Absolute quantitation of diffusion constants in human stroke.
Absolute quantitation of diffusion constants in human stroke.
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DOI：
10.1161/01.str.28.3.483
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发表时间：
1997-03
期刊：
影响因子：
8.3
通讯作者：
A. Uluğ;N. Beauchamp;R. Bryan;P. Zijl
中科院分区：
文献类型：
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作者：
A. Uluğ;N. Beauchamp;R. Bryan;P. Zijl
背景和目的的动物研究表明，MR扩散成像可以在发生不可逆损伤（梗塞）之前概述急性缺血区域。为了研究人类缺血性病变的进化，因此必须量化绝对扩散常数（d值）很重要，但是在不同诊所之间尚不可再现定量。解释了这些问题，并提出了一种可重复的定量方法。获取方法扩散加权和绝对扩散图像，并测量了三个正交空间方向（DXX，DYY和DZZ）中的绝对明显扩散常数。将它们组合在一起以计算非方向无关的表观扩散参数DAV = 1/3痕迹[D] = 1/3（DXX + Dyy + DZZ）。在6例患者和6名正常志愿者中评估了个体扩散常数和DAV的值。结果患者数据表明，缺血后对侧和同侧半球之间扩散常数的比较可能会使结果因取决于方向而变化超过100％。在正常出现区域中，患者（n = 5）和正常志愿者（n = 6）中包含灰色和白质的混合物的发现表明DAV =（0.92 +/- 0.11）x 10（-3）mm2/s ，具有小的主题间变化，而DXX，DYY和DZZ差异很大。这些受试者中的半球比（IPSILED/对侧[I/C]）为（I/C）DAV = 1.00 +/- 0.05，（I/C）DXX = 1.02 +/- 0.15，（I/C）（I/C）Dyy = 1.07 +/- 0.24，（I/C）DZZ = 0.96 +/- 0.28。该组中的个别受试者在统一的10％以内都有（I/C）DAV，而其他三个比率显示出较大的差异。结论（I/C）DAV比是一种可靠的手段，用于定量绝对扩散常数的变化，以研究中风进化，而不是组织取向，梯度取向和扩散时间。这些比率的使用将实现可重复的主体间和界面的定量。
BACKGROUND AND PURPOSE Animal studies have shown that MR diffusion imaging can outline acute ischemic regions before irreversible damage (infarction) occurs. To study evolution of ischemic lesions in humans, it is therefore important to quantify absolute diffusion constants (D values), but quantitation has not been reproducible among different clinics. These problems are explained, and a method for reproducible quantitation is suggested. METHODS Diffusion-weighted and absolute diffusion images were acquired, and the absolute apparent diffusion constants in three orthogonal spatial directions (Dxx, Dyy, and Dzz) were measured. These were combined to calculate images of the orientation-independent apparent diffusion parameter Dav = 1/3 Trace[D] = 1/3(Dxx + Dyy + Dzz). Values of the individual diffusion constants and Dav were evaluated in 6 patients and 6 normal volunteers. RESULTS Patient data show that comparison of diffusion constants between contralateral and ipsilateral hemispheres after ischemia may give results varying by more than 100% depending on orientation. Findings in normal-appearing regions containing a mixture of gray and white matter in patients (n = 5) and in normal volunteers (n = 6) show that Dav = (0.92+/-0.11) x 10(-3) mm2/s, with a small intersubject variation, whereas Dxx, Dyy, and Dzz vary strongly. Hemispheric ratios (ipsilateral/contralateral [I/C]) in these subjects were (I/C)Dav = 1.00+/-0.05, (I/C)Dxx = 1.02+/-0.15, (I/C)Dyy = 1.07+/-0.24, and (I/C)Dzz = 0.96+/-0.28. The individual subjects in this group all had an (I/C)Dav within 10% of unity, while the other three ratios showed intersubject variations as large as 100%. CONCLUSIONS (I/C)Dav ratios are a reliable means to quantitate changes in absolute diffusion constants for the study of stroke evolution independent of tissue orientation, gradient orientation, and diffusion time. The use of these ratios will enable reproducible intersubject and interclinic quantitation.