Implantable pressure indicator

An implantable pressure measurement device is effective to measure a physiological pressure, which pressure can be ascertained by external imaging of the device. In one embodiment, a predetermined amount of a fluid is sealed in a flexible member (26) which is disposed in a housing (14). A position indicating member (36) is coupled to one end of the flexible member. The fluid expands and contracts the flexible member in response to external pressure changes. A physiological pressure is determined by ascertaining the relative location of the position indicating member on the housing. An external imaging system is used to view scale markings located on the position indicating member and the housing. In another embodiment, an elongate member (108) is axially movable within a housing. A sealing member (104) seals an amount of air in a portion of the housing (102a) and is sealably engaged with one end of the elongate member. A physiological pressure is determined using an imaging system to determine the position of the elongate member.