Imaging Research Laboratories, Robarts Research Institute, London, Canada.
Department of Medical Biophysics, The University of Western Ontario, London, Canada.
Magn Reson Med. 2017 Dec;78(6):2334-2341. doi: 10.1002/mrm.26602. Epub 2017 Jan 23.
Hyperpolarized (HP) gas MRI of the rodent lung is of great interest because of the increasing need for novel biomarkers with which to develop new therapies for respiratory diseases. The use of fast gradient-recalled echo (FGRE) for high-resolution HP gas rodent lung MRI is challenging as a result of signal loss caused by significant diffusion weighting, particularly in the larger airways. In this work, a modified FGRE approach is described for HP He rodent lung MRI using a centric-out readout scheme (ie, x-centric), allowing high-resolution, density-weighted imaging.
HP He x-centric imaging was performed in a phantom and compared with a conventional partial-echo FGRE acquisition for in-plane spatial resolutions varying between 39 and 312 µm. Partial-echo and x-centric acquisitions were also compared for high spatial-resolution breath-hold (1 s) imaging of rodent lungs.
X-centric provided improved signal-to-noise ratio efficiency by a factor of up to 13/1.7 and 6.7/1.8, compared with the partial-echo FGRE for the airways/parenchyma of mouse and rat, respectively, at high spatial resolutions in vivo (<78 µm). In particular, rodent major airways with less restricted diffusion of He could only be visualized with the x-centric method.
The x-centric method significantly reduces diffusion weighting, allowing high spatial and temporal resolution HP He gas density-weighted rodent lung MRI. Magn Reson Med 78:2334-2341, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
由于需要开发新的治疗呼吸疾病的方法，需要新型生物标志物，因此人们对啮齿动物肺部的超极化（HP）气体 MRI 越来越感兴趣。由于扩散加权导致的信号损失较大，特别是在较大的气道中，使用快速梯度回波（FGRE）进行高分辨率 HP 气体啮齿动物肺部 MRI 具有挑战性。在这项工作中，描述了一种用于 HP He 啮齿动物肺部 MRI 的改进的 FGRE 方法，该方法使用中心向外读出方案（即 x 中心），允许进行高分辨率、密度加权成像。
在体模中进行 HP He x 中心成像，并与传统的部分回波 FGRE 采集进行比较，体模的平面分辨率在 39 至 312 μm 之间变化。还比较了部分回波和 x 中心采集在高空间分辨率（1 s）呼吸暂停成像中的性能。
与部分回波 FGRE 相比，x 中心在高空间分辨率下（<78 μm），在体内对小鼠和大鼠气道/实质的信噪比效率提高了 13/1.7 和 6.7/1.8 倍。特别是，He 扩散受限较小的啮齿动物主要气道只能用 x 中心方法进行可视化。
x 中心方法大大减少了扩散加权，从而可以进行高空间和时间分辨率的 HP He 气体密度加权啮齿动物肺部 MRI。磁共振医学杂志 78:2334-2341, 2017。© 2017 国际磁共振学会。
