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Description
Quantitative thermoacoustic tomography (QTAT) is a medical and biomedical imaging technique combining electromagnetic contrast and high resolution of ultrasound imaging. In QTAT, a short micro- or radio wave pulse is directed to the imaged target. As the electromagnetic waves propagate in the target tissue, they are absorbed leading to localized thermal expansion and rise in pressure. This pressure relaxes as broadband ultrasound waves that are measured on the boundary of the imaged target. In the inverse problem of QTAT, the dielectric parameters, such as electrical conductivity and permittivity, of the imaged target are estimated from the measured ultrasound waves.In this work, we propose an approach for simultaneous estimation of electrical conductivity and permittivity from the ultrasound waves in the inverse problem of QTAT. The inverse problem is approached in the Bayesian framework utilizing electromagnetic and acoustic forward models based on Maxwell’s equations and the acoustic wave-equation, respectively. The proposed approach is evaluated using numerical simulations. The results show that the dielectric parameters can be estimated accurately. However, the number of electromagnetic pulses and the ultrasound sensor geometry have a significant effect on the accuracy of the estimated parameters.