Computer-aided surgical simulation progressed significantly in the last decade. Careful planning is of great importance in order to limit the damage to healthy tissue during surgery. In particular, accurate modelling of the mechanical behaviour of the tissues is required. To achieve accurate prediction, biomechanical finite-element analysis (FEA) modelling of soft tissues is employed. Currently, many surgical procedures on human patients are not simulated yet can be relevant in minimally invasive surgeries to protect human health and to save human lives, particularly for surgeries with high accuracy requirements. Recent studies focused on colorectal cancer suggested that a 3D anatomical imaging segmentation could contribute in the definition of circumferential resection margin and in the pre-operative assessment of the pathological tumor regression grade, in this field literature is still scant. Although several researches have been introduced considering small displacements on the colorectal tissue, as a result of the forces exerted on adjacent tissues, FEA applied to colorectal surgical scenarios is still a challenge. To gain accurate models suitable for computer-aided surgical tools, many problems must be faced. In particular: a) free form surface modelling starting from MRI or CT scans; b) FEA pre-processing in terms of proper element selection and density (shell or solid according to the surgical district type and length characteristics) loads and boundary constraints definition; c) tissue constitutive material. In this research we aim to investigate these topics to enhance physical description of organs subjected to surgical operations. Therefore, this project has as goal provide a sensitivity analysis on three different geometric models, more in detail simulations will be performed using linear-elastic model and two hyperelastic models. The results will be valuated from multidisciplinary unit, bioengineering, engineering and surgeons involved in the research.
This proposal is part of a research cooperation aimed to develop Computer Aided Tools for colorectal surgery suitable for planning, verifying and teaching surgical operations. It has been started in the recent past, involving the researchers of the Department of Mechanical and Aerospace Engineering (DIMA) in different fields of interest, bioengineers (ING-IND/34), mechanical engineers expert in CAD (Computer Aided Design) techniques and virtual prototyping (ING-IND/15) and surgeons (MED/18). Although many research papers are present in the field, only few attempt to provide an overall discussion of the accuracy problems related to the interaction between different kind of simulations able to manage path planning and tool/soft tissue interaction. For this reason the proposed research is focused to one of this aspect, investigating tool/soft tissue interaction according to different FEA strategies and level of complexities. Thank to the integration of non-linear material characterisation, made by image analysis techniques, we intend to contribute to the adoption of computational methods in the medical field.
Moreover, in the recent past many works have been focused on the shape reconstruction of real images acquired by MRI and CT scans. In this work their adoption will be studied in terms of final accuracy of the FEA simulation just to understand how they can support a better understand of the surgical practice, thanks to the strict cooperation with the surgeon involved in the work. To the best of our knowledge, this is the first study based on 3D imaging in colorectal surgery settled in our Country. Although few data are emerging in relation to MRI segmentation and implementation of diagnosis (for CRM assessing and the prediction value of variation of volumetry), literature in this field is promising but very scant. Indeed, optimizing the selection criteria for patients requiring neo-adjuvant (chemo)radiation treatments (neoCHT-RT) could impact and implement surgical and multidisciplinary management of rectal cancer patients, avoiding e.g. unnecessary treatment with a consequent reduction of side-effects and cost. On the same extent, the prediction of response to neo-adjuvant treatments using variation in volumetry could aid in defining and in predicting complete pathologic responses which could benefit e.g. of a more conservative treatment if un-fit for extended resections.
Finally, the result of this research project, together with the investigation about tool-path simulation and planning, that is being provided by other activities of the proponents, will define the core for an educational platform, as reported in the Guidelines for Evaluation of Credentials of Individuals for the Purpose of Awarding Surgical Privileges in New Technologies published by the American College of Surgeons, that state: The surgeon must be a member in good standing of the department or service from which privileges are to be recommended. A defined educational program in the technology, including didactic and practical elements, must be completed and documented either as a post-residency course of instruction, or as a component of an approved residency program. The surgeon must be qualified, experienced and knowledgeable in the management of the diseases for which the technology is applied.
In future, the educational platform, could be also developed and tested by means of an experimental set-up that will be designed and sensor-equipped by the proponents and finally provided by means of rapid prototyping solutions. Rapid prototyping will also used for reverse engineering reconstructions of organs starting from image acquisition, reproducing soft tissue compliance via topological optimization.