Multiple blood flow measurements before and after carotid artery stenting via phase-contrast magnetic resonance imaging: An observational study.
ABSTRACT: After carotid artery stenting, the procurement of information about blood flow redistribution among brain-feeding arteries and its time trend is essential to understanding a patient's physiological background and to determine their care regimen. Cerebral blood flow has been measured twice following carotid artery stenting in few previous studies, with some discrepancies in the results. The purpose of this study was to measure cerebral blood flow at multiple time points after carotid artery stenting, and to elucidate the time trend of cerebral blood flow and redistribution among arteries. Blood flow rates in 11 subjects were measured preoperatively, at one day, one week, and about three months, respectively after carotid artery stenting by using phase-contrast magnetic resonance imaging. The target vessels were the bilateral internal carotid arteries, the basilar artery, and the bilateral middle cerebral arteries. Lumen was semi-automatically defined using an algorithm utilizing pulsatility. The results showed that blood flow rates in the stented internal carotid artery and the ipsilateral middle cerebral artery increased following carotid artery stenting. Blood flow rates in the contralateral internal carotid artery and the basilar artery gradually declined, and they were lower than the preoperative values at three months after stenting. The sum of blood flow rates of the bilateral internal carotid arteries and the basilar artery increased after carotid artery stenting, and then decreased over the next three months. There was no significant change in the blood flow rate in the contralateral middle cerebral artery. From these results, it was concluded that redistribution among the bilateral internal carotid arteries and the basilar artery occurs after carotid artery stenting, and that it takes months thereafter to reach another equilibrium.
Project description:Measurement of volume flow rates in major cerebral vessels can be used to evaluate the hemodynamic effects of cerebrovascular disease. However, both age and vascular anatomy can affect flow rates independent of disease. We prospectively evaluated 325 healthy adult volunteers using phase contrast quantitative magnetic resonance angiography to characterize these effects on cerebral vessel flow rates and establish clinically useful normative reference values. Flows were measured in the major intracranial and extracranial vessels. The cohort ranged from 18 to 84 years old, with 157 (48%) females. All individual vessel flows and total cerebral blood flow (TCBF) declined with age, at 2.6?mL/minute per year for TCBF. Basilar artery (BA) flow was significantly decreased in individuals with one or both fetal posterior cerebral arteries (PCAs). Internal carotid artery flows were significantly higher with a fetal PCA and decreased with a hypoplastic anterior cerebral artery. Indexing vessel flows to TCBF neutralized the age effect, but anatomic variations continued to impact indexed flow in the BA and internal carotid artery. Variability in normative flow ranges were reduced in distal vessels and by examining regional flows. Cerebral vessel flows are affected by age and cerebrovascular anatomy, which has important implications for interpretation of flows in the disease state.
Project description:The anatomy of the arterial system supplying blood to the brain can influence the development of arterial disease such as aneurysms, dolichoectasia and atherosclerosis. As the arteries supplying blood to the brain develop during embryogenesis, variation in their anatomy may occur and this variation may influence the development of arterial disease. Angiogenesis, which occurs mainly by sprouting of parent arteries, is the first stage at which variations can occur. At day 24 of embryological life, the internal carotid artery is the first artery to form and it provides all the blood required by the primitive brain. As the occipital region, brain stem and cerebellum enlarge; the internal carotid supply becomes insufficient, triggering the development of the posterior circulation. At this stage, the posterior circulation consists of a primitive mesh of arterial networks that originate from projection of penetrators from the distal carotid artery and more proximally from carotid-vertebrobasilar anastomoses. These anastomoses regress when the basilar artery and the vertebral arteries become independent from the internal carotid artery, but their persistence is not uncommon in adults (e.g., persistent trigeminal artery). Other common remnants of embryological development include fenestration or duplication (most commonly of the basilar artery), hypoplasia (typically of the posterior communicating artery) or agenesis (typically of the anterior communicating artery). Learning more about the hemodynamic consequence that these variants may have on the brain territories they supply may help understand better the underlying physiopathology of cerebral arterial remodeling and stroke in patients with these variants.
Project description:Congenital absence of the internal carotid artery is a rare occurrence. Even more infrequent are cases where the patient has a bilateral absence of the internal carotid arteries. Reported is a case of a 52-year-old woman who presented with optic nerve neuropathy, and was incidentally discovered to have a congenital bilateral absence of her internal carotid arteries. During computed tomography angiography imaging looking for cerebral venous thrombosis, related to her preexisting condition of bilateral elevated optic discs and residual left optic neuropathy, the findings were made. The absence of the arteries is not always recognizably symptomatic, with most findings being incidental through imaging studies only. This is because collateral flow allows for sufficient cerebral circulation. However, this condition puts such patients at higher risk for conditions such as aneurysms and subsequently strokes where the collateral flow exists.
Project description:High-flow causes the remodeling of arteries, in which smooth muscle cells play an important role. To know the profile of smooth muscle gene expression under high-flow conditions in vivo, flow of rabbit basilar artery was increased by ligation of both common carotid arteries. Microarrays were performed to profile the gene expression of smooth muscle cells isolated from rabbit basilar artery. Expression profiles indicate 43603 differentially expressed genes in smooth muscle cells exposed to high-flow insult compared with the sham control, of which 1470 genes were upregulated and 780 genes downregulated using 2 fold-changes and P<0.05 as a cut-off. Bilateral common carotid arteries of female New Zealand White rabbits were ligated to increase vascular flow.The control group was performed the same procedure to expose the CCAs without ligation. Rabbits were euthanized at day 5 after ligation or exposure of bilateral CCAs in both groups (n=3 for each group). The rabbits used and all procedures in this study were approved by the local Institutional Animal Care and Use Committee. Smooth muscle cells were isolated. After euthanization of rabbits, the whole basilar arteries were removed. The arteries were cleaned in PBS buffer,cannulated and perfused at a constant flow with a cocktail which contains PBS and 0.4 mg/ml elastase (Sigma) and 1 mg/ml collagenase (type 1A, Sigma). After an incubation time of 45 min, the tissue left was removed and stored in PBS. SMCs were released from the artery by trituration. Then Total RNA was extracted and gene chip tests were performed.
Project description:Purpose. Atherosclerosis is a diseased condition of blood vessel. It causes partial blockage in lumen of vessel and affects hemodynamic of localized flowing blood. Complex geometries like region of bifurcation also affects hemodynamic to a larger extent. Complexity further increases in presence of stenoses at region of bifurcation. Such morphological change in vessel largely affects parent as well as corresponding sister and daughter vessels. In this paper, complexity in hemodynamic of blood in pair of carotid arteries (left and right carotid arteries) is evaluated in presence of stenoses at basilar segment of right artery in three-dimensional domain using reconstructed tomographic images of patient. Methods. Transient information of blood flow is obtained using four-dimensional phase-contrast MRI technique. Haematocrit component of blood at diseased condition is considered using Power Law and Quemada model. Numerical techniques are used to solve pressure-coupled governing equations of flowing blood. Results. Dysfunctions of endothelial cells near the wall are characterised by evaluating shear stress markers. Wall shear stress and its gradient based and harmonic based descriptors are calculated over complete geometry during one cardiac cycle. Conclusion. Internal branch of left carotid artery and external branch of right carotid artery are found prone to secondary stenoses in presence of primary stenoses at basilar segment of right carotid artery.
Project description:A 68-year-old woman presented with segmental aplasia of bilateral internal carotid arteries accompanied by unruptured intracranial aneurysms. The abnormality was discovered incidentally at the age of 44 years. Cerebral angiography showed occlusion of bilateral internal carotid arteries, and the carotid territory was supplied by each posterior communicating artery with small intracranial aneurysms. Endovascular treatment for the intracranial aneurysms was planned. However, the patient did not want to undergo the endovascular procedure because of the increased risk due to the associated bilateral carotid abnormalities. Cerebral angiography was performed again at the age of 66 years, and the size of the aneurysms had not changed. Based on their segmental identity, aplasia of segment 6 of the internal carotid artery (ICA) including the first portion of the ophthalmic artery was observed bilaterally.
Project description:Cerebral blood flow is an important process for brain functioning and its dysregulation is implicated in multiple neurological disorders. While environmental risk factors have been identified, it remains unclear to what extent the flow is regulated by genetics. Here we performed heritability and genome-wide association analyses of cerebral blood flow in a population-based cohort study. We included 4472 persons free of cortical infarcts who underwent genotyping and phase-contrast magnetic resonance flow imaging (mean age 64.8?±?10.8 years). The flow rate, cross-sectional area of the vessel, and flow velocity through the vessel were measured in the basilar artery and bilateral carotids. We found that the flow rate of the basilar artery is most heritable (h2 (SE)?=?24.1 (9.8), p-value?=?0.0056), and this increased over age. The association studies revealed two significant loci for the right carotid artery area (rs12546630, p-value?=?2.0?×?10-8) and velocity (rs2971609, p-value?=?1.4?×?10-8), with the latter showing a concordant effect in an independent sample (N?=?1350, p-value?=?0.057, meta-analyzed p-value?=?2.5?×?10-9). These loci were also associated with other cerebral blood flow parameters below genome-wide significance, and rs2971609 lies in a known migraine locus. These findings establish that cerebral blood flow is under genetic control with potential relevance for neurological diseases.
Project description:Atherosclerosis is causally related to disturbed flow through low and oscillatory shear stress. In order to study the miR expression profile in atherosclerotic plaques induced by disturbed flow, partial ligation of the carotid artery was performed. This procedure results acutely in severly reduced blood flow and in stenotic lesion formation within 6 weeks in apoe-/- mice on a high fat diet. We compared the miR expression profile in partially ligated left carotid arteries with the untreated right carotid artery to identify miRs which are involved in plaque formation through flow disturbances. The left carotid arteries of 6 female apoe-/- mice (6-8 weeks) were partially ligated (i.e. the external and internal carotid artery as well as the occipital artery were occluded; blood flow out of the common carotid artery occurs mainly through the superior thyroid artery). Following partial ligation the animals were fed a high fat diet for 6 weeks. Total RNA was isolated from partially ligated left carotid arteries and untreated right carotid arteries (control). MiRs expression profile of the partially ligated carotid arteries were compared with the control group. Biological replicates: 6 per group. One replicate per array.
Project description:The arterial connections in the Circle of Willis are a central source of collateral blood flow and play an important role in pathologies such as stroke and mental illness. Analysis of the Circle of Willis and its variants can shed light on optimal methods of diagnosis, treatment planning, surgery, and quantification of outcomes. We developed an automated, standardized, objective, and high-throughput approach for categorizing and quantifying the Circle of Willis vascular anatomy using magnetic resonance angiography images. This automated algorithm for processing of MRA images isolates and automatically identifies key features of the cerebral vasculature such as branching of the internal intracranial internal carotid artery and the basilar artery. Subsequently, physical features of the segments of the anterior cerebral artery were acquired on a sample and intra-patient comparisons were made. We demonstrate the feasibility of using our approach to automatically classify important structures of the Circle of Willis and extract biomarkers from cerebrovasculature. Automated image analysis can provide clinically-relevant vascular features such as aplastic arteries, stenosis, aneurysms, and vessel caliper for endovascular procedures. The developed algorithm could facilitate clinical studies by supporting high-throughput automated analysis of the cerebral vasculature.
Project description:The cerebral circulation is unique in its ability to maintain blood flow to the brain under widely varying physiologic conditions. Incorporating this autoregulatory response is necessary for cerebral blood flow (CBF) modeling, as well as investigations into pathological conditions. We discuss a one-dimensional (1D) nonlinear model of blood flow in the cerebral arteries coupled to autoregulatory lumped-parameter (LP) networks. The LP networks incorporate intracranial pressure (ICP), cerebrospinal fluid (CSF), and cortical collateral blood flow models. The overall model is used to evaluate changes in CBF due to occlusions in the middle cerebral artery (MCA) and common carotid artery (CCA). Velocity waveforms at the CCA and internal carotid artery (ICA) were examined prior and post MCA occlusion. Evident waveform changes due to the occlusion were observed, providing insight into cerebral vasospasm monitoring by morphological changes of the velocity or pressure waveforms. The role of modeling of collateral blood flows through cortical pathways and communicating arteries was also studied. When the MCA was occluded, the cortical collateral flow had an important compensatory role, whereas the communicating arteries in the circle of Willis (CoW) became more important when the CCA was occluded. To validate the model, simulations were conducted to reproduce a clinical test to assess dynamic autoregulatory function, and results demonstrated agreement with published measurements.