Sparse parallel transmission using optimized sparse k-space trajectory by simulated annealing

Introduction: The combination of sparse pulses and parallel transmission [1, 2] can further reduce the excitation duration using both coil sensitivity and sparse k-space sampling. In this work, a novel sparse parallel transmission design is proposed to further shorten the pulse duration by using an optimal k-space trajectory. The k-space is firstly sampled using the Monto-Carlo sampling schemes [3]. Then an optimized k-trajectory traveling through all these samples is designed using the simulated annealing (SA) algorithm. Finally the gradient waveforms and parallel transmission pulses is designed and the feasibility of this method is verified using Bloch simulation. Theory and method: Fig.1 describes the design procedure of our proposed method. The MoteCarlo incoherent sampling strategy was firstly used to sample the k-space [3]. Then the SA was used to design an optimal single-shot k-space trajectory traveling through all these samples. The kspace trajectory was initiated by connecting all the samples using a curve and the cost function of the SA was defined as the curve length: