Radiation-induced changes in small world network in patients with nasopharyngeal carcinoma: a three-dimensional structure MRI imaging study

Objective To investigate the radiotherapy (RT)-induced changes in the brain structural network in patients with nasopharyngeal carcinoma (NPC). Methods Three-dimensional structural magnetic resonance data (3D-T1W) was adopted to investigate the structural network in 103 patients with NPC before and after receiving RT. The structural networks were then reconstructed using 3D-T1W. The radiation-induced changes in topology properties of small world network were analyzed by using graph theoretical analysis. Results Patients showed small world properties before and after RT. Compared with the pre-RT group, the global and local efficiency were lower, the shortest path length was longer and the clustering coefficient was less in the post-RT group. In addition, the hub regions in the post-RT group were significantly different from those in the pre-RT group, mainly located in the left rolandic operculum, right inferior frontal gyrus, right parahippocampal gyrus, right lingual gyrus, bilateral supramarginal gyrus, left superior temporal gyrus and temporal pole of the right middle temporal gyrus. Conclusion It is speculated that RT leads to high efficiency of network topology and information transmission, which provides a novel perspective for exploring the RT-induced brain changes, diagnosis of RT-induced injury and evaluation of RT efficacy. Key words: Nasopharyngeal neoplasm/radiotherapy; Voxel-based morphometry; Gray matter; Small world property