Magnetic induction tomography: Hardware for multi-frequency measurements in biological tissues

Hermann Scharfetter*, Helmut K. Lackner, Javier Rosell

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Magnetic induction tomography (MIT) is a contactless method for mapping the electrical conductivity of tissue. MIT is based on the perturbation of an alternating magnetic field by a conducting object. The perturbation is detected by a voltage change in a receiver coil. At physiologically interesting frequencies (10 kHz-10 MHz) and conductivities (<2 S m-1) the lower limit for the relative voltage change (signal/carrier ratio = SCR) to be resolved is 10-7-10-10. A new MIT hardware has been developed consisting of a coil system with planar gradiometers and a high-resolution phase detector (PD). The gradiometer together with the PD resolves an SCR of 2.5 × 10-5 (SNR = 20 dB at 150 kHz, acquisition speed: 100 ms). The system operates between 20 and 370 kHz with the possibility of extending the range up to 1 MHz. The feasibility of measuring conductivity spectra in the β-dispersion range of biological tissues is experimentally demonstrated. An improvement of the resolution towards SCR = 10-7 with an SNR of ≥20 dB at frequencies > 100 kHz is possible. On-line spectroscopy of tissue conductivity with low spatial resolution appears feasible, thus enabling applications such as non-invasive monitoring of brain oedema.

Original languageEnglish
Pages (from-to)131-146
Number of pages16
JournalPhysiological measurement
Volume22
Issue number1
DOIs
Publication statusPublished - 14 Mar 2001

Keywords

  • Brain oedema
  • Magnetic induction tomography
  • Multi-frequency
  • Planar gradiometer
  • Tissue conductivity

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Biomedical Engineering
  • Physiology (medical)

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