Acoustic dipole radiation based electrical impedance contrast imaging approach of magnetoacoustic tomography with magnetic induction. Issue 5 (12th April 2013)

• Record Type: Journal Article
• Authors: Sun, Xiaodong; Fang, Dawei; Zhang, Dong; Ma, Qingyu
• Is Part Of: Medical physics. Volume 40:Issue 5(2013)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2013-04-12
• Subjects: Electrical impedance tomography (EIT) -- Reconstruction -- Ultrasonographic imaging -- Numerical simulation; solution of equations; acoustic tomography -- biomagnetism -- electric impedance imaging -- electromagnetic induction -- image reconstruction -- magnetoacoustic effects -- medical image processing -- numerical analysis -- phantoms -- vibrations; magnetoacoustic tomography with magnetic induction (MAT‐MI) -- acoustic dipole radiation -- electrical impedance contrast imaging -- three‐dimensional simulation -- image reconstruction; Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom -- Digital computing or data processing equipment or methods, specially adapted for specific applications -- Image data processing or generation, in general; Sound pressure -- Aluminium -- Image reconstruction -- Medical imaging -- Transducers -- Numerical modeling -- Acoustic modeling -- Eddies -- Acoustic waves -- Spatial resolution; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4800639
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : Different from the theory of acoustic monopole spherical radiation, the acoustic dipole radiation based theory introduces the radiation pattern of Lorentz force induced dipole sources to describe the principle of magnetoacoustic tomography with magnetic induction (MAT‐MI). Although two‐dimensional (2D) simulations have been studied for cylindrical phantom models, layer effects of the dipole sources within the entire object along the z direction still need to be investigated to evaluate the performance of MAT‐MI for different geometric specifications. The purpose of this work is further verifying the validity and generality of acoustic dipole radiation based theory for MAT‐MI with two new models in different shapes, dimensions, and conductivities. Methods: : Based on the theory of acoustic dipole radiation, the principles of MAT‐MI were analyzed with derived analytic formulae. 2D and 3D numerical studies for two new models of aluminum foil and cooked egg were conducted to simulate acoustic pressures and corresponding waveforms, and 2D images of the scanned layers were reconstructed with the simplified back projection algorithm for the waveforms collected around the models. The spatial resolution for conductivity boundary differentiation was also analyzed with different foil thickness. For comparison, two experimental measurements were conducted for a cylindrical aluminum foil phantom and a shell‐peeled cooked egg. The collected waveforms and the reconstructed images of the scanned layers were achieved to verify the validation of the acoustic dipole radiation based theory for MAT‐MI. Results: : Despite the difference between the 2D and 3D simulated pressures, good consistence of the collected waveforms proves that wave clusters are generated by the abrupt pressure changes with bipolar vibration phases, representing the opposite polarities of the conductivity changes along the measurement direction. The configuration of the scanned layer can be reconstructed in terms of shape and size, and the conductivity boundaries are displayed in stripes with different contrast and bipolar intensities. Layer effects are demonstrated to have little influence on the collected waveforms and the reconstructed images of the scanned layers for the two new models. The experimental results have good agreements with numerical simulations, and the reconstructed 2D images provide conductivity configurations in the scanned layers of the aluminum foil and the egg models. Conclusions: : It can be concluded that the acoustic pressure of MAT‐MI is produced by the divergence of the induced Lorentz force, and the collected waveforms comprise wave clusters with bipolar vibration phases and different amplitudes, providing the information of conductivity boundaries in the scanned layer. With the simplified back projection algorithm for diffraction sources, collected waveforms can be used to reconstruct 2D conductivity contrast image and the conductivity configuration in the scanned layer can be obtained in terms of shape and size in stripes with the spatial resolution of the acoustic wavelength. The favorable results further verify the validity and generality of the acoustic dipole radiation based theory and suggest the feasibility of MAT‐MI as an effective electrical impedance contrast imaging approach for medical imaging.