[Insight-users] Q about header file of data download from Liver challenge 2007

[Luis Ibanez]

Hi ekyaya,


Line 199   of  itkImageBase.hxx

            says that your suspicions are well-founded:

    this->m_IndexToPhysicalPoint = this->m_Direction * scale;

as well as lines 94-99 in the itkImageTransformHelper.h

94   inline static void TransformIndexToPhysicalPointCol(
95     const MatrixType & matrix,
96     const IndexType & index, DoublePoint & point,
97     const UniqueTypeBoolFalse &)
98   {
99     point[R] = point[R] + matrix[R][C] * index[C];


The matrix in the MetaImage headers shouldn't have
combined the spacing with the direction cosines. This
composition is done for you in line 99 of the ImageBase
class.

You may want to contact the organizers of the
challenge and ask for clarification.


   BTW, Is this Challenge data available to the public ?


     Thanks


           Luis


-------------------------
On Mon, May 21, 2012 at 6:14 PM, erkang <ekyaya at gmail.com> wrote:

> Hi everyone:
>
> I play with the meta data downloaded from Liver challenge 2007. However, I
> confused with the "TransformMatrix" item in the header file.
>
> One example of the header file is as following:
>
> ObjectType = Image
> NDims = 3
> BinaryData = True
> BinaryDataByteOrderMSB = False
> TransformMatrix = 0.74219 0 0 0 0.74219 0 0 0 1.5
> Offset = 0 0 0
> CenterOfRotation = 0 0 0
> ElementSpacing = 0.74219 0.74219 1.5
> DimSize = 512 512 183
> AnatomicalOrientation = ???
> ElementSize = 0.58594 0.58594 1
> ElementType = MET_SHORT
> ElementDataFile = liver-orig001.raw
>
> I doubt that the header files of these data are not correct. I check the
> metaIO in ITK. ITK does first read the direction (TransformMatrix ) and
> then
> multiplied by spacing. I test it in ImageFileReader and transform of the
> loaded image is 0.74219*0.74219 0 0 0 0.74219*0.74219 0 0 0 1.5*1.5.
>
> But, I would like to guess the "TransformMatrix" of the header file is
> TransformMatrix = 1 0 0 0 1 0 0 0 1. And after multiplied by spacing, the
> actual transform matrix is 0.74219 0 0 0 0.74219 0 0 0 1.5.
>
> Is that correct? Or what's the best way to load these data? Thanks.
>
> --
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