Fraser Mark A, Shaw Marnie E, Anstey Kaarin J, Cherbuin Nicolas
Centre for Research on Ageing, Health and Wellbeing, Australian National University, Florey, Building 54, Mills Road, Canberra, ACT, 2601, Australia.
College of Engineering & Computer Science, Australian National University, Brian Anderson Building 115, 115 North Road, Canberra, ACT, 2601, Australia.
Brain Topogr. 2018 Nov;31(6):949-962. doi: 10.1007/s10548-018-0659-2. Epub 2018 Jul 4.
It is important to have accurate estimates of normal age-related brain structure changes and to understand how the choice of measurement technique may bias those estimates. We compared longitudinal change in hippocampal volume, laterality and atrophy measured by manual tracing and FreeSurfer (version 5.3) in middle age (n = 244, 47.2[1.4] years) and older age (n = 199, 67.0[1.4] years) individuals over 8 years. The proportion of overlap (Dice coefficient) between the segmented hippocampi was calculated and we hypothesised that the proportion of overlap would be higher for older individuals as a consequence of higher atrophy. Hippocampal volumes produced by FreeSurfer were larger than manually traced volumes. Both methods produced a left less than right volume laterality difference. Over time this laterality difference increased for manual tracing and decreased for FreeSurfer leading to laterality differences in left and right estimated atrophy rates. The overlap proportion between methods was not significantly different for older individuals, but was greater for the right hippocampus. Estimated middle age annualised atrophy rates were - 0.39(1.0) left, 0.07(1.01) right, - 0.17(0.88) total for manual tracing and - 0.15(0.69) left, - 0.20(0.63) right, - 0.18(0.57) total for FreeSurfer. Older age atrophy rates were - 0.43(1.32) left, - 0.15(1.41) right, - 0.30 (1.23) total for manual tracing and - 0.34(0.79) left, - 0.68(0.78) right, - 0.51(0.65) total for FreeSurfer. FreeSurfer reliably segments the hippocampus producing atrophy rates that are comparable to manual tracing with some biases that need to be considered in study design. FreeSurfer is suited for use in large longitudinal studies where it is not cost effective to use manual tracing.
准确估计与年龄相关的正常脑结构变化，并了解测量技术的选择如何可能使这些估计产生偏差，这很重要。我们比较了通过手工追踪和FreeSurfer（版本5.3）测量的中年（n = 244，47.2[1.4]岁）和老年（n = 199，67.0[1.4]岁）个体在8年期间海马体积、不对称性和萎缩的纵向变化。计算了分割海马之间的重叠比例（迪赛系数），我们假设由于萎缩程度较高，老年个体的重叠比例会更高。FreeSurfer生成的海马体积大于手工追踪的体积。两种方法都产生了左侧体积小于右侧的不对称差异。随着时间的推移，这种不对称差异在手工追踪中增加，而在FreeSurfer中减少，导致左右估计萎缩率的不对称差异。老年个体中两种方法之间的重叠比例没有显著差异，但右侧海马的重叠比例更大。手工追踪估计的中年年化萎缩率为左侧-0.39(1.0)、右侧0.07(1.01)、总体-0.17(0.88)，FreeSurfer为左侧-0.15(0.69)、右侧-0.20(0.63)、总体-0.18(0.57)。老年萎缩率手工追踪为左侧-0.43(1.32)、右侧-0.15(1.41)、总体-0.30(1.23)；FreeSurfer为左侧-0.34(0.79)、右侧-0.68(0.78)、总体-0.51(0.65)。FreeSurfer能够可靠地分割海马，生成与手工追踪相当的萎缩率，但存在一些偏差，在研究设计中需要考虑。FreeSurfer适用于大型纵向研究，在这些研究中使用手工追踪不具有成本效益。
