MRI Image Quality and Optimization Flashcards
7 cards from real MRI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 MRI Image Quality and Optimization flashcards as text
What is the primary consequence of using a high acceleration factor in parallel imaging?
Answer: Reduced SNR due to the g-factor penalty
High acceleration factors in parallel imaging introduce a geometry (g-factor) penalty that reduces SNR, especially in the center of the image where coil sensitivity overlap is less distinct.
Which phase-encoding direction choice can help reduce motion artifact from breathing in abdominal MRI?
Answer: Orient phase encoding in the right-left direction so respiratory motion projects away from the anatomy of interest
Placing phase encoding in the right-left direction directs respiratory ghosting away from critical abdominal structures, reducing diagnostic interference.
How does increasing the echo train length (ETL) in a fast spin echo (FSE) sequence affect image quality?
Answer: Scan time decreases but T2 blurring may increase
Longer ETL fills k-space faster (reducing scan time) but each echo has progressively more T2 decay, causing blurring particularly of edges and fine detail.
What is contrast-to-noise ratio (CNR) in MRI and why is it important?
Answer: The difference in SNR between two adjacent tissues; it determines the ability to distinguish lesions from normal tissue
CNR is the SNR difference between adjacent tissues; high CNR is essential for detecting lesions because it reflects how well two tissues can be discriminated from each other.
A technologist wants to reduce chemical shift artifact at the fat-water interface. Which parameter change is most appropriate?
Answer: Increase the receiver bandwidth
Increasing receiver bandwidth reduces the frequency difference between fat and water in pixel units, shrinking the spatial shift of fat signal relative to water signal.
Which of the following best explains why a phased-array coil improves SNR compared to a body coil?
Answer: Multiple smaller coil elements are positioned close to the anatomy, maximizing signal pickup while limiting noise volume
Each element of a phased-array coil is small and close to the anatomy, providing high sensitivity to local signal with limited noise, and their combined data significantly improves overall SNR.
What is the effect of reducing the number of phase-encoding steps while keeping FOV and frequency steps constant?
Answer: Scan time decreases and phase-direction spatial resolution decreases
Fewer phase-encoding steps means less time to fill k-space (shorter scan) but larger voxels in the phase direction, reducing spatial resolution in that dimension.