Fratini Michela, Moraschi Marta, Maraviglia Bruno, Giove Federico
MARBILab - Museo storico della fisica e Centro di studi e ricerche Enrico Fermi, Roma, Italy; Dipartimento di Fisica, Sapienza Universita' di Roma, Roma, Italy.
J Magn Reson Imaging. 2014 Oct;40(4):770-7. doi: 10.1002/jmri.24467. Epub 2013 Nov 7.
Functional magnetic resonance imaging (fMRI) techniques are widely exploited for the study of brain activation. In recent years, similar approaches have been attempted for the study of spinal cord function; however, obtaining good functional images of spinal cord still represents a technical and scientific challenge. Some of the main limiting factors can be classified under the broad category of "physiological noise," and are related to 1) the cerebrospinal fluid (CSF) flux in the subarachnoid space surrounding the spinal cord; 2) the cord motion itself; and 3) the small area of the cord, which makes it critical to have a high image resolution. In addition, the different magnetic susceptibility properties of tissues surrounding the spinal cord reduce the local homogeneity of the static magnetic field, causing image distortion, reduction of the effective resolution, and signal loss, all effects that are modulated by motion. For these reasons, a number of methods have been developed for the purpose of denoising spinal cord fMRI time series. In this work, after a short introduction on the relevant features of the spinal cord anatomy, we review the main sources of physiological noise in spinal cord fMRI and discuss the main approaches useful for its mitigation.
功能磁共振成像（fMRI）技术被广泛应用于脑激活研究。近年来，人们尝试采用类似方法研究脊髓功能；然而，获取高质量的脊髓功能图像仍然是一项技术和科学挑战。一些主要限制因素可归为“生理噪声”这一宽泛类别，与以下因素有关：1）脊髓周围蛛网膜下腔的脑脊液（CSF）流动；2）脊髓自身的运动；3）脊髓面积小，这使得高图像分辨率至关重要。此外，脊髓周围组织不同的磁化率特性会降低静磁场的局部均匀性，导致图像失真、有效分辨率降低和信号丢失，所有这些效应都会因运动而受到调制。出于这些原因，已开发出多种方法用于脊髓fMRI时间序列的去噪。在这项工作中，在简要介绍脊髓解剖结构的相关特征后，我们回顾了脊髓fMRI中生理噪声的主要来源，并讨论了有助于减轻这种噪声的主要方法。
