MRI Physics - Chapter 8 Questions and
Answers with Certified Solutions
What is the function of the Nyquist filter in MRI?
✔✔ To prevent aliasing artifacts
How does zero-filling interpolation affect MRI images?
✔✔ It improves perceived resolution by adding interpolated data
What is the benefit of using black blood imaging in MRI?
✔✔ It improves visualization of vascular walls by suppressing blood flow signal
Why is a long TR used in proton density-weighted imaging?
✔✔ To minimize T1 effects and highlight proton density differences
How does diffusion-weighted imaging (DWI) work?
✔✔ It detects the movement of water molecules within tissues
1
,Why is cardiac gating used in MRI?
✔✔ To synchronize imaging with the heartbeat and reduce motion artifacts
What is the purpose of using an MIP (Maximum Intensity Projection) in MRI?
✔✔ To enhance visualization of vascular structures in MR angiography
Why is gradient echo imaging preferred for susceptibility-weighted imaging (SWI)?
✔✔ Because it is highly sensitive to magnetic field inhomogeneities
How does BOLD (Blood Oxygen Level Dependent) imaging work in fMRI?
✔✔ It detects changes in blood oxygenation related to neural activity
What is the effect of increasing slice gap in MRI?
✔✔ It reduces crosstalk between slices
Why is a dual-echo sequence used in MRI?
✔✔ To acquire both T1- and T2-weighted images in a single scan
2
,What is the main advantage of using balanced steady-state free precession (bSSFP) sequences?
✔✔ High contrast between blood and tissues with fast acquisition times
What is the primary function of gradient coils in an MRI scanner?
✔✔ To spatially encode the MRI signals
How does increasing the magnetic field strength affect image resolution?
✔✔ It improves signal-to-noise ratio, leading to higher resolution
What is the purpose of the repetition time (TR) in an MRI sequence?
✔✔ It determines the time between successive RF pulses
Why is T2-weighted imaging useful in MRI?
✔✔ It enhances contrast between different soft tissues
What happens when the echo time (TE) is increased in an MRI sequence?
✔✔ It emphasizes T2 contrast and increases signal decay
3
, Why is shimming performed in MRI?
✔✔ To improve magnetic field homogeneity
How does voxel size affect MRI image quality?
✔✔ Smaller voxels improve spatial resolution but may reduce signal-to-noise ratio
What is the main cause of chemical shift artifact in MRI?
✔✔ Differences in resonance frequencies between fat and water
Why is parallel imaging used in MRI?
✔✔ To reduce scan time while maintaining image quality
What is the function of the k-space in MRI?
✔✔ It stores raw data before image reconstruction
What effect does increasing the number of signal averages (NEX) have on an MRI scan?
✔✔ It reduces noise and improves image clarity
4
Answers with Certified Solutions
What is the function of the Nyquist filter in MRI?
✔✔ To prevent aliasing artifacts
How does zero-filling interpolation affect MRI images?
✔✔ It improves perceived resolution by adding interpolated data
What is the benefit of using black blood imaging in MRI?
✔✔ It improves visualization of vascular walls by suppressing blood flow signal
Why is a long TR used in proton density-weighted imaging?
✔✔ To minimize T1 effects and highlight proton density differences
How does diffusion-weighted imaging (DWI) work?
✔✔ It detects the movement of water molecules within tissues
1
,Why is cardiac gating used in MRI?
✔✔ To synchronize imaging with the heartbeat and reduce motion artifacts
What is the purpose of using an MIP (Maximum Intensity Projection) in MRI?
✔✔ To enhance visualization of vascular structures in MR angiography
Why is gradient echo imaging preferred for susceptibility-weighted imaging (SWI)?
✔✔ Because it is highly sensitive to magnetic field inhomogeneities
How does BOLD (Blood Oxygen Level Dependent) imaging work in fMRI?
✔✔ It detects changes in blood oxygenation related to neural activity
What is the effect of increasing slice gap in MRI?
✔✔ It reduces crosstalk between slices
Why is a dual-echo sequence used in MRI?
✔✔ To acquire both T1- and T2-weighted images in a single scan
2
,What is the main advantage of using balanced steady-state free precession (bSSFP) sequences?
✔✔ High contrast between blood and tissues with fast acquisition times
What is the primary function of gradient coils in an MRI scanner?
✔✔ To spatially encode the MRI signals
How does increasing the magnetic field strength affect image resolution?
✔✔ It improves signal-to-noise ratio, leading to higher resolution
What is the purpose of the repetition time (TR) in an MRI sequence?
✔✔ It determines the time between successive RF pulses
Why is T2-weighted imaging useful in MRI?
✔✔ It enhances contrast between different soft tissues
What happens when the echo time (TE) is increased in an MRI sequence?
✔✔ It emphasizes T2 contrast and increases signal decay
3
, Why is shimming performed in MRI?
✔✔ To improve magnetic field homogeneity
How does voxel size affect MRI image quality?
✔✔ Smaller voxels improve spatial resolution but may reduce signal-to-noise ratio
What is the main cause of chemical shift artifact in MRI?
✔✔ Differences in resonance frequencies between fat and water
Why is parallel imaging used in MRI?
✔✔ To reduce scan time while maintaining image quality
What is the function of the k-space in MRI?
✔✔ It stores raw data before image reconstruction
What effect does increasing the number of signal averages (NEX) have on an MRI scan?
✔✔ It reduces noise and improves image clarity
4
