Hi everyone, <br><br>I am currently using itk::DiffeomorphicDemonsRegistrationFilter for 2D same-modality registration. I am getting negative values in the Jacobian Determinant of the deformation map. So I looked at the original paper and it says: <br>
<br>"Since statistical analysis and its biological interpretation often relies on the assumption that the Jacobian determinant is positive, potential negative values might appear like a true possible problem. A real solution to this issue would rely on a more powerfull representation of spatial transformations that would be consistent with the composition and the computation of the Jacobian. In practice though, negative Jacobians appear very seldom and if they do, they are only so slightly negative that dismissing them should not lead to any problems for biological interpretation."<br>
<br>1) I did not really understand what this means: "A real solution to this issue would rely on a more powerfull
representation of spatial transformations that would be consistent with
the composition and the computation of the Jacobian". Can someone please explain? <br><br>2) Typically about half the values in the Jacobian Determinant are negative, and examples of the smallest negative values from each deformation map are: -0.326896, -0.315346, -0.175188 etc. The largest positive values have similar magnitudes. So basically, the negative values are neither rare nor only slightly negative. Also, this is true of every registration I have tried so far. Why is this happening? Any <br>
<br>3) For the above I had SetStandardDeviations(1.0). I notice that for my data if I SetStandardDeviations(2.5), then things get better. The negative values decrease in magnitude - they are more like 0.005 etc. What's the intuition here? <br>
<br>Thanks in Anticipation,<br>Harish <br>