Development of a small wireless position sensor for medical capsule devices

T. Nagaoka*, A. Uchiyama

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


Medical capsule devices such as video capsule endoscopes are finding increasing use in clinical applications. At present, technologies capable of measuring capsule position in the digestive tract have not yet been established. The present study aims to develop a small wireless position sensor capable of measuring capsule position based on the phenomenon of mutual induction. Currents into primary coils are adjusted to maintain electromotive force induced in secondary coils at a constant level. Electromotive forces induced in the secondary coils are modulated to FM signals using an astable multivibrator, and the signals are passed directly through living tissue at low current and then demodulated by detectors on the surface of the body. A prototype wireless sensor was developed and evaluated in vitro. The sensor was capable of accurately measuring capsule position up to 500 (mm) from the primary coils with an accuracy of 5 (mm). Miniaturization of the sensor is necessary for commercialization.

Original languageEnglish
Pages (from-to)2137-2140
Number of pages4
JournalUnknown Journal
Volume26 III
Publication statusPublished - 2004


  • Biomedical telemetry
  • Digestive system
  • Position measurement

ASJC Scopus subject areas

  • Bioengineering


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