Respiratory Signal Processing and K-Space Reordering Quiz

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Which of the following is a cause of phase mismapping artifact?

Anatomy moving along the phase-encoding gradient (correct)

Anatomy moving along the frequency encoding gradient

Anatomy moving along the slice-select gradient

Anatomy moving during the TR period

What type of motion can cause phase mismapping?

Respiration

Heartbeat

Swallowing

All of the above (correct)

What is the effect of distance from the source of motion on ghosting artifact?

Ghosting becomes more obvious

Ghosting disappears completely

Ghosting becomes less obvious (correct)

Ghosting remains the same

What does the physical separation between each ghost depend on?

The amplitude of the phase-encoding gradient Signup and view all the answers

What is the result of repetitive motion during the scan?

Periodic perturbations of the data collected in k-space Signup and view all the answers

What is the term used to describe the incorrect spatial locations of moving anatomy in the image?

Phase mismapping Signup and view all the answers

Which gradient is applied at a different amplitude every TR?

Phase-encoding gradient Signup and view all the answers

Which direction does ghosting artifact occur along the phase encoding axis of the image?

Anterior to posterior Signup and view all the answers

What is the purpose of swapping phase and frequency in imaging?

To change the direction of ghosting artifact Signup and view all the answers

Which technique can be used to reduce or eliminate motion artifact from respiration in chest and abdominal imaging?

Respiratory compensation Signup and view all the answers

What factors affect the separation between ghosts in an image?

TR, phase matrix, and NSA Signup and view all the answers

What is the purpose of presaturation pulses in imaging?

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

Which type of respiratory sensor tracks the position of the diaphragm using a navigator echo?

Software-based strategy Signup and view all the answers

What is the purpose of reordering the lines of k-space in respiratory compensation techniques?

To reflect the periodic motion of breathing throughout the scan Signup and view all the answers

Which technique utilizes signal collected by the transducer or navigator echoes to select a threshold (gate) that only allows data through when a certain condition is met?

Respiratory gating 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 trade-off is associated with respiratory gating?

Up to 60% of the data may be rejected, increasing the acquisition time. Signup and view all the answers

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

To reduce motion artifact Signup and view all the answers

What is the trade-off associated with increasing the NSA in MRI?

Scan time is increased by an entire acquisition period for every additional signal average. Signup and view all the answers

What is the purpose of cardiac triggering in MRI?

To monitor cardiac motion Signup and view all the answers

Which form of triggering uses electrodes and lead wires attached to the patient's chest to produce an EKG for determining the timing of each RF excitation pulse?

Electrocardiogram (ECG, EKG) gating Signup and view all the answers

Which type of triggering is more accurate for imaging the heart itself?

EKG triggering Signup and view all the answers

Peripheral triggering is effective at reducing phase mismapping when imaging which structures?

Small vessels Signup and view all the answers

What does gradient moment rephasing help reduce?

Ghosting caused by flowing nuclei Signup and view all the answers

Which type of triggering is used to acquire each slice at the same phase of the cardiac cycle?

Pulsation triggering Signup and view all the answers

When is peripheral triggering not very useful for imaging the heart itself?

When imaging the heart itself Signup and view all the answers

What is the purpose of pulsation triggering?

To acquire each slice at the same phase of the cardiac cycle Signup and view all the answers

What is the main advantage of EKG triggering over peripheral triggering?

Being more accurate for imaging the heart itself Signup and view all the answers

When is peripheral triggering effective at reducing phase mismapping?

When imaging small vessels Signup and view all the answers

What is the main purpose of gradient moment rephasing?

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