[Insight-users] question regarding registration outputs

[Tim Bhatnagar]

Hmmm,

The coordinate system from my raw data matches up with my vtk data (not
disp fields, the actual image data) imported into Paraview for
visualization, as well as used in ITK to generate displacement fields. If
the coordinate systems of my input images are the same, is there any reason
why my displacement field should be in different coordinates?


On Wed, Oct 9, 2013 at 11:06 AM, Matt McCormick
<matt.mccormick at kitware.com>wrote:

> Hi Tim,
>
> If viewing the data with VTK or other library, deformation in the
> negative y-direction should be taken with care because of a difference
> in coordinate systems [1].
>
> HTH,
> Matt
>
> [1] http://www.slicer.org/slicerWiki/index.php/Slicer:VTK_ITK_Coordinates
>
> On Wed, Oct 9, 2013 at 5:59 PM, Tim Bhatnagar <tim.bhatnagar at gmail.com>
> wrote:
> > Thanks Matt,
> >
> > It is strange then, that I can extract data from the displacement field
> that
> > seems to represent the field that would transform the 'pre-deformation'
> > image into the 'deformation' image. (There is a significant deformation
> in
> > the 'deformation data' in the negative y-direction, which shows up
> nicely in
> > the displacement field.
> >
> > Must I be doing something strange for this to happen?
> >
> >
> > On Wed, Oct 9, 2013 at 10:31 AM, Matt McCormick <
> matt.mccormick at kitware.com>
> > wrote:
> >>
> >> Hi Tim,
> >>
> >> No, the WarpImageFilter should be generating a 'pre-deformation'
> >> look-alike.  For more information, see the Software Guide.
> >>
> >> HTH,
> >> Matt
> >>
> >> On Wed, Oct 9, 2013 at 4:48 PM, Tim Bhatnagar <tim.bhatnagar at gmail.com>
> >> wrote:
> >> > Hello all,
> >> >
> >> > I use the ITK examples ImageRegistration5, ImageRegistration8 and
> >> > DeformableRegistration2 (Demon's) for registration of normal and
> >> > deformed
> >> > data (same subject). Briefly, I do some pre-registration of my data
> >> > using
> >> > ImageReg5 and ImageReg8 (for gross alignment), after which I take the
> >> > produced displacement fields, and use them as the 'initial
> displacement
> >> > field' for DefReg2.
> >> >
> >> > In all cases, I am using my 'pre-deformation' data as my fixed source,
> >> > and
> >> > my 'deformation' data as my moving source.
> >> >
> >> > I have some fiducial markers to check the accuracy of the generated
> >> > displacement field, and it looks pretty good. However, when trying to
> >> > produce figures, my registration output looks much closer to my
> >> > 'deformation' data, and sometimes the output and the actual
> >> > 'deformation'
> >> > data are offset by a magnitude.
> >> >
> >> > In my situation, should I be aiming to have my registration output
> >> > appear
> >> > similar to my 'pre-deformation' data? (I get confused reading the ITK
> >> > explanation on that) Shouldn't I be able to produce the a
> 'deformation'
> >> > look-a-like by using WarpImageFilter with my 'pre-deformation' data
> and
> >> > my
> >> > generated displacement field?
> >> >
> >> > Sorry this was so wordy. Any help would be much appreciated.
> >> >
> >> > --
> >> > Tim Bhatnagar
> >> > PhD Candidate
> >> > Orthopaedic Injury Biomechanics Group
> >> > Department of Mechanical Engineering
> >> > University of British Columbia
> >> >
> >> > Rm 5000 - 818 West 10th Ave.
> >> > Vancouver, BC
> >> > Canada
> >> > V5Z 1M9
> >> >
> >> > Ph: (604) 675-8845
> >> > Fax: (604) 675-8820
> >> > Web: oibg.mech.ubc.ca
> >> >
> >> > _____________________________________
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> >
> >
> >
> >
> > --
> > Tim Bhatnagar
> > PhD Candidate
> > Orthopaedic Injury Biomechanics Group
> > Department of Mechanical Engineering
> > University of British Columbia
> >
> > Rm 5000 - 818 West 10th Ave.
> > Vancouver, BC
> > Canada
> > V5Z 1M9
> >
> > Ph: (604) 675-8845
> > Fax: (604) 675-8820
> > Web: oibg.mech.ubc.ca
>



-- 
Tim Bhatnagar
PhD Candidate
Orthopaedic Injury Biomechanics Group
Department of Mechanical Engineering
University of British Columbia

Rm 5000 - 818 West 10th Ave.
Vancouver, BC
Canada
V5Z 1M9

Ph: (604) 675-8845
Fax: (604) 675-8820
Web: oibg.mech.ubc.ca
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