Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

Abstract

Abstract-Magnetic induction spectroscopy (MIS) aims at the contactless measurement of the passive electrical properties (PEP), , and of biological tissues via magnetic fields at multiple frequencies. Whereas previous publications focus on either the conductive or the magnetic aspect of inductive measurements, this article provides a synthesis of both concepts by discussing two different applications with the same measurement system: 1) monitoring of brain edema and 2) the estimation of hepatic iron stores in certain pathologies. We derived the equations to estimate the sensitivity of MIS as a function of the PEP of biological objects. The system requirements and possible systematic errors are analyzed for a MIS-channel using a planar gradiometer (PGRAD) as detector. We studied 4 important error sources: 1) moving conductors near the PGRAD; 2) thermal drifts of the PGRAD-parameters; 3) lateral displacements of the PGRAD; and 4) phase drifts in the receiver. All errors were compared with the desirable resolution. All errors affect the detected imaginary part (mainly related to ) of the measured complex field much less than the real part (mainly related to and ). Hence, the presented technique renders possible the resolution of (patho-) physiological changes of the electrical conductivity when applying highly resolving hardware and elaborate signal processing. Changes of the magnetic permeability and permittivity in biological tissues are more complicated to deal with and may require chopping techniques, e.g., periodic movement of the object.Index Terms-Brain edema, impedance spectroscopy, iron overload, magnetic induction tomograpy, passive electrical properties of tissue.

3D model simulation on magnetic induction spectroscopy for fetal acidosis detection using COMSOL multiphysics

“…MIS requires an alternating magnetic excitation field to make the measurement of radiation intensity from the excitation coil to the biological soft tissue under investigation. Whereas, the changing in the complex conductivity will make a change in the relative magnetic permeability in the output, caused by the perturbation due to the radiation intensity coupled from the interaction between matter and radiated energy as a function of wavelength in the object under investigation [12], [14], [29].…”

“…Magnetic induction spectroscopy setup [14] This simulation focusing on magnetic field and current density that received at the receiver coil. The main purpose of the simulation is to prove the ability of MIS setup to detect acidosis in fetal blood and to test which types of coil is better for single channel MIS for biological tissue.…”

Use of Magnetic Induction Spectroscopy in the Characterization of the Impedance of the Material with Biological Characteristics

“…Because L1 and L2 have very similar characteristics, and considering the expression [9] may approximate the magnetic field concentric loops through both coils (see Figure 8a), B1 is the magnetic field of the first ring, the flow magnetic Φ2 through second ring we can determine from B1.…”

Reduction of low-frequency noise in magnetic induction tomography systems

“…The imaginary signal s s is the projection of s' to the axis Im LO and does not reflect correctly the magnitude of the true signal s. Hence mechanical vibrations can heavily deteriorate the SNR of the measured imaginary signal [7]. Also other errors which affect mainly the true real part (moving metallic parts, thermal drifts of the RXC [5]) project into Im LO . …”

“…20 MHz, [2], 10 MHz [1,4]. However, measurements in the β-dispersion range below 1 MHz are desirable because many pathological processes are reflected there [5]. Due to the poor SNR, however, this represents a real challenge.…”