Paul Katharina, Huelnhagen Till, Oberacker Eva, Wenz Daniel, Kuehne André, Waiczies Helmar, Schmitter Sebastian, Stachs Oliver, Niendorf Thoralf
Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.
MRI.TOOLS GmbH, Berlin, Germany.
NMR Biomed. 2018 Mar;31(3). doi: 10.1002/nbm.3872. Epub 2018 Jan 9.
Diffusion-weighted imaging (DWI) provides information on tissue microstructure. Single-shot echo planar imaging (EPI) is the most common technique for DWI applications in the brain, but is prone to geometric distortions and signal voids. Rapid acquisition with relaxation enhancement [RARE, also known as fast spin echo (FSE)] imaging presents a valuable alternative to DWI with high anatomical accuracy. This work proposes a multi-shot diffusion-weighted RARE-EPI hybrid pulse sequence, combining the anatomical integrity of RARE with the imaging speed and radiofrequency (RF) power deposition advantage of EPI. The anatomical integrity of RARE-EPI was demonstrated and quantified by center of gravity analysis for both morphological images and diffusion-weighted acquisitions in phantom and in vivo experiments at 3.0 T and 7.0 T. The results indicate that half of the RARE echoes in the echo train can be replaced by EPI echoes whilst maintaining anatomical accuracy. The reduced RF power deposition of RARE-EPI enabled multiband RF pulses facilitating simultaneous multi-slice imaging. This study shows that diffusion-weighted RARE-EPI has the capability to acquire high fidelity, distortion-free images of the eye and the orbit. It is shown that RARE-EPI maintains the immunity to B inhomogeneities reported for RARE imaging. This benefit can be exploited for the assessment of ocular masses and pathological changes of the eye and the orbit.
扩散加权成像（DWI）可提供有关组织微观结构的信息。单次激发回波平面成像（EPI）是脑部DWI应用中最常用的技术，但容易出现几何畸变和信号缺失。具有弛豫增强的快速采集[RARE，也称为快速自旋回波（FSE）]成像为DWI提供了一种具有高解剖学准确性的有价值替代方案。这项工作提出了一种多激发扩散加权RARE-EPI混合脉冲序列，它结合了RARE的解剖学完整性以及EPI的成像速度和射频（RF）功率沉积优势。在3.0 T和7.0 T的体模和体内实验中，通过对形态图像和扩散加权采集进行重心分析，证明并量化了RARE-EPI的解剖学完整性。结果表明，回波链中一半的RARE回波可以被EPI回波替代，同时保持解剖学准确性。RARE-EPI降低的RF功率沉积使得多频段RF脉冲能够促进同时多层成像。这项研究表明，扩散加权RARE-EPI有能力获取眼睛和眼眶的高保真、无畸变图像。研究表明，RARE-EPI保持了RARE成像所报道的对磁场不均匀性的免疫性。这一优势可用于评估眼部肿块以及眼睛和眼眶的病理变化。
