Wheeler-Kingshott Claudia A M, Hickman Simon J, Parker Geoffrey J M, Ciccarelli Olga, Symms Mark R, Miller David H, Barker Gareth J
NMR Research Unit, University Department of Clinical Neurology, Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, United Kingdom.
Neuroimage. 2002 May;16(1):93-102. doi: 10.1006/nimg.2001.1022.
This study describes a new technique for Diffusion Tensor Imaging (DTI) that acquires axial (transverse) images of the cervical spinal cord. The DTI images depict axonal fiber orientation, enable quantification of diffusion characteristics along the spinal cord, and have the potential to demonstrate the connectivity of cord white matter tracts. Because of the high sensitivity to motion of diffusion-weighted magnetic resonance imaging and the small size of the spinal cord, a fast imaging method with high in-plane resolution was developed. Images were acquired with a single-shot EPI technique, named ZOOM-EPI (zonally magnified oblique multislice echo planar imaging), which selects localized areas and reduces artefacts caused by susceptibility changes between soft tissue and the adjacent vertebrae. Cardiac gating was used to reduce pulsatile flow artefacts from the surrounding cerebrospinal fluid. Voxel resolution was 1.25 x 1.25 mm(2) in-plane with 5-mm slice thickness. Both the mean diffusivity (MD) and the fractional anisotropy (FA) indices of the cervical spinal cord were measured. The FA index demonstrated high anisotropy of the spinal cord with an average value of 0.61 +/- 0.05 (highest value of 0.66 +/- 0.03 at C3), comparable to white matter tracts in the brain. The diffusivity components parallel and orthogonal to the longitudinal axes of the cord were lambda( parallel) = (1648 +/- 123) x 10(-6) mm(2)s(-1) and lambda( perpendicular) = (570 +/- 47) x 10(-6) mm(2) s(-1), respectively. The high axial resolution allowed preliminary evaluation of fiber connectivity using the fast-marching tractography algorithm, which generated traces of fiber paths consistent with the well-known cord anatomy.
本研究描述了一种用于扩散张量成像（DTI）的新技术，该技术可获取颈脊髓的轴向（横向）图像。DTI图像描绘了轴突纤维的方向，能够对脊髓的扩散特性进行量化，并且有可能展示脊髓白质束的连通性。由于扩散加权磁共振成像对运动高度敏感且脊髓体积较小，因此开发了一种具有高平面分辨率的快速成像方法。使用单次激发EPI技术（称为ZOOM-EPI，即区域放大斜多层面回波平面成像）采集图像，该技术可选择局部区域并减少软组织与相邻椎体之间的磁化率变化所引起的伪影。采用心脏门控来减少周围脑脊液的搏动血流伪影。平面体素分辨率为1.25×1.25 mm²，层厚为5 mm。测量了颈脊髓的平均扩散率（MD）和分数各向异性（FA）指数。FA指数显示脊髓具有较高的各向异性，平均值为0.61±0.05（C3处最高值为0.66±0.03），与脑白质束相当。与脊髓纵轴平行和垂直的扩散率分量分别为λ（平行）=(1648±123)×10⁻⁶ mm²/s和λ（垂直）=(570±47)×10⁻⁶ mm²/s。高轴向分辨率允许使用快速行进纤维束成像算法对纤维连通性进行初步评估，该算法生成的纤维路径轨迹与众所周知的脊髓解剖结构一致。
