Jang Hyungseok, Wei Zhao, Wu Mei, Ma Ya-Jun, Chang Eric Y, Corey-Bloom Jody, Du Jiang
Department of Radiology, University of California San Diego, San Diego, California.
Radiology Service, VA San Diego Healthcare System, San Diego, California.
Magn Reson Med. 2020 Apr;83(4):1168-1177. doi: 10.1002/mrm.28082. Epub 2019 Nov 20.
Inversion recovery-based UTE (IR-UTE) sequences have been proposed to directly image myelin with extremely short (~0.3 ms). In this study, we demonstrate the feasibility of complex echo subtraction to improve 3D IR-UTE imaging of myelin in white matter of the brain in vivo.
In IR-UTE imaging, long T components in white matter (i.e., water) are suppressed using an adiabatic inversion recovery preparation pulse. Dual echo UTE data acquisition and magnitude echo subtraction are used to suppress the residual white matter and gray matter signals, providing high myelin contrast. Complex echo subtraction may further improve the myelin contrast by reducing the residual long T water signal contamination caused by regional T variations. To verify the efficacy of the complex subtraction technique, in vivo experiments were performed with 5 non-symptomatic healthy volunteers and 5 multiple sclerosis patients on a 3T clinical MR system. Signal enhancement between the complex subtraction and the magnitude subtraction was introduced to evaluate the improvement.
The complex subtraction improved myelin contrast over the magnitude subtraction in both healthy and patient groups, with more fine myelin structures being revealed. The foci of the demyelinated lesion were more clearly detected by complex subtraction. An average signal enhancement of up to 135.9% was achieved with the complex subtraction over the magnitude subtraction.
The complex echo subtraction improves 3D IR-UTE morphologic imaging of myelin in white matter of the brain.
基于反转恢复的UTE（IR-UTE）序列已被提出用于以极短（约0.3毫秒）的时间直接对髓磷脂进行成像。在本研究中，我们证明了采用复数回波减法来改善大脑白质中髓磷脂的三维IR-UTE体内成像的可行性。
在IR-UTE成像中，使用绝热反转恢复准备脉冲抑制白质中的长T成分（即水）。采用双回波UTE数据采集和幅度回波减法来抑制残留的白质和灰质信号，从而提供高髓磷脂对比度。复数回波减法可通过减少由区域T变化引起的残留长T水信号污染来进一步提高髓磷脂对比度。为验证复数减法技术的有效性，在一台3T临床MR系统上对5名无症状健康志愿者和5名多发性硬化症患者进行了体内实验。引入复数减法和幅度减法之间的信号增强来评估改善情况。
在健康组和患者组中，复数减法均比幅度减法改善了髓磷脂对比度，揭示出了更精细的髓磷脂结构。通过复数减法能更清晰地检测到脱髓鞘病变的病灶。与幅度减法相比，复数减法实现了高达135.9%的平均信号增强。
复数回波减法改善了大脑白质中髓磷脂的三维IR-UTE形态学成像。
