Magneto-acoustic tomography using magnetic induction

Background. Electrical properties of tissues are effective indicators of tissue health, possible pathologies, and  are required for determining the efficacy and safety of electric fields induced by commonly used electromagnetic medical and imaging devices. Current non-invasive electrical property measurement modalities suffer from accuracy and resolution limitations, which in turn limits their use for research and clinical applications. This is particularly true for methods imaging electrical properties at low frequencies (<10 MHz), as there are fundamental resolution limitations due to the long wavelengths (>30 m) of electromagnetic waves at these frequencies. 

Objective. This project aims to improve the resolution of electrical property measurements at low frequencies (<10 MHz).

Approach. We are currently studying an existing method called Magneto acoustic tomography with magnetic induction (MAT-MI) that determines electrical parameters from measurements of ultrasound pressure waves, which have a much smaller wavelength (<2mm). 

Main results. MAT-MI is known to result in improved resolution electrical property images. For example, MAT-MI has been applied at 500kHz frequency and shown to deliver 2 mm level resolution in an animal model. 

Ongoing work. Despite having high resolution MAT-MI is limited because the measured signals are weak, and current algorithms used to infer electrical properties from pressure waves do not account for the heterogeneity of acoustic parameters across tissues. This limits the accuracy of the reproduction and to imaging soft tissues. We are working on addressing these limitations by developing special purpose MAT-MI imaging coils and using strong static magnets that will increase the SNR of the measure pressure wave. Furthermore, are developing novel algorithms for incorporating and inferring tissue acoustic  inhomogeneity during the reconstruction.

Anticipated Significance. This will enable the use of MAT-MI to image both soft, bone, and lung applications, thereby enabling its use for general biomedical imaging for a wide range of applications.