Dear AFNI experts,
I am trying to calculate the frame displacement (FD) according to the formula given in Power et al. 2012. The goal is to compare FD values between two groups. However, I have some doubts regarding how I can implement this with the output I have access to (the data is already analyzed). If I understand correctly, frame displacement represents the absolute value of displacement changes in the x, y, z directions as well as rotational changes (roll, pitch and yaw–once converted to mm) between adjacent volumes.
I only have access to the motion files (2 runs) and the .1D matrix from 3dVolreg. The base for registration was the 10th volume of the 2nd run. With the output that I have, can I calculate an FD value per participant? If I understand correctly, the motion parameters in the motion file represent the displacement between the volume and the base volume used for registration, which are not adjacent.
Thank you in advance for your help,