MULTI-ECHO PHASE-BASED FAT/WATER SEPARATION

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。脂肪抑制对MRI的许多临床应用至关重要，包括心血管、腹部和肌肉骨骼成像。在之前的工作中，部分由本研究资源支持，研究人员开发了一种强大的迭代重建技术- IDEAL -使用具有不同回声时间的几张MR图像将水从脂肪中分离出来，从而导致脂肪和水信号之间的相位差不同。IDEAL的初步临床评估是成功的。然而，该技术可以从减少扫描时间和提高效率中获益，这是目前工作的两个目标。方法和讨论：IDEAL（迭代分解的水和脂肪与回声不对称和最小二乘估计）是一个鲁棒算法分离水和脂肪使用图像至少有3个不同的回声时间。通常，对每个回波时间使用一次完整采集。在这项工作中，我们使用一个多回波读出器，在一次采集中获取所有三个回波时间的数据。这将总扫描时间减少了大约两倍，而不会显著降低信噪比，并提高了对患者运动的鲁棒性。我们已经将这项技术应用于肌肉骨骼成像，以产生不到五分钟的3D软骨成像序列，以及3D肝脏成像，它可以在屏气中成像。结果显示，在大多数情况下，脂肪/水分离效果很好，尽管随着回波间距的增加，也会出现脂肪/水互换的情况。随着回波间距的增加，未来的工作将包括提高重建的鲁棒性，从而实现更高的分辨率成像。我们还将把这项技术应用于快速心脏成像，在这种情况下，运动使标准的IDEAL技术变得困难。

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. Introduction: Fat suppression is crucial to numerous clinical applications of MRI, including cardiovascular, abdominal and musculoskeletal imaging. In previous work, partially supported by this research resource, investigators have developed a robust iterative reconstruction technique, ¿IDEAL,¿ to separate water from fat using several MR images with different echo times resulting in different phase difference between fat and water signals. Initial clinical evaluation of IDEAL has been successful. However, the technique can benefit from scan time reduction, and improved efficiency, which are both goals of the present work. Methods and Discussion: IDEAL (Iterative Decomposition of water and fat with Echo Asymmetry and Least squares estimation) is a robust algorithm for separation of water and fat using images with at least 3 different echo times. Normally, a full acquisition is used for each echo time. In this work we use a multi-echo readout, that acquires data for all three echo times in a single acquisition. This reduces total scan time by about a factor of two, without reducing SNR significantly, and improves robustness to patient motion. We have applied this technique to musculoskeletal imaging to produce a sub-five-minute 3D cartilage imaging sequence, and to 3D liver imaging, which enables imaging within a breath-hold. Results show excellent fat/water separation in most cases, though as the echo spacing increases, there are cases where the fat/water swaps occur. Future work will involve improving the robustness of the reconstruction as the echo spacing increases, allowing higher resolution imaging. We will also apply this technique to rapid cardiac imaging, where motion makes the standard IDEAL technique difficult.