Posted: 2015/05/27 16:02 | Author: NICA

On May 25th, 3 o’clock P.M, Dr. Jieqiong Wang passed the Doctoral Dissertation Defense in the conference room on 9th floor of Automation Building. Her thesis topic is ” Investigation of Brain Structure, Function and Network in Primary Open Angle Glaucoma with Multi-modal Imaging”.

Here is the abstract:

Glaucoma is the second leading cause of blindness and has been the topic of intense study to uncover the underlying mechanisms of the disease. In this dissertation, we applied multi-modal imaging including T1-weighted imaging and resting-state fMRI to investigate the alterations of brain structure, function and network in primary open angle glaucoma (POAG) patients. The contents and contributions of this dissertation are as follows:

(1) We proposed an automatic lateral geniculate nucleus (LGN) segmentation algorithm based on T1-weighted imaging. First, we used the prior information of LGN, i.e. LGN is a part of ventral diencephalon area (VDC), to create a prior mask. Then we applied region growing with radius 5mm to delineate LGN. The experiment results proved the validity of the segmentation algorithm. In addition, we found LGN asymmetry as well as LGN atrophy along with age in the normal controls. We also applied the automatic LGN segmentation to investigate glaucoma effects on LGN volumes and found that the bilateral LGN volumes became smaller in glaucoma patients and the LGN volumes were correlated with clinical parameters in patients.

(2) We investigated brain structural changes comprehensively in POAG patients by three independent measurements: volume-based analysis (VBA), surface-based analysis (SBA) and ROI-based analysis. VBA showed no significant differences in gray matter volumes between two groups. SBA revealed significantly reduced cortical thickness in the right frontal pole, and ROI-based analysis showed volume shrinkage in bilateral LGN, right V1 (caused by reduced right V1 thickness) and left amygdala. Moreover, the bilateral LGN volumes and the right V1 thickness were correlated with clinical parameters in glaucoma. These results demonstrate that structures alterations not only affect vision-related structures but also other cortical regions in POAG patients.

(3) We investigated brain functional changes comprehensively in POAG patients by the analysis of ALFF (Amplitude of Low Frequency Fluctuation), fALFF (fractional ALFF) and ReHo (Regional Homogeneity). ALFF analysis showed lower ALFF in the bilateral occipital pole in patients. fALFF analysis showd lower fALFF in the left cuneus, the right fusiform gyrus and the right occipital pole and higher fALFF in the left temporal pole. ReHo analysis showed lower ReHo in the bilateral occipital pole and the left lingual gyrus. These results prove the functional alterations of the visual cortex in POAG patients, and also demonstrate that glaucoma is not only an eye disease but may also be associated with brain functional alterations.

(4) We applied the graphy theory to investigate the reorgazation of brain network pattern in POAG patients at both global and local level. No significant differences were found between the global measures of the network in two groups. However, all the local measures reorganized significantly in the patient group. Comparing with the normal controls, we found 6 disappeared cortical hubs and 9 appeared cortical hubs in the barin networks of POAG patients. The betweenness centrality of right fusiform gyrus and right ligunal gyrus were correlated with the visual field in patients. All these results declare the reorganization of the brain network pattern in POAG patients as well as the betweenness centrality of right fusiform gyrus and right ligunal gyrus can be used as the biomarkers of glaucoma severity.

(5) We investigated the alterations of visual network and default mode network (DMN) in POAG patients. Firtsly, we performed group independent component analysis on resting-state fMRI to obtain the visual network and DMN. Then we conducted both functional connectivity (FC) analysis and functional network connectivity (FNC) analysis on these two subnetworks. FC analaysis showed decreased FC in the occipital pole of visual network. FNC analysis showed i) decreased intraconnectivity within visual network, ii) two decreased interconnecitivities between two subnetworks and one increased interconnecitivity between two subnetworks that was negatively correlated with right visual filed. All these results demonstrate the subnetworks reorganization in POAG patients.