Quantification of the heterogeneity of cerebral blood flow SPECT in the patients with vascular dementia.

脑血流的不均匀分布是血管性痴呆SPECT的特征性表现之一。然而，尚未建立客观的方法来评价异质性。在这项研究中，我们将三维分形分析（3D-FA）应用于CBF SPECT图像，作为评估MID中CBF分布异质性的方法。首先，我们研究了18名MID患者和18名年龄匹配的对照组。使用^<99m>Tc-HMPAO获得CBF SPECT图像。在重建图像上，我们得到截断值（35% ~ 50%）与放射性超过截断值的体素数之间的线性回归方程，并将其转化为自然对数，然后计算分形维数（FD）作为由此得到的回归线的斜率。采用简易精神状态检查（MMSE）评估认知功能。MID组FD显著高于对照组（p < 0.0001）。MID组FD与MMSE评分呈显著负相关（r = 0.871, p < 0.0001）。第二，我们比较了老年痴呆症（AD）患者和MID患者的FDs，两组的FDs均显著低于对照组。两个FD（前区FD和后区FD: A/P比值）的比值AD大于1，MID小于1，MID的FD明显低于AD （P<0.001）。以上结果提示，脑血流SPECT分形维数可用于AD和MID痴呆的定量评价，FD的A/P比值可用于痴呆的鉴别诊断。

The heterogeneous distribution of CBF is one of the characteristic findings in SPECT for the vasucular dementia. However, no objective method to evaluate the heterogeneity has been established. In this study, we applied three-dimensional fractal analysis (3D-FA) to CBF SPECT images as a method for assessing the heterogeneity of the CBF distribution in MID. At first, we investigated 18 patients with MID and 18 age-matched controls. CBF SPECT images were obtained with ^<99m>Tc-HMPAO. On the reconstructed images, we obtained a linear regression equation between the cut-off values (from 35 to 50 %) and the number of voxels with a radioactivity exceeding the cut-off value transformed into natural logarithms, and then calculated the fractal dimension(FD) as the slope of the regression line thus obtained. The Mini-Mental State Examination (MMSE) was used to evaluate cognitive function. The FD was significantly greater in the MID group than in the control group (p < 0.0001). A significant negative correlation was observed between the FD and the MMSE score in the MID group (r = 0.871, p < 0.0001). In the second, we compared with the FDs of the patients with Alzheimer's disease(AD) and those of MID. The FDs of both groups were lower significantly than that of control subjects. The ratio of two FDs (FD of the anterior area and the FD of the posterior area: A/P ratio) was greater than 1 in the AD and lower 1 in the MID. The FD in the MID was siginificantly lower than that in the AD (P<0.001).These results suggested that the fractal dimension of CBF SPECT is useful in the quantitative evaluation of dementia in both the AD and the MID, and the A/P ratio of FD may be applied in differential diagnosis of dementia.