Insight Toolkit (ITK) -- Official Repository. ITK builds on a proven, spatially-oriented architecture for processing, segmentation, and registration of scientific images in two, three, or more dimensions.
My general preference would be to have the core reader code only handle completely standard dicom so that it is readable and maintainable. Any special code to handle malformed or vendor specific data should be detected and handled in dedicated classes, ideally with diagnostic info available so users know they have odd data and can report the issues to whoever created it.
As suggested by @pieper in https://github.com/InsightSoftwareConsortium/ITK/pull/4134#issuecomment-1691734111