MRI Off-Resonance RF Pulse Artifacts

The patent applies preliminary corrective actions by introducing auxiliary gradient magnetic fields before image acquisition to counteract the inhomogeneity effects. The method calculates compensation gradients based on measured field inhomogeneity and applies them in advance to cancel out the harmful phase variations that would otherwise create artifacts during the off-resonance RF pulse application.

The patent changes the parameters of the gradient magnetic fields by introducing auxiliary gradients with specific amplitudes and timings that are optimized to compensate for field inhomogeneity. The method adjusts gradient waveforms dynamically to match the actual field conditions, transforming the system parameters to achieve homogeneous fat saturation and magnetization transfer effects.

The patent substitutes the use of additional RF pulses with gradient magnetic field manipulation to achieve the same homogeneity correction goal. Instead of applying more electromagnetic energy through RF pulses, the method uses magnetic field gradients to induce phase corrections, thereby reducing SAR while maintaining image quality.

The patent introduces gradient magnetic fields as an intermediary mechanism to transfer the correction function from the RF domain to the gradient domain. The auxiliary gradients act as mediators that indirectly correct the inhomogeneity effects without requiring additional RF energy input, thus lowering SAR while achieving the desired homogeneity improvement.