[vtkusers] How get DICOM image intensity?
Jim Peterson
jimcp at cox.net
Sun Sep 12 11:37:16 EDT 2010
ok, I believe we have a registration problem between the vtk model
coordinates and the ITKSnap model coordinates. if I understand the data
you have given, we have some point data like:
tested point
ITKSnap value
ITK Snap Material
VTK Value
Vtk Material
pt1
2318
dense bone
-1024
air (-1000 is air at STP calibration)
pt2
2210
dense bone
1023
soft bone
pt3
2410
dense bone
41
watery liquid (0 is water at STP calibration)
pt4
2130
dense bone
993
soft bone
We agree all of these values are reasonable for some location in a
dental scan. I believe the problem is, in spite of expectations and
intentions, the location tested are not from the same input data, maybe
the coordinate schemes in vtk and itk do not match. Can you find
corresponding values in the ITKSnap? perhaps by transposing a coordinate
location? can we find locations to "sample" in the vtk model that
produce the dense bone values?
does that make sense?
Hope that helps,
Jim
Italo Ribeiro wrote:
> Hi Jim,
>
> The value not is same the entire tooth, the diferents values are the
> same point. In point (226, 100, 1) the values are:
>
> ITKsnap : 2130
> Mycode: 993
>
> 2010/9/12 Jim Peterson <jimcp at cox.net <mailto:jimcp at cox.net>>
>
> Hi Italo,
>
> I am not an ITKSnap user myself, you are suggesting ITKSnap
> reports the same value for the entire tooth? I think you would
> have to iterate over the points in the tooth to find the maximum
> value in vtk to duplicate that if it is true. Can you display the
> point coordinates that have that value in ITKSnap? Then see if vtk
> has the same value at that point? I have trouble believing vtk has
> incorrect pixel data by point for imaging content.
>
> Jim
>
> Italo Ribeiro wrote:
>
> Hi Jim,
>
> I have dicom image with teeth, i am looking intensity values
> of 2 front teeth.
>
> But some happen very strange, the tooth the left have greater
> intensity in ITKsnap 2518 and my code -1024. The tooth the
> right side have in ITKsnap 2402 and in my code 41. I do not
> know why the values are different.
>
> In my code i get 255 points of heigh and width, but when i get
> dimension the image, vtk show 512 x 512, same dimesion show in
> ITKsnap. ITKsnap get dimension of voxels, so i must get
> information the intensity value voxel of volume and no pixel
> the image?
>
> thanks.
>
> 2010/9/11 Jim Peterson <jimcp at cox.net <mailto:jimcp at cox.net>
> <mailto:jimcp at cox.net <mailto:jimcp at cox.net>>>
>
>
> Personally, I am sorry, but there is not enough information in
> your description of the problem to be sure you have a
> legitimate
> complaint. does your dicom data consist of only one point?
> how are
> you certain you have selected the exact same location?
>
> in my mainframe programming life we have a saying:
>
> "when expected results do not match observed results, check the
> library concatenation"
>
> .... in my opinion, chances are you are looking at
> different points.
>
> sorry, Hoping to be helpful not critical.
> Jim
>
> Italo Ribeiro wrote:
>
> No more ideas?
>
> 2010/9/10 Italo Ribeiro <italo.ribeiro at gmail.com
> <mailto:italo.ribeiro at gmail.com>
> <mailto:italo.ribeiro at gmail.com
> <mailto:italo.ribeiro at gmail.com>>
> <mailto:italo.ribeiro at gmail.com
> <mailto:italo.ribeiro at gmail.com>
> <mailto:italo.ribeiro at gmail.com
> <mailto:italo.ribeiro at gmail.com>>>>
>
>
> I am expecting MIP of image point. In my program the
> value
> for one
> point is 1023 and ITKsnap show 2210.
>
> Why the value is different?
>
> 2010/9/10 John Drescher <drescherjm at gmail.com
> <mailto:drescherjm at gmail.com>
> <mailto:drescherjm at gmail.com <mailto:drescherjm at gmail.com>>
> <mailto:drescherjm at gmail.com
> <mailto:drescherjm at gmail.com> <mailto:drescherjm at gmail.com
> <mailto:drescherjm at gmail.com>>>>
>
>
>
> > Using GetScalarType the type returned is
> short, i was
> using
> int. But the
> > value maximum showed is 1024 and i see the
> maximum short
> value is 32767 and
> > the intensity value is not corret.
> >
>
> Depending on how you read the dicom file the value
> should be in
> hounsfield units. I am confused on whether you
> mean you
> were
> expecting
> 32767 or hounsfield.
>
> John
>
>
>
>
> -- Ítalo Mendes
> ogre.irados.org <http://ogre.irados.org>
> <http://ogre.irados.org>
> <http://ogre.irados.org>
>
>
>
>
> -- Ítalo Mendes
>
> ogre.irados.org <http://ogre.irados.org>
> <http://ogre.irados.org> <http://ogre.irados.org>
>
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>
> --
> Ítalo Mendes
> ogre.irados.org <http://ogre.irados.org> <http://ogre.irados.org>
>
>
>
>
>
> --
> Ítalo Mendes
> ogre.irados.org <http://ogre.irados.org>
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