Aliasing - Video Lesson

Hey everybody and welcome back to our course on MRI artifacts. In this lesson, we will discuss aliasing. We will define what aliasing is and what it looks like, why it happens and its impact on diagnosis. Let's get started. First, let's discuss what aliasing is. Aliasing is one of the most common and most important artifacts you will encounter in MRI. It is sometimes called a wraparound artifact and it occurs when anatomy that lies outside the prescribed field of view or FOV is incorrectly displayed within the image. Instead of being outside the FOV, the anatomy is wrapped to the opposite side of the image. The result is an image that appears crowded, duplicated, or confusing even though the scanner is functioning properly. This artifact happens because the MRI system has not sampled spatial information frequently enough to correctly localize the signal. To understand why aliasing happens, it is helpful to briefly revisit how MRI encodes spatial information.