[vtkusers] vtkImageResliceMapper, vtkImageReslice and pixel intensity

[Kenji Tsumura]

Hi David,

Thank you for the advice.
I remember I tried to use vtkImageReslice, but I found it easier to use vtkImageResliceMapper, as all I have to do is to set camera information.

As for pixel intensity, it seems I messed up reading DICOM.

Thank you, again.

Kenji

From: David Gobbi [mailto:david.gobbi at gmail.com]
Sent: Friday, April 08, 2016 1:30 PM
To: Kenji Tsumura
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] vtkImageResliceMapper, vtkImageReslice and pixel intensity

Hi Kenji,

I advise against getting the vtkImageReslice object from the vtkImageResliceMapper.  This object is meant to be for the mapper's own private use, and it most certainly will not always behave in the manner that you expect.  Depending on the code path taken by vtkImageResliceMapper, the reslice object's spacing and the range of its output will change in tricky ways that are not documented and that might change from one version of VTK to the next.

I'm sure that this isn't the answer you wanted, but if you want to reslice the image, then create a separate vtkImageReslice object outside of vtkImageResliceMapper.

 - David



On Fri, Apr 8, 2016 at 12:08 PM, Kenji Tsumura <kenji.tsumura at neosoftmedical.com<mailto:kenji.tsumura at neosoftmedical.com>> wrote:
Hi,

I have 3D MRI dataset and I resliced the data using vtkImageResliceMapper.
I find it difficult to figure out why the pixel intensity of resliced images is so different from the original.
In the attached file, the resliced image (image on the left) shows the mean value of 21935.5, and the original image (image on the right) shows the mean value of 1447.5.

The following is the excerpt of my java source code.
vtkExtendedImageResliceMapper  extends vtkImageResliceMapper just to return  ImageReslice, as there is no such public method.

---- initialization
        vtkExtendedImageResliceMapper  planeMapper = new vtkExtendedImageResliceMapper();
        planeMapper.SetInputData(imageData);
        planeMapper.SliceFacesCameraOn();
        planeMapper.SliceAtFocalPointOn();
        planeMapper.BorderOff();
        planeMapper.SetSlabTypeToMean();

---- after reslice
        // Get the image re-slice
        vtkImageReslice imageReslice = planeMapper.GetImageReslice();

        // Get the image data
        vtkImageData reslicedImageData = imageReslice.GetOutput();

        // Get the data array
        vtkDataArray dataArray = reslicedImageData.GetPointData().GetScalars();

        // Get the data
        float[] image = null;
        if (dataArray instanceof vtkFloatArray) {
            vtkFloatArray floatArray = (vtkFloatArray) dataArray;
            image = floatArray.GetJavaArray();
        }

My environtment:
VTK 7.0.0
CMake 3.1.1
Visual Studio Professional 2013
Eclipse Luna 4.4.1 (for my java application)

I would appreciate any advice.
Thank you,

Kenji

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