Reconstruction Based On Reverse Engineering The Surface Of Organs Simulation Study

The restoration and reconstruction of surface organs remains the challenging field inmordern plastic surgery. There are still many technical obstacles for plastic surgeons to makea new vividely substitute. In traditional way, surgeons make the diagnostic analysis andoperative plan mainly depending on theire limitied personal experiences, which seems moresubjective and may jeopardize the final outcome. Originated from the idea of industrialreverse engineering, a new therapeutic model is developed with the aim to make a quickpreoperative three-dimensional imaging, a mimic model shaping, and a objectivepost-operative outcome evaluation. This dissertation includes the following 6 major parts:1.3-dimantional data acquisition3-dimantional data collection is the primary step in reverse project and based thecomputer-asisted operative manipulation. Two kind of method is adopted to efficiently andprecisely obtain the 3-dimantional data. The first method is Moire-fringe technology, which isbased on the phase measuring profilometry, to collect the 3-D surface data on a livingobjective. The other method is CT. CT scan can easily get the 2-dimentional data of a organ'sinternal structure. Processed by some special software, these data can be used to reestablishthe internal 3-D framwork of a specific organ. In reconstructive surgery, no matter external3-D data or the underface, internal 3-D data is required, the surgeon can readily get what theydesired through these two reliable methods, making a solid basis for further work.2. Data preprocessingAiming at character of body points cloud data measured by optical photogrammetryscanner, data disposal include mainly filter and registration. Combined with self-character ofbody data, this paper designed a Rectangle Window Weighted Median Fiter. Using of Fitercan eliminate most noise data with higher accuracy.3. Surface entity model constructionAfter scanning, point cloud is transmitted to work space and modelling under software ofreverse engineering. Several point cloud from different visual angle is obtained. Data registration can transform them to the same coordinate system and obtain registered 3D trigon.These trigonal patches can be processed further, such as hole-filling, smoothing, subdivision,surface merger, surface smoothing. Finally a precision intergrated digital surface entity modelis formed.The obtained CT scan data, which fulfill the DICOM standard, are modelling undersoftware of data transformation and 3-D reconstruction, and further produce the surface entitymodel of craniofacial bone.4. Body entity model reconstructionTransformed into STL format, the 3-D digital surface entity model is put into astereolithography and the body entity model is then manufactured. This model presents theprecise topograghy of the prototype, including the anatomic features and the surroundingrelationships. It is also beneficial to some complicated surgical cases, for preoperativepractice being feasible.5. Precision and erroe analysisThe primary goal of plastic surgical reverse engineering is to make a high precision finalmodel. In this study, traditional mearsuring method and computer-asisted mearsuring methodare used respectively to reveal the dimentional differences between the prototype and the finalmodel. In both method, less than 0.2 mm differences are found, which obviously meet theclinicla requirement.6. Clinical applicationOne part of this research is its clinical application. Some patients, such as those presentwith facial soft tissue deformities, microtia, cranial bone defects, breast deformities, arebeneficial from this study.(1) In some cases, artificial interact surface transformation of the 3-D digital model, ormirror simulation method is used. So the surgeons can get the desired post-operativeappearance and the specific data which need to be altered during operation. This methodprovides an objective basis for operative plan. (2) A body entity model can readily be obtained with the rapid-prototyping technique insome patients. On this model, the surgeons can make practice and whatever modification ifneeded, to fulfill the operative plan.(3) Also the implant can be produced with the modelling of CAD software and digitalmanufacturing. This kind of implant has the exact defect dimention, concaves andconcvexness, which apparently avoid in-operation shaping and tailoring, and make theoperative outcome more satisfactory.(4) A objective evaluation system can be established through the comparision of pre-op3-D imaging, in-op models, post-op 3D imaging. Also the feasibility of such kind of operationcan be appraised, if large sample is provieded.This study first introduces reverse engineering into plastic surgery, and successfullyestablished a new dianostic and therapeutic system consisting of rapid prototyping of surfaceorgans, computer-asisted preoperative design and objective outcome evaluation. The precisionof this system is high enough for clinical application. The feasibility is also confirmed by thelaboratory and clinic experiments, besides the satisfactory operative results being obtained.But this new system is not yet perfect. One disavantage is the too complicated process insimulation and manipulation. The other disavantage relate to the presumed tissue's physicalcharacter. In this system, not only the prototype's but also the substitute's tissue is presumedto be rigid, not as pliable as real one. This inevitably affects the final result of reconstruction.In further studies, the present system will evolve into a more friendly interface, easycontrolling, computer-asisted virtual 3-D modeling, biological physical limited elementsanalysis system.