Daniel Rüfenacht - Academia.edu (original) (raw)

Papers by Daniel Rüfenacht

Angiologie-Hémostase, 2010

... [Medline]; ↑ Merland JJ, Marache P, Herbreteau D. Les ... Valérie Schweizer; Troubles cogniti... more ... [Medline]; ↑ Merland JJ, Marache P, Herbreteau D. Les ... Valérie Schweizer; Troubles cognitifs et comportementaux après lésion cérébrale : impact sur la reprise professionnelle.Jean-Marie Annoni, Françoise Col; Pièges en orthopédie ambulatoire : le membre supérieur. ...

CardioVascular and Interventional Radiology, 2005

The biomaterials currently used in injectable implants (liquid embolics) for minimally invasive i... more The biomaterials currently used in injectable implants (liquid embolics) for minimally invasive image-guided treatment of vascular lesions undergo, once injected in situ, a phase transition based on a variety of physicochemical principles. The mechanisms leading to the formation of a solid implant include polymerization, precipitation and cross-linking through ionic or thermal process. The biomaterial characteristics have to meet the requirements of a variety of treatment conditions. The viscosity of the liquid is adapted to the access instrument, which can range from 0.2 mm to 3 mm in diameter and from a few centimeters up to 200 cm in length. Once such liquid embolics reach the vascular space, they are designed to become occlusive by inducing thrombosis or directly blocking the lesion when hardening of the embolics occurs. The safe delivery of such implants critically depends on their visibility and their hardening mechanism. Once delivered, the safety and effectiveness issues are related to implant functions such as biocompatibility, biodegradability or biomechanical properties. We review here the available and the experimental products with respect to the nature of the polymer, the mechanism of gel cast formation and the key characteristics that govern the choice of effective injectable implants.

AJNR. American journal of neuroradiology, 1999

The purpose of this study was to create and test an in vitro model of intracranial arteriovenous ... more The purpose of this study was to create and test an in vitro model of intracranial arteriovenous fistulas (AVFs) that simulates the geometry of human vasculature and allows realistic testing of devices used in endovascular therapy. The models were derived from corrosion casts of the main cervicocranial arteries and veins obtained from two nonfixed human specimens. Wax copies of the casts were produced and combined to create complex models simulating various types of intracranial AVFs. Wax assemblies were embedded with liquid silicone solidified into transparent blocks containing, after wax evacuation, hollow reproductions of the original vascular trees. The models were connected to a pulsatile pump and their compatibility with various imaging techniques and endovascular treatment materials was evaluated. The models were compatible with digital subtraction angiography, CT, MR imaging, and transcranial Doppler sonography. They provided a realistic endovascular environment for the simu...

Swiss Medical Forum ‒ Schweizerisches Medizin-Forum, 2017

Die autosomal-dominante polyzystische Nierenerkrankung ist eine familiäre, chronische Multisystem... more Die autosomal-dominante polyzystische Nierenerkrankung ist eine familiäre, chronische Multisystemerkrankung mit erheblicher Morbidität und Mortalität, die eine ganzheitliche und langfristige Betreuung von Patienten und Angehörigen erfordert. Einleitung Die autosomal-dominante polyzystische Nierenerkrankung («autosomal dominant polycystic kidney disease», ADPKD) ist eine multisystemische, monogene, vererbbare Erkrankung, die durch die Entwicklung von Zysten in beiden Nieren sowie durch variable extrarenale Organmanifestationen gekennzeichnet ist (Abb. 1). Charakteristisch für ADPKD ist die lange oligo-oder asymptomatische Phase bis in das Erwachsenenalter. Eine ganzheitliche Betreuung unter Berücksichtigung des bio-psycho-sozialen Umfeldes ist bei dieser familiären Erkrankung, die den Patienten und seine Angehörigen lebenslang begleitet, wichtig. Die progressive Niereninsuffizienz bis zur Nierenersatzpflichtigkeit,

British Journal of Neurosurgery, 2017

The Radiologist, 2003

ABSTRACT

RadioGraphics, 1998

A variety of benign and malignant non-squamous cell neoplasms may affect the larynx. Most of thes... more A variety of benign and malignant non-squamous cell neoplasms may affect the larynx. Most of these uncommon Abbreviation: AIDS acquired immunodeficiency syndrome

Journal of Neurosurgery, 1991

✓ Among 121 intracerebral aneurysms presenting at one institution between 1984 and 1989, 16 were ... more ✓ Among 121 intracerebral aneurysms presenting at one institution between 1984 and 1989, 16 were treated by endovascular means. All 16 lesions were intradural and intracranial, and had failed either surgical or endovascular attempts at selective exclusion with parent vessel preservation. The lesions included four giant middle cerebral artery (MCA) aneurysms, one giant anterior communicating artery aneurysm, six giant posterior cerebral artery aneurysms, one posterior inferior cerebellar artery aneurysm, one giant mid-basilar artery aneurysm, two giant fusiform basilar artery aneurysms, and one dissecting vertebral artery aneurysm. One of the 16 patients failed an MCA test occlusion and was approached surgically after attempted endovascular selective occlusion. Treatment involved pretreatment evaluation of cerebral blood flow followed by a preliminary parent vessel test occlusion under neuroleptic analgesia with vigilant neurological monitoring. If the test occlusion was tolerated, i...

Journal Of Craniofacial Surgery, 2000

CMBE 2013, Hong Kong, , 16-18 December 2013, 2013

We present a clinical perspective, supported by biological findings, reflecting the potential of ... more We present a clinical perspective, supported by biological findings, reflecting the potential of computational tools to understand and treat intracranial aneurysms. Thrombus formation and chronic inflammation are integral to disease progression, driven by blood flow energy. The interplay between flow energy, blood clotting and remodeling of the tissue is key to an enhanced disease understanding, to improve patient counseling and ultimately endovascular treatment planning. Current concepts suggest that blood governs wall remodeling by multiple biological steps. The process starts with flow induced thrombus adhesion (atherothrombosis) to the wall that secondarily leads to the release of biological mediators of inflammation entertaining destructive remodeling. Destructive wall remodeling jeopardizes the mechanical wall integrity with ensuing circumscribed softening and expansion of the aneurysm shape. The shape of an aneurysm is the visible result of these complex pathological processes and characterizes its disease status. Wall adherent thrombus formation, inflammatory reactions and the driving force of blood flow cause lumen shape changes. Here, shape irregularity is a distinctive sign of focal wall weakening. The integration of shape-analysis,vascular biology and phenotypical information will allow for personalized characterization of aneurysmal vascular disease and help to identify and establish shape as an image-based biomarker. Future translational efforts should aim at providing adequate IT tools and contributing to validation and disease understanding. Ensuing results will have a high likelihood to impact significantly on current clinical disease management

Objective: Giant intracranial aneurysms (GIA) are rare lesions that display the poorest treatment... more Objective: Giant intracranial aneurysms (GIA) are rare lesions that display the poorest treatment outcomes of all intracranial aneurysms (IA). The international GIA Registry was initiated as a dedicated health services project in 2008, dealing exclusively with GIA. Its main goal is to document current[for full text, please go to the a.m. URL]

Discussion p. 9-10 Conclusion p. 10-11 Part II: venous systems in the middle cranial fossa Backgr... more Discussion p. 9-10 Conclusion p. 10-11 Part II: venous systems in the middle cranial fossa Background p. 12-13 The termination of the superficial middle cerebral vein Angiographic anatomy of the termination of the superficial middle cerebral vein p. 19-20 Discussion Termination of the superficial middle cerebral vein in the middle cranial fossa p. 21-28 Embryological hypothesis p. 28-29 Clinical implications of the laterocavernous sinus p. 29 The sphenoparietal sinus of Breschet, the meningeal, and the diploic veins Introduction p. 30-31 Results Anatomic findings p. 31-35 Angiographic correlation p. 35-36 Clinical case p. 36-37 Discussion Anatomy p. 38-41 Clinical implications p. 41 The petrosquamosal sinus v Postmortem study p. 42 Clinical imaging cases p. 43 Results Postmortem study p. 43-44 Clinical imaging cases Case 1 p. 44-45 Case 2 p. 45-49 Discussion p. 50-53 Conclusion p. 54-56

Introduction: Current methods of medical imaging provide key information for the clinical assessm... more Introduction: Current methods of medical imaging provide key information for the clinical assessment of intracranial aneurysms. To date, broadly accepted quantitative criteria to compare aneurysm morphology are yet lacking. In this study, we relate established shape descriptors to expert assessments of aneurysm irregularity in view of establishing clinically meaningful descriptors. Method: To address morphology in an isolated manner, from 3D angiographies, we produced replicas of aneurysms and adjacent segments of the parent vascular tree, extracted computed geometry indices and measures based on curvature, surface writhe number and geometry moments. Independently, experts evaluated the morphology of these aneurysms in a 3D viewer by inspecting their shapes and rating the degree of irregularity on a 9-point rating scale. Besides these 3D views, no further information was given to the raters. We then examined the univariate and multivariate correlations between the aggregated ratings and the quantitative descriptions of the 3D models. Results: Preliminary results are based on 134 aneurysm models and 15 raters, who all assessed the perceived irregularity of the aneurysm shape. Univariate analysis shows that curvature metrics reproduce the rater assessment of shape irregularity the best (Spearman correlation ρ=0.86, p<0.001). Furthermore, a writhe-based index (entropy of the writhe number distribution, ρ=0.75, p<0.001) and shape indices (non-sphericity, ρ=0.71, p<0.001) predict the ratings on average well. Consistent with observational data, our rater assessment of irregularity degree increased with increasing aneurysm size (ρ=0.78, p<0.001). Discussion: We identified and validated quantitative measures mirroring well the qualitative raters’ assessments of morphological irregularity characteristics. In the future, such quantitative measures could be used in rating schemes for aneurysm assessment. Furthermore, these metrics could be employed in the context of a databank, allowing for retrieving and grouping cases of similar morphological properties

The shape of intracranial aneurysms is used by clinicians for risk assessment. It has been sugges... more The shape of intracranial aneurysms is used by clinicians for risk assessment. It has been suggested that irregular shape is linked to degenerate wall conditions and rupture. With the goal to better characterize shape irregularity, we acquired rating data of 27 participants (9 clinical experts, 18 laypersons) that assessed 134 aneurysms for perceived irregularity. 9 raters additionally examined the presence of 5 morphological attributes. Alongside with quantitative metrics for morphology, we used this rating data to model perceived irregularity. Preliminary results suggest that a combination of quantitative and qualitative shape assessment may characterize perceived irregularity the best

Introduction: To date, it is difficult for clinicians to judge the associated risks of intracrani... more Introduction: To date, it is difficult for clinicians to judge the associated risks of intracranial aneurysms reliably. Because the 3D-shape of an aneurysm is strongly linked to the underlying formation processes it is very likely that the presence or absence of certain shape features indicate the disease status of the aneurysm. Shape (extracted from medical imaging data) already plays a significant role in the qualitative assessment of the aneurysm by the clinician and has been associated with risk prediction. Still, no consensus exists about which shape features reliably predict instability or whether there exist any that qualify as biomarkers at all. In an effort to find support for the assumption that aneurysm shape carries information about the aneurysm status, we developed a flexible classification pipeline that extracts shape features and tests their applicability. Methods: 3D models of aneurysms are extracted from medical imaging data (mostly 3DRA) by a standardized vessel segmentation method. The aneurysm is cut from its parent vessels according to a simple and reproducible cut protocol. Different representations of the 3D shape that have been suggested by literature are calculated for the extracted aneurysm. So far we have looked at Zernike moments (ZM), their invariants (ZMI) and simple geometry indices such as undulation or non-sphericity. Different feature reduction techniques (for ZMI) and machine-learning methods are applied to find linking patterns between shape features and aneurysm stability. This processing pipeline is applied to a relatively large clinical dataset (ca. 400 cases), whereas the collection of new cases is an on-going effort. We will present the findings on the latest state of the database. Results: Initial results indicate that the ZMI alone are insufficient to classify aneurysms reliably in terms of rupture or stability status. Because of their global support, ZMI bare a strong dependency on the placement of the cuts. In a preliminary study, ZMI were only slightly superior regarding rupture prediction compared to much simpler geometry indices. Conclusions: We implemented a framework to test the performance of different combinations of shape features and machine learning techniques. While the shape-only representation of an aneurysm does carry information about its disease status, the classification results will benefit from the stratification of the aneurysms in terms of location, size and clinical factors.

Acta Neurochirurgica, 2020

BACKGROUND Morphological irregularity is linked to intracranial aneurysm wall instability and man... more BACKGROUND Morphological irregularity is linked to intracranial aneurysm wall instability and manifests in the lumen shape. Yet there is currently no consent on how to assess shape irregularity. The aims of this work are to quantify irregularity as perceived by clinicians, to break down irregularity into morphological attributes, and to relate these to clinically relevant factors such as rupture status, aneurysm location, and patient age or sex. METHODS Thirteen clinicians and 26 laypersons assessed 134 aneurysm lumen segmentations in terms of overall perceived irregularity and five different morphological attributes (presence/absence of a rough surface, blebs, lobules, asymmetry, complex geometry of the parent vasculature). We examined rater agreement and compared the ratings with clinical factors by means of regression analysis or binary classification. RESULTS Using rank-based aggregation, the irregularity ratings of clinicians and laypersons did not differ statistically. Perceived irregularity showed good agreement with curvature (coefficient of determination R 2 = 0.68 ± 0.08) and was modeled very accurately using the five morphological rating attributes plus shape elongation (R 2 = 0.95 ± 0.02). In agreement with previous studies, irregularity was associated with aneurysm rupture status (AUC = 0.81 ± 0.08); adding aneurysm location as an explanatory variable increased the AUC to 0.87 ± 0.09. Besides irregularity, perceived asymmetry, presence of blebs or lobules, aneurysm size, non-sphericity, and curvature were linked to rupture. No association was found between morphology and any of patient sex, age, and history of smoking or hypertension. Aneurysm size was linked to morphology. CONCLUSIONS Irregular lumen shape carries significant information on the aneurysm's disease status. Irregularity constitutes a continuous parameter that shows a strong association with the rupture status. To improve the objectivity of morphological assessment, we suggest examining shape through six different morphological attributes, which can characterize irregularity accurately.

Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2020