Three-dimensional multiexcitation magnetoacoustic tomography with magnetic induction

Abstract

Magnetoacoustic tomography with magnetic induction ͑MAT-MI͒ is a hybrid imaging modality proposed to image electrical conductivity contrast of biological tissue with high spatial resolution. This modality combines magnetic excitations with ultrasound detection through the Lorentz force based coupling mechanism. However, previous studies have shown that MAT-MI method with single type of magnetic excitation can only reconstruct the conductivity boundaries of a sample. In order to achieve more complete conductivity contrast reconstruction, we proposed a multiexcitation MAT-MI approach. In this approach, multiple magnetic excitations using different coil configurations are applied to the object sequentially and ultrasonic signals corresponding to each excitation are collected for conductivity image reconstruction. In this study, we validate the new multiexcitation MAT-MI method for three-dimensional ͑3D͒ conductivity imaging through both computer simulations and phantom experiments. 3D volume data are obtained by utilizing acoustic focusing and cylindrical scanning under each magnetic excitation. It is shown in our simulation and experiment results that with a common ultrasound probe that has limited bandwidth we are able to correctly reconstruct the 3D relative conductivity contrast of the imaging object. As compared to those conductivity boundary images generated by previous single-excitation MAT-MI, the new multiexcitation MAT-MI method provides more complete conductivity contrast reconstruction, and therefore, more valuable information in possible clinical and research applications.

<italic>In Vivo</italic> Electrical Conductivity Contrast Imaging in a Mouse Model of Cancer Using High-Frequency Magnetoacoustic Tomography With Magnetic Induction (hfMAT-MI)

“…transplanted tumors. To improve this z-directional resolution, focused ultrasound transducers or an acoustic lens [40] can be used. In summary, this work addresses significant technical challenges of in vivo magneto-acoustic imaging and paves the way for future work in early detection of cancer using hfMAT-MI.…”

“…The high-frequency technique introduced in hfMAT-MI also lays a foundation for further detecting the anisotropic property of biological tissues with the 1-mm spatial resolution. The multi-excitation MAT-MI technique have been validated through 2D experiments [20] and 3D trials [40]. Besides reconstructing the conductivity distribution, the multiple coil sets and the corresponding algorithms introduced by the multi-excitation research can also be used to compute the conductivity gradients along both x and y directions, and potentially along z direction if ultrasound elevational resolution can also be further improved.…”

Magnetoacoustic tomography with magnetic induction (MAT-MI) for imaging electrical conductivity of biological tissue: a tutorial review

“…Thus 3D scanning and mapping of the Lorentz force induced acoustic source is needed to map the 3D electrical conductivity distribution. Three-dimensional MAT-MI systems have been previously developed based on ultrasound focusing and cylindrical scanning (Xia et al , 2007; Li et al , 2010). As shown in Fig.…”

A Reconstruction Algorithm of Magnetoacoustic Tomography With Magnetic Induction for an Acoustically Inhomogeneous Tissue

“…If the relative error between acoustic source Q ( Step=n ) and Q ( Step = n +1) is larger than the given tolerance ε, go back to step 2. Otherwise finish the procedure and use the Q as the final solution. Using the multiple excitation method of MAT-MI [20] [23], the distribution of the eddy current can be calculated using Eq. (15).…”

“…After using multi-excitation algorithm [20] or ‘Potato-peeling method’ [23], we can finally reconstruct the electrical impedance.…”