[Insight-users] Applying two 2D registration transforms into a 3D image

Fri Apr 9 18:07:03 EDT 2010

Hi Ganesh,

Thanks for describing the clinical constraints of your application.

Unfortunately the pair of 2D images do not have enough information
to be considered equivalent to a 3D image. Should that be the case,
we would not need CT scanners, and would have been fine with
dual plane X-Ray machines.

but, ... for the sake of being pragmatic, you can certainly claim that
the 2D images carry "some" valuable information that allows you to
"estimate" a "reasonable" deformation in 3D space for a small price.

For example, if you have patient bending over her/his abdomen
between the T1 and T2 images, then you could get most of this
"bending" information from the YZ plane (using LPS coordinates):
http://www.cmake.org/Wiki/Proposals:Orientation#DICOM_LPS_Orientation_-_Full_Body_Graphical_Example

You could project that 2D deformation field in 3D, (by simply adding
that the displacement along X is zero), and apply such field to the
3D image using the itkWarpImageFilter.

Note that in that "restricted bending" case, the image in plane XZ
will not be of much use, since tissue in the patient's back will move
upwards, while tissue in the patient's front will move downwards
in that plane, and the projection image will hardly allow you to
disambiguate these two opposite displacements.

So, you probably can use the YZ plane for a "coarse" estimation
of deformations such as Breathing, and bending.

You should be very careful not to extrapolating those estimations
for critical application such as image guided therapy....

The case of a "general deformation" certainly can't be solve with
just a pair of 2D projection images.

    Regards,

         Luis

------------------------------------------------------------------------------------------
On Thu, Apr 8, 2010 at 3:58 PM, Ganesh Narayanasamy
<nganesh76 at hotmail.com>wrote:

>
> The main reason for not doing a 3D-3D registration is that we do not,
> obviously, have the luxury of acquiring 3D data sets every time the patients
> come by. The 3D-CT scan is acquired once with which radiotherapy planning is
> done initially. After that visit, the patients are scanned daily using a
> kV-imager twice that gives two 2D images in orthogonal planes (as described
> below).
> I think these 2 orthogonal projection images have enough information to be
> considered "equivalent" to a 3D image. Am i right ? If not, then why not?
>
> When these 2 orthogonal projection images acquired on 2 different days are
> registered to each other, I would like to obtain the corresponding
> deformation fields in XZ and YZ. For every point P in the fixed image, I
> want to evaluate its new location P' in the moving image (using say,
> WarpImageFilter).
>
>
> Thank you,
>
> Ganesh
>
> ************************************************************************
> "What the mind of man can conceive and believe, It can achieve" - Napolean
> Hill
> -Ganesh Narayanasamy,Ph.D., PostDoc-University of Kentucky Cancer Center
> Earlier work:
> http://www.sciencedaily.com/releases/2007/05/070504133017.htm
> ************************************************************************
>
>
>
> > Date: Thu, 8 Apr 2010 14:43:28 -0400
> > Subject: Re: [Insight-users] Applying two 2D registration transforms into
> a 3D image
> > From: luis.ibanez at kitware.com
> > To: nganesh76 at hotmail.com
> > CC: insight-users at itk.org
>
> >
> > Hi Ganesh,
> >
> > Thanks for the detailed description of the problem that you are working
> on.
> >
> > Unfortunately, the deformation fields of the two 2D deformable
> registrations
> > do not carry enough information for you to do a 3D deformation of the T1
> > and T2 original 3D-images.
> >
> >
> > Any reason for not doing real 3D deformable registration in the
> > original images ?
> >
> > [...ITK will do registration on N-D images...]
> >
> >
> > Please let us know,
> >
> >
> > Thanks
> >
> >
> > Luis
> >
> >
> >
> >
> ------------------------------------------------------------------------------------
> > On Wed, Apr 7, 2010 at 1:06 PM, Ganesh Narayanasamy
> > <nganesh76 at hotmail.com> wrote:
> > >
> > > I have a pair of 3D-CT images acquired on a phantom with some internal
> > > changes (known).
> > > A 2D-DRR (digitally reconstructed radiograph)  image is constructed
> such
> > > that the pixel value on the DRR image should be given by the
> accumulated
> > > intensities of the 3D image volume along the direction. With the T1 or
> fixed
> > > 3D-CT image, we have created two such DRRs, say along the XZ and YZ
> axes.
> > > Let us call these 2 DRRs as T1DRR_XZ and T1DRR_YZ.
> > >
> > > Likewise, we have created 2 DRRs from the T2 3D-CT image namely,
> T2DRR_XZ
> > > and T2DRR_YZ.
> > >
> > > Using a deformable 2D registration model (say, Bspline), we would like
> to
> > > register T1DRR_XZ with T2DRR_XZ and also T1DRR_YZ with T2DRR_YZ. From
> these
> > > 2 transformations along the 2 orthogonal planes (XZ and YZ), is it
> possible
> > > to "compute" the 3D transform between the two 3D-CT images ?
> > >
> > > Can I then "apply" these two 2D transforms or the single computed 3D
> > > transform into the T1 image to obtain a T(T1) image that is comparable
> with
> > > the T2 image.
> > >
> > > Thanks a ton,
> > > -Ganesh
> > >
> > >
> > >
> ************************************************************************
> > > "What the mind of man can conceive and believe, It can achieve" -
> Napolean
> > > Hill
> > > -Ganesh Narayanasamy,Ph.D., PostDoc-University of Kentucky Cancer
> Center
> > > Earlier work:
> http://www.sciencedaily.com/releases/2007/05/070504133017.htm
> > >
> ************************************************************************
> > >
> > >
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