Han Xiao, Jovicich Jorge, Salat David, van der Kouwe Andre, Quinn Brian, Czanner Silvester, Busa Evelina, Pacheco Jenni, Albert Marilyn, Killiany Ronald, Maguire Paul, Rosas Diana, Makris Nikos, Dale Anders, Dickerson Bradford, Fischl Bruce
Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02129, USA.
Neuroimage. 2006 Aug 1;32(1):180-94. doi: 10.1016/j.neuroimage.2006.02.051. Epub 2006 May 2.
In vivo MRI-derived measurements of human cerebral cortex thickness are providing novel insights into normal and abnormal neuroanatomy, but little is known about their reliability. We investigated how the reliability of cortical thickness measurements is affected by MRI instrument-related factors, including scanner field strength, manufacturer, upgrade and pulse sequence. Several data processing factors were also studied. Two test-retest data sets were analyzed: 1) 15 healthy older subjects scanned four times at 2-week intervals on three scanners; 2) 5 subjects scanned before and after a major scanner upgrade. Within-scanner variability of global cortical thickness measurements was <0.03 mm, and the point-wise standard deviation of measurement error was approximately 0.12 mm. Variability was 0.15 mm and 0.17 mm in average, respectively, for cross-scanner (Siemens/GE) and cross-field strength (1.5 T/3 T) comparisons. Scanner upgrade did not increase variability nor introduce bias. Measurements across field strength, however, were slightly biased (thicker at 3 T). The number of (single vs. multiple averaged) acquisitions had a negligible effect on reliability, but the use of a different pulse sequence had a larger impact, as did different parameters employed in data processing. Sample size estimates indicate that regional cortical thickness difference of 0.2 mm between two different groups could be identified with as few as 7 subjects per group, and a difference of 0.1 mm could be detected with 26 subjects per group. These results demonstrate that MRI-derived cortical thickness measures are highly reliable when MRI instrument and data processing factors are controlled but that it is important to consider these factors in the design of multi-site or longitudinal studies, such as clinical drug trials.
通过活体磁共振成像（MRI）测量人类大脑皮层厚度，为正常和异常神经解剖学提供了新的见解，但对其可靠性却知之甚少。我们研究了MRI仪器相关因素如何影响皮层厚度测量的可靠性，这些因素包括扫描仪场强、制造商、升级情况和脉冲序列。还研究了几个数据处理因素。分析了两个重测数据集：1）15名健康老年受试者在三台扫描仪上每隔两周扫描四次；2）5名受试者在扫描仪进行重大升级前后进行扫描。全球皮层厚度测量的扫描仪内变异性<0.03毫米，测量误差的逐点标准差约为0.12毫米。对于跨扫描仪（西门子/通用电气）和跨场强（1.5 T/3 T）比较，变异性平均分别为0.15毫米和0.17毫米。扫描仪升级并未增加变异性，也未引入偏差。然而，跨场强测量存在轻微偏差（3 T时更厚）。采集次数（单次与多次平均）对可靠性的影响可忽略不计，但使用不同的脉冲序列以及数据处理中采用的不同参数影响更大。样本量估计表明，两组之间区域皮层厚度差异为0.2毫米时，每组仅需7名受试者即可识别，差异为0.1毫米时，每组26名受试者即可检测到。这些结果表明，当控制MRI仪器和数据处理因素时，MRI衍生的皮层厚度测量具有高度可靠性，但在多中心或纵向研究（如临床药物试验）的设计中考虑这些因素很重要。
