20 research outputs found
Trends in Cerebrovascular Surgery and Interventions
This is an open access proceeding book of 9th European-Japanese Cerebrovascular Congress at Milan 2018. Since many experts from Europe and Japan had very important and fruitful discussion on the management of Cerebrovascular diseases, the proceeding book is very attractive for the physician and scientists of the area
3D reconstruction of cerebral blood flow and vessel morphology from x-ray rotational angiography
Three-dimensional (3D) information on blood
flow and vessel morphology is important when
assessing cerebrovascular disease and when monitoring interventions. Rotational angiography
is nowadays routinely used to determine the geometry of the cerebral vasculature. To this end,
contrast agent is injected into one of the supplying arteries and the x-ray system rotates around
the head of the patient while it acquires a sequence of x-ray images. Besides information on the
3D geometry, this sequence also contains information on blood flow, as it is possible to observe
how the contrast agent is transported by the blood. The main goal of this thesis is to exploit
this information for the quantitative analysis of blood flow.
I propose a model-based method, called
flow map fitting, which determines the blood flow
waveform and the mean volumetric flow rate in the large cerebral arteries. The method uses a
model of contrast agent transport to determine the
flow parameters from the spatio-temporal
progression of the contrast agent concentration, represented by a flow map. Furthermore, it
overcomes artefacts due to the rotation (overlapping vessels and foreshortened vessels at some
projection angles) of the c-arm using a reliability map.
For the flow quantification, small changes to the clinical protocol of rotational angiography
are desirable. These, however, hamper the standard 3D reconstruction. Therefore, a new method
for the 3D reconstruction of the vessel morphology which is tailored to this application is also presented.
To the best of my knowledge, I have presented the first quantitative results for blood flow
quantification from rotational angiography. Additionally, the model-based approach overcomes
several problems which are known from flow quantification methods for planar angiography.
The method was mainly validated on images from different phantom experiments. In most
cases, the relative error was between 5% and 10% for the volumetric mean flow rate and between
10% and 15% for the blood flow waveform. Additionally, the applicability of the flow model was shown on clinical images from planar angiographic acquisitions. From this, I conclude that the method has the potential to give quantitative estimates of blood flow parameters during
cerebrovascular interventions
Malformation artério-veineuses cérébrales : d'une amélioration des techniques d'imagerie vers un changement de paradigme des traitements
Brain arteriovenous malformations (bAVMs) are aggressive vascular malformations presenting a haemorrhagic complication risk that may lead to severe consequences in terms of morbi-Ââmortality. Available imaging tools poorly help in understanding their angio-Ââarchitecture. We have developed two imaging tools improving our understanding of the anatomy of these malformations: a semi-Ââautomated segmentation algorithm and a convex spherical anamorphosis algorithm. These algorithms have been elaborated for use on 3D rotational angiography acquisitions; they provide a better visualisation of the bAVMsâ main draining vein, especially for venous stenosis or for focal ectasia. They also help in depicting accurately intranidal aneurysms. These improvements in the analysis of the bAVMsâ angioarchitecure may help in reducing the therapeutic risk for these malformations. For a further testing of the potential of anti-Ââangiogenic agents for the treatment of bAVMs, we have elaborated a simplified swine AVM model consisting in the occlusion of a common carotid artery by endovascular means. The comparison between the volume of the rete mirabile at D0 and 3 months and those measured in a control group showed a significant increasing of the retia in the occlusion group. Moreover, a tendency was observed concerning an increase in VEGF (vascular endothelial growth factor) serum levels close to the rete mirabile in the occlusion group. Finally, pathological changes close to those seen in human bAVMs were observed on autopsy samples in the occlusion group.Les malformations artĂ©rio-Ââveineuses cĂ©rĂ©brales (MAVc) sont des pathologies vasculaires agressives prĂ©sentant un risque hĂ©morragique lourd de consĂ©quence en terme de morbi-ÂâmortalitĂ©. Les outils dâimagerie disponibles actuellement ne permettent de comprendre que difficilement leur angio-Ââ architecture. Nous avons dĂ©veloppĂ© dans notre travail deux outils dâimagerie permettant dâaffiner la comprĂ©hension de lâanatomie des ces malformations : un algorithme de segmentation semi-ÂâautomatisĂ© et un algorithme dâanamorphose sphĂ©rique convexe. Ces algorithmes ont Ă©tĂ© Ă©laborĂ©s pour ĂȘtre utilisĂ©s sur les acquisitions dâangiographie rotationnelle 3D ; ils permettent de mieux visualiser la veine de drainage principale des MAVc, notamment dâidentifier une stĂ©nose ou une ectasie focale sur cette veine, et Ă©galement de dĂ©celer de façon plus fiable la prĂ©sence dâun anĂ©vrysme intra-Âânidal. Ces amĂ©liorations dans lâanalyse de lâangio-Ââarchitecture des MAVc permettront vraisemblablement de rĂ©duire le risque thĂ©rapeutique pour ces malformations. En vue de tester le potentiel des agents anti-ÂâangiogĂ©niques pour le traitement des MAVc, nous avons Ă©laborĂ© un modĂšle porcin simplifiĂ© de MAVc consistant en une occlusion unilatĂ©rale dâartĂšre carotide primitive par voie endovasculaire. La comparaison entre le volume de rete mirabile Ă J0 et Ă 3 mois et les valeurs obtenues pour un groupe tĂ©moin a montrĂ© une augmentation significative du volume du rete mirabile chez les porcs ayant eu lâocclusion carotidienne. Dâautre part, une tendance nette Ă lâaugmentation des taux de VEGF (vascular endothelial growth factor) Ă proximitĂ© du rete mirabile Ă©tait observĂ©e dans le groupe occlusion. Enfin, des modifications anatomopathologiques proches de celles des MAVc humaines Ă©taient visualisĂ©es sur les piĂšces autopsiques des rete mirabile dans le groupe occlusion
Visual Perception and Cognition in Image-Guided Intervention
Surgical image visualization and interaction systems can dramatically affect the efficacy and efficiency of surgical training, planning, and interventions. This is even more profound in the case of minimally-invasive surgery where restricted access to the operative field in conjunction with limited field of view necessitate a visualization medium to provide patient-specific information at any given moment. Unfortunately, little research has been devoted to studying human factors associated with medical image displays and the need for a robust, intuitive visualization and interaction interfaces has remained largely unfulfilled to this day. Failure to engineer efficient medical solutions and design intuitive visualization interfaces is argued to be one of the major barriers to the meaningful transfer of innovative technology to the operating room. This thesis was, therefore, motivated by the need to study various cognitive and perceptual aspects of human factors in surgical image visualization systems, to increase the efficiency and effectiveness of medical interfaces, and ultimately to improve patient outcomes. To this end, we chose four different minimally-invasive interventions in the realm of surgical training, planning, training for planning, and navigation: The first chapter involves the use of stereoendoscopes to reduce morbidity in endoscopic third ventriculostomy. The results of this study suggest that, compared with conventional endoscopes, the detection of the basilar artery on the surface of the third ventricle can be facilitated with the use of stereoendoscopes, increasing the safety of targeting in third ventriculostomy procedures. In the second chapter, a contour enhancement technique is described to improve preoperative planning of arteriovenous malformation interventions. The proposed method, particularly when combined with stereopsis, is shown to increase the speed and accuracy of understanding the spatial relationship between vascular structures. In the third chapter, an augmented-reality system is proposed to facilitate the training of planning brain tumour resection. The results of our user study indicate that the proposed system improves subjects\u27 performance, particularly novices\u27, in formulating the optimal point of entry and surgical path independent of the sensorimotor tasks performed. In the last chapter, the role of fully-immersive simulation environments on the surgeons\u27 non-technical skills to perform vertebroplasty procedure is investigated. Our results suggest that while training surgeons may increase their technical skills, the introduction of crisis scenarios significantly disturbs the performance, emphasizing the need of realistic simulation environments as part of training curriculum