Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany.
Experimental Physics 5, University of Würzburg, Würzburg, Germany.
Magn Reson Med. 2021 May;85(5):2771-2780. doi: 10.1002/mrm.28585. Epub 2020 Nov 9.
Accurate and artifact-free T quantification is still a major challenge due to a susceptibility of the spin-locking module to B and/or B field inhomogeneities. In this study, we present a novel spin-lock preparation module (B-SL) that enables an almost full compensation of both types of inhomogeneities.
The new B-SL module contains a second 180° refocusing pulse to compensate each pulse in the preparation block by a corresponding pulse with opposite phase. For evaluation and validation of B-SL, extensive simulations as well as phantom measurements were performed. Furthermore, the new module was compared to three common established compensation methods.
Both simulations and measurements demonstrate a much lower susceptibility to artifacts for the B-SL module, therefore providing an improved accuracy in T quantification. In the presence of field inhomogeneities, measurements revealed an increased banding compensation by 79% compared with the frequently used composite module. The goodness of the mono-exponential T fitting procedure was improved by 58%.
The B-SL preparation enables the generation of accurate relaxation maps with significantly reduced artifacts, even in the case of large field imperfections. Therefore, the B-SL module is suggested to be highly beneficial for in vivo T quantification.
由于锁相模块对 B 和/或 B 场非均匀性敏感，因此准确且无伪影的 T 定量仍然是一个主要挑战。在本研究中，我们提出了一种新的锁相准备模块（B-SL），它几乎可以完全补偿两种类型的不均匀性。
新的 B-SL 模块包含第二个 180°重聚焦脉冲，通过具有相反相位的相应脉冲对准备块中的每个脉冲进行补偿。为了评估和验证 B-SL，进行了广泛的模拟和体模测量。此外，还将新模块与三种常见的现有补偿方法进行了比较。
模拟和测量都表明 B-SL 模块对伪影的敏感性要低得多，因此在 T 定量方面提供了更高的准确性。在存在磁场不均匀性的情况下，与常用的复合模块相比，测量结果显示带补偿增加了 79%。单指数 T 拟合过程的拟合优度提高了 58%。
B-SL 准备可生成具有显著减少伪影的准确弛豫图，即使在大的场不完美的情况下也是如此。因此，建议 B-SL 模块对体内 T 定量非常有益。
