Spatio-temporal encoding (SPEN) MRI is a non-Fourier imaging technique that encodes the spatial information in such a way that there is a direct relation between the signal intensity recorded during the acquisition and the spin density at a given position. In current spatio-temporal encoding methods, the first crucial step requires imparting a quadratic phase onto the transverse magnetization. Usually, this is achieved by simultaneous application of a frequency-swept (chirp) pulse and a linear magnetic field gradient. In this work, we show that a quadratic phase can be imparted by using quadratic encoding gradients. This leads to smaller specific absorption rates (SARs). Furthermore, the proposed sequence can be used for multi-slice applications similar to ordinary multi-slice sequences, but without the limitations of traditional SPEN.

时空编码（SPEN）MRI是一种非傅里叶成像技术，以一种在空间上编码信息的方式，使得在采集过程中记录的信号强度与给定位置的自旋密度之间存在直接关系。在当前的时空编码方法中，第一个关键步骤要求在横向磁化强度上赋予一个二次相位。通常，这是通过同时施加扫频（线性调频）脉冲和线性磁场梯度来实现的。在这项工作中，我们表明可以通过使用二次编码梯度来赋予二次相位。这导致较小的比吸收率（SAR）。此外，所提出的序列可以用于类似于普通多层序列的多层应用，但不受传统SPEN的限制。