Intravascular diagnosis apparatus and methods are disclosed. In one aspect of the disclosed technology, a monitoring guidewire includes a core wire having or made of one or more of MP35N, L605, Elgiloy, and an alloy of nickel, cobalt, molybdenum and chromium, a sensor disposed in a distal region of the core wire, and a housing substantially coextensive with the core wire and surrounding the core wire, the housing being more flexible than the core wire for at least the distal portion of the housing.
