MRI in Practice Chapter 5 Spatial
Encoding Questions and Answers
Already Passed
What is the primary purpose of spatial encoding in MRI?
✔✔ To determine the location of signals within the body
How do gradient coils contribute to spatial encoding?
✔✔ They create variations in magnetic field strength to encode spatial information
What are the three main types of spatial encoding gradients?
✔✔ Frequency encoding, phase encoding, and slice selection
Why is slice selection important in MRI?
✔✔ It allows imaging of a specific plane within the body
What determines the thickness of an MRI slice?
✔✔ The bandwidth of the RF pulse and the strength of the slice-select gradient
1
,How does increasing the gradient strength affect slice thickness?
✔✔ It produces thinner slices for higher spatial resolution
What is the role of phase encoding in MRI?
✔✔ It differentiates signals along one spatial axis
Why is phase encoding performed before frequency encoding?
✔✔ To systematically assign spatial information before signal readout
What happens when more phase encoding steps are used?
✔✔ Image resolution improves, but scan time increases
Why does frequency encoding occur during signal readout?
✔✔ To separate signals based on their frequency differences
What determines the direction of the frequency-encoding gradient?
✔✔ The orientation of the applied gradient field
2
, How does k-space relate to spatial encoding?
✔✔ It stores raw data before image reconstruction
Why is the center of k-space important for image quality?
✔✔ It contains the majority of image contrast and signal intensity
What effect does increasing the field of view (FOV) have on spatial encoding?
✔✔ It captures a larger area but reduces resolution
How does aliasing occur in spatial encoding?
✔✔ When signals outside the FOV are misrepresented due to undersampling
What is the Nyquist limit in MRI?
✔✔ The minimum sampling rate required to avoid aliasing artifacts
Why are gradient lobes used in phase encoding?
✔✔ To create controlled variations in spatial phase shifts
3
Encoding Questions and Answers
Already Passed
What is the primary purpose of spatial encoding in MRI?
✔✔ To determine the location of signals within the body
How do gradient coils contribute to spatial encoding?
✔✔ They create variations in magnetic field strength to encode spatial information
What are the three main types of spatial encoding gradients?
✔✔ Frequency encoding, phase encoding, and slice selection
Why is slice selection important in MRI?
✔✔ It allows imaging of a specific plane within the body
What determines the thickness of an MRI slice?
✔✔ The bandwidth of the RF pulse and the strength of the slice-select gradient
1
,How does increasing the gradient strength affect slice thickness?
✔✔ It produces thinner slices for higher spatial resolution
What is the role of phase encoding in MRI?
✔✔ It differentiates signals along one spatial axis
Why is phase encoding performed before frequency encoding?
✔✔ To systematically assign spatial information before signal readout
What happens when more phase encoding steps are used?
✔✔ Image resolution improves, but scan time increases
Why does frequency encoding occur during signal readout?
✔✔ To separate signals based on their frequency differences
What determines the direction of the frequency-encoding gradient?
✔✔ The orientation of the applied gradient field
2
, How does k-space relate to spatial encoding?
✔✔ It stores raw data before image reconstruction
Why is the center of k-space important for image quality?
✔✔ It contains the majority of image contrast and signal intensity
What effect does increasing the field of view (FOV) have on spatial encoding?
✔✔ It captures a larger area but reduces resolution
How does aliasing occur in spatial encoding?
✔✔ When signals outside the FOV are misrepresented due to undersampling
What is the Nyquist limit in MRI?
✔✔ The minimum sampling rate required to avoid aliasing artifacts
Why are gradient lobes used in phase encoding?
✔✔ To create controlled variations in spatial phase shifts
3
