Simultaneous Quantitative MRI Mapping of T1, T2* and Magnetic Susceptibility with Multi-Echo MP2RAGE.
Simultaneous Quantitative MRI Mapping of T1, T2* and Magnetic Susceptibility with Multi-Echo MP2RAGE.
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DOI：
10.1371/journal.pone.0169265
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Schäfer A
中科院分区：
文献类型：
--
作者：
Metere R;Kober T;Möller HE;Schäfer A
了解弛豫时间对于理解磁共振成像对比度的生物物理机制至关重要。定量实验虽然在重现性方面具有重大优势，但可能会受益于同时采集。在这项工作中，我们展示了使用原型多回波 (ME) 磁化准备 2 RApid 梯度回波 (MP2RAGE) 序列同时记录弛豫时间和磁化率图的可能性。 T1 图可以使用 MP2RAGE 序列获得，该序列对射频发射场的不均匀性相对不敏感。作为扩展，可以在每个 MP2RAGE 读出块中采集多个梯度回波，从而允许计算磁化率图。我们使用计算机模拟来探索参数对测绘精度和准确度的影响。 19 名健康志愿者在 7 T 下获得了标称分辨率高达 0.6 mm 的体内参数图。体素间相关性和重测再现性用于评估结果的可靠性。当使用优化的参数时，使用 ME-MP2RAGE 和标准 MP2RAGE 获得的 T1 图谱与脑组织中发现的整个值范围表现出极好的一致性。同时获得的磁化率图的质量与快速低角度 SHot (FLASH) 结果相当。 ME-MP2RAGE（约 19 分钟）序列的采集时间比 MP2RAGE（约 12 分钟）和 FLASH（约 10 分钟）采集的总和更有利。在不牺牲准确度、精确度或灵活性的情况下，只要对采集参数进行适当的优化，多回波版本就可以在减少采集时间和内在共同配准方面产生优势。
The knowledge of relaxation times is essential for understanding the biophysical mechanisms underlying contrast in magnetic resonance imaging. Quantitative experiments, while offering major advantages in terms of reproducibility, may benefit from simultaneous acquisitions. In this work, we demonstrate the possibility of simultaneously recording relaxation-time and susceptibility maps with a prototype Multi-Echo (ME) Magnetization-Prepared 2 RApid Gradient Echoes (MP2RAGE) sequence. T1 maps can be obtained using the MP2RAGE sequence, which is relatively insensitive to inhomogeneities of the radio-frequency transmit field, . As an extension, multiple gradient echoes can be acquired in each of the MP2RAGE readout blocks, which permits the calculation of and susceptibility maps. We used computer simulations to explore the effects of the parameters on the precision and accuracy of the mapping. In vivo parameter maps up to 0.6 mm nominal resolution were acquired at 7 T in 19 healthy volunteers. Voxel-by-voxel correlations and the test-retest reproducibility were used to assess the reliability of the results. When using optimized paramenters, T1 maps obtained with ME-MP2RAGE and standard MP2RAGE showed excellent agreement for the whole range of values found in brain tissues. Simultaneously obtained and susceptibility maps were of comparable quality as Fast Low-Angle SHot (FLASH) results. The acquisition times were more favorable for the ME-MP2RAGE (≈ 19 min) sequence as opposed to the sum of MP2RAGE (≈ 12 min) and FLASH (≈ 10 min) acquisitions. Without relevant sacrifice in accuracy, precision or flexibility, the multi-echo version may yield advantages in terms of reduced acquisition time and intrinsic co-registration, provided that an appropriate optimization of the acquisition parameters is performed.