The aim of this study was to propose an algorithm for three-dimensional projection onto convex sets (3D POCS) to achieve super resolution reconstruction of 3D lung computer tomography (CT) images, and to introduce multi-resolution mixed display mode to make 3D visualization of pulmonary nodules. Firstly, we built the low resolution 3D images which have spatial displacement in sub pixel level between each other and generate the reference image. Then, we mapped the low resolution images into the high resolution reference image using 3D motion estimation and revised the reference image based on the consistency constraint convex sets to reconstruct the 3D high resolution images iteratively. Finally, we displayed the different resolution images simultaneously. We then estimated the performance of provided method on 5 image sets and compared them with those of 3 interpolation reconstruction methods. The experiments showed that the performance of 3D POCS algorithm was better than that of 3 interpolation reconstruction methods in two aspects, i.e. subjective and objective aspects, and mixed display mode is suitable to the 3D visualization of high resolution of pulmonary nodules.
ObjectiveTo investigate the biomechanical properties of artificial ligament in the treatment of injuries to distal tibiofibular syndesmosis so as to provide a scientific basis for clinical application. MethodsSixteen fresh ankle specimens were harvested from 8 normal fresh-frozen cadavers. The initial tests were performed on 16 intact specimens (group A) and then the distal tibiofibular syndesmosis injury models were made (group B); the distal tibiofibular syndesmosis was fixed with artificial ligament in 8 specimens (group C) and with cannulated lag screw in the other 8 specimens (group D). The pros and cons of different fixation methods were analyzed by displacement, stress shielding effect, the strength and stiffness of ankle joints, the contact area of tibiotalar articular surface and the contact stress. ResultsUnder the physiological loading or combined with external rotation moment, the displacement of group C was significantly lower than that of groups B and D (P < 0.05), but no significant difference was found between groups A and C (P > 0.05); and there were significant differences among groups A, B, and D (P < 0.05). The rates of stress shielding in the tibia and fibula of group C were significantly lower than those of group D (t=-71.288, P=0.000;t=-97.283, P=0.000). The stress strength in tibia of group C was significantly higher than that of groups A and D (P < 0.05), but no significant difference was found between groups A and D (P > 0.05). Group C had the highest stress strength in fibula, followed by group A, group D had the lowest; differences were significant among 3 groups (P < 0.05). There was no significant difference in shear strength among groups A, C, and D (P > 0.05). The axial stiffness in tibia of group D was significantly lower than that of groups A and C (P < 0.05), but no significant difference was found between groups A and C (P > 0.05). The axial stiffness in fibula of group C was significantly higher than that of groups A and D (P < 0.05), but no significant difference was found between groups A and D (P > 0.05). Group C had the highest shear stiffness in tibia and fibula, followed by group D, group A had the lowest; differences were significant among 3 groups (P < 0.05). In groups A, C, and D, the contact area of tibiotalar articular surface gradually reduced, and the contact stress gradually increased, and differences were significant among 3 groups (P < 0.05). ConclusionFixation of distal tibiofibular syndesmosis injury with artificial ligament can better meet the physiological functions of the distal tibiofibular syndesmosis and has lower stress shielding, better stress distribution. Hopefully, it can reduce the complications of the distal tibiofibular syndesmosis injuries and become a better treatment choice.