Motion correction parameter definitions

[Paul Wright]

Hi

I am using the motion parameters estimated by ExploreDTI and would like to know exactly what the numbers represent. I am interested in translation and rotation, but it would be good to know all four in case others need it.

1) What are the axes and directions?

I think:

x: posterior to anterior / roll

y: right to left / pitch

z: inferior to superior / yaw

I am not sure what direction the rotations are in, e.g. does positive y mean pitch back or forward?

2) What are the units?

Is translation in voxels or mm?

Is rotation in degrees or radians?

Many thanks

Paul

[Jill Miller]

Following. Also, would you mind sharing how you got these parameters? 

Thanks!

Jill VM 

[Paul Wright]

@Jill short answer: load the .mat file and look in the DM_info field.

Here's a script I wrote to get the translation and rotation (can easily add the other two, which I think are squeeze and shear). You can batch it with a wrapper script.

function mpout = E_DTI_MP(filename)

% Save motion parameters from a corrected ExploreDTI data set

% FORMAT: mpout = E_DTI_MDC_graph(filename)

% INPUT:

%   filename    -   ExploreDTI file with motion corrected

% OUTPUT:

%   mpout       -   Movement parameters, images in rows, translation and 

%                   rotation in columns (xt, yt, zt, xr, yr, zr)

if ~exist(filename,'file')

    error('File not found: %s\n\n',filename)

end

fprintf('Loading %s ...', filename)

try

    input = load(filename,'DM_info');

catch

    error('\nCannot find motion correction information. Are you sure this file has been corrected?\n\n')

end

if ~isfield(input,'DM_info')

    error('\nCannot find motion correction information. Are you sure this file has been corrected?\n\n')

end

fprintf('\n')

nimg = length(input.DM_info);

mp = nan(4,3,nimg);

fprintf('Reading data 000 / %03d',nimg)

for img = 1:nimg

    fprintf('\b\b\b\b\b\b\b\b\b%03d / %03d',img,nimg)

    mp(:,:,img) = input.DM_info{img}{1};

end %img

fprintf('\nDone\n\n')

rot = squeeze(mp(1,:,:))';

trans = squeeze(mp(2,:,:))';

mpout = [trans,rot];

[Jill Miller]

Thanks Paul! I don't know the answer to your other questions, but, I'm happy to know where to find the motion parameters using ExploreDTI now. 

[samane pirmoradian]

hi

I want use harvard atlas in explore dti .i dont find this atlas.

please help me.

[samane pirmoradian]

hi

I want use harvard atlas in explore dti .i dont find this atlas.

please help me.

On Friday, March 5, 2021 at 7:22:34 PM UTC+3:30 Jill Miller wrote: