[MINC-users] minctracc/masking bug?

[Alex Zijdenbos]

Thanks, Claude!

> This is a strange behaviour indeed.
>
> Can you tell me which line of code to change? :-)

I wish :-)

> One thought: is the resulting grid symmetric with respect to
> the field of view? If the grid is asymmetric, the support of
> the masked image may be insufficient for some grid points
> lying very near the border of the masked image. I dealt with
> this in the old N3 where the control points for the splines
> were defined from the bottom-left corner. I made them centered
> from version 1.11.0. Maybe we can try the same in minctracc
> if it's not already the case. Also, what happens when you
> reduce the grid size? Does the error go away? Have you looked
> at the masked blurred (or blurred masked) images?

I'm running experiments to look at all of the above. It turns out that
in my initial tests, the source- and target images did not have a
symmetric x-extent. Fixing that by changing the image lattice to be
symmetric about x=0, it turned out that a) the change in image lattice
(2 yz slices removed from the left) did change the resulting
deformation field; but it still has roughly the same pattern (in other
words, the final grid is affected by the extent of the lattice, but it
doesn't fix the problem). The resulting grid is symmetric about x=0
though, so minctracc does seem to to the right thing in terms of
deciding on the grid lattice.

To be continued.

-- A