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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.
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Objective To analyze the setup errors of external?beam and intracavitary radiotherapy for cervical cancer based on the data of cone?beam computed tomography ( CBCT) , and to provide a basis for clinical practice. Methods Sixty patients with stage ⅡA?ⅢB cervical cancer who were admitted to our hospital and underwent external?beam and intracavitary radiotherapy from March to June, 2015 were enrolled as subjects. Sixty patients with stage ⅡA?ⅢB cervical cancer undergoing conventional external?beam radiotherapy within the same period were also enrolled. The CBCT?based setup errors, containing setup errors in x, y, and z directions and three?dimensional vector deviation, in the initial treatment were obtained from each patient. Comparison of errors between the two treatment approaches was made by independent?samples t test. Results Fitting the data to a linear model revealed that the setup errors in x, y, and z directions increased with the increase in the distance between the position reference point and the center point of the target volume. External?beam radiation combined with intracavitary radiation had significantly reduced setup errors in x, y, and z directions than the conventional external?beam radiation ( 0.13± 0?12 vs. 0.31± 0?24, P=0?000;0.23±0?18 vs. 0.47±0?36, P=0?001;0.18±0?11 vs. 0.27±0?18, P=0?001). Conclusions In order to reduce the setup errors, CT scan needs not only a reference marker as close as possible to the center of the tumor, but also a reliable and accurate approach for postural fixation.