Magneto-acousto-electrical tomography utilizing line-shaped acoustic beams

Abstract

Magneto-acousto-electrical tomography (MAET) that couples magnetic, acoustic, and electronic fields, enables the detection of electrical conductivity changes for biological tissues, and holds advantages of high spatial resolution and contrast. However, the traditional B-mode imaging is significantly distorted due to the wide radiation pattern of planar transducers, necessitating extensive rotation in practical applications. To address this limitation, a MAET technique utilizing line-shaped acoustic beams is developed to improve image quality for objects with arbitrary shapes using minimal rotations. The principle of MAE measurements is derived based on distributions of acoustic pressure of ideal line-shaped Bessel beams and electrical conductivity of objects. It is demonstrated that MAE signals generated by inclined conductivity boundaries can be enhanced by a narrower line-shaped beam with a larger wavenumber k_r, resulting in improved B-mode images with more accurate information of conductivity boundaries. The relative error is introduced to assess the agreement between the B-mode image and the conductivity boundary of a cylindrical phantom model. The results show that the maximum coincidence angle of B-mode imaging increases as k_r increases, and leads to reduced rotations for MAET, with the minimum of just 4 for an infinite k_r. Theoretical predictions and numerical simulations are validated by experimental B-mode imaging of a prismatic object with an inclined boundary, using a line-focused beam with k_r = 516 m⁻¹ generated by an anti-axicon phase modulation lens. The improved performance of MAET is also demonstrated by 24 rotations, which has a nearly continuous and uniform boundary for the phantom model. The line-shaped beam is proved to be an effective source to improve the speed and quality of MAET, exhibiting promising potentials in biomedical applications.