Numerical optimization of a three‐channel radiofrequency coil for open, vertical‐field, MR‐guided, focused ultrasound surgery using the hybrid method of moment/finite difference time domain method

Abstract

The numerical optimization of a three-channel radiofrequency (RF) coil with a physical aperture for the open, vertical-field, MR-guided, focused ultrasound surgery (MRgFUS) system using the hybrid method of moment (MoM)/finite difference time domain (FDTD) method is reported. The numerical simulation of the current density distribution on an RF coil with a complicated irregular structure was performed using MoM. The electromagnetic field simulation containing the full coil-tissue interactions within the region of interest was accomplished using the FDTD method. Huygens' equivalent box with six surfaces smoothly connected the MoM and FDTD method. An electromagnetic model of the human pelvic region was reconstructed and loaded in the FDTD zone to optimize the three-channel RF coil and compensate for the lower sensitivity at the vertical field. In addition, the numerical MoM was used to model the resonance, decoupling and impedance matching of the RF coil in compliance with engineering practices. A prototype RF coil was constructed to verify the simulation results. The results demonstrate that the signal-to-noise ratio and the homogeneity of the B(1) field were both greatly improved compared with previously published results.

Review of Temperature Dependence of Thermal Properties, Dielectric Properties, and Perfusion of Biological Tissues at Hyperthermic and Ablation Temperatures

“…Specific examples include planning and monitoring thermal treatments facilitating radiofrequency (RF), microwave (MW), focused ultrasound (FUS), and laser energy where the goal is to obtain defined temperatures in a targeted tissue region. Recently, FUS combined with magnetic resonance imaging (MRI) has gained interest due to the ability to non-invasively heat tissue, as well as to provide non-invasive monitoring of tissue temperature via MR thermometry (8–12)…”

Inverse design of an organ-oriented RF coil for open, vertical-field, MR-guided, focused ultrasound surgery

“…However, in engineering, it is impractical to construct an RF coil exactly according to the coil windings shown in Fig. 3 because of the high inductance of the structure [11,14]. The asteroid winding pattern (in red color in Fig.…”

Numerical assessment of the reduction of specific absorption rate by adding high dielectric materials for fetus MRI at 3 T

“…An established adult female pelvis model, the same as that used in [28], was used to generate a pregnant woman pelvis model by merging a numerical fetal model into it. The numerical fetal model came from the report of Chen [6], which was a fetus model at 13 weeks.…”