（fo-dicom）如何修改DICOM文件并将其保存到新目录？

Question

I want to modify the header of a DICOM and set two tags. This works but then when I want to save it in a new file I get this Exception:

NullReferenceException: Object reference not set to an instance of an object
Dicom.Network.NetworkManager.get_MachineName ()
Dicom.DicomFileMetaInformation.CreateSourceApplicationEntityTitle ()
Dicom.DicomFileMetaInformation..ctor (Dicom.DicomFileMetaInformation metaInfo)
Dicom.DicomFile.PreprocessFileMetaInformation ()
Dicom.DicomFile.Save (System.String fileName,   
Dicom.IO.Writer.DicomWriteOptions options)
DICOMConverter.addMaxMin () (at Assets/Scripts/DICOMConverter.cs:67)

My code of DICOMConverter.addMaxMin() is:

 var dicomFile = DicomFile.Open(DICOMFilePath);
 var dicomImage = new DicomImage(dicomFile.Dataset);
 var header = DicomPixelData.Create(dicomImage.Dataset);

 var pixelData = PixelDataFactory.Create(header, 0);

 for (int x = 0; x < Convert.ToInt32(dicomFile.Dataset.Get<string>(DicomTag.Columns)); x++)
 {
    for (int y = 0; y < Convert.ToInt32(dicomFile.Dataset.Get<string>(DicomTag.Rows)); y++)
    {
         if (pixelData.GetPixel(x, y) < minValue)
                    minValue = pixelData.GetPixel(x, y);
         if (pixelData.GetPixel(x, y) > maxValue)
                    maxValue = pixelData.GetPixel(x, y);
     }
  }

  dicomFile.Dataset.AddOrUpdate(DicomTag.LargestImagePixelValue, Convert.ToString(maxValue));
  dicomFile.Dataset.AddOrUpdate(DicomTag.SmallestImagePixelValue, Convert.ToString(minValue));

  dicomFile.Save(@"newDicom"); 

It throws the exception always when I try to use the Save() Method.
I used for this the file operation example from https://github.com/fo-dicom/fo-dicom , but it doesn't work properly.

Has someone an idea for a better save solution or can me explain what I am missing?

Answer 1

This exception happens, because for some reason your application has no platform specific implementation of NetworkManager set up correctly. This happens in the static constructor of NetworkManager class. But you can set it manually any time by NetworkManager.SetImplementation(..). Without any further information it is hard to say why there is no instance initialized, but there will be an other solution in next release of fo-dicom:

When writing the file to disk, fo-dicom sets the SourceApplicationEntityTile (0002,0016) and therefore tries to access the NetworkManager.LocalMachineName. This pull request wants to reuse the SourceApplicationEntityTitle if the file was not created newly but cloned from an other file and therefore already has a SourceApplicationEntityTitle. This would solve your problem. Take a closer look at https://github.com/fo-dicom/fo-dicom/pull/615