Multiple-Input–Multiple-Output (MIMO) MRI: Combining Parallel Excitation and Parallel Reception for Enhanced Imaging

Magnetic resonance imaging (MRI) plays a critical role in visualizing the structure and functions of the human body. In order to accelerate imaging time and improve the image quality, radio-frequency (RF) coil receive arrays which are commonly employed to acquire the magnetic resonance signal. Similarly, multiple transmit coils have been shown to accelerate and refine the RF excitation. In this paper, we investigate the optimization of the total imaging time and image accuracy when considering both the transmit and receive coil arrays; we term this strategy as multiple-input- multiple-output (MIMO) MRI. Our RF pulse design method is modeled by minimizing the excitation errors while simultaneously maximizing the signal-to-noise ratio (SNR) of the reconstructed MR image. It further allows a key tradeoff between the two optimizers. Additionally, multiple acceleration factors, varying numbers of receive coils used, maximum excitation error tolerance, and different excitation patterns are simulated and analyzed in this model. For a given excitation pattern, our method is shown to improve the SNR by 18-130% under certain acceleration schemes, as compared to conventional parallel transmission methods, while simultaneously controlling the excitation error within a desired scope (NRMSE ≤ 0.12).