Aortic aneurysms are permanent and irreversible dilations of the aortic wall and constitute a potenti ally serious health problem. Currently, several treatment options are available, and the most common is the endovascular treatment of aneurysms. The challenging anatomy and inadequate landing zones create limitations to its application. Customized solutions including branched or fenestrated devices are available and represent a primary option in elective operations. However, urgents, life saving situations may require the off-label adaptation of off-the-shelf devices. Due to these, advanced endovascular techniques, as Octopus technique, have been developed. In all of them, a main endograft is used, and inside or outside, it is deployed parallel endografts to perfuse in the visceral branches involved. However, associated with these procedures, there are several postoperative complications with a high incidence rate, such as the migration of the endograft and the formation of endoleaks. This work aims to develop an algorithm using the MATLAB 2020a platform that recommend the optimal size of the endograft to decrease the probability of postoperative problems, as endoleaks. To achieve this, several mathematical and physical concepts were considered, like thin-walled cylinder theory and fluid mechanics. The algorithm workflow is based on the relationship between the deformation that each parallel endograft experiences due to the others inside the main endograft. The developed algorithm has been compared with two methods, the Double Barrel method and the segmentation of computed tomography images, to validate the results. In the first method, the diameter of the main endograft was calculated using the developed algorithm and the Double Barrel method. Then these two values were compared. On the other hand, the second validation method compared the values of the internal endograft area obtained through the developed algorithm and the segmentation of computed tomography images.This validation was performed using images that were given to us, from 4 patients who had already undergone surgery. The results of the first validation method show that the diameters obtained through the algorithm are smaller than those obtained through the Double Barrel method. This may be due to the fact that in the developed algorithm the effect of forces and deformation of the endograft is considered, which in the Double Barrel method does not happen. Regarding the second validation method, the results have shown that when the diameter used in the Octopus procedure and the diameter proposed by the algorithm are equal, the difference between the area values is not higher than 10%. The observed differences were about 30% and 50% when the diameters didn’t match. The difference in the diameters can justify that. In the Octopus procedure, the diameter used is higher than the proposed algorithm. Because of that, the internal endografts have more space to expand and, therefore, the endografts deformation is lower. In conclusion, this algorithm can help vascular surgeons choose the optimal endograft diameter to decrease the probability of having postoperative complications in endovascular procedure, like Octopus procedure. In the future, it will be crucial to include in this model to be blood pressure and temperature dependent and validate them in the laboratory, using a phantom model.

Tese de mestrado integrado, Engenharia Biomédica e Biofísica (Sinais e Imagens Médicas), Universidade de Lisboa, Faculdade de Ciências, 2022