Thanks Juan. I think Martin is right, the discarding of gradients happens before the QC process.

Hi Martin. At first I did the DICOM conversion with DTIPrep but I have now repeated it with Slicer. Unfortunately it results in the same error message.
ERROR: VectorImage(0x3c20f50): A spacing of 0 is not allowed: Spacing is [0, 0, 3]

Is it possible that our DICOM files are not compatible with the DWIconverter module?
Susanne