The invention relates to a further medical use of a polyglycerol derivative, namely to a use for diagnosing a disease at an early stage of the disease by site-specific imaging of angiogenesis, of extracellular matrix remodeling and/or of activated lymph nodes in a human or an animal, wherein the early stage of the disease is characterized by the absence of obvious clinical symptoms due to the disease. Thereby, the polyglycerol derivative comprises a dendritic polyglycerol backbone comprising a plurality of hydroxyl groups that are optionally at least partly substituted by sulfate groups and a diagnostic effector residue.
