A new method for the simulation of the mass distribution of cancellous bone is presented on the basis of finite element analysis (FEA). In this method,the process of bone remodelling is considered as a process of the topology optimization of a corresponding continuum structure. Fabric tensor is used to express the microstructure and the constitutive properties of cancellous bone. The effective volume fraction or the relative density of a point in the design domain is expressed by the invariables of the fabric tensor. A reference strain interval, which is corresponding to the strain dead zone of a bone in biomechanics, is applied to detect the the final topology of the structure. By the present approach, several numerical results are given, i. e., the simulation on the shape of the coronal plane of vertebrae, the predictions of the mass distributions of the two-dimensional and the three-dimensional proximal femurs. The validity and feasibility of this new method are verified by the comparison between the results of the present work and those in the published literatures.
Adaptation, Physiological ; Algorithms ; Biomechanical Phenomena ; Bone Density ; physiology ; Bone Remodeling ; physiology ; Bone and Bones ; physiology ; Computer Simulation ; Femur Head ; physiology ; Finite Element Analysis ; Humans ; Models, Biological ; Stress, Mechanical

Objective To evaluate 18F-FDG hPET/CT in the diagnosis of postoperative recurrence and metastasis of colorectal cancer. Methods GE HAWKEYE coincidence SPECT was carried out in 81 colorectal cancer patients with suspected recurrence or metastasis after intravenous injection of 259 ~ 298 MBq (7-8 mCi) 18F-FDG. The acquired data were reconstructed using iterative algorithm and attenuation-corrected X-ray. The results were compared with the final diagnosis established by histological examination of resected specimens、and clinical follow-up. Results The sensitivity, specificity, positive predictive value (PPV)and negative predictive value(NPV)was 93% (57/61)、80% (16/20)、93% (57/61)、80% (16/20) for 18F-FDG hPET/CT respectively. For conventional CT the sensitivity, specificity, PPV and NPV was 67% (37/55)、73% (19/26)、84% (37/44)、51% (19/37) respectively; 18F-FDG hPET/CT detected 91 recurrent or metastatic lesions whereas only 46 lesions were detected by conventional CT in 65 patients. Conclusions 18 F-FDG hPET/CT has unique value in the diagnosis of recurrence and metastasis in postoperative colorectal cancer patients which was superior to conventional CT. Combined 18 F-FDG coincidence imaging with localizing CT improves the detection and localization of postoperative recurrence and/or metastasis in colorectal cancer patients.