MR Physics, German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.
Commissariat à l'Energie Atomique, CNRS, NeuroSpin, BAOBAB, Université Paris-Saclay, Gif sur Yvette, France.
Magn Reson Med. 2024 Nov;92(5):2037-2050. doi: 10.1002/mrm.30212. Epub 2024 Jul 25.
T -weighted turbo-spin-echo (TSE) sequences are a fundamental technique in brain imaging but suffer from field inhomogeneities at ultra-high fields. Several methods have been proposed to mitigate the problem, but were limited so far to nonselective three-dimensional (3D) measurements, making short acquisitions difficult to achieve when targeting very high resolution images, or needed additional calibration procedures, thus complicating their application.
Slab-selective excitation pulses were designed for flexible placement utilizing the concept of k -spokes. Phase-coherent refocusing universal pulses were subsequently optimized with the Gradient Ascent Pulse Engineering algorithm and tested in vivo for improved signal homogeneity.
Implemented within a 3D variable flip angle TSE sequence, these pulses led to a signal-to-noise ratio (SNR) improvement ranging from 10% to 30% compared to a two-dimensional (2D) T2w TSE sequence employing -shimmed pulses. field inhomogeneities could be mitigated and artifacts from deviations reduced. The concept of universal pulses was successfully applied.
We present a pulse design method which provides a set of calibration-free universal pulses (UPs) for slab-selective excitation and phase-coherent refocusing in slab-selective TSE sequences.
T 加权涡轮自旋回波（TSE）序列是脑成像的基本技术，但在超高场中会受到场不均匀性的影响。已经提出了几种方法来减轻这个问题，但到目前为止，这些方法仅限于非选择性三维（3D）测量，使得在针对非常高分辨率图像时，很难实现短采集，或者需要额外的校准程序，从而使它们的应用变得复杂。
利用 k spokes 的概念设计了用于灵活放置的片状选择性激发脉冲。随后，利用梯度上升脉冲工程算法对相干重聚焦通用脉冲进行了优化，并在体内进行了测试，以提高信号均匀性。
在 3D 可变翻转角 TSE 序列中实现这些脉冲，与采用 - 形脉冲的二维（2D）T2w TSE 序列相比，信噪比（SNR）提高了 10% 至 30%。可以减轻场不均匀性并减少来自偏差的伪影。通用脉冲的概念得到了成功应用。
我们提出了一种脉冲设计方法，该方法为片状选择性 TSE 序列中的片状选择性激发和相干重聚焦提供了一组无需校准的通用脉冲（UP）。
