Unable to read DRTImage

[nbeck]

Hello,

I tried to read an RT image using DRTImage::read(DcmItem *dataset). However, this fails even though I am fairly confident that the data is valid.

Looking at the code, I noticed that DRTImage::read() appears to call DRTImageIOD::read() with the argument *format_.getDataset() although format_ hasn't been set.

Code: Select all

OFCondition DRTImage::read(DcmItem *dataset)
{
    /* get rid of the old image before we mess with its dataset */
    reset();

    dataset_ = dataset;
    OFCondition cond = DRTImageIOD::read(*format_.getDataset());
    if (cond.good())
    {
        image_ = new DicomImage(&format_,
                EXS_Unknown, CIF_MayDetachPixelData);
    }
    else
        clear();
    return cond;
}

So I changed the argument to *dataset. But reading still fails with the error "W: SOPClassUID (0008,0016) absent in SOPCommonModule (type 1)" .

Stepping through the code in the debuger I noticed that DRTImage::read first sets the member dataset_ to dataset before calling DRTImageIOD::read, which in turn calls clear(). This method is overriden in DRTImage

Code: Select all

void DRTImage::clear()
{
    reset();
    DRTImageIOD::clear();
}

finally, reset() deletes the dataset:

Code: Select all

void DRTImage::reset()
{
    delete image_;
    delete dataset_;
    format_.clear();
    image_ = NULL;
    dataset_ = NULL;
}

Therefore, the subsequent call to checkDatasetForReading fails.

I suggest to move the assignemt of dataset_ after the call to read, i.e.

Code: Select all

OFCondition DRTImage::read(DcmItem *dataset)
{
    /* get rid of the old image before we mess with its dataset */
    reset();

    //dataset_ = dataset;
    OFCondition cond = DRTImageIOD::read(*dataset);
    if (cond.good())
    {
        dataset_ = dataset;
        image_ = new DicomImage(dataset,
                EXS_Unknown, CIF_MayDetachPixelData);
    }
    else
        clear();
    return cond;
}

Let me know what you think about this.

[J. Riesmeier]

Thank you for your report and detailed analysis. It seems that no one ever used this method before - including the author of this class

The version I would propose is the following:

Code: Select all

OFCondition DRTImage::read(DcmItem *dataset)
{
    /* get rid of the old image before we mess with its dataset */
    reset();

    if (dataset == NULL)
        return EC_IllegalCall;

    OFCondition cond = DRTImageIOD::read(*dataset);
    if (cond.good())
    {
        dataset_ = dataset;
        image_ = new DicomImage(dataset_, EXS_Unknown, CIF_MayDetachPixelData);
    }
    else
        clear();
    return cond;
}

Of course, error handling could be further improved, e.g. by checking the return value of "image_->getStatus()", but at least the above version should do what it is supposed to do.

[nbeck]

Yes, that looks good to me. Checking for NULL is definitely a good idea.

Thank you for your report and detailed analysis. It seems that no one ever used this method before - including the author of this class

I was also surprised that nobody had found this issue until now. Probably everyone else just loads data from a file.

We probably aren't going to use this class in our software, but I wanted to report it anyway.

[J. Riesmeier]

Thank you for the feedback. I've just committed the required changes to the internal "testing" branch of the DCMTK. The changes should be visible in the public git repository soon.