Existing radiation treatments for prostate cancer can damage healthy tissue. Calypso, a medical start-up, had a revolutionary idea. By injecting a transponder into cancerous tissue, radiation could be better targeted at the tumor, sparing healthy tissue. However, Calypso’s innovative technology needed to be packaged into a product and a procedure that oncologists would accept as a viable alternative to existing methods. An iterative approach of field research, scenario creation, prototyping and user testing defined an interaction strategy and a product concept that delivered the right balance of efficiency and accuracy.