Galois structure of K-groups of rings of integers

Let N/K be a Galois extension of number fields with finite Galois group G. We describe a new approach for constructing invariants of the G-module structure of the K-groups of the ring of integers of N in the Grothendieck group of finitely generated projective Z[G]-modules. In various cases we can relate these classes, and their function field counterparts, to the root number class of Frohlich and Cassou-Nogues.