<div dir="ltr">Oh yes, of course! That is a subtle point.<div><br></div><div style>May I ask a follow up question then? In inverting a deformation field then, how do we decide the sampling of this grid of the inverse field?</div>
<div style><br></div><div style>Say our original deformation field has a displacement at every voxel and these displacement vectors can point to any real location. So, is the inverse deformation field going to be calculated at these real locations? However, we need to have a uniform grid and this is not guaranteed by this scheme now. Can someone explain this to me on how this is done? </div>
<div style><br></div><div style>Sorry for asking these naive questions. I could use the ITK filters out of the box but I would like to know some of these basics.</div><div style><br></div><div style>Thanks,</div><div style>
Anja</div><div class="gmail_extra"><br><br><div class="gmail_quote">On 10 April 2013 20:06, Matt McCormick <span dir="ltr"><<a href="mailto:matt.mccormick@kitware.com" target="_blank">matt.mccormick@kitware.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Anja,<br>
<br>
If displacement vector field gives the displacement at location x, but<br>
the negative of the displacement at location x is not the inverse;<br>
what is required is negative of the displacement vector at x + \delta<br>
x.<br>
<br>
HTH,<br>
Matt<br>
<div><div class="h5"><br>
On Wed, Apr 10, 2013 at 5:47 PM, Anja Ende <<a href="mailto:anja.ende@googlemail.com">anja.ende@googlemail.com</a>> wrote:<br>
> Hello all,<br>
><br>
> This is a very naive question and I would be very grateful if someone can<br>
> clarify this doubt for me.<br>
><br>
> I see that there are quite a few filters and some very sophisticated methods<br>
> for inverting deformation fields.<br>
><br>
> If I have a dense deformation field, why is it not enough to simply negate<br>
> the displacement vector to compute the inverse? I am sure there is a simple,<br>
> logical explanation for this but I am having trouble figuring it out.<br>
><br>
> Thanks a lot for your help!<br>
><br>
> Anja<br>
><br>
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