Digital Expression And Analysis Method Of Generalized Body Cavity For Planning Of Minimally Invasive Surgery

Minimally invasive surgery (MIS) is very difficult and has high risk because of the small field of view, the narrow cavity space and the way that surgeons perform an operation only through the endoscopic video. With the aid of a computer, visualization and digital analysis of the internal structures of surgical cavity will greatly improve the accuracy and reliability of minimally invasive surgery.In order to achieve the above purposes, this dissertation focuses on the key issues involved in the geometric modeling, shape analysis and understanding of the GBC, and surgery planning. The main work and achievements of this dissertation are summarized as follows:(1) The creation of the geometry model of generalized body cavity (GBC). The geometry modeling of GBC is a challenging problem because it is enclosed by multiple organs and its shape will change with the operation process. To solve the problem, the algorithm for creating GBC model was proposed. Using the models of the enclosing organs as input, the initial cavity model was created first from the cross sections, and then the dynamic model of the GBC was reconstructed based on the results of numerical simulation.(2) In order to obtain the high-level semantic information for shape understanding of the GBC model,a set of index system for evaluating the geometry space was presented first. The semantic information, such as compactness, connectivity, directionality and bottleneck, can be obtained by the evaluation indexes. Then, the semantic segmentation algorithm based on the extraction of explicit boundary contour was proposed. The geometry and topology information are both considered in the algorithm, and it enables the cavity model to be segmented into a number of sub-cavities at branches of paths. A graph-like structure representation, the sub-cavity network (SCN), was defined to store the semantic information.After analyzing its properties, the algorithm of creating the SCN was put forward. The SCN reflects the connectivity among the sub-cavities, and it can encode geometrical, topological and physiological information that support for the generation of candidate paths, and for path planning.(3) In order to quantitatively evaluate the candidate path, to guide the path selection and the quantitative shaping of the cavity space, the definition and calculation method of the intrinsic space accessibility and intrinsic-instrumental space accessibility were proposed.When evaluating the accessibility of candidate paths or target spaces, the factors to be considered in the intrinsic space accessibility include the formation of the cavity space to be measured, the distribution of the space, and the physical properties of the adjacent anatomic structures of space elements. On the basis of the intrinsic space accessibility, the influences of several factors on the spatial accessibility were considered in intrinsic-instrumental space accessibility, such as the shape and the mechanism of instruments, and the interaction between instrument and tissue.(4) Aiming at the complex minimally invasive operation, the approach based on the digital analysis of GBC was proposed for surgical planning and the visualization of surgical scheme. An algorithm of surgical path planning in which the space accessibility is served as the evaluation metric was proposed, and the method to quantitative shaping of operating space was also presented. To make the surgical program of individualized patient, the approach using the statistics surgical process model (SSPM) as a template was put forward.The technique of multiple sequence alignment and merging was employed to merge the surgical process models (SPM) to obtain an SSPM.(5) In order to meet the needs of knee arthroscopic surgery planning, the knee arthroscopic surgery planning system was developed by using the approaches of geometric modeling and digital analysis of the GBC space. In the end, the function and effect of the system were verified by taking the removal of multiple loose bodies as an example. The experimental results showed that the system could well support surgery planing.