Vanderbilt University Institute of Imaging Science,Vanderbilt University Medical Center, Nashville, TN 37235, USA; Department of Radiology and Radiological Sciences,Vanderbilt University Medical Center, Nashville, TN 37235, USA.
Department of Biomedical Engineering, Case Western Reserve University Cleveland, OH 44106, USA.
Magn Reson Imaging. 2024 Dec;114:110238. doi: 10.1016/j.mri.2024.110238. Epub 2024 Sep 12.
Prospective motion correction (PMC) with inductively-coupled wireless NMR markers has been shown to be an effective plug-and-play method for dealing with head motion at 7 Tesla [29,30]. However, technical challenges such as one-to-one identification of three wireless markers, generation of hyper-intense marker artifacts and low marker peak SNR in the navigators has limited the adoption of this technique. The goal of this work is to introduce solutions to overcome these issues and extend this technique to PMC for brain imaging at 3 Tesla.
PMC with 6 degrees of freedom (DOF) was implemented using a novel ∼8 ms, ultrashort echo time (UTE) navigator in concert with optimally chosen MnCl marker samples to minimize marker artifacts. Distinct head coil sensitivities were leveraged to enable identification and tracking of individual markers and a variable flip angle (VFA) scheme and real time filtering were used to boost marker SNR. PMC was performed in 3D T weighted brain imaging at 3 Tesla with voluntary head motions in adult volunteers.
PMC with wireless markers improved image quality in 3D T weighted images in all subjects compared to non-motion corrected images for similar motions with no noticeable marker artifacts. Precision of motion tracking was found to be in the range of 0.01-0.06 mm/degrees. Navigator execution had minimal impact on sequence duration.
Wireless NMR markers provide an accurate, calibration-free and economical option for 6 DOF PMC in brain imaging across field strengths. Challenges in this technique can be addressed by combining navigator design, sample selection and real time data processing strategies.
在 7T 磁共振系统中，基于感应耦合无线 NMR 标记的前瞻性运动校正（PMC）已被证明是一种有效的即插即用方法，可以解决头部运动问题[29,30]。然而，由于存在一些技术挑战，例如三个无线标记的一一对应识别、超强度标记伪影的产生以及导航器中标记峰值 SNR 较低，限制了该技术的应用。本研究旨在提出解决方案，克服这些问题，并将该技术扩展到 3T 磁共振的 PMC 中。
采用一种新的约 8ms 超短回波时间（UTE）导航器与最优选择的 MnCl 标记样本相结合，实现了 6 自由度（DOF）的 PMC，以最小化标记伪影。利用独特的头部线圈灵敏度，实现了对单个标记的识别和跟踪，并采用可变翻转角（VFA）方案和实时滤波来提高标记 SNR。在成人志愿者的自愿头部运动下，在 3T 磁共振系统中进行了 3D T 加权脑成像的 PMC。
与非运动校正图像相比，在所有受试者中，使用无线标记的 PMC 均可改善 3D T 加权图像的图像质量，且对于类似运动，无明显的标记伪影。运动跟踪的精度被发现处于 0.01-0.06mm/deg 的范围内。导航器执行对序列持续时间的影响最小。
无线 NMR 标记为不同场强的脑成像提供了一种准确、免校准且经济的 6DOF PMC 方法。通过结合导航器设计、样本选择和实时数据处理策略，可以解决该技术中的挑战。
