Mesh Fusion Research Articles

LOD2-Level+ Low-Rise Building Model Extraction Method for Oblique Photography Data Using U-NET and a Multi-Decision RANSAC Segmentation Algorithm

Oblique photography is a regional digital surface model generation technique that can be widely used for building 3D model construction. However, due to the lack of geometric and semantic information about the building, these models make it difficult to differentiate more detailed components in the building, such as roofs and balconies. This paper proposes a deep learning-based method (U-NET) for constructing 3D models of low-rise buildings that address the issues. The method ensures complete geometric and semantic information and conforms to the LOD2 level. First, digital orthophotos are used to perform building extraction based on U-NET, and then a contour optimization method based on the main direction of the building and the center of gravity of the contour is used to obtain the regular building contour. Second, the pure building point cloud model representing a single building is extracted from the whole point cloud scene based on the acquired building contour. Finally, the multi-decision RANSAC algorithm is used to segment the building detail point cloud and construct a triangular mesh of building components, followed by a triangular mesh fusion and splicing method to achieve monolithic building components. The paper presents experimental evidence that the building contour extraction algorithm can achieve a 90.3% success rate and that the resulting single building 3D model contains LOD2 building components, which contain detailed geometric and semantic information.

A new stress-driven composite porous structure design method based on triply periodic minimal surfaces

Replacing the solid infills with porous structure infill is a reliable method in the field of 3D-printed model lightweight. Triply periodic minimal surfaces (TPMSs) provide a smooth and fully connected porous structure and can be mathematically described, making itself an ideal infilling structure for lightweight design. In this paper, a design method of composite porous structure based on TPMSs is proposed, which takes the multi-scale bionic porous structure for reference, performs the stress-driven weighted random sampling on the basis of the finite element analysis results, and combines the offset geodesic B-splines with the Geodesic Voronoi Tessellations (GVT). The method can not only optimize the structure by reasonably selecting the inherent parameters of TPMSs, but also can realize the mechanical optimization by controlling the distribution of Voronoi sites and the offsetting weight of the geodesic B-splines based on the stress distribution. Both the Finite Element Analysis (FEA) results and mechanical experiments show that the proposed composite porous structure has better mechanical continuity and 19% lower initial peak stress than the TPMSs basic structure, and has better compressive performance and 48% stronger energy absorption capacity than the lattice structure. Additionally, a mesh fusion optimization strategy is proposed to avoid the stress concentration and improve the structural strength.

Imaging study of soft tissue swelling after anterior cervical corpectomy

To study the changes of anterior soft tissue swelling after anterior cervical subtotal corpectomy, titanium mesh fusion and internal fixation. From November 2015 to July 2018, 151 patients with cervical spondylotic myelopathy were treated with anterior single corpectomy, titanium mesh fusion and internal fixation, including 109 males and 42 females, aged 44 to 81 (59.77±8.34) years. Through postoperative follow up observation, the C2-C7 level of anterior intervertebral space distance was measured to evaluate the changes of anterior soft tissue swelling. All patients were followed up for 15 to 40(28.00±3.52) months. One week after the operation, the swelling of anterior soft tissue reached the peak, and then decreased. At 8 months after the operation, the swelling of anterior soft tissue on C5, C6 and C7 plane returned to normal. At 12 months after the operation, the swelling of anterior soft tissue on C2, C3 and C4 plane returned to normal. Anterior subtotal cervical corpectomy, titanium mesh bone graft fusion and internal fixation can cause swelling of the anterior soft tissue. One week after operation, we should pay more attention to the aggravation of the swelling of the anterior soft tissue to avoid the occurrence of dysphagia, respiratory obstruction, asphyxia and other complications.

Single-stage posterior-only debridement, decompression and interbody fusion for the treatment of thoracolumbar spinal tuberculosis complicated with psoas abscesses

BackgroundTo explore the clinical safety and efficacy of single-stage posterior-only debridement, decompression, allograft bone using titanium mesh and interbody fusion combined for the treatment of thoracolumbar spinal tuberculosis complicated with psoas abscesses.MethodsA total of 38 patients diagnosed with thoracolumbar spinal tuberculosis complicated with psoas abscesses underwent surgery via single-stage posterior-only debridement, decompression, allograft bone using titanium mesh and interbody fusion from January 2010 to September 2016 were enrolled in the study. The clinical efficacy of the approach was assessed based on parameters including operating time, blood loss, Cobb angle, visual analogue scale (VAS) scores, Frankel grade, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).ResultsThe surgery duration was 224.4 ± 71.1 min with a blood loss of 731.8 ± 585.8 ml. The Cobb angle was corrected from 16.0 ± 15.4° preoperatively to 8.1 ± 7.4° postoperatively (P < 0.001, t = − 4.38), and returned to a level of 11.0 ± 8.5° at the final follow-up (P = 0.002, t = 3.38). Back pain was relieved, with the mean preoperative VAS of 3.5 ± 1.1 decreased to 0.7 ± 0.8 postoperatively (P < 0.001, t = 23.21) and then to 0.6 ± 0.5 at the final follow-up (P < 0.001, t = 17.07). Neurological function was improved in various degrees and psoas abscesses disappeared in all patients. The ESR and CRP decreased gradually after surgery and returned to normal at the final follow-up in all patients. All patients achieved bone fusion thoroughly and no recurrence of TB or surgical related complications was found at the final follow-up.ConclusionSingle-stage posterior-only debridement, decompression, allograft bone using titanium mesh and interbody fusion is a safe and effective approach for the management of thoracolumbar spinal tuberculosis complicated with psoas abscesses.

Research on Optimizing the Recovery Strategy of a Distribution Network Communication System Under Extreme Disasters

Extreme disasters, such as typhoons, cause great damage to distribution network communication systems, affecting the perception of disaster situations and the repair speed of the distribution networks. To realize the rapid recovery of a distribution network, an optimal recovery strategy of the distribution network communication system is proposed in this paper from the perspectives of predisaster prediction and postdisaster rush repair. First, based on multivariate data, the space-time mesh fusion method is used to predict the fault position of the distribution network communication system, guiding the accurate allocation of emergency repair resources, and the fault position is corrected using man-made statistics after a disaster. Then, combining fiber optics, mobile nets and emergency communication vehicles, rush repair rules for the distribution network communication system after extreme disasters are put forward, and the shortest route search algorithm is used to solve the minimum rush repair time under the rules, which is the optimal rush repair scheme for the distribution network communication system after an extreme disaster. Finally, the proposed strategy is applied to a practical topology, and the results demonstrate that the strategy is reasonable and effective.

Gender classification using mesh networks on multiresolution multitask fMRI data.

Brain connectivity networks have been shown to represent gender differences under a number of cognitive tasks. Recently, it has been conjectured that fMRI signals decomposed into different resolutions embed different types of cognitive information. In this paper, we combine multiresolution analysis and connectivity networks to study gender differences under a variety of cognitive tasks, and propose a machine learning framework to discriminate individuals according to their gender. For this purpose, we estimate a set of brain networks, formed at different resolutions while the subjects perform different cognitive tasks. First, we decompose fMRI signals recorded under a sequence of cognitive stimuli into its frequency subbands using Discrete Wavelet Transform (DWT). Next, we represent the fMRI signals by mesh networks formed among the anatomic regions for each task experiment at each subband. The mesh networks are constructed by ensembling a set of local meshes, each of which represents the relationship of an anatomical region as a weighted linear combination of its neighbors. Then, we estimate the edge weights of each mesh by ridge regression. The proposed approach yields 2CL functional mesh networks for each subject, where C is the number of cognitive tasks and L is the number of subband signals obtained after wavelet decomposition. This approach enables one to classify gender under different cognitive tasks and different frequency subbands. The final step of the suggested framework is to fuse the complementary information of the mesh networks for each subject to discriminate the gender. We fuse the information embedded in mesh networks formed for different tasks and resolutions under a three-level fuzzy stacked generalization (FSG) architecture. In this architecture, different layers are responsible for fusion of diverse information obtained from different cognitive tasks and resolutions. In the experimental analyses, we use Human Connectome Project task fMRI dataset. Results reflect that fusing the mesh network representations computed at multiple resolutions for multiple tasks provides the best gender classification accuracy compared to the single subband task mesh networks or fusion of representations obtained using only multitask or only multiresolution data. Besides, mesh edge weights slightly outperform pairwise correlations between regions, and significantly outperform raw fMRI signals. In addition, we analyze the gender discriminative power of mesh edge weights for different tasks and resolutions.

Clinical Efficacy of Anterior Partial Corpectomy and Titanium Mesh Fusion and Internal Fixation for Treatment of Old Fracture Dislocation of the Lower Cervical Spine.

BackgroundThe aim of this study was to analyze the clinical features and to evaluate the efficacy of anterior partial corpectomy and titanium mesh fusion and internal fixation of old fracture dislocation of the lower cervical spine.Material/MethodsWe retrospectively analyzed the clinical data of 52 patients with old lower cervical fracture and dislocation treated with anterior partial corpectomy and titanium mesh fusion fixation between January 2008 and December 2013, with a mean follow-up period of 4.1 years. There were 35 males and 17 females. Patient radiological data and clinical parameters were recorded and compared before and after the operations.ResultsThe average follow-up was 4.1 years. Intervertebral height and physiological curvature were well-reconstructed for all cases. No loosening or rupturing of titanium plate or screw occurred. The neurological function of the patients with incomplete spinal cord injury was significantly improved, and the function of the nerve roots at the injury level was also improved in patients with complete spinal cord injury. Bone fusion was completed within 6 months to 1 year after surgery.ConclusionsCompleted decompression, sequence and physiological curvature of the cervical vertebra, immediate and long-term anterior cervical column support, and nerve function restoration can be achieved by using anterior partial corpectomy and titanium mesh fusion and internal fixation to treat old fracture dislocation of the lower cervical spine. For cases with locked facet joints or posterior structures invading the vertebral canal, the combined anterior and posterior approaches should be performed, when necessary, to achieve better results.

Cognitive information delivery in geo‐location database based cognitive radio networks

AbstractFor the problem of spectrum scarcity and wastage, cognitive radio (CR) technology provides a solution to utilizing the vacant spectrum more efficiently. As one of the most promising techniques to obtain the cognitive information in TV white spaces, geo‐location database approach has attracted a lot of recent attentions, with its goal of enhancing the efficiency of spectrum usage and avoiding the interference to TV receivers. However, existing works mainly focus on the construction and applications of geo‐location database, and seldom consider how to deliver the cognitive information from the database to TV band devices. In this paper, we investigate the tradeoff between increasing the accuracy of cognitive information delivery and reducing the overhead. We design two mesh fusion algorithms to reduce the redundancy of cognitive information and improve the efficiency of cognitive information delivery. Finally, we verify our analysis and evaluate the efficiency of the proposed mesh fusion algorithms through numerical studies. Copyright © 2016 John Wiley &amp; Sons, Ltd.

MASCG: Multi-Atlas Segmentation Constrained Graph method for accurate segmentation of hip CT images.

This paper addresses the issue of fully automatic segmentation of a hip CT image with the goal to preserve the joint structure for clinical applications in hip disease diagnosis and treatment. For this purpose, we propose a Multi-Atlas Segmentation Constrained Graph (MASCG) method. The MASCG method uses multi-atlas based mesh fusion results to initialize a bone sheetness based multi-label graph cut for an accurate hip CT segmentation which has the inherent advantage of automatic separation of the pelvic region from the bilateral proximal femoral regions. We then introduce a graph cut constrained graph search algorithm to further improve the segmentation accuracy around the bilateral hip joint regions. Taking manual segmentation as the ground truth, we evaluated the present approach on 30 hip CT images (60 hips) with a 15-fold cross validation. When the present approach was compared to manual segmentation, an average surface distance error of 0.30 mm, 0.29 mm, and 0.30 mm was found for the pelvis, the left proximal femur, and the right proximal femur, respectively. A further look at the bilateral hip joint regions demonstrated an average surface distance error of 0.16 mm, 0.21 mm and 0.20 mm for the acetabulum, the left femoral head, and the right femoral head, respectively.

Multimodal Neurosurgery Force Feedback System Based on Mesh Fusion Modeling

Virtual reality based force feedback system is spotlighted as a safe and efficient training environment to obtain surgical skills. Neurosurgery utilizes multimodal patient images for visualization of a variety of functions in head. The aim of this study is to establish a concept of multimodal neurosurgery force feedback system based on mesh fusion modeling. In the model of mesh fusion, we developed an algorithm to detect overlapped region between the multiple meshes that are obtained from multimodal images, and to determine a new boundary between the meshes. Then, the method solved interaction between the newly defined mesh boundaries using the interaction model based on a finite element method. The proposed method was implemented, and applied to both simple and patient datasets for evaluating its applicability. As a result, the method succeeded to be applied to both simple and patient datasets. Finally, we demonstrated the early stage of the surgical approach in neurosurgery. Simulation results showed a real-time simulation of brain tissue deformation with force feedback.

Automatic Grid Resolution and Efficient Triangulation of Implicit Vector Field

In this paper we propose an automatic grid resolution to compute the vector field distance transform of triangle meshes. This implicit representation is useful in performing many mesh processing operations such as mesh fusion and mesh filtering in object surface reconstruction. Setting an appropriate grid resolution is mandatory for obtaining good quality results from these operations. Grid resolution is usually set experimentally by operators until satisfying results are obtained. An automated process is demonstrated that improves this parameter setting step. We also introduce a new marching cube triangulation adaptation to the vector field distance transform. Unlike the previous adaptation, our algorithm allows vertex interpolation on cube faces instead of only on cube edges. We compare our new design to the previous one using a reliable error metric evaluation. Results show our triangulation outperforms the previous one in terms of mesh quality and runtime performances. The new algorithm takes advantage of the more accurate vector field definition to better approximate the implicit isosurface.

A finite element analysis of comparision study on mechanical changes in cage-endplate interface between titanium mesh cages with or without augmentation of internal end ring system after anterior cervical corpectomy

Objective To study the mechanical changes in cage-endplate interface between titanium mesh cages with or without augmentation of internal end ring system after anterior cervical corpectomy by finite element analysis. Methods Based on the intact finite element model (FE/Intact) ,two models were generated by simulating anterior cervical titanium mesh fusion cage and plate after C5 corpectomy according to the applied titanium mesh cage conditions ;? 10 mm titanium mesh cage without internal end ring (S-) and ?10 mm titanium mesh cage with internal end ring (S + ). von Mises stress of seven parts on the superior and inferior cage-endplate interface was comparatively analyzed between model with S-and model with S + after loading of each model being simulated using multidirectional moment loads of 1.8 Nm combined with a compressive preload of 80 N in compression, flexion and extension. Results The stress on the superior (7.61,8.23,9.97) Mpa and inferior cage-endplate interface (5.43,5.74,6.88) Mpa in the model with S-was bigger than that (10.65,11. 59,14. 27 and 7.46,8. 12,10.04) Mpa in the model with S + under the three loading conditions. Conclusion A titanium mesh cage with internal end ring produces a significant decrease of the cage-endplate interface stress and lower incidence of titamium mesh cage subsidence after anterior cervical corpectomy. Key words: Cervical spine; Corpectomy; Endplate; Titanium mesh cage

A clinical study on different decompression methods in cervical spondylosis

To analyze the different decompression methods to treat cervical spondylosis based on imageological evaluation. Two hundred and sixty three consecutive patients with cervical spondylosis between Nov. 2004 and Oct. 2007 were involved in this study. Patients were distributed to different operation groups based on the preoperative imageological evaluation, including anterior or posterior decompression methods. The Anterior method is to use the discectomy of one to three segments, autogenous iliac graft or titanium mesh or cage fusion and titanium plate fixation, or subtotal vertebrectomy of one to two segments autogenous iliac graft or titanium mesh fusion and titanium plate fixation, or discectomy plus subtotal vertebrectomy, The posterior expansive single open door laminoplasty and other operation types. All the patients were divided into different groups by the preoperative imageological evaluation, age, sex and course of diseases. Then we collected each group's preoperative and postoperative JOA scores and mean improvement rate to evaluate the postoperative effect by different decompression methods. Two hundred and thirty five patients were followed up with a mean period of 18 months (range, 4 to 36 months). JOA scores of all patients were improved by different degrees after operations. Anterior and posterior decompression methods both can achieve higher mean improvement rates. There were no significant differences in mean improvement rates between anterior groups, and so did male and female (P > 0.05). The effect will decrease as age increases or the course of disease prolongs. Statistical significance existed among the different age groups and between course groups (P < 0.05). Anterior and posterior decompression methods both can achieve good effect. The key point is to choose the surgical indication correctly, decompress thoroughly, and make the fusion reliable and fixation firm. In regard to the patients' imageological evaluation, the methods should be differentiated. The anterior operation type included discectomy of one to three segments, subtotal vertebrectomy of one to two segments and discectomy plus subtotal vertebra ectomy.

Microscope-assisted anterior cervical decompression and plating techniques: Clinical experience in 225 cases of cervical spondylosis

目的 总结颈前入路显微手术治疗颈椎病的临床经验.方法 借助手术显微镜和高速磨钻对225例颈椎病患者进行颈前入路显微减压手术,采用自体骨、钛网或Cage融合后使用钉板系统固定;术中用体感诱发电位(SEP)进行监护.结果 本组术后均无重大并发症发生.随访5～120个月,影像学资料证实受累脊髓、神经根减压彻底,自体骨、钛网或Cage融合良好,无移动、塌陷或滑脱,钛板内固定位置准确,无螺钉松脱或钛板断裂.各组的JOA评分较术前提高.结论 颈前入路显微手术治疗颈椎病,手术创伤小,术后恢复快,手术成功率高。

Mesh fusion using functional blending on topologically incompatible sections

Three-dimensional mesh fusion provides an easy and fast way to create new mesh models from existing ones. We introduce a novel approach of mesh fusion in this paper based on functional blending. Our method has no restriction of disk-like topology or one-ring opening on the meshes to be merged. First of all, sections with boundaries of the under-fusing meshes are converted into implicit representations. An implicit transition surface, which joins the sections together while keeping smoothness at the boundaries, is then created based on cubic Hermite functional blending. Finally, the implicit surface is tessellated to form the resultant mesh. Our scheme is both efficient and simple, and with it users can easily construct interesting, complex 3D models.

Mesh Fusion Based on Variational Implicit Surfaces

3D object fusion provides an easy way to generate novel models from two or more existing geometric models by using 3D cutting and pasting operations. As a new kind of geometric modeling tool, it is now attracting much more attention. In this paper, a new montage mesh fusion method based on variational interpolating implicit surfaces is proposed. The approach first calculates mesh regions to be fused by cutting original meshes with boundless planes, then constructs a variational implicit surface by interpolating mesh regions to be fused and polygonalizes the implicit surface to obtain a blending surface between/among original meshes to be fused. Smooth mesh fusion is finally obtained by cutting away unwanted portions of the blending surface and performing topology merging operations. Compared with current methods that fuse mesh objects by directly connecting mesh regions to be fused, this approach has the advantages of no restriction on topologies of the mesh regions to be fused, and thus enabling the fusion among multiple objects, fast running speed with robustness, and easiness to use. The approach shows a promising future in applications for geometry modeling as well as computer animation.