4D Scans

The second video (~4.75 minutes) discusses 4D datasets (dMRI and fMRI).

4D scans consist of a series of 3D volumes.
For dMRI (a.k.a. Diffusion-Weighted Imaging (DWI)) the sequence consists of volumes acquired with different gradients.
For functional Magnetic Resonance Imaging (fMRI), the sequence consists of volumes at consecutive time points.
Both fMRI and dMRI images are EPI (echo-planar images). Individual volumes in the 4D sequence are acquired very quickly and suffer from distortion which must be corrected. You'll learn more about distortion correction later.
Crucially, for fMRI, the order of volumes matters. For dMRI, the order does not matter

Note

dMRI scans should be collected with an accompanying RPE (Reverse Phase Encode) image. You'll learn more about these when you study distortion correction.

You will process 4D fMRI series in the fMRI preprocessing module, and 4D dMRI series in the dMRI module.

MRI Scans 1