MULTI-ECHO WATER-FAT SEPARATION

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 目的：该项目旨在使用多回波序列实现快速高效的扫描和稳健的水-脂肪分离。为了实现这一目标，需要结合稳健的场图估计和与新的多回波序列一起工作的成像技术。 方法：我们开发了一种多分辨率视野MAP估计方法，该方法直接在粗分辨率下定位可能的视野MAP值，然后逐步将视野MAP估计细化到全分辨率。为了提高成像效率和减少运动引起的伪影，我们实现了一种双极多回波序列，该序列 使用交替读出梯度获取不同回声时间的图像，以最大限度地提高扫描效率。在实际应用中，必须解决由交替读出梯度引起的问题，包括k空间回波不对准、场不均匀引起的对准错误和化学位移引起的对准错误。 摘要：与标准多回波序列相比，所开发的技术和序列具有许多优点，例如高信噪比效率、减小的回波间隔、减少运动引起的伪影、可靠的场图估计和水脂分离。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Purpose: This project aims to enable fast and efficient scanning with robust water-fat separation using multi-echo sequences. To achieve this aim, requires a combination of robust field-map estimation and imaging techniques that work with novel multi-echo sequences. Methods: We have developed a multi-resolution field map estimation method that directly locates possible field map values at a coarse resolution and then progressively refines field map estimation to full resolution. To improve imaging efficiency and reduce motion induced artifacts, we have implemented a bipolar multi-echo sequence that acquires images at different echo times using alternating readout gradients to maximize scan efficiency. For practical use, the problems caused by the alternating readout gradients, including k-space echo misalignment, field-inhomogeneity induced misregistration, and chemical-shift induced misregistration must be addressed. Summary: The developed techniques and sequences offer many advantages such as high SNR efficiency, reduced echo-spacing compared to standard multi-echo sequences, reduced motion induced artifacts, and reliable field-map estimation and water-fat separation.