dMRI (a.k.a. DWI or DTI)

There should be two dMRI images (a.k.a. DTI=Diffusion Tensor Image, DWI=Diffusion Weighted Image), the main one acquired anterior to posterior (AP) and a reverse-phase encoded one (Bzero_verify_P-A below) acquired posterior to anterior (PA). It is important to get reverse phase encode images, and personal experimentation suggests it is better if the main image is AP and the reverse phase encode image is PA.

Caution

It is especially easy for the tech to accidentally acquire both images (AP and PA) with the same phase encode direction because, under certain circumstances, the scanner resets the phase-encode value without informing the tech! This means you should check phase encoding at the scanner (before releasing your participant) and recheck later.

✅ Check that DTI_30_DIRS_A-P has image dimensions=128x128, & 32 volumes (a.k.a. frames).

✅ With DTI_30_DIRS_A-P still open, also open Bzero_verify_P-A. The easiest way to check for the correct phase encoding is to look for stretchy vs squishy eyeballs in the axial plane (see below). Move the cursor in the sagittal view so that it is aligned with the eyeballs. Several slices meet this criterion, move to the most dramatic difference (For this subject, ~z=48 displayed in the main Mango interface):

DTI Images: Left: A-P with stretchy eyeballs; Right: P-A with squishy eyeballs

✅ Close Mango

🟢 MRI Scans 2: Pr (5)