Ok, I've seen this kind of thing before, but it doesn't make a whole lot of sense. The notes convert a bit over $32 a share and the warrants are for purchase over $37 a share. And since both are issued pursuant to a shelf registration, the dilution ought to have been allowed for already. And a decent chunk of proceeds will go to retire a higher-interest (and also convertible, at a lower price) bond issue.
We know that Volcano internally has a lot of exposure to OCT (partly acquired with Cardio Spectra), but ongoing litigation has caused them to be pretty quiet in public for the last two years.