How to read DICOM string value with backslash (VR=LO, Value=“0.4323\0.2325”)?

Question

Our C++ software use ITK to write DICOM files. In it we have a Private Tag with LO (Long String) as VR and 2 decimal values as value like 0.3234\0.34223.

The LO choice is inherent to ITK.

In other java application, I use dcm4che3 to read/write them. Since it respects the DICOM protocol, backslash are forbidden, and dcm4che interpret the value as "0.3234" and never reach the second value.

All DICOM viewer applications I use can display this value.

So my question is: Is there a trick in dcm4che to read this complete value as a string "0.3234\0.34223" despite the presence of a backslash?

Below, the code I use:

     public DicomInfo uploadFile(MultipartFile file) throws IOException, ParseException {

       DicomInfo infos = new DicomInfo();

       Attributes attrs = readDicomAttributes(file);
       infos.setTags(toAttributesObject(attrs).toString());
    }

    private static JsonObject toAttributesObject(Attributes targetSeriesAttrs) 
    {
       StringWriter strWriter = new StringWriter();
       JsonGenerator gen = Json.createGenerator(strWriter);
       JSONWriter writer = new JSONWriter(gen);
       writer.write(targetSeriesAttrs);
       gen.flush();
       gen.close();
       return Json.createReader(new 
          StringReader(strWriter.toString())).readObject();
  }
  
  public Attributes readDicomAttributes(MultipartFile file) throws IOException 
  {
    DicomInputStream dis = new DicomInputStream(file.getInputStream());
    Attributes dataSet = dis.readDataset(-1, Tag.PixelData);
    Attributes fmi = dis.readFileMetaInformation();
    dis.close();

    fmi.addAll(dataSet);

    return fmi;
  }

In the JSON I get for this tag:

\"00110013\":{\"vr\":\"LO\",\"Value\":[\"0.4323\"]},

As you can see it is LO and the second part is already lost.

The method I use to get the specific attribute:

attr.getStrings(0x00110013)

send back a table with only one value, 0.4323.

The problem happens during the readDataSet function.

When I open tags with software like free dicom viewer, I have the complete data, so data is here.

Ok I found the source of the problem... It is the addAll fmi.addAll(dataSet);

In dataSet, getStrings works perfectly. In fmi after addAll, the attributes lost the second value.

So my problem is to solve this addAll issue now: dcm4che3 java lib: Attributes.addAll method seems to lost multiple LO values

Backslash is not forbidden, I guess that you somehow have to tell dcm4che that your private attribute has a value multiplicity of 2. I do not know how to do this exactly, but usually this configuration is referred to as "private dictionary" — kritzel_sw
in LO backslash should not be used, cf documentation, so even getStringS doesn't work. And I can't modify the VR. — MilacH
I think the only solution is to forget dcm4che and use ITK impl in java ... — MilacH
I haven't used dcm4che, but a quick look at the sources shows that StringValueType.getStrings() does the right thing, e.g. splits the tag content by the '\' delimiter and returns the strings. Can you show the code you use to read the tag contents? — MrBean Bremen

MilacH MilacH · Accepted Answer · 2020-08-05T16:29:06

The solution of this problem is to write

dataSet.addAll(fmi);
return dataSet;

instead of

fmi.AddAll(dataSet);
return fmi;

since the addAll methods lost multiple values of private LO

How to read DICOM string value with backslash (VR=LO, Value=“0.4323\0.2325”)?

3 Answers