[Insight-developers] Image as an OrientedImage Progress : Introducing Coordinate System Tree ?

[Rupert Brooks]

Hi Luis, and everyone,

I wont be able to attend the tcon today, but I just wanted to quickly
comment that I think this proposal of Luis' makes a lot of sense.   It
seems to me a much more natural place to deal with the concept of
embedding in spaces.

Cheers,

Rupert

On Tue, Sep 23, 2008 at 11:01 AM, Luis Ibanez <luis.ibanez at kitware.com> wrote:
>
> Here is a proposal:
>
>
> It seems that we could go around the challenges of the ImageOrientation
> by introducing in ITK a formal representation of coordinate system
> hierarchies. (most of which is already implemented in SpatialObjects).
>
>
> This is something that has been done already in Slicer (with the MRML tree),
> and in IGSTK with the coordinate system representation classes.
>
>
> Here is how it could work:
>
> Case A: Image 2D embedded in a 3D Space:
> ========================================
>
>   The image Directions will be 2D x 2D, and the image will
>   be the child node of another node that represents the
>   3D host space. The link between the two nodes will contain
>   a 2D x 3D matrix transform mapping the two coordinate axes
>   of the 2D image to the 3D host space.
>
>   When reading a 2D image from an Analyze file, the 3D direction
>   cosines will go to the transform between the image node and
>   the host space node.
>
>
> Case B: Image 3D embedded in a 3D space:
> ========================================
>
>   The image directions will be 3D x 3D.
>   There is no need of parent node, but for consistency we could
>   always have a parent node representing the 3D host space.
>   The transform between the image node and the host space node
>   will be an identity transform of 3Dx3D.
>
>
> Case C: Image 4D embedded in a 3D space:
> =========================================
>
>   The image directions will be 4Dx4D and they will represent
>   the concept of "simultaneity of acquisition" from the scanner.
>
>   The image node will be a child of the parent host space node.
>   and the transform relating them will be a 4D x 3D transform,
>   that will represent the actual orientation of the dataset
>   in the 3D world.
>
>
> In the context of IGSTK and MRML we have found that using a
> "scene graph" representation for describing the spatial relationships
> of objects in space is a great way of simplifying applications and
> ensuring the consistent representation of their relative positions.
>
> In ITK we already have the coordinate systems of the SpatialObject,
> and they could be a base for representing this SceneGraph.
>
>
> One way to proceed could be to have the itk::ImageSpatialObject
> become the type that Readers will actually return. In this way,
> the ImageSpatialObject internally holds an itk::Image, and also
> is connected to the parent host space.
>
>
>   Luis
>
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>



-- 
--------------------------------------------------------------
Rupert Brooks