A wireless medical system prototype for implantable applications

This paper presents a wireless medical system (WMS) for continuous monitoring of biological parameters with special emphasis on the implantable unit prototype. The proposed WMS consists of three subsystems: implantable medical device (IMD), base station (BS) and graphical user interface (GUI). The IMD and BS communicate through an RF link that operates in both the industrial, scientific and medical (ISM, at 2.4GHz-2.48 GHz) and the medical implantable communication service (MICS, at 402MHz-405MHz) bands. The IMD and BS are based on two commercially-available ultra-low power integrated circuits. The main design issues and implementation challenges are discussed. Details on the analog front-end, a low-power-oriented-algorithm, an analysis of power consumption vs. lifetime and link budget considerations for implantable applications are presented. In vitro measurements of the WMS show successful communication up to 2.1m. The IMD average current consumption is 0.572mA (including RF transmission) in continuous operation. This allows a two year IMD lifetime in periodic operation, delivering one hour of information per day.