Surface Coil with an Inductively Coupled Wireless Surface and Volume Coil for Improving the Magnetic Field Sensitivity at 400-MHz MRI

Abstract

This work presents the use of combinations between a wireless radio-frequency surface coil and a wireless 16-leg birdcage coil that are inductively coupled to improve the magnetic field sensitivity and uniformity. A single surface loop coil operating as transmission/reception (Tx/Rx) coil was designed for mouse head imaging at a magnetic field strength of 9.4-T. Numerical analyses using finite-difference time-domain were performed to compute the sensitivity and homogeneity of magnetic and electric flux density fields for each of the coil combinations. Maximum field values and standard deviation were used as statistical parameters to compare the sensitivity and homogeneity of the fields produced by the Tx/Rx surface coil for each case, when the wireless inductively coupled coils were used. The electromagnetic analyses were applied to a cylindrical oil-based phantom and a mouse model. The proposed combinations of the surface coil with the inductively coupled wireless surface and wireless volume coils offer an enhanced magnetic-flux sensitivity and RF excitation field distribution at 9.4-T. The modifications to the surface coil geometry by adding the inductively coupled radio-frequency coil combinations could be applied to the generally used transmit/receive surface coils and extended to parallel radio-frequency transmission array at ultra-high-field magnetic resonance imaging.