Int Neurourol J.  2017 Apr;21(Suppl 1):S32-S38. 10.5213/inj.1734878.439.

Realistic Electric Field Mapping of Anisotropic Muscle During Electrical Stimulation Using a Combination of Water Diffusion Tensor and Electrical Conductivity

• Choi BK
• Oh TI
• Sajib SZ
• Kim JW
• Kim HJ
• Kwon OI
• Woo EJ

• KMID: 2378436
• DOI: http://doi.org/10.5213/inj.1734878.439

Abstract

PURPOSE
To realistically map the electric fields of biological tissues using a diffusion tensor magnetic resonance electrical impedance tomography (DT-MREIT) method to estimate tissue response during electrical stimulation.
METHODS
Imaging experiments were performed using chunks of bovine muscle. Two silver wire electrodes were positioned inside the muscle tissue for electrical stimulation. Electric pulses were applied with a 100-V amplitude and 100-μs width using a voltage stimulator. During electrical stimulation, we collected DT-MREIT data from a 3T magnetic resonance imaging scanner. We adopted the projected current density method to calculate the electric field. Based on the relation between the water diffusion tensor and the conductivity tensor, we computed the position-dependent scale factor using the measured magnetic flux density data. Then, a final conductivity tensor map was reconstructed using the multiplication of the water diffusion tensor and the scale factor.
RESULTS
The current density images from DT-MREIT data represent the internal current flows that exist not only in the electrodes but also in surrounding regions. The reconstructed electric filed map from our anisotropic conductivity tensor with the projected current density shows coverage that is more than 2 times as wide, and higher signals in both the electrodes and surrounding tissues, than the previous isotropic method owing to the consideration of tissue anisotropy.
CONCLUSIONS
An electric field map obtained by an anisotropic reconstruction method showed different patterns from the results of the previous isotropic reconstruction method. Since accurate electric field mapping is important to correctly estimate the coverage of the electrical treatment, future studies should include more rigorous validations of the new method through in vivo and in situ experiments.

Keyword

Electric Field; Electrical Stimulation; Anisotropy; Magnetic Resonance Electrical Impedance Tomography; Diffusion Tensor Imaging

MeSH Terms

Anisotropy
Diffusion Tensor Imaging
Diffusion*
Electric Conductivity*
Electric Impedance
Electric Stimulation*
Electrodes
Magnetic Resonance Imaging
Methods
Silver
Water*
Silver
Water