Schmierer Klaus, Wheeler-Kingshott Claudia A M, Tozer Daniel J, Boulby Phil A, Parkes Harold G, Yousry Tarek A, Scaravilli Francesco, Barker Gareth J, Tofts Paul S, Miller David H
NMR Research Unit, Institute of Neurology, University College London, Queen Square, London, UK.
Magn Reson Med. 2008 Feb;59(2):268-77. doi: 10.1002/mrm.21487.
Unfixed and fixed postmortem multiple sclerosis (MS) brain is being used to probe pathology underlying quantitative MR (qMR) changes. Effects of fixation on qMR indices in MS brain are unknown. In 15 postmortem MS brain slices T(1), T(2), MT ratio (MTR), macromolecular proton fraction (f(B)), fractional anisotropy (FA), and mean, axial, and radial diffusivity (MD, D(ax), and D(rad)) were assessed in white matter (WM) lesions (WML) and normal appearing WM (NAWM) before and after fixation in formalin. Myelin content, axonal count, and gliosis were quantified histologically. Student's t-test and regression were used for analysis. T(1), T(2), MTR, and f(B) obtained in unfixed MS brain were similar to published values obtained in patients with MS in vivo. Following fixation T(1), T(2) (NAWM, WML) and MTR (NAWM) dropped, whereas f(B) (NAWM, WML) increased. Compared to published in vivo data all diffusivity measures were lower in unfixed MS brain, and dropped further following fixation (except for FA). MTR was the best predictor of T(myelin) (inversely related to myelin) in unfixed MS brain (r = -0.83; P < 0.01) whereas postfixation T(2) (r = 0.92; P < 0.01), T(1) (r = 0.89; P < 0.01), and f(B) (r = -0.86; P < 0.01) were superior. All diffusivity measures (except for D(ax) in unfixed tissue) were predictors of myelin content.
未固定和固定后的多发性硬化症（MS）尸检脑正被用于探究定量磁共振成像（qMR）变化背后的病理机制。固定对MS脑qMR指标的影响尚不清楚。在15个MS尸检脑切片中，在福尔马林固定前后，对白质（WM）病变（WML）和正常外观白质（NAWM）中的T(1)、T(2)、磁化传递比率（MTR）、大分子质子分数（f(B)）、各向异性分数（FA）以及平均、轴向和径向扩散率（MD、D(ax)和D(rad)）进行了评估。对髓鞘含量、轴突计数和胶质增生进行了组织学定量分析。采用学生t检验和回归分析。在未固定的MS脑中获得的T(1)、T(2)、MTR和f(B)与在MS患者体内获得的已发表值相似。固定后，T(1)、T(2)（NAWM、WML）和MTR（NAWM）下降，而f(B)（NAWM、WML）增加。与已发表的体内数据相比，未固定的MS脑中所有扩散率测量值均较低，固定后进一步下降（FA除外）。在未固定的MS脑中，MTR是T(髓鞘)（与髓鞘呈负相关）的最佳预测指标（r = -0.83；P < 0.01），而固定后T(2)（r = 0.92；P < 0.01）、T(1)（r = 0.89；P < 0.01）和f(B)（r = -0.86；P < 0.01）更优。所有扩散率测量值（未固定组织中的D(ax)除外）均为髓鞘含量的预测指标。
