Spread-spectrum magnetic resonance imaging.

Purpose: A novel method for the acceleration of MRI acquisition is proposed that relies on the local modulation of magnetic fields. These local modulations provide additional spatial information for image reconstruction that is used to accelerate image acquisition. Methods: In experiments and simulations, eight local coils connected to current amplifiers were used for rapid local magnetic field variation. Acquired and simulated data were reconstructed to quantify reconstruction errors as a function of the acceleration factor and applied modulation frequency and strength. Results: Experimental results demonstrate a possible acceleration factor of 2 to 4. Simulations demonstrate the challenges and limits of this method in terms of required magnetic field modulation strengths and frequencies. A normalized mean squared error of below 10% can be achieved for acceleration factors of up to 8 using modulation field strengths comparable to the readout gradient strength at modulation frequencies in the range of 5 to 20 kHz. Conclusion: Spread-spectrum MRI represents a new approach to accelerate image acquisition, and it can be independently combined with traditional parallel imaging techniques based on local receive coil sensitivities.