Dear All,
I wanted to reproduce the transformation of the EDDY routine based on the coefficients in .eddy_parameters. The quadratic model was used in EDDY. I would like to know if I am doing it the right way.
First, I applied the topup + eddy process to a diffusion data set and get the .eddy_parameters. Then, I ran applytopup to the same data set with the output from topup to correct the susceptibility induced field. After that, I applied eddy current correction to the output image of applytopup in two steps, 1. apply the motion correction using the first 6 parameters in each row in the .eddy_parameters, 2. calculate the eddy current induced field with the next 10 parameters in each row and correct the error in PE direction.
My questions are: 1) Is this process correct? 2) What coordinates should I use for both motion and EC field calculation? Are the translation and rotation relative to the center of FOV or the iso center? 3) When calculating the eddy current induced field, are the 10 parameters the coefficients in front of x,y,z,x^2,y^2,z^2,xy,xz,yz,1, is this the right order? I assumed that x,y,z are in mm and the sum of the 10 terms will be the EC induced field in Hz.
Thank you very much for your help.
Regards,
Hua Wu
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