Carotid Intern Aneurysms

Cerebral aneurysms (CA) are acquired lesions, affecting 5–10% of the population, being about three times more common in women than in men. The absolute majority of CA is asymptomatic. However, in symptomatic cases, cerebral aneurysms present without about 80% of cases with severe intracranial hemorrhage, with mortality up to 50% and severe morbidity of up to 80%. At this point, the carotid siphon is particularly important because it is the blood gateway to the anterior cerebral circulation, being the most sinuous portion of the internal carotid artery, and because it houses about 30% of the intracranial aneurysm. The constant interactions of blood flow with carotid siphon curvatures are apparently intrinsically related to the epidemiology of these lesions in the various locations of the intracranial circulation and their presentation form. It is well established that a greater anterior knee angle has a significant independent relation with intracranial aneurysms located after carotid siphon, larger aneurysms, and greater risk of rupture. These findings may be associated with the hemodynamic interactions of blood flow and the curvature of carotid siphon. Little is known about the anatomical changes in carotid siphon and, consequently, the repercussions of the hemodynamic changes that the neurosurgical interventions mechanisms could entail. Devices such as intracranial stents, detachable coils, and even clips of aneurysms can modify the morphology of carotid siphon, and the knowledge of these consequences could be used to obtain better therapeutic results. In the last 10 years, a new device for the treatment of intracranial aneurysms has been presenting promising results, flow diverters stents (FDS), and its use to treat aneurysms in carotid siphon appears to cause morphological changes characterized by increased anterior and posterior angles. Specifically, the anterior angle increase was associated with better angiographic results. Aneurysms of the extracranial carotid artery (ECAA) are rare and little is known about its natural history. The etiology is diverse and most ECAA are asymptomatic, but they may progress to a pulsatile mass, cranial nerve compression, or cause a stroke. ECAA treatment is still controversial and a better insight into natural history and risk of complications of the different treatments is needed in order to get the consensus

Decomposition of Velocity Field Along a Centerline Curve Using Frenet-Frames: Application to Arterial Blood Flow Simulations

This paper presents a novel method for the evaluation of three-dimensional blood-flow simulations based, on the decomposition of the velocity field into localized coordinate systems along the vessels centerline. The method is based on the computation of accurate centerlines with the Vascular Modeling Toolkit (VMTK) library, to calculate the localized Frenet-frames along the centerline and the morphological features, namely the curvature and torsion. Using the Frenet-frame unit vectors, the velocity field can be decomposed into axial, circumferential and radial components and visualized in a diagram along the centerline. This paper includes case studies with four idealized geometries resembling the carotid siphon and two patient-specific cases to demonstrate the capability of the method and the connection between morphology and flow. The proposed evaluation method presented in this paper can be easily extended to other derived quantities of the velocity fields, such as the wall shear stress field. Furthermore, it can be used in other fields of engineering with tubular cross-sections with complex torsion and curvature distribution

Influência da anatomia do sifão carotídeo na apresentação e resposta ao tratamento de aneurismas cerebrais

Tese (doutorado)—Universidade de Brasília, Faculdade de Medicina, Programa de Pós-Graduação em Ciências Médicas, 2017.Introdução: Os Aneurismas Cerebrais ainda são considerados como patologias devastadoras de etiologia complexa e não completamente compreendidas. A anatomia do sifão carotídeo pode estar relacionada à formação e desenvolvimento dessas lesões. Os Stents Redirecionadores de Fluxo (SRF) são dispositivos que podem alterar a anatomia do sifão carotídeo. Objetivos: O objetivo desse estudo é avaliar a correlação entre a anatomia do sifão carotídeo com a formação e evolução de aneurismas cerebrais e as repercussões nessa anatomia após a liberação de SRF. Método: Entre janeiro de 2007 e dezembro de 2016, angiografias digitais com subtração em incidência de perfil estrito de 692 pacientes tratados consecutivamente com o diagnóstico de aneurisma cerebral (AC) no Departamento de Neurorradiologia intervencionista do Hospital Universitário de Limoges – França foram analisados. Desses, 183 pacientes com AC localizados no Sifão Carotídeo tratados foram tratados com SRF tipo Pipeline® e acompanhados por 6 meses. Os ângulos anteriores e posteriores do sifão carotídeo foram medidos e correlacionados com dados como relação a localização, apresentação, tamanho das lesões e resultado conforme a classificação de O’Kelly-Marotta utilizando análises multivariadas. Resultados: De 692 aneurismas, 225 (32,51%) eram rotos e 467 (67,49%) não rotos, 218 (31,50%) se localizavam no sifão carotídeo e 474 (68,50%) eram distais ao sifão. O tamanho médio dos aneurismas foi de 7,99±6,95mm. A análise multivariada evidenciou relação entre o ângulo anterior do sifão > 15,40° com: Ruptura (P=0,005), localização do aneurisma após o sifão carotídeo (P = 0,034) ,aneurismas de maiores tamanhos (P=0,015), e aumento anual de 1,002mm do tamanho aneurismático (P = 0,015). A implantação de SRF esteve associada à mudanças imediatas da morfologia do sifão carotídeo e na angiografia de controle após 6 meses. O ângulo anterior aumentou de 3,97º±25,06º para 22,05º±25,18º (P 15,40 ° and rupture (P = 0.005), location after carotid siphon (P = 0.034) and larger aneurysms (P = 0.015). Multivariate analysis also showed an increase of 1.002 mm in aneurysmal size per patient year (P = 0.015). The FDS deployment was associated with immediate changes and at the 6-month control angiography of the carotid siphon morphology. The anterior angle increased from 3.97 ° ± 25.06 ° to 22.05 ° ± 25.18 ° (P < 0.001) and the posterior angle from 71.98 ° ± 31.27 ° to 79.43 ° ± 31.80 ° (P < 0.001) . The multivariate analysis showed a progressive and statistically significant increase in total occlusion frequency (grade D) of aneurysm at 6-month control as the anterior angle increases (PR = 1.42, for increases between 5.3 and 12o = 0.017), RP = 1.56, for increases between 12.1o to 27.6o (P = 0.002), RP = 1.83, for increases above 27.6o (P <0.001), in relation to smaller increases Than 5.3). Conclusion: There was a right, significant and independent relation to the anterior angle increase with aneurysm located after the carotid siphon, greater lesions and greater risk of rupture. FDS deployment generated morphological changes in the carotid siphon, particularly the anterior angle increase that was shown to be directly and statistically related to a greater chance of lesion occlusion in the 6-month angiographic control. These findings show that the morphology of the carotid siphon causes hemodynamic changes that may be associated in brain aneurysms formation and evolution

Virtual cochlear electrode insertion via parallel transport frame

International audienceWe present an automatic, fast and parametrizable algorithm to perform the virtual insertion of a cochlear electrode array into a pre-existent mesh of the human cochlea. Our method reorients the electrode according to the parallel transport frame, a local parameterization of the cochlear centerline directions, robust to the centerline curvature changes. It allows to control the initial roll angle and the extension of insertion from full to partial. Such a virtual insertion, chained with finite element simulations on the electrical activity of the electrode and the cochlear nerves, will enable to test in silico the effects of implant design and positioning on a given patient, and optimize these parameters accordingly