Podcast
Questions and Answers
Which artifact produces replications of moving anatomy across the image in the phase encoding axis?
Which artifact produces replications of moving anatomy across the image in the phase encoding axis?
- Phase mismapping (correct)
- Frequency encoding
- Ghosting
- Slice-select gradient
What is the main cause of phase mismapping in MRI?
What is the main cause of phase mismapping in MRI?
- Anatomy moving during the pulse sequence
- Anatomy moving along the slice-select gradient
- Anatomy moving along the phase-encoding gradient (correct)
- Anatomy moving along the frequency encoding gradient
Which of the following can cause phase mismapping in MRI?
Which of the following can cause phase mismapping in MRI?
- Respiration
- Pulsation of vessels and CSF
- Swallowing
- All of the above (correct)
What happens to ghosting with distance from the source of motion?
What happens to ghosting with distance from the source of motion?
What does the physical separation between each ghost depend on?
What does the physical separation between each ghost depend on?
What is the purpose of the phase-encoding gradient in MRI?
What is the purpose of the phase-encoding gradient in MRI?
What results in periodic perturbations of the data collected in k-space?
What results in periodic perturbations of the data collected in k-space?
Which axis does ghosting artifact typically occur along in the image?
Which axis does ghosting artifact typically occur along in the image?
What factors affect the separation between ghosts in an image?
What factors affect the separation between ghosts in an image?
What does swapping phase and frequency encoding directions accomplish?
What does swapping phase and frequency encoding directions accomplish?
What is the purpose of presaturation pulses in MRI?
What is the purpose of presaturation pulses in MRI?
What technique can be used to reduce or eliminate respiratory motion artifact in chest and abdominal imaging?
What technique can be used to reduce or eliminate respiratory motion artifact in chest and abdominal imaging?
What is the purpose of respiratory bellows in MRI?
What is the purpose of respiratory bellows in MRI?
What does a transducer do in the context of respiratory bellows?
What does a transducer do in the context of respiratory bellows?
Which technique utilizes signal collected by the transducer or navigator echoes to trigger an action?
Which technique utilizes signal collected by the transducer or navigator echoes to trigger an action?
What is the main drawback of respiratory triggering?
What is the main drawback of respiratory triggering?
What is the main trade-off of using respiratory gating?
What is the main trade-off of using respiratory gating?
What is the purpose of increasing the NSA (number of signal averages)?
What is the purpose of increasing the NSA (number of signal averages)?
What is the trade-off of increasing the NSA?
What is the trade-off of increasing the NSA?
What is the purpose of immobilizing the patient with pads and straps during an MRI scan?
What is the purpose of immobilizing the patient with pads and straps during an MRI scan?
What is the purpose of administering antispasmodic agents during an MRI scan?
What is the purpose of administering antispasmodic agents during an MRI scan?
Which of the following is the purpose of peripheral pulse triggering in medical imaging?
Which of the following is the purpose of peripheral pulse triggering in medical imaging?
What is the main limitation of peripheral pulse triggering compared to EKG triggering in medical imaging?
What is the main limitation of peripheral pulse triggering compared to EKG triggering in medical imaging?
What does peripheral pulse triggering use to detect the pulsation of blood through the capillaries?
What does peripheral pulse triggering use to detect the pulsation of blood through the capillaries?
When is peripheral pulse triggering most effective in reducing phase mismapping?
When is peripheral pulse triggering most effective in reducing phase mismapping?
What is the purpose of gradient moment rephasing in medical imaging?
What is the purpose of gradient moment rephasing in medical imaging?
Which of the following is NOT a limitation of peripheral pulse triggering in medical imaging?
Which of the following is NOT a limitation of peripheral pulse triggering in medical imaging?
What is the main advantage of EKG triggering compared to peripheral pulse triggering in medical imaging?
What is the main advantage of EKG triggering compared to peripheral pulse triggering in medical imaging?
What is used to trigger RF excitation pulses in peripheral pulse triggering?
What is used to trigger RF excitation pulses in peripheral pulse triggering?
When is peripheral pulse triggering not very useful in medical imaging?
When is peripheral pulse triggering not very useful in medical imaging?
Flashcards
Phase mismapping
Phase mismapping
Artifact that produces replications of moving anatomy across the image in the phase encoding axis.
Main cause of phase mismapping
Main cause of phase mismapping
Anatomy moving along the phase-encoding gradient during the scan.
Ghosting and Distance
Ghosting and Distance
Ghosting becomes less obvious with increased distance from the source of motion.
Ghost Separation Factors
Ghost Separation Factors
Scan time parameters and period of motion.
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Periodic Perturbations in K-space
Periodic Perturbations in K-space
Motion of anatomy during the scan.
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Ghosting Axis
Ghosting Axis
Along the phase encoding axis.
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Factors Affecting Ghost Separation
Factors Affecting Ghost Separation
TR, phase matrix, NSA, and the period of motion.
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Phase and Frequency Swap
Phase and Frequency Swap
Changes the direction of ghosting artifact.
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Presaturation Pulses
Presaturation Pulses
To null signal from specified areas, reducing artifacts.
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Reduce Respiratory Motion Artifact
Reduce Respiratory Motion Artifact
Using a navigator echo to track and correct for motion.
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Purpose of Respiratory Bellows
Purpose of Respiratory Bellows
To reduce motion artifact from respiration by monitoring patient breathing.
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Transducer Function
Transducer Function
Converts the change in pressure within the bellows to an electrical signal.
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Respiratory Triggering
Respiratory Triggering
Respiratory triggering to synchronize data acquisition with the respiratory cycle.
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Drawback of Respiratory Triggering
Drawback of Respiratory Triggering
The periodicity of the patient's respiratory cycle becomes the TR and determines the image contrast.
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Trade-off of Respiratory Gating
Trade-off of Respiratory Gating
Increased scan time due to not filling every line of data.
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Purpose of Increasing NSA
Purpose of Increasing NSA
To reduce motion artifact by averaging multiple signals.
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Trade-off of Increasing NSA
Trade-off of Increasing NSA
Increased scan time.
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Immobilization Purpose
Immobilization Purpose
To reduce voluntary motion.
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Antispasmodic Agents
Antispasmodic Agents
To reduce involuntary motion.
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Peripheral Pulse Triggering
Peripheral Pulse Triggering
To acquire each slice at the same phase of the cardiac cycle.
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Limitation of Peripheral Pulse Triggering
Limitation of Peripheral Pulse Triggering
Less accurate in detecting the pulsation of blood through the capillaries
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Peripheral Pulse Triggering Uses
Peripheral Pulse Triggering Uses
A light sensor attached to the patient's finger.
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When Peripheral Pulse Triggering Most Effective
When Peripheral Pulse Triggering Most Effective
When imaging small vessels or the spinal cord.
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Gradient Moment Rephasing
Gradient Moment Rephasing
To reduce ghosting caused by flowing nuclei moving along gradients.
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Advantage of EKG Triggering
Advantage of EKG Triggering
More effective at reducing phase mismapping.
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Device to Trigger RF Excitation pulses
Device to Trigger RF Excitation pulses
A light sensor attached to the patient's finger.
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Peripheral Pulse Triggering Not Useful
Peripheral Pulse Triggering Not Useful
When imaging the heart itself.
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