Mulder Emma R, de Jong Remko A, Knol Dirk L, van Schijndel Ronald A, Cover Keith S, Visser Pieter J, Barkhof Frederik, Vrenken Hugo
Image Analysis Center, VU University Medical Center, Amsterdam, The Netherlands; Department of Radiology, VU University Medical Center, Amsterdam, The Netherlands.
Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands.
Neuroimage. 2014 May 15;92:169-81. doi: 10.1016/j.neuroimage.2014.01.058. Epub 2014 Feb 9.
To measure hippocampal volume change in Alzheimer's disease (AD) or mild cognitive impairment (MCI), expert manual delineation is often used because of its supposed accuracy. It has been suggested that expert outlining yields poorer reproducibility as compared to automated methods, but this has not been investigated.
To determine the reproducibilities of expert manual outlining and two common automated methods for measuring hippocampal atrophy rates in healthy aging, MCI and AD.
From the Alzheimer's Disease Neuroimaging Initiative (ADNI), 80 subjects were selected: 20 patients with AD, 40 patients with mild cognitive impairment (MCI) and 20 healthy controls (HCs). Left and right hippocampal volume change between baseline and month-12 visit was assessed by using expert manual delineation, and by the automated software packages FreeSurfer (longitudinal processing stream) and FIRST. To assess reproducibility of the measured hippocampal volume change, both back-to-back (BTB) MPRAGE scans available for each visit were analyzed. Hippocampal volume change was expressed in μL, and as a percentage of baseline volume. Reproducibility of the 1-year hippocampal volume change was estimated from the BTB measurements by using linear mixed model to calculate the limits of agreement (LoA) of each method, reflecting its measurement uncertainty. Using the delta method, approximate p-values were calculated for the pairwise comparisons between methods. Statistical analyses were performed both with inclusion and exclusion of visibly incorrect segmentations.
Visibly incorrect automated segmentation in either one or both scans of a longitudinal scan pair occurred in 7.5% of the hippocampi for FreeSurfer and in 6.9% of the hippocampi for FIRST. After excluding these failed cases, reproducibility analysis for 1-year percentage volume change yielded LoA of ±7.2% for FreeSurfer, ±9.7% for expert manual delineation, and ±10.0% for FIRST. Methods ranked the same for reproducibility of 1-year μL volume change, with LoA of ±218 μL for FreeSurfer, ±319 μL for expert manual delineation, and ±333 μL for FIRST. Approximate p-values indicated that reproducibility was better for FreeSurfer than for manual or FIRST, and that manual and FIRST did not differ. Inclusion of failed automated segmentations led to worsening of reproducibility of both automated methods for 1-year raw and percentage volume change.
Quantitative reproducibility values of 1-year microliter and percentage hippocampal volume change were roughly similar between expert manual outlining, FIRST and FreeSurfer, but FreeSurfer reproducibility was statistically significantly superior to both manual outlining and FIRST after exclusion of failed segmentations.
为了测量阿尔茨海默病（AD）或轻度认知障碍（MCI）患者海马体积的变化，由于其准确性，常采用专家手动勾勒法。有人认为，与自动化方法相比，专家勾勒的可重复性较差，但尚未对此进行研究。
确定专家手动勾勒法以及两种常见的自动化方法在测量健康老年人、MCI和AD患者海马萎缩率方面的可重复性。
从阿尔茨海默病神经影像倡议（ADNI）中选取80名受试者：20例AD患者、40例轻度认知障碍（MCI）患者和20名健康对照者（HCs）。使用专家手动勾勒法以及自动化软件包FreeSurfer（纵向处理流程）和FIRST评估基线和第12个月随访之间左右海马体积的变化。为了评估测量的海马体积变化的可重复性，对每次随访可用的连续两次（BTB）MPRAGE扫描进行分析。海马体积变化以微升表示，并以基线体积的百分比表示。通过使用线性混合模型计算每种方法的一致性界限（LoA），从BTB测量值估计1年海马体积变化的可重复性，反映其测量不确定性。使用德尔塔法计算方法之间成对比较的近似p值。在纳入和排除明显错误的分割的情况下均进行了统计分析。
在FreeSurfer的纵向扫描对中，一次或两次扫描中出现明显错误的自动化分割的海马占7.5%，在FIRST中占6.9%。排除这些失败病例后，对1年体积变化百分比的可重复性分析得出，FreeSurfer的LoA为±7.2%，专家手动勾勒法为±9.7%，FIRST为±10.0%。对于1年微升体积变化的可重复性，方法排名相同，FreeSurfer的LoA为±218微升，专家手动勾勒法为±319微升，FIRST为±333微升。近似p值表明，FreeSurfer的可重复性优于手动勾勒法或FIRST，而手动勾勒法和FIRST之间没有差异。纳入失败的自动化分割导致两种自动化方法在1年原始体积和体积变化百分比方面的可重复性变差。
专家手动勾勒法、FIRST和FreeSurfer在1年微升和海马体积变化百分比的定量可重复性值大致相似，但在排除失败分割后，FreeSurfer的可重复性在统计学上显著优于手动勾勒法和FIRST。
