Research On The Design Of Nasal Prosthesis Based On Facial Point Cloud Model

Nasal prosthesis implantation is one of the medical cosmetic surgeries with high demand.Nasal prostheses are mass-produced by manufacturers according to limited models and require doctors to manually polish and modify the shape of the prosthesis during the surgical implantation process based on experience,which is a large workload and difficult to meet the individual needs of patients.At present,the value of engineering technology applied to the medical field is gradually emerging.In this paper,we use the idea of reverse engineering to establish a three-dimensional point cloud model of the face,and study several aspects such as data pre-processing,feature extraction,nasal prosthesis model construction and three-dimensional printing to realize a prosthesis model design method to meet the personalized nasal characteristics of patients.The main research contents are as follows:First,the facial point cloud data is collected by a handheld laser scanner,and for the problems that the collected data is often accompanied by a large number of noise,redundant points,useless points and a large point cloud base,which is not convenient for its subsequent processing,a filtering and noise reduction algorithm and a point cloud streamlining algorithm are used to process the sampled facial point clouds,so as to obtain a point cloud model without noise,with a smooth surface and a small number of point clouds for subsequent processing.Secondly,to address the problems that traditional point cloud streamlining methods tend to filter out important feature points and extract key points of the facial point cloud model by human picking,resulting in low efficiency.The curvature information and normal vector information are used to extract the model feature points after filtering and noise reduction and merge with the model processed by the streamlining algorithm to remove the redundant points,thus obtaining the facial point cloud data with small volume,uniform distribution and complete features.The density clustering(DBSCAN)algorithm and intrinsic shape signatures(ISS)algorithm are used to extract the key points of the model to improve the efficiency of key point extraction,and the key points are interpolated and fitted with quasi-uniform B-spline curves to achieve the construction of facial point cloud model feature curves efficiently and accurately.Thirdly,to address the problem of how to design the prosthesis under the condition of ensuring the accurate fit of the nasal prosthesis to the facial model,a suitable surface reconstruction algorithm was first selected to reconstruct the surface of the facial point cloud model,and the reconstructed surface was intercepted by the contour curve of the prosthesis to obtain the lower surface of the prosthesis model.Next,the aesthetic standards of rhinoplasty were used as constraints to reconstruct the feature curves to obtain the new feature curves,and the upper surface of the prosthesis model was obtained by combining the B-spline surface construction.The upper and lower surfaces of the prosthesis were filled and processed with magics software,and then the surface of the model was refined to obtain the orthopedic nasal prosthesis model.Finally,the nasal prosthesis model was printed by Stereolithography(SLA)Three dimensional printing experiment to obtain the solid model to verify the feasibility of the nasal prosthesis design method in this paper.In addition,we design and build the interactive system of the nasal prosthesis,design the facial model pre-processing module,feature curve reconstruction module,facial model surface reconstruction module and nasal prosthesis upper surface fitting module to realize the personalized design of the nasal prosthesis.