| abstract |
A system for enabling the acquisition from outside the body of a patient (10) of data pertaining to a medical device (14) implanted therein. A characterization tag (90) is secured to the medical device (14) prior to the implantation thereof. The characterization tag (90) is powered by energy absorbed through the mutual inductive coupling of circuitry (398) in the characterization tag (90) with an alternating magnetic field (204) generated outside the body of the patient (10). That circuitry (398) in the characterization tag (90) is selectively loaded and unloaded in a predetermined sequence of loading conditions that correspond to data about the implanted medical device (14). The alternating magnetic field (204) is generated in a characterization probe (60) moveable external to the body of the patient (10). The characterization probe (60) includes electrical circuitry (420) for sensing variations in the amount of energy absorbed from the field (204) by the circuitry (398) in the characterization tag (90). The characterization tag (90) is secured in a characterization tag recess (106) on the exterior of the medical device (14) by a biocompatible potting material (104). If the medical device is assembled from a plurality of constituent parts, the characterization tag (90) may be permanently captured between a pair of those parts. Two single fluid reservoir access ports (14,230), a double fluid reservoir access port (280), a septum-free access port (320), and a prosthetic hip joint (370) are disclosed as examples of devices with which the system may be employed. |