Improvements for use with tissue expanders are provided. A tissue expander includes: a selectively inflatable and deflatable shell that is configured to be implanted； and an access port for selectively inflating and deflating the shell, the access port comprising a sidewall, a base at a first end, and a membrane at a second end opposite the first end wherein the sidewall and the base of the access port are constructed of a material that is non-reactive with a magnetic resonance imaging (MRI) machine； and a structure of the access port is composed of a material that has a rate of temperature change lower than that of human tissue.
