MRI K-space

What happens if frequencies are insufficiently sampled?

Aliasing

Why does motion artefact only occur in the phase axis of k-space?

Because the sampling interval between data points in each column is much longer than the sampling interval between data points in each row.

In which direction is k-space traversal when frequency encoding is negative?

Right to left.

When we select the NSA in the scan protocol - what is going on behind the scenes in k-space?

The NSA is the number of times each line is filled with the same slope and amplitude of phase encoding gradient.

If the frequency matrix doubles and the receive bandwidth is unchanged what other parameter changes and why?

The TE increases because more date points are required for the same sampling frequency. Therefore, the sampling window and therefore, TE increases.

What happens in k-space when the phase FOV is doubled?

The incremental step between each line is halved.

What is the digital sampling frequency?

The number of data points acquired per second during the sampling window.

When the frequency matrix is selected, what is altered in k-space?

The number of data points in each row.

When we place a certain number of slices through the patient's anatomy - what is going on behind the scenes in k-space?

The system allocates the same number of k-space areas as there are slices in the stack.

Why does the phase encoding gradient slope change every TR?

To ensure that the data look different, every TR is therefore placed in a different line of k-space. This ensures that there are multiple pixels in the phase direction of the image.