30 Questions
Which artifact produces replications of moving anatomy across the image in the phase encoding axis?
Phase mismapping
What is the main cause of phase mismapping in MRI?
Anatomy moving along the phase-encoding gradient
Which of the following can cause phase mismapping in MRI?
All of the above
What happens to ghosting with distance from the source of motion?
Ghosting becomes less obvious
What does the physical separation between each ghost depend on?
The scan time parameters and period of motion
What is the purpose of the phase-encoding gradient in MRI?
To produce phase mismapping
What results in periodic perturbations of the data collected in k-space?
Motion of anatomy during the scan
Which axis does ghosting artifact typically occur along in the image?
Phase encoding axis
What factors affect the separation between ghosts in an image?
TR, phase matrix, NSA, and the period of motion
What does swapping phase and frequency encoding directions accomplish?
Changes the direction of ghosting artifact
What is the purpose of presaturation pulses in MRI?
To null signal from specified areas
What technique can be used to reduce or eliminate respiratory motion artifact in chest and abdominal imaging?
Using a navigator echo
What is the purpose of respiratory bellows in MRI?
To reduce motion artifact from respiration
What does a transducer do in the context of respiratory bellows?
Converts the change in pressure within the bellows to an electrical signal
Which technique utilizes signal collected by the transducer or navigator echoes to trigger an action?
Respiratory triggering
What is the main drawback of respiratory triggering?
The periodicity of the patient's respiratory cycle becomes the TR and determines the image contrast.
What is the main trade-off of using respiratory gating?
Increased scan time due to filling every line of data.
What is the purpose of increasing the NSA (number of signal averages)?
To reduce motion artifact.
What is the trade-off of increasing the NSA?
Increased scan time.
What is the purpose of immobilizing the patient with pads and straps during an MRI scan?
To reduce voluntary motion.
What is the purpose of administering antispasmodic agents during an MRI scan?
To reduce involuntary motion.
Which of the following is the purpose of peripheral pulse triggering in medical imaging?
To acquire each slice at the same phase of the cardiac cycle
What is the main limitation of peripheral pulse triggering compared to EKG triggering in medical imaging?
It is not accurate in detecting the pulsation of blood through the capillaries
What does peripheral pulse triggering use to detect the pulsation of blood through the capillaries?
A light sensor attached to the patient's finger
When is peripheral pulse triggering most effective in reducing phase mismapping?
When imaging small vessels or the spinal cord
What is the purpose of gradient moment rephasing in medical imaging?
To reduce ghosting caused by flowing nuclei moving along gradients
Which of the following is NOT a limitation of peripheral pulse triggering in medical imaging?
Not effective at acquiring each slice at the same phase of the cardiac cycle
What is the main advantage of EKG triggering compared to peripheral pulse triggering in medical imaging?
It is more effective at reducing phase mismapping
What is used to trigger RF excitation pulses in peripheral pulse triggering?
A light sensor attached to the patient's finger
When is peripheral pulse triggering not very useful in medical imaging?
When imaging the heart itself
This quiz tests your knowledge of RF pulses and their role in tracking diaphragm position during respiration. Explore concepts such as amplitude signals, spin excitation, and k-space reordering.
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