Flow-Pattern Details in an Aneurysm Model Using High-Speed 1000-Frames-per-Second Angiography.

Traditional digital subtraction angiography provides rather limited evaluation of contrast flow dynamics when studying and treating intracranial brain aneurysms. A 1000-frames-per-second photon-counting x-ray detector was used to image detailed iodine-contrast flow patterns in an internal carotid artery aneurysm of a 3D-printed vascular phantom. High-speed imaging revealed differences in vortex and inflow patterns with and without a Pipeline Embolization Device flow diverter in more detail and clarity than could be seen in standard pulsed angiography. Improved temporal imaging has the potential to impact the outcomes of endovascular interventions by allowing clinicians to better understand and act on flow dynamics in real-time.

A Patient Dose-Reduction Technique for Neuroendovascular Image-Guided Interventions: Image-Quality Comparison Study.

BACKGROUND AND PURPOSE: The ROI-dose-reduced intervention technique represents an extension of ROI fluoroscopy combining x-ray entrance skin dose reduction with spatially different recursive temporal filtering to reduce excessive image noise in the dose-reduced periphery in real-time. The aim of our study was to compare the image quality of simulated neurointerventions with regular and reduced radiation doses using a standard flat panel detector system. MATERIALS AND METHODS: Ten 3D-printed intracranial aneurysm models were generated on the basis of a single patient vasculature derived from intracranial DSA and CTA. The incident dose to each model was reduced using a 0.7-mm-thick copper attenuator with a circular ROI hole (10-mm diameter) in the middle mounted inside the Infinix C-arm. Each model was treated twice with a primary coiling intervention using ROI-dose-reduced intervention and regular-dose intervention protocols. Eighty images acquired at various intervention stages were shown twice to 2 neurointerventionalists who independently scored imaging qualities (visibility of aneurysm-parent vessel morphology, associated vessels, and/or devices used). Dose-reduction measurements were performed using an ionization chamber. RESULTS: A total integral dose reduction of 62% per frame was achieved. The mean scores for regular-dose intervention and ROI dose-reduced intervention images did not differ significantly, suggesting similar image quality. Overall intrarater agreement for all scored criteria was substantial (Kendall τ = 0.62887; P < .001). Overall interrater agreement for all criteria was fair (κ = 0.2816; 95% CI, 0.2060-0.3571). CONCLUSIONS: Substantial dose reduction (62%) with a live peripheral image was achieved without compromising feature visibility during neuroendovascular interventions.

Endovascular intracranial treatment of acute ischemic strokes.

Acute ischemic stroke (AIS) is the leading cause of long-term disability and the second cause of death worldwide. Intravenous (IV) tissue plasminogen activator (tPA) remains the only FDA-approved treatment for AIS. The use of IV tPA in AIS related to large-vessel occlusion (LVO) has shown low recanalization rates and poor clinical outcomes. Over the last decade, endovascular treatment has demonstrated safety and effectiveness in the management of LVO-associated AIS due to the evolution of endovascular techniques and technologies, beginning with intraarterial thrombolysis, aspiration, self- expanding intracranial stents, and now retrievable stents. With the recent publication of the results of 5 randomized controlled studies, mechanical thrombectomy in combination with IV tPA demonstrated significant radiographic and clinical benefit over traditional strategies with IV tPA alone. In light of these results, endovascular therapy has been placed at the forefront of stroke treatment, redefining the standard of care. This review presents the evolution of endovascular treatment of AIS resulting from LVO; provides an analysis of the initial and latest RCTs; and discusses the association between endovascular mechanical thrombectomy and clinical outcomes, functional outcomes, and rates of revascularization, intracranial hemorrhage, morbidity, and mortality. Finally, shortcomings of the recent technological advances, such as clot fragmentation, and potential solutions to overcome these drawbacks are presented.

Is acute reperfusion therapy safe in acute ischemic stroke patients who harbor unruptured intracranial aneurysm?

BACKGROUND: Intracranial aneurysms are currently considered as contraindication for intravenous thrombolysis in acute ischemic stroke, very likely due to a possible increase in the risk of bleeding from aneurysm rupture; however, there is limited data available on whether intravenous thrombolysis is safe for acute ischemic stroke patients with pre-existing intracranial aneurysms. AIMS AND/OR HYPOTHESIS: To find out the safety of intravenous thrombolysis in acute ischemic stroke patients who harbor unruptured intracranial aneurysms. METHODS: We retrospectively reviewed the medical records and cerebrovascular images of all the patients treated with intravenous thrombolysis for acute ischemic stroke in our center from the beginning of 2006 till the end of April 2014. Those with unruptured intracranial aneurysm present on cerebrovascular images prior to acute reperfusion therapy were identified. Post-thrombolysis brain imaging was reviewed to evaluate for any intraparenchymal or subarachnoid hemorrhage related or unrelated to the aneurysm. RESULTS: A total of 637 patients received intravenous thrombolysis for acute ischemic stroke in our center during an 8·3-year period. Thirty-three (5·2%) were found to have at least one intracranial aneurysms. Twenty-three (70%) of those received only intravenous thrombolysis, and 10 patients received combination of intravenous and intra-arterial thrombolysis. The size of the largest aneurysm was 10 mm in maximum diameter (range: 2-10 mm). The mean size of aneurysms was 4·8 mm. No symptomatic intracranial hemorrhage occurred among the 23 patients receiving only intravenous thrombolysis. Out of those who received a combination of intravenous and intra-arterial thrombolysis, one developed symptomatic intracranial hemorrhage in the location of acute infarct, distant to the aneurysm location. CONCLUSION: Our findings suggest that neither intravenous thrombolysis nor combination of intravenous and intra-arterial thrombolysis increases the risk of aneurysmal hemorrhage in acute ischemic stroke patients who harbor unruptured intracranial aneurysms less than 10 mm in diameter. Their listing in exclusion criteria for intravenous thrombolysis should be reconsidered to assure appropriate use of acute reperfusion therapy in this group of patients.

Evaluation of intracranial aneurysm coil embolization in phantoms and patients using a high-resolution Microangiographic Fluoroscope (MAF).

Intracranial aneurysm (IA) embolization using Gugliemi Detachable Coils (GDC) under x-ray fluoroscopic guidance is one of the most important neuro-vascular interventions. Coil deposition accuracy is key and could benefit substantially from higher resolution imagers such as the micro-angiographic fluoroscope (MAF). The effect of MAF guidance improvement over the use of standard Flat Panels (FP) is challenging to assess for such a complex procedure. We propose and investigate a new metric, inter-frame cross-correlation sensitivity (CCS), to compare detector performance for such procedures. Pixel (P) and histogram (H) CCS's were calculated as one minus the cross-correlation coefficients between pixel values and histograms for the region of interest at successive procedure steps. IA treatment using GDC's was simulated using an anthropomorphic head phantom which includes an aneurysm. GDC's were deposited in steps of 3 cm and the procedure was imaged with a FP and the MAF. To measure sensitivity to detect progress of the procedure by change in images of successive steps, an ROI was selected over the aneurysm location and pixel-value and histogram changes were calculated after each step. For the FP, after 4 steps, the H and P CCSs between successive steps were practically zero, indicating that there were no significant changes in the observed images. For the MAF, H and P CCSs were greater than zero even after 10 steps (30 cm GDC), indicating observable changes. Further, the proposed quantification method was applied for evaluation of seven patients imaged using the MAF, yielding similar results (H and P CCSs greater than zero after the last GDC deposition). The proposed metric indicates that the MAF can offer better guidance during such procedures.

Use of the Outreach Distal Access Catheter for microcatheter stabilization during intracranial arteriovenous malformation embolization.

The Outreach DAC is an intermediate-sized catheter designed for use with the Merci clot retriever in acute stroke. We investigated its utility as an adjunctive device during AVM pedicle embolization. In the authors' opinion, the DAC provided additional guide-catheter and microcatheter support, improved selective angiographic visualization of AVM angioarchitecture, aided microcatheter removal from its embedded position in the AVM Onyx cast, and enhanced local microcatheter control and safety, compared with embolization with the guide and microcatheter alone.

New head equivalent phantom for task and image performance evaluation representative for neurovascular procedures occurring in the Circle of Willis.

Phantom equivalents of different human anatomical parts are routinely used for imaging system evaluation or dose calculations. The various recommendations on the generic phantom structure given by organizations such as the AAPM, are not always accurate when evaluating a very specific task. When we compared the AAPM head phantom containing 3 mm of aluminum to actual neuro-endovascular image guided interventions (neuro-EIGI) occurring in the Circle of Willis, we found that the system automatic exposure rate control (AERC) significantly underestimated the x-ray parameter selection. To build a more accurate phantom for neuro-EIGI, we reevaluated the amount of aluminum which must be included in the phantom. Human skulls were imaged at different angles, using various angiographic exposures, at kV's relevant to neuro-angiography. An aluminum step wedge was also imaged under identical conditions, and a correlation between the gray values of the imaged skulls and those of the aluminum step thicknesses was established. The average equivalent aluminum thickness for the skull samples for frontal projections in the Circle of Willis region was found to be about 13 mm. The results showed no significant changes in the average equivalent aluminum thickness with kV or mAs variation. When a uniform phantom using 13 mm aluminum and 15 cm acrylic was compared with an anthropomorphic head phantom the x-ray parameters selected by the AERC system were practically identical. These new findings indicate that for this specific task, the amount of aluminum included in the head equivalent must be increased substantially from 3 mm to a value of 13 mm.

Evaluation of a second-generation self-expanding variable-porosity flow diverter in a rabbit elastase aneurysm model.

BACKGROUND AND PURPOSE: The self-expanding V-POD is a second-generation flow-diverting device with a low-porosity PTFE patch on a self-expanding microstent. The authors evaluated this device for the treatment of elastase-induced aneurysms in rabbits. MATERIALS AND METHODS: Three V-POD types (A, circumferential patch closed-cell stent [n = 9]; B, asymmetric patch closed-cell stent [n = 7]; and C, asymmetric patch open-cell stent [n = 4]) were evaluated by using angiography, conebeam micro-CT, histology, and SEM. Aneurysm flow modifications were expressed in terms of immediate poststent/prestent ratios of maximum CA volume entering the aneurysm dome tracked on procedural angiograms. Flow modifications were correlated with 4 weeks' follow-up angiographic, micro-CT, histologic, and SEM results. RESULTS: Mechanical stent-deployment difficulties in 4 aneurysms (1 type A; 3 type B) led to suboptimal results and exclusion from analysis. Of the remaining 16 aneurysms, 4-week post-treatment angiograms showed no aneurysm filling in 10 (63%), 3 (∼19%) had no filling with a small remnant neck, and 3 (∼19%) had <0.25 filling. Successfully treated aneurysms (n = 16) demonstrated an immediate poststent/prestent CA maximum volume ratio of 0.13 ± 0.18% (0.0%-0.5%). Favorable contrast-flow modification on immediate angiography after deployment correlated significantly with aneurysm occlusion on follow-up angiography, micro-CT, and histology. The occlusion percentage derived from micro-CT was 96 ± 6.8%. Histology indicated advanced healing (grade ≥3) in the aneurysm dome in 13 of 16 cases. SEM revealed 15 of 16 stents in an advanced state of endothelialization. CONCLUSIONS: This study showed the feasibility and effectiveness of V-POD for aneurysm healing in a rabbit elastase model.

Whole-brain dynamic CT angiography and perfusion imaging.

The availability of whole brain computed tomography (CT) perfusion has expanded the opportunities for analysing the haemodynamic parameters associated with varied neurological conditions. Examples demonstrating the clinical utility of whole-brain CT perfusion imaging in selected acute and chronic ischaemic arterial neurovascular conditions are presented. Whole-brain CT perfusion enables the detection and focused haemodynamic analyses of acute and chronic arterial conditions in the central nervous system without the limitation of partial anatomical coverage of the brain.

Navigability trumps all: stenting of acute middle cerebral artery occlusions with a new self-expandable stent.

Acute stroke intervention is rapidly evolving. New technologies are improving device deliverability and rates of recanalization. We describe 2 cases of acute middle cerebral artery occlusions wherein Wingspan stents could not be delivered to the occlusive site because of excessive vascular tortuosity. Merci thrombectomy was also unsuccessful. Revascularization was only achieved with deployment of the highly navigable Enterprise stent, resulting in thrombolysis in myocardial infarction 2/3 flow. Thus, all devices should be considered in the armamentarium of stroke therapy.

Clinical endpoints in peripheral endovascular revascularization trials: a case for standardized definitions.

BACKGROUND: Endovascular therapy is a rapidly expanding option for the treatment of patients with peripheral arterial disease (PAD), leading to a myriad of published studies reporting on various revascularization strategies. However, these reports are often difficult to interpret and compare because they do not utilize uniform clinical endpoint definitions. Moreover, few of these studies describe clinical outcomes from a patients' perspective. METHODS AND RESULTS: The DEFINE Group is a collaborative effort of an ad-hoc multidisciplinary team from various specialties involved in peripheral arterial disease therapy in Europe and the United States. DEFINE's goal was to arrive at a broad based consensus for baseline and endpoint definitions in peripheral endovascular revascularization trials for chronic lower limb ischemia. In this project, which started in 2006, the individual team members reviewed the existing pertinent literature. Following this, a series of telephone conferences and face-to-face meetings were held to agree upon definitions. Input was also obtained from regulatory (United States Food and Drug Administration) and industry (device manufacturers with an interest in peripheral endovascular revascularization) stakeholders, respectively. The efforts resulted in the current document containing proposed baseline and endpoint definitions in chronic lower limb PAD. Although the consensus has inevitably included certain arbitrary choices and compromises, adherence to these proposed standard definitions would provide consistency across future trials, thereby facilitating evaluation of clinical effectiveness and safety of various endovascular revascularization techniques. CONCLUSION: This current document is based on a broad based consensus involving relevant stakeholders from the medical community, industry and regulatory bodies. It is proposed that the consensus document may have value for study design of future clinical trials in chronic lower limb ischemia as well as for regulatory purposes.

Influence of patient age and stenosis location on wingspan in-stent restenosis.

BACKGROUND AND PURPOSE: Wingspan is a self-expanding, microcatheter-delivered microstent specifically designed for the treatment of symptomatic intracranial atherosclerotic disease. Our aim was to discuss the effect of patient age and lesion location on in-stent restenosis (ISR) rates after percutaneous transluminal angioplasty and stenting (PTAS) with the Wingspan system. MATERIALS AND METHODS: Clinical and angiographic follow-up results were recorded for all patients from 5 participating institutions. ISR was defined as >50% stenosis within or immediately adjacent (within 5 mm) to the implanted stent and >20% absolute luminal loss. For the present analysis, patients were stratified into younger (55 years) age groups. RESULTS: ISR occurred at a rate of 45.2% (14/31) in the younger group and 24.2% (15/62) in the older group (odds ratio, 2.6; 95% confidence interval, 1.03-6.5). In the younger group, ISR occurred after treatment of 13/26 (50%) anterior circulation lesions versus only 1/5 (20%) posterior circulation lesions. In the older group, ISR occurred in 9/29 (31.0%) anterior circulation lesions and 6/33 (18.2%) posterior circulation lesions. In young patients, internal carotid artery lesions (10/17 treated, 58.8%), especially those involving the supraclinoid segment (8/9, 88.9%), were very prone to ISR. When patients of all ages were considered, supraclinoid segment lesions had much higher rates of both ISR (66.6% versus 24.4%) and symptomatic ISR (40% versus 3.9%) in comparison with all other locations. CONCLUSION: Post-Wingspan ISR is more common in younger patients. This increased risk can be accounted for by a high prevalence of anterior circulation lesions in this population, specifically those affecting the supraclinoid segment, which are much more prone to ISR and symptomatic ISR than all other lesions.

Self-expanding stents for recanalization of acute cerebrovascular occlusions.

BACKGROUND AND PURPOSE: Stent-assisted revascularization increases prevailing recanalization rates ( congruent with 50%-69%) for vessel occlusions recalcitrant to thrombolytics. Although balloon-mounted coronary stents can displace thrombus (via angioplasty) and retain clot along vessel walls, intracranial self-expanding stents are more flexible and exert less radial outward force during deployment, increasing deliverability and safety. To understand the effectiveness of self-expanding stents for recanalization of acute cerebrovascular occlusions, we retrospectively reviewed our preliminary experience with these stents. MATERIALS AND METHODS: Eighteen patients (19 lesions) presenting with a clinical diagnosis of acute stroke underwent catheter-based angiography documenting focal occlusion of an intracranial artery. A self-expanding stent was delivered to the occlusion and deployed. Stent placement was the initial mechanical maneuver in 6 cases; others involved a combination of pharmacologic and/or mechanical maneuvers prestenting. GP IIb/IIIa inhibitors were administered in 10 cases intraprocedurally or immediately postprocedurally to avoid acute in-stent thrombosis. RESULTS: Stent deployment at the target occlusion (technical success) was achieved in all cases. Thrombolysis in Cerebral Ischemia (TICI)/Thrombolysis in Myocardial Ischemia (TIMI) 2/3 recanalization (angiographic success) was achieved in 15 of 19 lesions (79%). All single-vessel lesions (n=8) were recanalized, but only 7 of 11 combination internal carotid artery and middle cerebral artery lesions were recanalized. No intraprocedural complications occurred. Seven in-hospital deaths occurred: stroke progression, 4; intracranial hemorrhage, 2; respiratory failure, 1. Seven patients had >or=4-point National Institutes of Health Stroke Scale improvement within 24 hours after the procedure, 6 had modified Rankin Score (mRS)

Treatment of unruptured intracranial aneurysms: a nationwide assessment of effectiveness.

BACKGROUND AND PURPOSE: With advances in neuroimaging, unruptured cerebral aneurysms are being diagnosed more frequently. Until 1995, surgical clipping of the aneurysm was the only treatment available. Since then, a less invasive endovascular technique has been found effective in a trial of ruptured aneurysms. No efficacy studies comparing the 2 procedures for unruptured aneurysms exist to guide clinical decisions. The objective of this study was to assess effectiveness and outcomes of endovascular versus neurosurgical treatment for unruptured intracranial aneurysms. METHODS: This was a retrospective cohort study, using data collected over a 1-year time interval (between 1998 and 2000), from 429 hospitals, in 18 states, and representing 58% of the US population. A total of 2535 treated, unruptured cerebral aneurysm cases were evaluated. The measurements used were effectiveness as measured by hospital discharge outcomes: 1) mortality (in-hospital death), 2) adverse outcomes (death or discharge to a rehabilitation or nursing facility), 3) length of stay, and 4) hospital charges. Univariate analyses compared endovascular versus neurosurgical discharge outcomes. Multivariable models were adjusted for age, sex, region, Medicaid insurance status, year, hospital case volume, comorbidity score, and admission source. RESULTS: Endovascular treatment was associated with fewer adverse outcomes (6.6% versus 13.2%), decreased mortality (0.9% versus 2.5%), shorter lengths of stay (4.5 versus 7.4 days), and lower hospital charges (42,044 dollars versus 47,567 dollars) compared with neurosurgical treatment (P < .05). After multivariable adjustment, neurosurgical cases had 70% greater odds of an adverse outcome, 30% increased hospital charges, and 80% longer length of stay compared with endovascular cases (P < .05). CONCLUSIONS: The current analysis indicates that endovascular therapy is associated with significantly less morbidity, less mortality, and decreased hospital resource use at discharge, compared with conventional neurosurgical treatment for all unruptured aneurysms. Endovascular therapy, as a treatment alternative to surgical clipping, should be offered as a viable therapeutic option for all patients considering treatment of an unruptured cerebral aneurysm.

Self-expanding versus balloon-mounted stents for vessel recanalization following embolic occlusion in the canine model: technical feasibility study.

BACKGROUND AND PURPOSE: Despite advances in mechanical thrombolysis for acute stroke, recanalization rates remain approximately 50%-60%. Technologic improvements allowed safe intracranial delivery of stents. To study the feasibility of stent-assisted recanalization for acute stroke, we deployed self-expanding or balloon-mounted stents in 2- to 3.5-mm canine vessels acutely occluded with clot emboli. METHODS: Six mongrel dogs were placed under general anesthesia. A guiding catheter was placed in the distal vertebral artery or an external carotid artery branch. A 7 x 3 mm (length x diameter) soft or hard clot was injected into the catheter and allowed to embolize distally; 20 vessels were successfully occluded. After systemic heparin anticoagulation, recanalization with a self-expanding stent was attempted in 11 vessels (5 occluded with soft clot; 6, with hard clot). Balloon-mounted stents were placed in an attempt to revascularize 9 vessels (4 occluded with soft clot; 5, with hard clot). Vessel recanalization was assessed as the primary end point. Side-branch occlusion and stent-induced vasospasm were also assessed. RESULTS: Thrombolysis in Myocardial Infarction/Thrombolysis in Cerebral Infarction flow for 11 vessels treated with self-expanding stents versus 9 treated with balloon-mounted stents was as follows: grade 3, 91% of vessels versus 78% of vessels; grade 2, 0% versus 11%; grade 1, 9% versus 0%; grade 0, 0% versus 11%. Lower rates of spasm and side-branch occlusion were noticed with self-expanding stents. Grade 2/3 flow was achieved in 18/20 vessels (90%). CONCLUSIONS: Excellent recanalization was demonstrated with both stents. Recanalization in self-expanding stents was achieved without pre- or post-balloon dilation. Stents may prove to be a useful adjunct for intra-arterial acute stroke treatment.

Saccular aneurysms on straight and curved vessels are subject to different hemodynamics: implications of intravascular stenting.

Our aim was to examine hemodynamic implications of intravascular stenting in the canine venous pouch (sidewall or straight-vessel) and rabbit elastase (curved-vessel) aneurysm models. Flow dynamics in stented (Wallstent) and nonstented versions were studied by using computational fluid dynamics simulations and in vitro flow visualization, with a focus on stent placement effects on aneurysmal flow stagnancy and flow impingement. Results show that sidewall and curved aneurysm models have fundamentally different hemodynamics (shear-driven versus inertia-driven) and thus stent placement outcomes.

Randomized comparison of intra-arterial and intravenous thrombolysis in a canine model of acute basilar artery thrombosis.

We compared the rates of recanalization cerebral infarct and hemorrhage between intra-arterial (i.a.) reteplase and intravenous (i.v.) alteplase thrombolysis in a canine model of basilar artery thrombosis. Thrombosis was induced by injecting a clot in the basilar artery of 13 anesthetized dogs via superselective catheterization. The animals were randomized in a blinded fashion, 2 h after clot injection and verification of arterial occlusion, to receive i.v. alteplase 0.9 mg/kg over 60 min and i.a. placebo, or i.a. reteplase 0.09 units/kg over 20 min, equivalent to one-half the alteplase dose, and i.v. placebo. Recanalization was studied for 6 h after treatment with serial angiography; the images were later graded in a blinded fashion. Blinded interpretation of postmortem MRI was performed to assess the presence of brain infarcts and/or hemorrhage. At 3 h after initiation of treatment, partial or complete recanalization was observed in one of six dogs in the i.v. alteplase group and in five of seven in the i.a. reteplase group (P = 0.08). At 6 h, no significant difference in partial or complete recanalization was observed between the groups (two of six vs. five of seven; P = 0.20). Postmortem MRI revealed infarcts in four of six animals treated with i.v. alteplase and three of seven treated with i.a. reteplase (P = 0.4). Intracerebral hemorrhage was more common in the i.v. alteplase group (four of six vs. none of seven; P = 0.02). This study thus suggests that i.a. thrombolysis affords a recanalization rate similar to that of i.v. thrombolysis, but with a lower rate of intracerebral hemorrhage.