increase SNR
c) Increase scan time
d) Decrease pixel size
b) Increase SNR
Decreasing pixel size will:
a) Improve spatial resolution
b) Decrease scan time
c) Increase SNR
d) Reduce T2 contrast
a) Improve spatial resolution
Smaller pixels mean finer image details, improving resolution
Increasing FOV but keeping matrix constant will:
a) Decrease spatial resolution
b) Increase scan time
c) Increase contrast
d) Reduce blurring
a) Decrease spatial resolution
Increasing phase matrix affects scan time by:
a) Increasing it
b) Decreasing it
c) Keeping it unchanged
d) Reducing blurring
a) Increasing it
Increasing NSA/NEX will:
a) Reduce motion artifacts
b) Decrease SNR
c) Decrease scan time
d) Improve spatial resolution
a) Reduce motion artifacts
What is a disadvantage of increasing NSA/NEX?
a) Increased blurring
b) Increased scan time
c) Increased chemical shift
d) Reduced SNR
b) Increased scan time
More averages (NSA/NEX) reduce noise but take longer to scan
Reducing NSA/NEX will primarily affect:
a) Spatial resolution
b) Motion artifacts
c) T1 contrast
d) Scan time
b) Motion artifacts
Fewer averages mean less correction for motion, so motion artifacts increase
Why does increasing NSA/NEX help reduce noise?
a) It improves spatial resolution
b) It averages out random noise
c) It shortens TE
d) It increases pixel size
a) It improves spatial resolution
How does reducing NSA/NEX affect motion artifacts?
a) Increases them
b) Decreases them
c) No effect
d) Improves resolution
a) Increases them
Decreasing receive bandwidth has what effect?
a) Reduces noise
b) Increases SNR
c) Reduces chemical shift artifacts
d) Decreases scan time
b) Increases SNR
A lower bandwidth allows more signal collection time, increasing SNR but also increasing chemical shift artifacts
What does increasing receive bandwidth (rBW) do?
a) Increases SNR
b) Reduces chemical shift artifacts
c) Increases scan time
d) Increases motion artifacts
b) Reduces chemical shift artifacts
Higher bandwidth captures signals faster, reducing the misalignment that causes chemical shift artifacts
A lower rBW leads to:
a) Higher SNR
b) Shorter scan time
c) Less chemical shift
d) Lower resolution
a) Higher SNR
Less bandwidth means less noise, leading to a better SNR
Which artifact is most affected by rBW?
a) Motion artifact
b) Chemical shift
c) Truncation artifact
d) Gibbs ringing
b) Chemical shift
If metal artifacts are a concern, how should rBW be adjusted?
a) Increased
b) Decreased
c) Unchanged
d) Reduced NSA/NEX
a) Increased
Higher bandwidth helps reduce distortion from metal because it captures signals faster
Increasing ETL will:
a) Increase scan time
b) Reduce scan time
c) Improve SNR
d) Reduce blurring
b) Reduce scan time
What is a drawback of a long ETL?
a) Increased blurring
b) Higher SNR
c) Reduced scan time
d) Reduced motion artifacts
a) Increased blurring
More echoes in one sequence mean less time for accurate signal recovery, leading to blurring
What does a short ETL do?
a) Increases scan time
b) Reduces blurring
c) Decreases SNR
d) Increases T2 contrast
a) Increases scan time
Fewer echoes per repetition mean more repetitions are needed, increasing scan time
A long ETL is beneficial for:
a) Reducing motion artifacts
b) Enhancing T1 contrast
c) Increasing T2 contrast
d) Decreasing chemical shift
c) Increasing T2 contrast
More echoes allow better visualization of T2-weighted structures
Increasing ETL too much can result in:
a) Increased resolution
b) Image blurring
c) Shorter scan time
d) Higher SNR
b) Image blurring
Which factor increases Specific Absorption Rate (SAR)?
a) Increasing FOV
b) Increasing flip angle
c) Increasing TR
d) Decreasing ETL
b) Increasing flip angle
A larger flip angle uses more energy, increasing SAR (which is heat absorbed by the body)
Reducing SAR exposure can be done by:
a) Increasing TR
b) Increasing flip angle
c) Decreasing FOV
d) Increasing NSA/NEX
a) Increasing TR
Longer TR means more time between pulses, allowing the body to cool down
Higher SAR is a concern with:
a) Low field MRI
b) High flip angles
c) Low TR values
d) Long TE values
b) High flip angles
If a patient is overheating during an MRI, which adjustment can help reduce SAR?
a) Increase TR
b) Increase flip angle
c) Decrease FOV
d) Increase ETL
a) Increase TR
Giving more time between pulses helps reduce heat buildup in the patient
What parameter has the least impact on SAR?
a) TR
b) TE
c) Flip angle
d) NSA/NEX
d) NSA/NEX
Averaging scans (NSA/NEX) mainly affects noise and motion but has little effect on heating (SAR)
