Computational Analysis of Overlapping Birdcage Coil for Artificial Circular-Polarized Mode in Magnetic Resonance Imaging

Abstract

In this computational analysis-based study, we proposed an overlapping birdcage (BC) coil with a particular interval distance along the z-axis in order to provide an artificial circular-polarized (CP) magnetic flux (B-1) field based on a linear-polarized (LP) B-1 field given by two single-channel BC coils. Overlapping BC coils were spaced at a specific overlapping distance in the main magnetic field (B-0) direction by two identical BC coils through electromagnetic (EM) calculations and compared with B-1 field and pointing vector distribution for the non-overlapping region at 7 Tesla of 297.2 MHz. These results clearly show that, unlike the general method for generating the CP mode using the quadrature driving method, overlapping LP modes that are individually used do not form a perfect CP mode, but instead a quasi-CP mode, in the form of an elliptical-polarized (EP) mode.