<div dir="ltr">You are absolutely corrcet - the data set is from dicompyler.<br><br>Thanks for providing the data set as part of the dicompyler.<br><br>Jothy<br><br><div class="gmail_quote">On Thu, Feb 24, 2011 at 6:16 AM, Adit Panchal <span dir="ltr"><<a href="mailto:apanchal@bastula.org">apanchal@bastula.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">The dataset looks like the test data from dicompyler. If that is the<br>
case, then I know for a fact that the CT images and the dose planes<br>
are coincident, since they I exported them from Varian Eclipse.<br>
<br>
The only issue I can think of is that the incorrect rendering has<br>
something to do with the pixel spacing of [1.074, 1.074] vs [2.5, 2.5]<br>
for the dose grid and the CT data respectively along with an incorrect<br>
origin. The top right corner of the dose plane is almost at the center<br>
of the CT image, which needs to be transposed. The same test data<br>
renders correctly in dicompyler.<br>
<br>
Adit<br>
<div><div></div><div class="h5"><br>
On Wed, Feb 23, 2011 at 23:39, Karthik Krishnan<br>
<<a href="mailto:karthik.krishnan@kitware.com">karthik.krishnan@kitware.com</a>> wrote:<br>
> As others already mentioned, you need to re-inteprolate the dose volume onto<br>
> the CT data. To do that you must use the grid frame offset vectors.<br>
><br>
> For all dose images I've encountered, the spacing between these grid planes<br>
> (as specified by the grid frame offset vectors) is a constant, but this need<br>
> not always be the case. If you want to be thorough you need to account for<br>
> this. Several folks don't (for instance below is an excerpt from Varian's<br>
> conformance statement):<br>
><br>
> "Dose Plane Spacing:<br>
> If Grid Frame Offset Vector (3004,000C) is present, it must contain offset<br>
> values yielding equally spaced dose planes. Therefore, those values follow<br>
> option a. in C.8.8.3.1 in Part 3 of [1]. RT Dose Instances having unequally<br>
> spaced dose planes are not supported."<br>
><br>
> So for this specific case, where the grid plane spacing is the same, you<br>
> could use the using the starting grid frame offset vector and the grid plane<br>
> spacing and use the itk::ResampleImageFilter. Simply use GDCM to convert the<br>
> images to MHD. Then set the spacing and origin to match the starting grid<br>
> plane offset vector and the grid plane spacing..<br>
><br>
> If you load the images in to 3DSlicer, I believe they should already be<br>
> re-interpolated and placed in the right coordinate system.<br>
><br>
><br>
> --<br>
> karthik<br>
><br>
><br>
><br>
><br>
> On Thu, Feb 24, 2011 at 2:36 AM, Mark Roden <<a href="mailto:mmroden@gmail.com">mmroden@gmail.com</a>> wrote:<br>
>><br>
>> Hi Jothy,<br>
>><br>
>> What are the direction cosines?<br>
>><br>
>> There is a problem where VTK reinterprets the direction cosines to<br>
>> change the directions of images produced by the dicom reader.<br>
>><br>
>> DICOM specifies that the image patient position is always the upper<br>
>> left pixel (if you look at the image as a 2D image on a plane like a<br>
>> monitor). VTK will take the direction cosine and potentially flip the<br>
>> image along those cosines.<br>
>><br>
>> Mark<br>
>><br>
>> On Wed, Feb 23, 2011 at 9:38 AM, Jothy <<a href="mailto:jothybasu@gmail.com">jothybasu@gmail.com</a>> wrote:<br>
>> > Hi all,<br>
>> ><br>
>> > I am trying to overlay an dose shade on a CT slice.I am using<br>
>> > vtkDICOMImageReader to read the CT and vtkGDCMImageReader to display the<br>
>> > dose shade.But I am having problem with the coordinates.How to relate<br>
>> > the<br>
>> > coordinates? For e.g: I get ImagePositionPatient of CT image for<br>
>> > central<br>
>> > slice as [-275,-524,-128.25] and ImagePositionPatient for dose as<br>
>> > [-228.65,-419.25,-122.5] adn their spacings are [1.074,1.074,3] and<br>
>> > [2.52.5.2.5] respectively for CT and Rt dose.<br>
>> ><br>
>> > The image looks as in the attached figure.<br>
>> ><br>
>> > Any hint<br>
>> ><br>
>> > Thanks<br>
>> ><br>
>> > Jothy<br>
>> ><br>
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</blockquote></div><br></div>