Changes of intra-aneurysmal pressure during coiling.
Explore the source record for details and available documents.
Blood Pressure↗
Biomedical subjects
Baruch B Lieber
Publications and source records attributed to Baruch B Lieber.
Correlation of hemodynamic events with clinical and pathological observations.
The correlation of hemodynamic events with clinical or pathological observations is represented by a variety of applications reflecting the broad range of this theme. The position paper describes several cases in which benefits of combining imaging information with transport models of contrast material, can cause a gain in hemodynamic information. What appears to be lack of cohesiveness among the cases illustrates the variety in the application of hemodynamic research to the practice of medicine. Some of the contributions presented at the symposium do not directly apply to clinical medicine, but instead described mathematical models or applications to animal physiology or technical advancements in measuring blood rheology. Although related to this theme topic they fall somewhat outside the main scope. The topics summarized below demonstrate four examples in which translation of the research to the clinical arena can be realized in a short period of time. Overall recommendations for priority objectives related to this topic are provided at the end of this position paper.
Animals↗
Morphological age-dependent development of the human carotid bifurcation.
The unique morphology of the adult human carotid bifurcation and its sinus has been investigated extensively, but its long-term, age-dependent development has not. It is important fundamentally and clinically to understand the hemodynamics and developmental forces that play a role in remodeling of the carotid bifurcation and maturation of the sinus in association with brain maturation. This understanding can lead to better prognostication and therapy of carotid disease. We analyzed the change of sinus morphology and the angle of the carotid bifurcation in four postnatal developmental stages (Group I: 0-2 years, Group II: 3-9 years, Group III: 10-19 years, and Group IV: 20-36 years, respectively) using multiprojection digital subtraction angiograms and image post-processing techniques. The most significant findings are the substantial growth of the internal carotid artery (ICA) with age and the development of a carotid sinus at the root of the ICA during late adolescence. The bifurcation angle remains virtually unchanged from infancy to adulthood. However, the angle split between the ICA and external carotid artery (ECA) relative to the common carotid artery (CCA) undergoes significant changes. Initially, the ICA appears to emanate as a side branch. Later in life, to reduce hydraulic resistance in response to increased flow demand by the brain, the bifurcation is remodeled to a construct in which both daughter vessels are a skewed continuation of the parent artery. This study provides a new analysis method to examine the development of the human carotid bifurcation over the developmental years, despite the small and sparse database. A larger database will enable in the future a more extensive analysis such as gender or racial differences.
Adolescent↗
Functional angiography.
The discovery of X-rays over a century ago enabled noninvasive examination of the human body. Contrast agents that enhanced X-ray images were soon developed that advanced angiology by allowing exploration of the vascular tree. Starting as a diagnostic tool, angiography underwent technological transformations over the last century and became a basis for interventional therapy as well. Initially a static two-dimensional record of the vasculature on screen films, angiography has evolved to real-time two-dimensional display of the vasculature on television monitors, three-dimensional reconstruction from computerized tomographic (CT) scans, and, more recently, three-dimensional cone-beam reconstruction. Cinematographic angiography is referred to as dynamic angiography in current terminology, but it essentially provides no more than images of vascular structures and changes therein. Although dynamic angiography has facilitated advances in image-guided interventions, the evaluation of blood flow rate, or perfusion, and blood flow velocity using angiography remains elusive. Many lines of research have been pursued toward enabling such evaluations, but none have found their way into clinical practice. This article reviews angiographic flow assessment methods attempted over the past several decades and explores some new avenues that may facilitate the transfer of such methods into the clinical practice of diagnostic and interventional angiography and, eventually, contribute to better patient care.
Angiography↗
Morphology of elastase-induced cerebral aneurysm model in rabbit and rapid prototyping of elastomeric transparent replicas.
In this work, we describe a methodology to fabricate transparent elastomeric vascular replicas using rapid prototyping techniques. First, the three-dimensional morphology of an elastase-induced aneurysm model in rabbit is acquired. The morphology is reconstructed from in vivo rotational angiography and it is compared with three-dimensional reconstructions obtained by computerized tomography and magnetic resonance imaging of an intraluminal arterial cast that was obtained from the same animal at sacrifice. Results show that resolution of the imaging modality strongly influences the level of detail, such as small side branches, in the final reconstruction. We developed an average morphology model for elastase-induced aneurysms in rabbits including the surrounding vasculature and describe a method for rapid prototyping of vascular models from the three-dimensional morphology. Our replicas can be manufactured in a short period of time and the final product is optically clear. In addition, the elasticity of the models can be controlled to represent arterial elasticity, which makes them ideal for optical investigations of detailed flow dynamics using measurement tools such as particle image velocimetry.
Animals↗
Hemodynamics of carotid artery atherosclerotic occlusive disease.
Hemodynamic mechanisms for the initiation and progression of carotid bifurcation atherosclerotic occlusive disease have been extensively researched during the past few decades. Attention has focused on the carotid bulb, or sinus, where most atherosclerotic plaques are found. Herein, the authors review the seminal works that have led to an understanding of not only complex local hemodynamics but also the elicited specific biologic response. In addition, new analysis of the age-dependent morphologic maturation of the human carotid bifurcation is unveiled. Understanding the role of hemodynamics in atherogenesis may lead to the improvement of minimally invasive endovascular therapy and noninvasive strategies.
Brain↗
Fate of branch arteries after intracranial stenting.
OBJECTIVE: One concern with respect to stent procedures performed to treat patients with intracranial lesions is the fate of normal major arterial branches after stents are placed across them. Because most of these lesions occur at vessel bifurcations or at branch points, a normal major branch often arises near the lesion and may be difficult to avoid during stent positioning. The aim of this article is to describe the angiographic outcome of intracranial major branch arteries crossed by a stent in the intracranial circulation. METHODS: We examined the immediate postprocedural cerebral angiograms of the 40 patients who underwent intracranial stenting at the University at Buffalo, Buffalo, NY, between June 1998 and April 2000. In each of 10 patients, the stent was placed across a normal major branch artery. Stents were used to treat aneurysms in seven patients and intracranial stenosis in three patients. The latest cerebral angiogram available was reviewed, and the patency of the major branch arteries was evaluated. RESULTS: The angiographic follow-up period ranged from 4 days to 35 months (mean follow-up, 10 mo). Each of the 10 major branch arteries was patent. No infarcts were associated with the territory of the major branch arteries crossed by the stents, and no patient experienced a related episode of clinical ischemia. Four patients died as a result of causes unrelated to the stenting procedure. The histology of a middle cerebral artery stent that was placed across a lenticulostriate perforator is presented. CONCLUSION: The flexible, low-profile stents used in this study had no angiographically or clinically apparent effect on the major intracranial branches across which they were placed.
Adult↗
Particle image velocimetry assessment of stent design influence on intra-aneurysmal flow.
Endovascular stenting appears to be an appealing treatment modality to selected complex intracranial aneurysms. However, stents currently used for endovascular treatment are not specifically designed for the cerebrovasculature. Stent parameters, such as porosity and filament size, have to be carefully optimized for long-term successful treatment. We investigated the influence of the stent filament size on the intraaneurysmal flow dynamics in a sidewall aneurysm model in vitro. Three helical stents with 76% porosity but different filament sizes of 178, 153, and 127 microm were studied using particle image velocimetry. Twenty-four pulsatile flow conditions were investigated. The results show that stenting significantly reduces intra-aneurysmal vorticity and the mean circulation inside the aneurysm is reduced to less than 3% of its value before stenting. For constant porosity, a further reduction of the mean circulation, up to 30% can be obtained by reducing the filament diameter. For a constant Womersley number, this further reduction is accentuated with increase in the peak Reynolds number. Further reduction in the mean circulation inside the aneurysm was not achieved for the 127 microm stent. With further reduction in filament diameter, the helical stent filaments positioned against the aneurysm neck started wavering with the flow transferring added momentum into the aneurysm. For stents of smaller filament diameter, a supporting ultrastructure is required.
Alloys↗
The physics of endoluminal stenting in the treatment of cerebrovascular aneurysms.
Endovascular stenting of aneurysms offers potential advantages over surgical clipping. Stenting is minimally invasive, and with the implementation of rapidly developing micro and nano technologies, it will in the future be possible to deploy stents in more remote locations of the cerebrovasculature. The key advantage of stenting is that in addition to impeding flow into the aneurysm, it provides the parent artery with a scaffold over which the artery can remodel. However, for a stent to be effective in this goal, it must be tailored to the local hemodynamics at the aneurysm site. This paper is a review of the qualitative and quantitative in vitro and in vivo experimentation as well as computer simulations that have been performed to elucidate the effects of various stent design parameters and the prevailing parent vessel hemodynamics on intra-aneurysmal flow patterns. Our results in numerous studies have shown that stenting substantially alters intra-aneurysmal flow. Furthermore, it is demonstrated that techniques have been developed in order to assess the efficacy of the stent in promoting intra-aneurysmal flow stagnation, thus creating the potential to optimize the device design for the treatment of intracranial aneurysms.
Angioplasty↗
Angiographic quantification of contrast medium washout from cerebral aneurysms after stent placement.
BACKGROUND AND PURPOSE: Endovascular stent placement is an emerging technique in treating cerebral aneurysms. Thus far, no quantitative method is available to determine the effectiveness of stent deployment in reducing intraaneurysmal flow circulation, and thereby, in excluding the aneurysm from the cerebral vasculature. Our purpose was to develop a mathematical model congruent with flow transport phenomena observed in cerebral aneurysms and based on the washout of angiographic contrast medium from these aneurysms to provide quantitative indices for predicting the likelihood of stable thrombus formation after stent placement. METHODS: Angiographic data from an in vitro experiment involving an elastomer side-wall aneurysm model and data from five patients with cerebral aneurysms were collected and analyzed. A region of interest (ROI) delineating the aneurysm was selected in each case, and the temporal variation in average gray-scale intensity within this ROI was assessed. The mathematical model was fit to the gray-scale intensity curves by using least-squares minimization. Variations in model parameters before and after stent placement were studied. RESULTS: A marked variation in the model parameters was observed in both in vitro cases and when data suitable for mathematical modeling were available from the clinical setting. This variation supported the hypothesis of the model. CONCLUSION: On the basis of our results, we conclude that the model developed herein can be used to quantitatively depict and characterize alterations in aneurysmal blood-flow transport before and after endovascular stent placement. By inference, future versions of the model will be useful in predicting the long-term effectiveness of endovascular stent placement for cerebral aneurysms immediately after the procedure is performed.
Angiography↗
Device malfunction in endovascular treatment of intracranial aneurysms: shared responsibilities of physician and manufacturer.
Explore the source record for details and available documents.
Embolization, Therapeutic↗
Effect of glacial acetic acid and ethiodized oil concentration on embolization with N-butyl 2-cyanoacrylate: an in vivo investigation.
BACKGROUND AND PURPOSE: Precise control of the polymerization dynamics of cyanoacrylate mixtures used in the embolization of cerebral arteriovenous malformations is required to achieve a safe and permanent obliteration of the lesion. In this study, in vivo embolization using mixtures of Histoacryl, Lipiodol Ultra-Fluid, and glacial acetic acid (GAA) was investigated. The present study investigated whether increased ethiodized oil concentration or the addition of GAA increased rate of embolization. METHODS: Using embolic mixtures containing Histoacryl (N-butyl 2-cyanoacrylate [NBCA]), the embolization process in the femoral and subclavian arteries of the rabbit was examined. Various embolic agents composed of ethiodized oil and N-BCA mixtures, either with or without the addition of minute quantities of GAA, were injected. Blood flow through the aforementioned arteries was measured during embolization. The transient decay of blood flow to zero was modeled, and an optimized model parameter, termed the time elapsed to flow arrest (TEFA) factor, was compared with the experimental data related to the embolization process. RESULTS: The TEFA factor was independent of the variation of the ethiodized oil concentration in the mixture (P >.05). In contradistinction, the addition of GAA significantly increased the TEFA factor (P <.05). Moreover, a linear relation between the TEFA factor and the quantity of GAA in the mixture was discerned. CONCLUSION: Predictable control of the embolization process with N-BCA in vivo is attained by varying the amount of GAA in the embolic mixture.
Acetic Acid↗