Departments of Radiology, University of North Carolina, Chapel Hill, NC, USA; Biomedical Research Imaging Center (BRIC), University of North Carolina at Chapel Hill, NC, USA.
Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Neuroimage. 2019 Feb 1;186:782-793. doi: 10.1016/j.neuroimage.2018.11.038. Epub 2018 Nov 22.
Quantitative assessments of normative brain development using MRI are of critical importance to gain insights into healthy neurodevelopment. However, quantitative MR imaging poses significant technical challenges and requires prohibitively long acquisition times, making it impractical for pediatric imaging. This is particularly relevant for healthy subjects, where imaging under sedation is not clinically indicated. MR Fingerprinting (MRF), a novel MR imaging framework, provides rapid, efficient, and simultaneous quantification of multiple tissue properties. In this study, a 2D MR Fingerprinting method was developed that achieves a spatial resolution of 1 × 1 × 3 mm with rapid and simultaneous quantification of T, T and myelin water fraction (MWF). Phantom experiments demonstrated that accurate measurements of T and T relaxation times were achieved over a wide range of T and T values. MRF images were acquired cross-sectionally from 28 typically developing children, 0 to five years old, who were enrolled in the UNC/UMN Baby Connectome Project. Differences associated with age of R1 (=1/T), R2 (=1/T) and MWF were obtained from several predefined white matter regions. Both R1 and R2 exhibit a marked increase until ∼20 months of age, followed by a slower increase for all WM regions. In contrast, the MWF remains at a negligible level until ∼6 months of age for all predefined ROIs and gradually increases afterwards. Depending on the brain region, rapid increases are observed between 6 and 12 months to 6-18 months, followed by a slower pace of increase in MWF. Neither relaxivities nor MWF were significantly different between the left and right hemispheres. However, regional differences in age-related R1 and MWF measures were observed across different white matter regions. In conclusion, our results demonstrate that the MRF technique holds great potential for multi-parametric assessments of normative brain development in early childhood.
使用 MRI 对正常脑发育进行定量评估对于深入了解健康神经发育至关重要。然而，定量磁共振成像存在重大技术挑战，需要极其长的采集时间，因此在儿科成像中不切实际。这在健康受试者中尤其相关，在这些受试者中，镇静下的成像在临床上并不需要。MR 指纹成像（MRF）是一种新的磁共振成像框架，可快速、高效、同时定量多种组织特性。在这项研究中，开发了一种 2D MR 指纹成像方法，可实现 1×1×3mm 的空间分辨率，快速且同时定量 T1、T2 和髓鞘水分数（MWF）。体模实验表明，在很宽的 T1 和 T2 值范围内实现了 T1 和 T2 弛豫时间的准确测量。从 UNC/UMN Baby Connectome 项目中招募的 28 名典型发育的 0 至 5 岁儿童中获得了横断面 MRF 图像。从几个预先定义的白质区域获得了与年龄相关的 R1（=1/T1）、R2（=1/T2）和 MWF 的差异。R1 和 R2 均表现出明显的增加，直到约 20 个月大，然后所有 WM 区域的增加速度较慢。相比之下，MWF 在所有预定义 ROI 中直到约 6 个月大时保持在可忽略的水平，之后逐渐增加。根据大脑区域的不同，在 6 至 12 个月至 6 至 18 个月之间观察到快速增加，然后 MWF 的增加速度较慢。弛豫率和 MWF 在左右半球之间没有显著差异。然而，在不同的白质区域观察到与年龄相关的 R1 和 MWF 测量的区域差异。总之，我们的结果表明，MRF 技术在儿童早期对正常大脑发育进行多参数评估具有很大的潜力。
