Skip to main content
This site will look better in a browser that supports web standards, but it is accessible to any browser or Internet device.

QUESTIONS
» K-Space

These questions are concerned with k-space.

« Question list

Phase Oversampling

Answer this...

What is phase oversampling?

Oversampling avoids aliasing by taking more samples (more k-space lines with the same overall k-space coverage). If the original k-space data was the data the following image:

original

then oversampled k-space may be the same as the data in this image:

oversampled

There are twice the number of lines (a greater density of lines) in this k-space, which increases the field-of-view (FOV). Since we're still sampling the same coverage of k-space, the resolution is the same. Then the image is cropped back down to represent the FOV which was originally requested, but now with aliasing removed.

This is also known as "no phase wrap", or phase oversampling. Phase oversampling literally moves the replicates which appear within the FOV, out of the FOV.

Here are two helpful rules:

  • The line spacing in k-space is inversely proportional to the FOV in real space.
  • How "far out" we acquire data in k-space is inversely proportional to the resolution in real space.

k_im_relation

See the remove even lines page of the K-Space Tool.

Further reading on this topic:
Books: MRI The Basics p251, Q&A in MRI p139
Online: e-MRI

« Back to K-Space question list

 
(This page: http://www.revisemri.com/questions/kspace/phase_oversampling)