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Wireless Communication with Medical Implants: Antennas and Propagation

Johansson, Anders J LU (2004)
Abstract (Swedish)
Popular Abstract in Swedish

Teknikutvecklingen leder till att vi får allt mer avancerade elektroniska medicinska implantat. Dessa spänner idag från den välkända hjärtpacemakern till avancerade hörselimplantat, hjärnstimulatorer och implanterbara medicinpumpar. Med de allt mer avancerade implantaten har också deras behov av att ta emot styrsignaler från utsidan av kroppen, och deras förmåga att sända ut mätdata inifrån kroppen, ökat. Idag sker denna kommunikation med hjälp av en induktiv länk via spolar, som har nackdelar i att de har väldigt kort räckvidd och att datahastigheten är låg. Ett frekvensband har därför avdelats för medicinska implantat vid 400 MHz, under namnet MICS, Medical Implant Communication... (More)
Popular Abstract in Swedish

Teknikutvecklingen leder till att vi får allt mer avancerade elektroniska medicinska implantat. Dessa spänner idag från den välkända hjärtpacemakern till avancerade hörselimplantat, hjärnstimulatorer och implanterbara medicinpumpar. Med de allt mer avancerade implantaten har också deras behov av att ta emot styrsignaler från utsidan av kroppen, och deras förmåga att sända ut mätdata inifrån kroppen, ökat. Idag sker denna kommunikation med hjälp av en induktiv länk via spolar, som har nackdelar i att de har väldigt kort räckvidd och att datahastigheten är låg. Ett frekvensband har därför avdelats för medicinska implantat vid 400 MHz, under namnet MICS, Medical Implant Communication Systems.



Vi har tittat på det som är nytt när ett sådant system skall implementeras. Dels hur man på bästa sätt skall konstruera antenner som skall sitta inuti människan, dels hur radiovågorna utbreder sig i människokroppen och i rummet utanför. Antennkonstruktionen påverkas av de stora förlusterna i kroppens vävnader och av kravet på att antennen skall vara liten så den får plats på implantatet. Vi har undersökt nödvändig tjocklek på isoleringen runt antennen och kontrollerat att gränsvärden för uppvärmning av vävnaden (SAR) inte överskrids. Vågutbredningen i kroppen visar sig bero på kroppens storlek och form och på kroppsställningen. Systemet är främst tänkt att användas inomhus. Eftersom våglängden är relativt lång, 74 cm, kommer all kommunikation att ske inom det så kallade närfältet. Denna vågutbredning skiljer sig från den klassiska, och vi har därför undersökt den både genom simuleringar och mätningar. Datorutvecklingen har lett till att vi idag exakt kan simulera hur det elektromagnetiska fältet utbreder sig i ett möblerat rum vid dessa frekvenser. Vi har sedan använt resultaten från våra undersökningar för att verifiera att MICS systemet skall gå att implementera. Från undersökningarna kan man också dra slutsater om nödvändig komplexitet hos basstationen som skall komunicera med implantatet. (Less)
Abstract
With the increased sophistication of medical implants, there is a growing need for flexible high-speed communication with the implant from outside the body. Today the communication is done by an inductive link between the implant and an external coil at a low carrier frequency. Extended range and communication speed are possible to achieve by increasing the carrier frequency and the bandwidth. One frequency band that is available for this application is the newly standardized 400 MHz MICS band, which has the benefit of being reserved mainly for medical and metrological applications. In addition, the 2.45 GHz ISM band is a possibility, but has the drawback of being heavily used by other applications, such as wireless computer networks and... (More)
With the increased sophistication of medical implants, there is a growing need for flexible high-speed communication with the implant from outside the body. Today the communication is done by an inductive link between the implant and an external coil at a low carrier frequency. Extended range and communication speed are possible to achieve by increasing the carrier frequency and the bandwidth. One frequency band that is available for this application is the newly standardized 400 MHz MICS band, which has the benefit of being reserved mainly for medical and metrological applications. In addition, the 2.45 GHz ISM band is a possibility, but has the drawback of being heavily used by other applications, such as wireless computer networks and microwave ovens. In order to assess the usability of wireless communication with medical implants, we have investigated the design of implantable antennas to be used in the body. Both theoretical limits and practical designs of the antennas are described. The SAR levels of the implanted antennas have been calculated and have been found to be at a safe level. We have investigated the wave-propagation from the implanted antenna to the outside, and its dependence on the position of the patient’s limbs and the size of the body. Full wave 3D-simulations of the wave propagation are feasible, as the radio link between the patient and a base station placed in the same room is very short in terms of wavelengths in the MICS band. We have simulated the wave propagation in a furnished room and compared the results with measurements of the same room. The results from these investigations are evaluated in terms of their impact on the link budget for a prototype MICS system. From these calculations conclusions on the necessary complexity of the transceivers are drawn, such as the need for both spatial and polarization diversity to fully exploit the potential of the communication link. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr. Scanlon, William G, School of Electrical & Electronic Engineering, Queen’s University, Belfast
organization
publishing date
type
Thesis
publication status
published
subject
keywords
medical implant communication, electromagnetic propagation, biomedical telemetry, antennas in matter, MICS, Electronics, Elektronik
pages
173 pages
publisher
Department of Electroscience, Lund University
defense location
Lokal E:1406. E-Huset, LTH
defense date
2004-09-19 10:15
ISSN
1402-8662
language
English
LU publication?
yes
id
3cffe66f-f586-45e9-829c-a1bbf1607dc2 (old id 21891)
date added to LUP
2007-05-28 14:55:43
date last changed
2016-09-19 08:44:56
@phdthesis{3cffe66f-f586-45e9-829c-a1bbf1607dc2,
  abstract     = {With the increased sophistication of medical implants, there is a growing need for flexible high-speed communication with the implant from outside the body. Today the communication is done by an inductive link between the implant and an external coil at a low carrier frequency. Extended range and communication speed are possible to achieve by increasing the carrier frequency and the bandwidth. One frequency band that is available for this application is the newly standardized 400 MHz MICS band, which has the benefit of being reserved mainly for medical and metrological applications. In addition, the 2.45 GHz ISM band is a possibility, but has the drawback of being heavily used by other applications, such as wireless computer networks and microwave ovens. In order to assess the usability of wireless communication with medical implants, we have investigated the design of implantable antennas to be used in the body. Both theoretical limits and practical designs of the antennas are described. The SAR levels of the implanted antennas have been calculated and have been found to be at a safe level. We have investigated the wave-propagation from the implanted antenna to the outside, and its dependence on the position of the patient’s limbs and the size of the body. Full wave 3D-simulations of the wave propagation are feasible, as the radio link between the patient and a base station placed in the same room is very short in terms of wavelengths in the MICS band. We have simulated the wave propagation in a furnished room and compared the results with measurements of the same room. The results from these investigations are evaluated in terms of their impact on the link budget for a prototype MICS system. From these calculations conclusions on the necessary complexity of the transceivers are drawn, such as the need for both spatial and polarization diversity to fully exploit the potential of the communication link.},
  author       = {Johansson, Anders J},
  issn         = {1402-8662},
  keyword      = {medical implant communication,electromagnetic propagation,biomedical telemetry,antennas in matter,MICS,Electronics,Elektronik},
  language     = {eng},
  pages        = {173},
  publisher    = {Department of Electroscience, Lund University},
  school       = {Lund University},
  title        = {Wireless Communication with Medical Implants: Antennas and Propagation},
  year         = {2004},
}