Objective To study the value of three-dimensional (3D) visualization and virtual surgery system in piggyback liver transplantation. Methods Two patients who suffered from choledocholithiasis were scanned by 64-slice spiral CT and the data were collected. The segmentation of the hepatic CT images was carried out. The 3D model of the liver and the intrahepatic vessels was reconstructed, and was imported to the FreeForm Modeling System in STL format for smoothing and modifying. Piggyback liver transplantation was simulated with the force-feedback equipment (PHANToM). Results The reconstructed 3D model of the liver was vivid, and the process of the virtual piggyback liver transplantation was verisimilar. Conclusions The 3D model of the liver enables the simulation of piggyback liver transplantation. It can reduce the risk and complications of the surgery, and enhance the communication between doctor and patient through designing surgical plan and demonstrating visualized operation before surgery. Virtual liver transplantation is also helpful during the training of medical workers.

Objective To examine the association between social isolation and cognitive function among the elderly living in the communities of Daqing city.Methods A total of 981 community residents aged 60 years or over,were surveyed with a questionnaire.Both Lubben Social Network Scale-6 (LSNS-6) and Montreal Congnitive Assessment (MoCA) Changsha Versions were used to respectively screen the status of social isolation and cognitive function,on these elderly.Results The average age was 71 years old for the 981 study participants.10.60％ (104/981) of the participants were assessed as having the status of social isolation,9.48％ (93/981) as having marginal family ties and 13.97％ (137/981) as having marginal friendship ties.Results from the multivariate linear regression analysis revealed that participants with higher scores of LSNS-6 presenting better cognitive function score,with a partial regression coefficient as 0.10 (P＜0.01).The MoCA scores in participants with social isolation (20.38 ± 5.54) were significantly lower than the ones without social isolation (22.10 ± 5.01) and the difference was statistically significant (P＜0.01).Social isolation was significantly related to the domain scores on visuo-spatial constructional executive functions (P=0.02),naming (P=0.03),language (P=0.01) and delayed memory functions (P＜0.01),but not with other domains as concentration (P=0.33),orientation (P=0.27) or abstraction (P=0.49).Conclusion The findings suggested that social isolation was mainly caused by the lack of friendship ties and associated with cognitive function and among the elderly in Daqing city,Heilongjiang province.