Medical Implant Communication Service

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Medical Implant Communication Service (MICS) is the name of the specification for the use of a frequency band from 401 to 406 MHz (depending on the region only 402 to 405 MHz) for radio communication with medical implants . It allows bidirectional communication with e.g. B. Pacemakers . The MICS band is divided into 25 kHz channels, with an implant taking up to 300 kHz. Data rates of up to 800 kbit / s are then possible. The transmission power is very low at 25 µW EIRP (−16 dBm) in order to avoid interference.

Difference to conventional methods

Conventional methods for parameterizing active implants are often based on load modulation at low frequencies (e.g. Medtronic systems communicate at 175 kHz), whereby an external transmitter coil must be brought very close to the patient. This is associated with sterility problems, particularly with initial settings during the implantation operation. In contrast, communication via the MICS band allows a distance of 2 m and more for the implanted system; During the operation in the not yet implanted state, this distance is significantly greater, as there is no tissue attenuation (10 dB and more).

Antenna sizes

Assuming a simple wire antenna, based on the center frequency of 403.5 MHz, λ / 4 = 186 mm. However, human tissue has a relative dielectric permittivity of 50 to 60, so that the antenna can be significantly smaller. However, it depends on how thick the insulation surrounding the antenna is (e.g. through silicone encapsulation). A rectangular spiral antenna with 4-5 turns has z. B. External dimensions of 7mm x 14mm. In pacemakers, the antenna is often cast in the header. B. recognize it as a meandering structure.

realization

The implementation of an RF transceiver can either be done within the scope of in-house ASIC development, use of existing commercial ICs (the declaration as an implant-compatible solution is incumbent on the medical device manufacturer), or through solutions developed explicitly for medical implants. Due to the narrow frequency bands, only appropriate telemetry crystals with a very narrow tolerance of 10 ppm can be used as clock generators or reference clocks. Microsemi is the only manufacturer of a commercially available module (currently ZL70323) that is explicitly declared as "implant-grade".

Standards

  • FCC Rules and Regulations, “MICS Band Plan,” Part 95, Jan. 2003.
  • 47 CFR 95.601-95.673 Subpart E, Federal Communications Commission, 1999.
  • ETSI EN 301 839-1 "Electromagnetic compatibility and Radio spectrum Matters (ERM); Radio equipment in the frequency range 402 MHz to 405 MHz for Ultra Low Power Active Medical Implants and Accessories; Part 1: Technical characteristics, including electromagnetic compatibility requirements, and test methods. ", European Telecommunications Standards Institute, 2002.

Individual evidence

  1. ↑ Patent US005861019A
  2. ↑ X. Qing, ZN Chen, TSP See, CK Goh, TM Chiam: RF Transmission Characteristics in / Through the Human Body , 2010 IEEE Conf. on Cybernetics and Intelligent Systems, ISBN 978-1-4244-6502-6 , 2010.
  3. ^ AJ Johansson: Performance measures of implant antennas , Proc. EuCAP 2006, Nice, France, doi: 10.1109 / EUCAP.2006.4584861 , 2006.
  4. ↑ V. Shirvante, F. Todenschini, X. cheng, Y.-K. Yoon: Compact Spiral Antennas for MICS band Wireless Endoscope toward Pediatric Applications , Antennas and Propagation Society International Symposium (APSURSI), doi: 10.1109 / APS.2010.5561085 , 2010.
  5. ↑ http://www.microsemi.com/products/ultra-low-power-wireless/implantable-medical-transceivers/zl70323