Homogenous nuclear magnetic resonance probe using the space harmonics suppression method

Abstract

Abstract. Nuclear magnetic resonance imaging (MRI) has became an unavoidable medical tool in spite of its poor sensitivity. This fact motivates the efforts to enhance the nuclear magnetic resonance (NMR) probe performance. Thus, the nuclear spin excitation and detection, classically performed using radio-frequency coils, are required to be highly sensitive and homogeneous. The space harmonics suppression (SHS) method, already demonstrated to construct coil producing homogenous static magnetic field, is used in this work to design radio-frequency coils. The SHS method is used to determine the distribution of the electrical conductive wires which are organized in a saddle-coil-like configuration. The theoretical study of these SHS coils allows one to expect an enhancement of the signal-to-noise ratio with respect to saddle coil. Coils prototypes were constructed and tested to measure 1H NMR signal at a low magnetic field (8 mT) and perform MRI acquired at a high magnetic field (3 T). The signal-to-noise ratios of these SHS coils are compared to the one of saddle coil and birdcage (in the 3 T case) of the same size under the same pulse sequence conditions demonstrating the performance enhancement allowed by the SHS coils.

Biot–Savart-Based Design and Workbench Validation at 100 MHz of Transverse Field Surface RF Coils

“…Although a complete RF coil design should include the estimation of the loaded RF magnetic field pattern, we believe that the first design step can be performed with a priori estimation of the unloaded RF coil, useful to avoid time-consuming and expensive approaches in the RF coil design process. Moreover, as reported in the literature [39], the magnetostatic assumption is often verified at frequencies routinely used in clinical MRI applications.…”

Magnetostatic Simulation and Design of Novel Radiofrequency Coils Based on Transverse Field Current Elements for Magnetic Resonance Applications

“…The freely available simulator [ 7 ], based on the magnetostatic approach, can be useful for the first optimization of the unloaded RF coil, avoiding time-consuming and expensive approaches based on full-wave simulations. Moreover, as reported in the literature [ 22 ], such magnetostatic assumption is often verified at frequencies routinely used in clinical MRI applications, with the great advantage that reasonably accurate field calculation can be performed in a very short computation time (seconds), as compared to the full wave methods (hours) [ 23 , 24 , 25 ].…”