MRI Studio Forum » DTI Studio

Registration-induced decrease in FA

(2 posts)
  • Started 7 years ago by yongzhangdti
  • Latest reply from susumu
  1. yongzhangdti

    Dear everyone,

    We performed the AIR-based rigid-body registration before tensor calculation. There was not much translation (~0.2-0.5 mm) and rotation as we observed from the saved transformation file. However, the registered raw diffusion weighted images were a lot smoother and had much less contrast compared to those without registration. Hangyi mentioned there was no internal smoothing associated with the rigid-body registration. Just wonder if the tri-linear interpolation alone can cause this. Our raw diffusion weighted images were acquired with a 128x128 matrix and the in-plane resolution is 1.5x1.5 mm.

    We observed ~16% decrease in FA,~15% decrease in Eigen Value 0, ~12% decrease in Eigen Value 1, ~19% increase in Eigen Value 2. Just wonder if anybody else experienced the same issue. We also tried the gradient adjustment option but there was not much change. So far we suspect that the interpolation associated with registration could be a major cause. Any suggestion will be greatly appreciated!


    Posted 7 years ago #
  2. susumu

    Hi Yong,

    Sorry for my slow response.
    I believe any registration inevitably leads to interpolation and resultant smoothing (SNR goes up but resolution goes down). You can see noticeable SNR improvement and smoothing as you observed. I think there is no way to avoid it.


    Posted 7 years ago #

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