Simulation Study of Radio Frequency Safety and the Optimal Size of a Single‐Channel Surface Radio Frequency Coil for Mice at 9.4 T Magnetic Resonance Imaging

Abstract

The optimized size of a single‐channel surface radio frequency (RF) coil for mouse body images in a 9.4 T magnetic resonance imaging (MRI) system was determined via electromagnetic-field analysis of the signal depth according to the size of a single‐channel coil. The single‐channel surface RF coils used in electromagnetic field simulations were configured to operate in transmis-sion/reception mode at a frequency of 9.4 T–400 MHz. Computational analysis using the finite‐dif-ference time‐domain method was used to assess the single‐channel surface RF coil by comparing single‐channel surface RF coils of varying sizes in terms of |B1|‐, |B1+|‐, |B1−|‐ and |E|‐field distri-bution. RF safety for the prevention of burn injuries to small animals was assessed using an analysis of the specific absorption rate. A single‐channel surface RF coil with a 20 mm diameter provided optimal B1‐field distribution and RF safety, thus confirming that single‐channel surface RF coils with ≥25 mm diameter could not provide typical B1‐field distribution. A single‐channel surface RF coil with a 20 mm diameter for mouse body imaging at 9.4 T MRI was recommended to preserve the characteristics of single‐channel surface RF coils, and ensured that RF signals were applied correctly to the target point within RF safety guidelines.