RF Pulses and Diaphragm Tracking

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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?

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?

Respiration

Pulsation of vessels and CSF

Swallowing

All of the above (correct)

What happens to ghosting with distance from the source of motion?

Ghosting becomes less obvious Signup and view all the answers

What does the physical separation between each ghost depend on?

The scan time parameters and period of motion Signup and view all the answers

What is the purpose of the phase-encoding gradient in MRI?

To produce phase mismapping Signup and view all the answers

What results in periodic perturbations of the data collected in k-space?

Motion of anatomy during the scan Signup and view all the answers

Which axis does ghosting artifact typically occur along in the image?

Phase encoding axis Signup and view all the answers

What factors affect the separation between ghosts in an image?

TR, phase matrix, NSA, and the period of motion Signup and view all the answers

What does swapping phase and frequency encoding directions accomplish?

Changes the direction of ghosting artifact Signup and view all the answers

What is the purpose of presaturation pulses in MRI?

To null signal from specified areas Signup and view all the answers

What technique can be used to reduce or eliminate respiratory motion artifact in chest and abdominal imaging?

Using a navigator echo Signup and view all the answers

What is the purpose of respiratory bellows in MRI?

To reduce motion artifact from respiration Signup and view all the answers

What does a transducer do in the context of respiratory bellows?

Converts the change in pressure within the bellows to an electrical signal Signup and view all the answers

Which technique utilizes signal collected by the transducer or navigator echoes to trigger an action?

Respiratory triggering Signup and view all the answers

What is the main drawback of respiratory triggering?

The periodicity of the patient's respiratory cycle becomes the TR and determines the image contrast. Signup and view all the answers

What is the main trade-off of using respiratory gating?

Increased scan time due to filling every line of data. Signup and view all the answers

What is the purpose of increasing the NSA (number of signal averages)?

To reduce motion artifact. Signup and view all the answers

What is the trade-off of increasing the NSA?

Increased scan time. Signup and view all the answers

What is the purpose of immobilizing the patient with pads and straps during an MRI scan?

To reduce voluntary motion. Signup and view all the answers

What is the purpose of administering antispasmodic agents during an MRI scan?

To reduce involuntary motion. Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What does peripheral pulse triggering use to detect the pulsation of blood through the capillaries?

A light sensor attached to the patient's finger Signup and view all the answers

When is peripheral pulse triggering most effective in reducing phase mismapping?

When imaging small vessels or the spinal cord Signup and view all the answers

What is the purpose of gradient moment rephasing in medical imaging?

To reduce ghosting caused by flowing nuclei moving along gradients Signup and view all the answers

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 Signup and view all the answers

What is the main advantage of EKG triggering compared to peripheral pulse triggering in medical imaging?

It is more effective at reducing phase mismapping Signup and view all the answers

What is used to trigger RF excitation pulses in peripheral pulse triggering?