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遺忘型輕度認知障礙患者中定量擴散拓撲模型特徵研究
Characterizing Topological Patterns inAmnestic Mild Cognitive Impairment by Quantitative Water Diffusivity
J Alzheimers Dis. 2015;43(2):687-97.doi: 10.3233/JAD-140882
Zhang B1, Zhang X1, Zhang F2, Li M1, SchwarzCG3, Zhang J2, Yin Z4, Qian L4, Zhao H4, Wang K1, Tian C1, Yu H1, Chen W5, Lu F1, Wu W1, Yang QX6, Xu Y4, Zhu B1
1Departmentof Radiology, The Affiliated Drum Tower Hospital of Nanjing University MedicalSchool, Nanjing, China.
2Departmentof Biomedical Engineering, Shanghai Jiao-tong University, School of Medicine,Shanghai, China.
3Departmentof Radiology, Mayo Clinic, Rochester, Minnesota, MN, USA.
4Departmentof Neurology, The Affiliated Drum Tower Hospital of Nanjing University MedicalSchool, Nanjing, China.
5PhilipsMedical Care Division, China.
6Departmentof Radiology, Pennsylvania State College of Medicine, Hershey, PA, USA.
【MR scanner：Achieva 3.0T TX dual-source parallel RFexcitation and transmission technology, Philips Medical Systems, TheNetherlands】
Abstract. Mean diffusivity (MD) derived from diffusion tensor imaging has shown its ability to assess the microscopic structural integrity damage of gray matter in amnestic mild cognitive impairment (aMCI), a prodromal stage of Alzheimer’s disease (AD). However, little is known about the small world topology networks constructed by cortical MD in cognitive disease. In this work, we measured the cortical MD in the entire brain in patients with aMCI (n = 30) and AD (n= 30) compared with cognitive-normal (CNs) controls (n = 30), and then constructed the cortical diffusivity network by using graph-theoretical analysis. Compared with CNs,patients with aMCI and AD showed abnormal small-world property of cortical diffusivity networks (higher degree of clustering and longer path length),reflecting a less optimal topological organization. Moreover, the mean degree of connections of network in aMCI patients was characterized by lower than CNs but higher than AD. In addition, 11 hub regions were identified by negative correlations between MD and the score of Montreal Cognitive Assessment aftermultiple regression analysis, including bilateral hippocampi and related limbic system. Among those hub regions, the connectivity of the right olfactory cortexand middle orbital gyrus to the rest of brain regions were disrupted earlier than the other 9 regions in aMCI when compared to CN. In conclusion, the change of cortical diffusivity in topological network organization, mean degree of connections, and disrupted hub regions in aMCI may serve to identify patients in the prodromal stage of AD and reflect microstructural deterioration of neurodegeneration.
摘要:基於彌散張量成像模型所得平均彌散係數可以用於評估遺忘型輕度認知障礙患者（aMCI）中其灰質結構微觀完整性受損情況。然而，對於小世界拓撲結構在認知疾病中皮層平均擴散係數構建的網絡則缺乏了解。本研究中, 我們納入遺忘型輕度認知障礙患者（30例），阿爾茲海默患者（30例）以及認知正常的對照組（30例），然後採用圖論分析構建皮層彌散網絡。與正常對照組相比，遺忘型輕度認知障礙以及阿爾茲海默患者的皮層彌散網絡中顯示出異常小世界網絡特徵（更高級別聚類以及更長路徑），呈現出非最優化拓撲結構。此外，遺忘型輕度認知障礙患者相比正常對照組在網絡平均連接度方面要低，但較阿爾茲海默患者要高。此外，經多元回歸分析判別出在11個樞紐區的平均彌散係數和蒙特婁認知評估分數存在負相關，包括雙側海馬以及相關的邊緣系統。在這些樞紐區中，遺忘型輕度認知障礙患者較正常對照組的右側嗅皮質和眶中回與大腦其它區域的連結相比其它9個區域的連結最早被中斷。總之，在阿爾茲海默先兆期遺忘型輕度認知障礙患者拓撲網絡結構中皮層彌散變化，平均連接度，以及樞紐中斷可能作為退行性疾病中反映微觀結構惡化的指標。
Fig. 1. Brain regions showing affectedsignificantly by the cognitive status in whole brain networks p < 0.05 (corrected). A graph-theoreticalanalysis was performed by Brainnetviewer software (NKLCNL, Beijing NormalUniversity) to explore the connections pattern at Pearson correlation r > 0.7. The node sizes indicate the numberof connections to that node. The edge between nodes indicate the statisticallyassociation in MD value between 2 brain areas. Red and blue nodes indicate theregions where the brain areas affected MoCA scores significantly, which weredefined as hub nodes. Red nodes indicate the bilateral hippocampi. L, left; R,right. In total, there is 11 hub nodes, mainly in the limbic system, includingthe bilateral hippocampi (HP), the right parahippocampus (PHG), and limbiccortex as following, the right olfactory cortex (OLF), the right middle orbitalfrontal gyrus (ORBsupmed), the right precuneus (PCUN), the right insula (INS),the right Rolandic operculum (ROL), as well as the left superior parietal lobe(SPG), the left lingual gyrus (LING), and the right supplementary motor area(SMA). The number of the hub nodes decreased from 11 in CNs (A) to 9 in aMCI(B). There only are 7 hub nodes in AD (C).
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