背景:最近由国际脊柱研究信托基金(ISRT)和生命之翼基金会赞助的国际成像专家会议确定了5种最先进的MRI技术,这些技术有可能通过阐明微观结构和功能的元素来改变脊髓成像领域:扩散张量成像(DTI),磁化转移(MT),髓鞘水组分(MWF),MR波谱(MRS),和功能磁共振成像(fMRI)。然而,这些技术的临床转化进展尚未确定。
方法:使用MEDLINE对英语文献进行了系统回顾,MEDLINE正在进行中,Embase,和Cochrane数据库来识别所有调查效用的人类研究,在诊断方面,与残疾的相关性,以及对结果的预测,这些有前途的技术在影响脊髓的病理。有关研究设计的数据,主题特征,MRI方法,损害的临床措施,和分析技术进行了提取和制表,以确定趋势和共性。这些研究评估了偏倚的风险,并使用建议分级评估对每个具体发现的总体证据质量进行评估,发展和评价(等级)框架。
结果:在数据库搜索中总共发现了6597篇独特的引文,在对274篇文章进行全文审查后,共有104项相关研究被确定为最终纳入研究(97%来自初始数据库搜索).其中,69项研究使用了DTI,25项使用了MT,这两种技术显示近年来出版物数量增加。审查还确定了1MWF研究,11MRS研究,和8个fMRI研究。大多数研究都是探索性的,缺乏先验假设,并显示出高(72%)或中等高(20%)的偏见风险,由于研究设计的问题,采集技术,和分析方法。每种技术的收购在不同的研究中差异很大,呈现度量的直接比较无效。DTI度量分数各向异性(FA)具有最强的效用证据,具有中等质量的证据,证明其用作生物标志物,表明在几种临床病理中与残疾相关,和低水平的证据表明,与健康对照组相比,它识别组织损伤(在组差异方面)。然而,没有足够的证据来确定其作为敏感和特异性的诊断测试或作为预测临床结果的工具的效用.非常低的质量证据表明,与对照组相比,其他指标也显示出群体差异,包括DTI指标平均扩散系数(MD)和径向扩散系数(RD),扩散峰度成像(DKI)度量平均峰度(MK),MT指标MT比率(MTR)和MT脑脊液比率(MTCSF),和N-乙酰天冬氨酸(NAA)浓度的MRS度量,尽管这些结果有些不一致。
结论:最先进的脊髓MRI技术正在兴起,在改善各种脊柱病变的诊断和治疗方面具有巨大潜力,但是到目前为止,目前的证据仅显示出有限的临床实用性。在这些成像工具中,DTI是最成熟的,但是在临床领域采用之前,还需要进一步的工作来标准化和验证其使用。大,精心设计的具有先验假设的研究,标准化的获取方法,详细的临床数据收集,和强大的自动分析技术需要充分展示这些快速发展的技术的潜力。
BACKGROUND: A recent meeting of international imaging experts sponsored by the International Spinal Research Trust (ISRT) and the Wings for Life Foundation identified 5 state-of-the-art MRI techniques with potential to transform the field of spinal cord imaging by elucidating elements of the microstructure and function: diffusion tensor imaging (DTI), magnetization transfer (MT), myelin water fraction (MWF), MR spectroscopy (MRS), and functional MRI (fMRI). However, the progress toward clinical translation of these techniques has not been established.
METHODS: A systematic
review of the English literature was conducted using MEDLINE, MEDLINE-in-Progress, Embase, and Cochrane databases to identify all human studies that investigated utility, in terms of diagnosis, correlation with disability, and prediction of outcomes, of these promising techniques in pathologies affecting the spinal cord. Data regarding study design, subject characteristics, MRI methods, clinical measures of impairment, and analysis techniques were extracted and tabulated to identify trends and commonalities. The studies were assessed for risk of bias, and the overall quality of evidence was assessed for each specific finding using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.
RESULTS: A total of 6597 unique citations were identified in the database search, and after full-text
review of 274 articles, a total of 104 relevant studies were identified for final inclusion (97% from the initial database search). Among these, 69 studies utilized DTI and 25 used MT, with both techniques showing an increased number of publications in recent years. The
review also identified 1 MWF study, 11 MRS studies, and 8 fMRI studies. Most of the studies were exploratory in nature, lacking a priori hypotheses and showing a high (72%) or moderately high (20%) risk of bias, due to issues with study design, acquisition techniques, and analysis methods. The acquisitions for each technique varied widely across studies, rendering direct comparisons of metrics invalid. The DTI metric fractional anisotropy (FA) had the strongest evidence of utility, with moderate quality evidence for its use as a biomarker showing correlation with disability in several clinical pathologies, and a low level of evidence that it identifies tissue injury (in terms of group differences) compared with healthy controls. However, insufficient evidence exists to determine its utility as a sensitive and specific diagnostic test or as a tool to predict clinical outcomes. Very low quality evidence suggests that other metrics also show group differences compared with controls, including DTI metrics mean diffusivity (MD) and radial diffusivity (RD), the diffusional kurtosis imaging (DKI) metric mean kurtosis (MK), MT metrics MT ratio (MTR) and MT cerebrospinal fluid ratio (MTCSF), and the MRS metric of N-acetylaspartate (NAA) concentration, although these results were somewhat inconsistent.
CONCLUSIONS: State-of-the-art spinal cord MRI techniques are emerging with great potential to improve the diagnosis and management of various spinal pathologies, but the current body of evidence has only showed limited clinical utility to date. Among these imaging tools DTI is the most mature, but further work is necessary to standardize and validate its use before it will be adopted in the clinical realm. Large, well-designed studies with a priori hypotheses, standardized acquisition methods, detailed clinical data collection, and robust automated analysis techniques are needed to fully demonstrate the potential of these rapidly evolving techniques.