Dear Ed,
One of the distortions due to eddy currents is scalings.
So why do you want to remove them?
All the best,
Mark
On 10 Apr 2012, at 11:24, Ed Gronenschild wrote:
> Hi,
>
> In eddy_correct FLIRT is used to register the b volumes to
> the B0 volume. As already described in an earlier post,
> I frequently notice a scaling, see output of avscale for the
> derived affine transformations for one of the b volumes:
>
> Rotation & Translation Matrix:
> 0.999991 -0.003124 -0.002873 -1.394440
> 0.003120 0.999994 -0.001635 -3.587220
> 0.002878 0.001626 0.999995 -1.920300
> 0.000000 0.000000 0.000000 1.000000
>
> Scales (x,y,z) = 1.018279 1.039003 1.017240
>
> Skews (xy,xz,yz) = -0.001957 -0.001985 -0.005259
>
> Average scaling = 1.02484
>
> Determinant = 1.07623
> Left-Right orientation: preserved
>
> Forward half transform =
> 1.009096 -0.002589 -0.002446 -0.697537
> 0.001575 1.019312 -0.003477 -1.777544
> 0.001452 0.000828 1.008578 -0.954807
> 0.000000 0.000000 0.000000 1.000000
>
> Backward half transform =
> 0.990976 0.002540 0.002411 0.698059
> -0.001524 0.981047 0.003344 1.745984
> -0.001426 -0.000816 0.991492 0.944238
> 0.000000 0.000000 0.000000 1.000000
>
> I would like to remove the scaling from the matrix.
> How to proceed?
>
> Ed
>
|