High SNR rapid T₁-weighted MPRAGE using spiral imaging with long readouts and improved deblurring

Purpose: The goal of this work is to present the implementation of 3D spiral high-resolution MPRAGE and to demonstrate that SNR and scan efficiency increase with the increment of readout time. Theory: Simplified signal equations for MPRAGE indicate that the T₁ contrast can be kept approximately the same by a simple relationship between the flip angle and the TR. Furthermore, if T₁ contrast remains the same, image SNR depends on the square root of the product of the total scan time and the readout time. Methods: MPRAGE spiral sequences were implemented with distributed spirals and spiral staircase on 3 Tesla scanners. Brain images of three volunteers were acquired with different readout times. Spiral images were processed with a joint water–fat separation and deblurring algorithm and compared to Cartesian images. Pure noise data sets were also acquired for SNR evaluation. Results: Consistent T₁ weighting can be achieved with various spiral readout lengths, and between spiral MPRAGE imaging and the traditional Cartesian MPRAGE imaging. Noise performance analysis demonstrates higher SNR efficiency of spiral MPRAGE imaging with matched T₁ contrast compared to the Cartesian reference imaging. Conclusion: Fast, high SNR MPRAGE imaging is feasible with long readout spiral trajectories.