Jovicich Jorge, Czanner Silvester, Han Xiao, Salat David, van der Kouwe Andre, Quinn Brian, Pacheco Jenni, Albert Marilyn, Killiany Ronald, Blacker Deborah, Maguire Paul, Rosas Diana, Makris Nikos, Gollub Randy, Dale Anders, Dickerson Bradford C, Fischl Bruce
Center for Mind-Brain Sciences, Department of Cognitive and Education Sciences, University of Trento, Italy.
Neuroimage. 2009 May 15;46(1):177-92. doi: 10.1016/j.neuroimage.2009.02.010. Epub 2009 Feb 20.
Automated MRI-derived measurements of in-vivo human brain volumes provide novel insights into normal and abnormal neuroanatomy, but little is known about measurement reliability. Here we assess the impact of image acquisition variables (scan session, MRI sequence, scanner upgrade, vendor and field strengths), FreeSurfer segmentation pre-processing variables (image averaging, B1 field inhomogeneity correction) and segmentation analysis variables (probabilistic atlas) on resultant image segmentation volumes from older (n=15, mean age 69.5) and younger (both n=5, mean ages 34 and 36.5) healthy subjects. The variability between hippocampal, thalamic, caudate, putamen, lateral ventricular and total intracranial volume measures across sessions on the same scanner on different days is less than 4.3% for the older group and less than 2.3% for the younger group. Within-scanner measurements are remarkably reliable across scan sessions, being minimally affected by averaging of multiple acquisitions, B1 correction, acquisition sequence (MPRAGE vs. multi-echo-FLASH), major scanner upgrades (Sonata-Avanto, Trio-TrioTIM), and segmentation atlas (MPRAGE or multi-echo-FLASH). Volume measurements across platforms (Siemens Sonata vs. GE Signa) and field strengths (1.5 T vs. 3 T) result in a volume difference bias but with a comparable variance as that measured within-scanner, implying that multi-site studies may not necessarily require a much larger sample to detect a specific effect. These results suggest that volumes derived from automated segmentation of T1-weighted structural images are reliable measures within the same scanner platform, even after upgrades; however, combining data across platform and across field-strength introduces a bias that should be considered in the design of multi-site studies, such as clinical drug trials. The results derived from the young groups (scanner upgrade effects and B1 inhomogeneity correction effects) should be considered as preliminary and in need for further validation with a larger dataset.
通过自动化磁共振成像（MRI）测量活体人类脑容量，能为正常和异常神经解剖学提供新的见解，但对于测量可靠性却知之甚少。在此，我们评估了图像采集变量（扫描时段、MRI序列、扫描仪升级、供应商和场强）、FreeSurfer分割预处理变量（图像平均、B1场不均匀性校正）以及分割分析变量（概率图谱）对年龄较大（n = 15，平均年龄69.5岁）和年龄较小（均为n = 5，平均年龄分别为34岁和36.5岁）的健康受试者所得图像分割体积的影响。在同一台扫描仪上不同日期进行的各次扫描中，老年组海马体、丘脑、尾状核、壳核、侧脑室和总颅内体积测量值之间的变异性小于4.3%，而年轻组则小于2.3%。在同一台扫描仪内，各次扫描的测量结果非常可靠，受多次采集平均、B1校正、采集序列（MPRAGE与多回波FLASH）、主要扫描仪升级（索纳塔 - 阿凡托、 Trio - TrioTIM）以及分割图谱（MPRAGE或多回波FLASH）的影响极小。跨平台（西门子索纳塔与通用电气Signa）和场强（1.5 T与3 T）的体积测量会导致体积差异偏差，但方差与同一台扫描仪内测量的方差相当，这意味着多中心研究不一定需要大得多的样本量就能检测到特定效应。这些结果表明，即使经过升级，在同一扫描仪平台内，从T1加权结构图像的自动分割得出的体积是可靠的测量值；然而，跨平台和跨场强合并数据会引入偏差，在多中心研究（如临床药物试验）设计中应予以考虑。来自年轻组的结果（扫描仪升级效应和B1不均匀性校正效应）应视为初步结果，需要用更大的数据集进行进一步验证。
