A Simple Auxiliary Model for Field Amplitude Shaping in Complex Environments, and Application to MRI Shimming

Abstract

The canonical problem of designing the complex excitations feeding an array such to ensure a desired field intensity distribution inside a given region of interest, while keeping it under control in some other regions, is addressed. To this end, an auxiliary physics inspired model for the induced total field is proposed, whose off-line analysis allows a simplified approach to understand the convenient and non-convenient field interferences between canonical solutions for the induced total field, that are zero order Bessel functions. Moreover, its analysis drastically reduces the computational burden associated to the multi-control points based approaches. The problem at hand plays a key role in many different applications, including radio communications, wireless power transfer as well as hyperthermia treatment planning, and in this paper attention is paid to radiofrequency shimming in magnetic resonance imaging. In fact, the proposed model and tools are tailored to the challenging case of leveling of the magnetic field intensity within an MRI scanner and in case of a bidimensional realistic head phantom.

Keywords

• Antenna array
• electromagnetic field
• inverse problem
• intensity shaping
• magnetic resonance imaging
• shimming