Uotani Shunsuke, Kanazawa Yuki, Haga Akihiro, Taniguchi Yo, Takizawa Masahiro, Sasaki Motoharu, Harada Masafumi
Graduate School of Health Sciences, Faculty of Medicine, Tokushima University, Tokushima, Japan.
Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo-Ku, Kumamoto, 862-0976, Japan.
Radiol Phys Technol. 2025 May 13. doi: 10.1007/s12194-025-00913-2.
The myelin sheath is a multilayered structure that surrounds the axons of nerve cells. It acts as an insulator to ensure rapid and accurate transmission of electrical signals in the nervous system. Myelin water fraction (MWF) serves as a biomarker for the myelin sheath. Several methods for determining the MWF have been proposed; however, the inconsistency of MWF values is a challenge. In this study, we attempted to derive the MWF using quantitative parameter mapping (QPM). QPM ensures reproducibility by maintaining consistent imaging conditions across different scanners, enabling stable acquisition of quantitative parameters. This is expected to improve the reliability of the MWF measurements. Additionally, a significant correlation between QPM-derived parameters and the MWF has been reported. Five healthy volunteers were included in this study. QPM-MRI was performed using a 3-Tesla MR scanner with a three-dimensional radio frequency-spoiled steady-state gradient-echo (3D-RSSG) method. Using the derived quantitative values, pseudo-intensity images were generated for arbitrary continuous echo time values. Subsequently, a model equation for the brain tissue was defined. The generated signals were fitted with triexponential curve to estimate the amplitudes of each tissue component. Finally, the MWF was calculated using the amplitude ratio of each tissue. The mean MWF values for white matter and gray matter were 8.20 ± 4.97% and 7.99 ± 3.45%, respectively. This method using QPM allows for 3D data collection within a scan time applicable to standard clinical examinations and provides high accuracy in relaxation time estimation, thereby enabling stable quantification of MWF and suggesting its potential for clinical implementation.
髓鞘是一种围绕神经细胞轴突的多层结构。它起到绝缘体的作用，以确保神经系统中电信号的快速准确传输。髓鞘水分数（MWF）作为髓鞘的生物标志物。已经提出了几种测定MWF的方法；然而，MWF值的不一致是一个挑战。在本研究中，我们尝试使用定量参数映射（QPM）来推导MWF。QPM通过在不同扫描仪之间保持一致的成像条件来确保可重复性，从而能够稳定地获取定量参数。这有望提高MWF测量的可靠性。此外，已有报道称QPM推导的参数与MWF之间存在显著相关性。本研究纳入了五名健康志愿者。使用3特斯拉磁共振扫描仪，采用三维射频扰相稳态梯度回波（3D-RSSG）方法进行QPM-MRI。利用推导的定量值，针对任意连续回波时间值生成伪强度图像。随后，定义了脑组织的模型方程。将生成的信号用三指数曲线拟合，以估计每个组织成分的幅度。最后，使用每个组织的幅度比计算MWF。白质和灰质的平均MWF值分别为8.20±4.97%和7.99±3.45%。这种使用QPM的方法允许在适用于标准临床检查的扫描时间内进行三维数据采集，并在弛豫时间估计中提供高精度，从而能够稳定地定量MWF，并表明其临床应用潜力。
