Accelerating compressed sensing in parallel imaging reconstructions using an efficient circulant preconditioner for cartesian trajectories

• Published in: Magnetic resonance in medicine Vol. 81; no. 1; pp. 670 - 685
• Main Authors: Koolstra, Kirsten, van Gemert, Jeroen, Börnert, Peter, Webb, Andrew, Remis, Rob
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.01.2019; John Wiley and Sons Inc
• Subjects: Algorithms; Approximation; Brain - diagnostic imaging; compressed sensing; Computer Simulation; Conjugate gradient method; Conjugates; Data Compression - methods; Fast Fourier transformations; Fourier Analysis; Fourier transforms; Full Papers—Computer Processing and Modeling; Humans; Image Processing, Computer-Assisted - methods; Linear Models; Linear systems; Magnetic Resonance Imaging; Mathematical analysis; Matrix methods; Models, Theoretical; parallel imaging; Preconditioning; Reconstruction; Regularization; Software; Spine - diagnostic imaging; split bregman; System effectiveness; Trajectories; Wavelet Analysis; parallel imaging; compressed sensing; split bregman; preconditioning
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.27371

Purpose Design of a preconditioner for fast and efficient parallel imaging (PI) and compressed sensing (CS) reconstructions for Cartesian trajectories. Theory PI and CS reconstructions become time consuming when the problem size or the number of coils is large, due to the large linear system of equations that has to be solved in ℓ1 and ℓ2‐norm based reconstruction algorithms. Such linear systems can be solved efficiently using effective preconditioning techniques. Methods In this article we construct such a preconditioner by approximating the system matrix of the linear system, which comprises the data fidelity and includes total variation and wavelet regularization, by a matrix that is block circulant with circulant blocks. Due to this structure, the preconditioner can be constructed quickly and its inverse can be evaluated fast using only two fast Fourier transformations. We test the performance of the preconditioner for the conjugate gradient method as the linear solver, integrated into the well‐established Split Bregman algorithm. Results The designed circulant preconditioner reduces the number of iterations required in the conjugate gradient method by almost a factor of 5. The speed up results in a total acceleration factor of approximately 2.5 for the entire reconstruction algorithm when implemented in MATLAB, while the initialization time of the preconditioner is negligible. Conclusion The proposed preconditioner reduces the reconstruction time for PI and CS in a Split Bregman implementation without compromising reconstruction stability and can easily handle large systems since it is Fourier‐based, allowing for efficient computations.