Aeromedical Research Department U.S. Air Force School of Aerospace Medicine Wright-Patterson AFB Dayton OH USA.
Department of Neurology 59th Medical Wing Joint Base San Antonio-Lackland San Antonio TX USA.
Brain Behav. 2017 Aug 2;7(9):e00759. doi: 10.1002/brb3.759. eCollection 2017 Sep.
Quantitative longitudinal magnetic resonance imaging and spectroscopy (MRI/S) is used to assess progress of brain disorders and treatment effects. Understanding the significance of MRI/S changes requires knowledge of the inherent technical and physiological consistency of these measurements. This longitudinal study examined the variance and reproducibility of commonly used quantitative MRI/S measurements in healthy subjects while controlling physiological and technical parameters.
Twenty-five subjects were imaged three times over 5 days on a Siemens 3T Verio scanner equipped with a 32-channel phase array coil. Structural (T1, T2-weighted, and diffusion-weighted imaging) and physiological (pseudocontinuous arterial spin labeling, proton magnetic resonance spectroscopy) data were collected. Consistency of repeated images was evaluated with mean relative difference, mean coefficient of variation, and intraclass correlation (ICC). Finally, a "reproducibility rating" was calculated based on the number of subjects needed for a 3% and 10% difference.
Structural measurements generally demonstrated excellent reproducibility (ICCs 0.872-0.998) with a few exceptions. Moderate-to-low reproducibility was observed for fractional anisotropy measurements in fornix and corticospinal tracts, for cortical gray matter thickness in the entorhinal, insula, and medial orbitofrontal regions, and for the count of the periependymal hyperintensive white matter regions. The reproducibility of physiological measurements ranged from excellent for most of the magnetic resonance spectroscopy measurements to moderate for permeability-diffusivity coefficients in cingulate gray matter to low for regional blood flow in gray and white matter.
This study demonstrates a high degree of longitudinal consistency across structural and physiological measurements in healthy subjects, defining the inherent variability in these commonly used sequences. Additionally, this study identifies those areas where caution should be exercised in interpretation. Understanding this variability can serve as the basis for interpretation of MRI/S data in the assessment of neurological disorders and treatment effects.
定量纵向磁共振成像和光谱（MRI/S）用于评估脑部疾病的进展和治疗效果。了解 MRI/S 变化的意义需要了解这些测量的固有技术和生理一致性。这项纵向研究在控制生理和技术参数的情况下，检查了健康受试者中常用的定量 MRI/S 测量的方差和可重复性。
25 名受试者在配备 32 通道相控阵线圈的西门子 3T Verio 扫描仪上进行了 3 次扫描，共 5 天。采集了结构（T1、T2 加权和弥散加权成像）和生理（伪连续动脉自旋标记、质子磁共振波谱）数据。通过平均相对差异、平均变异系数和组内相关系数（ICC）评估重复图像的一致性。最后，根据需要达到 3%和 10%差异的受试者数量计算了“再现性评分”。
结构测量通常表现出极好的可重复性（ICC 0.872-0.998），但也有一些例外。穹窿和皮质脊髓束的各向异性分数测量、内嗅、岛叶和内侧眶额皮质灰质厚度以及室周强化白质区的计数表现出中等到低的可重复性。生理测量的可重复性从大多数磁共振波谱测量的极好到扣带灰质的渗透性-扩散系数的中等到灰质和白质的区域血流的低不等。
这项研究在健康受试者中展示了结构和生理测量的高度纵向一致性，确定了这些常用序列固有的可变性。此外，本研究还确定了在解释时需要谨慎的领域。了解这种可变性可以为评估神经疾病和治疗效果的 MRI/S 数据解释提供基础。
