Four patients underwent angioplasty and stenting of medically refractory symptomatic intracranial atherosclerosis with the new Wingspan stent system. In all 4 patients, CT angiography (CTA) showed an ...abnormality within the stented segment that was suggestive of nonocclusive in-stent thrombus. However, subsequent conventional angiography findings were typical for in-stent restenosis. The CTA imaging features of in-stent restenosis are important to recognize, and the misinterpretation of in-stent restenosis as in-stent thrombus may result in inappropriate management.
Abstract
Background and Study Aim
To enhance the visualization of the intracranial vasculature of cadavers under gross examination with a combination of imaging modalities.
Material and Methods
A ...total of 20 cadaver heads were used to test two different perfusion techniques. First, fixed cadaver heads were perfused with water; second, fresh cadavers were perfused with saline and 10% formalin. Subsequently, brains were removed and fixed. The compounds used were silicone rubber, silicone rubber mixed with powdered barium sulfate, and silicone rubber mixed with tantalum dioxide prepared by the first perfusion technique and gelatin mixed with liquid barium prepared with the second technique. Conventional X-ray imaging, computed tomography (CT), dynamic computed tomography (dCT), and postprocessing three-dimensional (3D) images were used to evaluate all the heads.
Results
Gelatinized barium was better visualized when compared with tantalum dioxide in conventional X-ray images. The blood vessels injected with either tantalum dioxide or gelatinized barium demonstrated a higher enhancement than the surrounding soft tissues with CT or dCT. The quality of the 3D reconstruction of the intracranial vasculature was significantly better in the CT images obtained from the gelatinized barium group.
Conclusions
Radiologic examinations of the heads injected with gelatinized barium facilitates the 3D understanding of cerebrovascular anatomy as an important tool for neuroanatomy training.
Experience with a variety of intra-luminal “flow diverters” has demonstrated the ability of these high-density, metallic mesh devices to disrupt flow into intracranial aneurysms to a degree where ...thrombosis will occur. Thus far, limitations in their use includes the inability to treat aneurysms of some geometries, for example, bifurcation, as well as the need for the use of dual antiplatelet therapy during, immediately after and for some months following treatment. Over the last 3 years Sequent Medical has designed and developed a novel intra-saccular flow diverter aimed at expanding the utility and ease of use of these devices in aneurysm treatment. In this presentation I will illustrate some of the steps in the development, testing and evolution of the WEB as well as describe and illustrate a computational comparison of the flow diversion achieved by use of a Sequent WEB device or a generic intra-luminal flow diverter in two human aneurysms. Since 2007 we have evaluated a variety of WEB designs using the canine bifurcation aneurysm model. Our aim in these studies was to identify a design which allowed: (1) controlled and reproducible device delivery, retrieval and detachment; (2) aneurysm isolation from the circulation within minutes of deployment; (3) stable aneurysm occlusion at follow-up. A final device design consisting of a high density, two-layer nitinol mesh with variable porosity was selected for clinical use. Using examples from our canine studies, I will discuss and illustrate how changes in pore distribution (density), pore size and the addition of an internal compartment impacted the WEBs performance. To assess the differences between the extent of flow diversion achieved by the WEB as compared to a generic intra-luminal flow diverter, we performed computational studies comparing the two devices imbedded in two human aneurysms from our in-house data base (one a ICA sidewall aneurysm and the other a basilar apex aneurysm). To reduce computational requirements a porous media approach was used for these simulations. In these two aneurysms a comparison of the TA-WSS, flow entering the aneurysms and, changes in a surrogate of kinetic energy before and after virtual “treatment” all indicated potential advantages of the WEB over the generic intra-luminal device. Over the course of our studies, the Sequent WEB evolved into a device that was effective in the treatment of the canine bifurcation aneurysm. Computational studies in two human aneuyrms illustrate the potential advantages of this intra-saccular flow diverter over a generic intra-luminal flow diverter.
PurposeColor coding of digital subtraction angiography (DSA) is a temporal and intensity post-processing color coded algorithm that generates a single composite image containing all information ...contained in a standard DSA acquisition. The composite image enhances the conspicuity of findings on DSA images done before and after therapeutic interventions. To date, analysis of images processed with this algorithm has been entirely qualitative. In a series of patients, we sought to add quantification to the color coded images.Materials and methodsAngiographic acquisitions were obtained by a single operator using the same volume of contrast medium injected through a catheter at the same location before and after treatment. Using the time to peak parameter, the effect of neuroendovascular treatment of cerebral artery vasospasm and intracranial stenosis was quantified in three patients. A time contrast concentration curve was generated from a group of pixels in the extracranial segment of the vertebral artery or internal carotid artery (proximal to the area of pathology) to confirm that delivery of the contrast bolus was equivalent before and after treatment. Next, a time contrast concentration curve from a group of pixels in a vessel distal to the lesion was used to quantify the treatment effect. Quantitative analysis was obtained by directly comparing the time to peak before and after treatment at these two locations.ResultsColor coded DSA was quantified in two patients treated for vasospasm and in one with an intracranial stenosis. In all cases, composite color images were generated with the only variable between pretreatment and post-treatment images being the treatment itself. In all cases, time–concentration curves distal to the lesion demonstrated quantifiable changes in time to peak following treatment. Overall, there was a 1–1.25 s decrease in time to peak after verapamil infusion for vasospasm. There was a 0.5 s decrease in time to peak after angioplasty for intracranial stenosis.ConclusionsColor coded DSA not only presents all the information from a standard acquisition as a composite qualitative image but also contains readily quantifiable parametric data. The full usefulness of these data remains to be determined and is the topic of ongoing investigations. Furthermore, animal experiments on the effects of varying stenosis on quantitative data proximal and distal to the stenosis are ongoing and will be presented.
Computed tomography (CT) perfusion is traditionally performed using iodinated contrast, but this can be problematic in patients with impaired renal function or contrast allergy. We report a case of a ...63-year-old man whose medical history was complicated by chronic renal failure, which was exacerbated after placement of a left cervical internal carotid artery stent by 70% stenosis and left hemisphere perfusion deficit. On a follow-up clinic visit, because of the patient s chronic renal failure, CT perfusion was performed successfully using gadolinium without further renal complications.
BackgroundCarotid artery stenosis may be a cause of reduced cognitive performance. We have previously demonstrated that stent revascularization resulted in short term improvement in cognitive ...testing. The goal of this study was to demonstrate the long term durability of improved cognitive performance 1 year after carotid stenting.MethodsPatients referred for stenting of a unilateral carotid artery stenosis were enrolled in the study. Neuropsychological testing was performed with a Mini-Mental Status Examination, an extended mental status examination, a subjective cognitive status measure and a psychomotor performance speed test. The severity of stenosis was measured on angiography performed prior to stenting. One year after stenting, CT angiography was performed to ensure no restenosis had occurred and neuropsychological testing was repeated. Differences in neuropsychological test scores pre- and post-stenting were calculated and tested for significance with a Student t test.Result13 patients with a single unilateral greater than 50% carotid stenosis completed the study. The stenosis of the carotid artery averaged 84% prior to treatment and 9% after treatment. Post-stenting, the extended mental status examination was significantly improved. There was also significant improvement in delayed memory at 1 year that was not present at the 3 month follow-up. The subjective cognitive status measure also improved. No significant change was noted in the Mini-Mental Status Examination or in the speed of psychomotor performance.ConclusionCarotid artery stenting in patients with a unilateral carotid artery stenosis resulted in significant long term improvements in cognitive test scores, most notably delayed memory.
A regional key comparison of dc voltage ratio has been carried out in Europe. The method to evaluate the comparison reference value, the resulting degrees of equivalence for the voltage ratios 1000 ...V/10 V and 100 V/10 V and the link to the corresponding worldwide key comparison CCEM-K8 are reported.
Exposure of the lung to concentrations of ozone in ambient air is known to cause toxicity to lung epithelial cells. Because of the chemical reactivity of ozone, it likely reacts with target molecules ...in pulmonary surfactant, a lipid rich material which lines the epithelial cells in the airways. Unsaturated phospholipids and cholesterol would be susceptible to attack by ozone, which may lead to the formation of cytotoxic products. While free radical derived oxidized cholesterol products have been frequently studied for their cytotoxic effects, ozonized cholesterol products have not been studied, though they could reasonably play a role in the toxicity of ozone. The studies described in this thesis involved detailed structural analysis of the products formed during the reaction of cholesterol with ozone, and the potential biological effects of these compounds. Vigorous ozonolysis of cholesterol in solution was found to primarily yield 5-hydroperoxy-B-homo-6-oxa-cholestan-3β,7α-diol, a very unstable molecule that was successfully analyzed intact by electrospray ionization mass spectrometry. Mass spectrometry and radioactive monitoring were used to identify the major cholesterol derived product during the reaction of 2 ppm ozone with surfactant as 5β,6β-epoxycholesterol, which was only a minor product during ozonolysis of cholesterol in solution. The dose dependent formation of 5β,6β-epoxycholesterol was studied in a number of model systems, including direct exposure of intact cultured human bronchial epithelial cells (16-HBE) and rat primary lung epithelial cells to ozone. These studies suggested that the identified cholesterol ozonides may be formed in higher concentrations than the phospholipid derived products that were previously described as lipid mediators for ozone toxicity. The relative formation of these products correlated with susceptibility to cytotoxicity mediated by ozone exposure. Studies of the metabolism of 5β,6β-epoxide in lung epithelial cells yielded small amounts of the expected metabolite, cholestan-3β,5α,6β-triol, and more abundant levels of an unexpected metabolite, cholestan-6-oxo-3β,5β-diol. Both 5β,6β-epoxycholesterol and cholestan-6-oxo-3β,5α-diol were shown to be cytotoxic to cultured 16-HBE cells. A possible mechanism for the observed cytotoxicity was inhibition of isoprenoid based cholesterol biosynthesis. The dose dependent formation of cholesterol ozonide products was subsequently studied in vivo in both ozone sensitive (C57BL/6j) and ozone resistant (BALB/c) mice. The quantitative level of the cholesterol ozonolysis products formed in the lung tissue and lung lavage was found to correlate with ozone dose.
The secretion pathway of Saccharomyces cerevisiae was challenged by constitutively overexpressing plasmid-encoded acid phosphatase, a secreted endogenous glycoprotein. A 2-microns-based multicopy ...plasmid carrying the coding sequence of acid phosphatase under the control of a truncated variant of the strong constitutive glyceraldehyde-3-phosphate dehydrogenase promoter was used for expression. Selection for the promoterless dLEU2 marker leads to a growth arrest. This is not per se due to leucine starvation, but due to intracellular accumulation of highly glycosylated enzymatically active acid phosphatase. Immunofluorescence and cytological analysis indicate that intracellular accumulation of acid phosphatase occurs in a subpopulation of cells. By Ludox-AM density centrifugation, these cells can be enriched on the basis of their higher density. The dense accumulating cells have a higher average plasmid copy number and produce more acid phosphatase than non-accumulating cells of low density. These cells are defective in directed secretion and bud formation, therefore can no longer grow and show dramatic changes in cell morphology. We suggest that the secretion pathway in these cells is overloaded with the high level of acid phosphatase leading to a shutdown in vectorial secretion, subsequently to a standstill in growth and to the intracellular accumulation of further expressed acid phosphatase. We have indications that accumulation of acid phosphatase occurs in the late Golgi, suggesting a limitation of the overall secretion at this stage.
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