Du Yiping P, Jin Zhaoyang, Hu Yuzheng, Tanabe Jody
Department of Psychiatry, University of Colorado Denver, School of Medicine, Denver, Colorado 80045, USA.
J Magn Reson Imaging. 2009 Aug;30(2):449-54. doi: 10.1002/jmri.21833.
To improve the visibility of veins in susceptibility-weighted imaging (SWI) using a multi-gradient echo acquisition.
A three-dimensional multi-echo gradient-echo pulse sequence was developed for simultaneous acquisition of MR angiography and multiple volumes of MR venography (MRV) of the brain. The first echo was acquired for MR angiography using the time-of-flight in-flow effect. The subsequent echoes were acquired for SWI-based MRV at different echo times (TEs).
Multiple MRV datasets acquired at different TEs were complementary in depicting the venous vasculature. MRV data acquired at a longer TE had a higher venous contrast and stronger susceptibility weighting, whereas MRV data acquired at a shorter TE had a higher signal-to-noise ratio and less severe off-resonance artifacts. Three-dimensional mapping of local field gradients was calculated and the transverse relaxivity (R(2)) at each voxel was quantified using multi-TE exponential fitting.
Multi-echo acquisition of MR angiography and venography demonstrated improved visibility of venous vasculature especially in regions with severe field inhomogeneity compared with conventional acquisition of SWI and dual-echo acquisition of MR angiography and venography.
利用多梯度回波采集提高 susceptibility-weighted imaging（SWI）中静脉的可视性。
开发了一种三维多回波梯度回波脉冲序列，用于同时采集脑磁共振血管造影（MR angiography）和多组脑磁共振静脉造影（MR venography，MRV）。利用流入时间效应采集第一个回波用于 MR angiography。随后在不同回波时间（TEs）采集用于基于 SWI 的 MRV 的回波。
在不同 TE 采集的多个 MRV 数据集在描绘静脉血管系统方面具有互补性。在较长 TE 采集的 MRV 数据具有更高的静脉对比度和更强的敏感性加权，而在较短 TE 采集的 MRV 数据具有更高的信噪比和更不严重的失谐伪影。计算了局部场梯度的三维映射，并使用多 TE 指数拟合对每个体素的横向弛豫率（R(2)）进行了量化。
与传统的 SWI 采集以及 MR angiography 和 MRV 的双回波采集相比，MR angiography 和 venography 的多回波采集显示出静脉血管系统的可视性得到改善，尤其是在具有严重场不均匀性的区域。
