dolphin and dicom files on nfs mounts

Hi *, using dolphin I'd like to open dicom files from a locally mounted nfs share, but instead of opening the appropriate app (i.e. xmedcon), dolphin presents the "Choose Application" dialog. When opening the properties dialog of such a dicom file, it shows an unknown type, but dicom image as "content". Trying the same on a local filesystem, xmedcon is started directly, and the properties dialog shows DICOM image as "type" and "open with" xmedcon. With thunar for example the behaviour is the same for local or nfs filesystems. In both cases xmedcon is started on double clicking such a file. Any idea, what configuration for dolphin/plasma I am missing here? System is Tumbleweed with the latest snapshot. TIA. Bye. Michael.