Hesham Morsi

Wall Shear Stress on Ruptured and Unruptured Intracranial Aneurysms at the Internal Carotid Artery

BACKGROUND AND PURPOSE: Hemodynamics is often recognized as one of the major factors in aneurysm rupture. Flow impingement, greater pressure, and abnormal wall shear stress are all indications for aneurysm rupture. Characterizing wall shear stress for intracranial aneurysms at similar anatomic locations may help in understanding its role. MATERIALS AND METHODS: Twenty-six intracranial aneurysms at the paraclinoid and superclinoid segments of the internal carotid artery from 25 patients between July 2006 and July 2007 were studied retrospectively. Among them, 8 aneurysms were ruptured and 18 were unruptured. Computational fluid dynamics was used to determine the wall shear distribution. Morphologic and hemodynamic variables was analyzed by using the Mann-Whitney rank sum test. RESULTS: Wall shear stress was qualitatively the same throughout the cardiac cycle; thus, only wall shear stress at the end of diastole was compared. Both ruptured and unruptured aneurysms have similar maximal wall shear stress (26 versus 23 N/m2), and mean wall shear stress is shown to be a function of the aneurysm area. Ruptured aneurysms also have a greater portion of aneurysm under low wall shear stress (27% versus 11% for unruptured aneurysms, P = .03). CONCLUSION: For intracranial aneurysms at the internal carotid artery, an area of low wall shear is associated with aneurysm rupture.

Dual Antiplatelet Therapy Monitoring for Neurointerventional Procedures Using a Point-of-Care Platelet Function Test: A Single-Center Experience

BACKGROUND AND PURPOSE: Growing evidence of the relationship between poor antiplatelet response and occurrence of clinical events elicited the need of monitoring the response which has not been part of our daily practice. We present our initial experience with a new point-of-care antiplatelet-function test (VerifyNow assay) in neurointerventional procedures. MATERIALS AND METHODS: Among the 106 consecutive patients from July 2006 to April 2007, ninety-eight met the inclusion criteria. Our preferred antiplatelet regimen was aspirin (325 mg daily) and clopidogrel (300 mg of loading dose followed by 75 mg daily) starting 5–10 days before the procedure. The test results were reported as aspirin-reaction unit (ARU) for aspirin and P2Y12 reaction units (PRU), baseline (BASE), and percentage inhibition for the P2Y12 assay and were summarized as mean ± SD of the values. We analyzed the effects of several factors of poor clopidogrel response (<40% inhibition). The occurrence of thrombotic events was recorded. RESULTS: The mean ARU of aspirin assays was 438.3 ± 47.9 (range, 350–632), and the response was poor in 2 patients (2.1%). For clopidogrel, the mean of the BASE, PRU, and percentage inhibition was 356.8 ± 56.3 (range, 234–495), 198.9 ± 104.4 (range, 8–401), and 45.2 ± 27.1% (range, 0–98), respectively. Forty-two patients (42.9%) showed poor response. Multivariate analysis showed greater body weight (81.9 Kg ± 19.1 kg versus 69.9 ± 15 kg) in the poor-response group. All 3 cases of intraprocedural thrombosis (3.1%) were observed only in the poor-response group. CONCLUSION: We observed a high frequency of poor clopidogrel responses in the neurointerventional setting. Routine monitoring of the drug response would be helpful for the early identification of poor antiplatelet responders so that we may modify the regimen and/or treatment plan.

Endovascular Treatment of Sigmoid Sinus Aneurysm Presenting as Devastating Pulsatile Tinnitus: A Case Report and Review of Literature

Pulsatile tinnitus is a rare yet potentially disabling symptom that can have either vascular or nonvascular etiologies. A recently described vascular cause is an aneurysm of dural venous sinuses. To our knowledge, eight of such cases have been published, five of which were treated surgically and three by endovascular approach. We describe one additional case treated successfully by endovascular coiling and review the current data on this subject.

Neck localization and geometry quantification of intracranial aneurysms

We present an approach for accurate localization of the neck of intracranial aneurysms and quantification of their geometry that is useful for their treatment through endovascular embolization. In particular, we first obtain a vessel segmentation using a topology-preserving level set method and extract the surface of the segmented vessel. We then separate the aneurysm from the parent vessels and localize its neck by formulating the aneurysm segmentation problem as an s-t minimum cut problem. Finally, we estimate clinically relevant geometric parameters of the aneurysm. The results indicate that there is good agreement between the measurements obtained by the proposed approach and two independent manual sets of measurements obtained by two experienced interventional neuroradiologists.

Intimal Thickening after Placement of a Neuroform Stent: Its Incidence and Relation to Angiographic Follow-up Results of Aneurysm Embolization

Little attention has been given to the intimal thickening of the parent artery associated with the use of Neuroform stent. The purposes of this study were are to analyze quantifyanalyze the incidence of the parent artery intimal thickening the incidence and pattern of luminal changes, to to see somedetermine possible predictors of the phenomenonof the intimal thickening, to to evaluate the its effectthe phenomenonrestenosis on the aneurysm treatment results. We reviewed the initial and six-month follow-up angiographic images in 32 intracranial aneurysm patients treated with Neuroform stent and coilsin wide-necked aneurysm treatment. The initial embolization results were evaluated by the Raymond and Roy classification. The angiographic changes from immediate post-embolization to the six-month follow-up were classified as ‘improved’, ‘unchanged’ and ‘worse’. The occurrencerates of parent artery intimal thickening was observed. Any perceivable change in the stented segment of the parent artery was considered as ‘intimal thickening’ and any change of ≥50% as ‘significant thickening’. Fisher exact tests and logistic regression analysis were applied to determine the relation between the occurrence of the intimal thickening and several variables. The incidence of the intimal thickening was 18.8% (6/32) and of significant thickening, 3.1% (1/32). The change in angiographic occlusion of the aneurysm was ‘improved’ in 40.6% (13/32), ‘unchanged’ in 37.5% (12/32), and ‘worse’ in 21.9% (7/32). Among the variables, patients age (≥55) and follow-up angiographic results (‘improved’) correlated with the occurrence of the intimal thickening. Of notable finding was all six cases with intimal thickening of the parent artery were associated with ‘improved’ in their follow-up angiographic result. Neuroform-associated intimal thickening usually occurs in younger patients and is frequently associated with improved angiographic result of the aneurysm embolization on follow-up.

Computer-aided planning for endovascular treatment of intracranial aneurysms (CAPETA)

Endovascular treatment planning of intracranial aneurysms requires accurate quantification of their geometric parameters, including the neck length, dome height and maximum diameter. Today, the geometry of intracranial aneurysms is typically quantified manually based on three-dimensional (3D) Digital Subtraction Angiography (DSA) images. Since the repeatability of manual measurements is not guaranteed and their accuracy is dependent on the experience of the treating physician, we propose a semi-automated approach for computer-aided measurement of these parameters. In particular, a tubular deformable model, initialized based on user-provided points, is first fit to the surface of the parent artery. An initial estimate of the aneurysmal segment is obtained based on differences between the two surfaces. A 3D deformable contour model is then used to localize the aneurysmal neck and to separate its dome surface from the parent artery. Finally, approaches for estimation of the clinically relevant geometric parameters are applied based on the aneurysmal neck and dome surface. Results on 19 3D DSA datasets of saccular aneurysms indicate that, for the maximum diameter, the standard deviation of the difference between the proposed approach and two independent manual sets of measurements obtained by expert readers is similar to the inter-rater standard deviation. For the neck length and dome height, the results improve considerably if we exclude datasets with high deviation from the manual measurements.

Hemodynamic relationship between intracranial aneurysm and carotid stenosis: review of clinical cases and numerical analyses

Abstract Objective: Coexistence of both an intracranial aneurysm and a stenosis at the same internal carotid artery is infrequent, but it may complicate therapeutic management of either disease. It is unclear if a stenosis plays any role in development of intracranial aneurysms. We study patients with intracranial aneurysms at our hospital and investigate if there is a relationship between a carotid stenosis and an intracranial aneurysm. Methods: Two hundred and nine patients who were treated for their intracranial aneurysms in a 2-year period were reviewed. Fifty-four patients were found to have at least one intracranial aneurysm and one intracranial or extracranial carotid stenosis. Ten of them had bilateral stenoses; 17 aneurysms were on the ipsilateral side of the stenosis, and eight on the contralateral side. Nineteen aneurysms were elsewhere. Two cases were selected for detailed computational fluid dynamics (CFD) analyses: one with an intracranial and the other with an extracranial stenosis. Results: Aneurysms on the contralateral side of a carotid stenosis are significantly larger than those aneurysms on the ipsilateral side or with bilateral stenoses (13.6 versus 6.6 mm; P < 0.01). CFD studies show that wall shear stress at the aneurysm is more likely affected by an adjacent intracranial stenosis than by an extracranial stenosis. Conclusions: Intracranial carotid aneurysms contralateral to a carotid stenosis are significantly larger than aneurysms with a carotid stenosis elsewhere. Rupture can occur on aneurysms with an extracranial carotid stenosis on the contralateral side or with an intracranial carotid stenosis on the ipsilateral side.

Endovascular Recanalization in Acute Ischemic Stroke Using the Solitaire FR Revascularization Device with Adjunctive C-Arm CT Imaging

SUMMARY: In this clinical report, we examined a single-center experience by using the Solitaire FR Revascularization Device in the treatment of acute ischemic stroke in which there was poor initial visualization of the occluded arterial branches by using biplanar cerebral angiography. In all cases, adjunctive C-arm CT was used during the deployment of the thrombectomy device to gain additional information regarding device placement and expansion. Outcome measures included the extent of reperfusion, posttreatment changes in NIHSS scores, posttreatment TICI scores, cerebral hemorrhage, and survival. Clot removal with successful arterial recanalization was achieved in 15/18 cases (83.3%) with TICI scores of 2b/3 in all patients who had initial recanalization. The NIHSS score improved, on average, from 19 pretreatment to 11 posttreatment, and 72% of patients survived. In cases of acute stroke in which there is little information available regarding the positioning and deployment of a retrievable stent during mechanical thrombectomy, the use of C-arm CT may provide more information about device placement across an area of thrombus.

The Added Value of Volume-of-Interest C-Arm CT Imaging during Endovascular Treatment of Intracranial Aneurysms

VOI C-arm CT images were obtained in 28 patients undergoing endovascular treatment of intracranial aneurysms and the VOI images were reconstructed by using a novel prototype reconstruction algorithm to minimize truncation artifacts from double collimation. The reconstruction accuracy of VOI C-arm CT images was assessed quantitatively by comparing them with the full-head noncollimated images. Quality of VOI C-arm CT images was comparable with that of the standard Feldkamp, Davis, and Kress reconstruction of noncollimated C-arm CT images. The authors conclude that VOI imaging allows multiple 3D C-arm CT acquisitions and provides information related to device expansion, parent wall apposition, and neck coverage during the procedure, with very low additional radiation exposure to the patient. BACKGROUND AND PURPOSE: Successful endovascular treatment of intracranial aneurysms requires understanding the exact relationship of implanted devices to the aneurysm, parent artery, and other branch vessels during the treatment. Intraprocedural C-arm CT imaging has been shown to provide such information. However, its repeated use is limited due to increasing radiation exposure to the patient. The goal of this study was to evaluate a new volume-of-interest C-arm CT imaging technique, which would provide device-specific information through multiple 3D acquisitions of only the region of interest, thus reducing cumulative radiation exposure to the patient. MATERIALS AND METHODS: VOI C-arm CT images were obtained in 28 patients undergoing endovascular treatment of intracranial aneurysms. VOI images were acquired with the x-ray source collimated around the deployed device, both horizontally and vertically. The images were reconstructed by using a novel prototype robust reconstruction algorithm to minimize truncation artifacts from double collimation. The reconstruction accuracy of VOI C-arm CT images was assessed quantitatively by comparing them with the full-head noncollimated images. RESULTS: Quantitative analysis showed that the quality of VOI C-arm CT images is comparable with that of the standard Feldkamp, Davis, and Kress reconstruction of noncollimated C-arm CT images (correlation coefficient = 0.96 and structural similarity index = 0.92). Furthermore, 91.5% reduction in dose-area product was achieved with VOI imaging compared with the full-head acquisition. CONCLUSIONS: VOI imaging allows multiple 3D C-arm CT acquisitions and provides information related to device expansion, parent wall apposition, and neck coverage during the procedure, with very low additional radiation exposure to the patient.

Evaluation of C-arm CT metal artifact reduction algorithm during intra-aneurysmal coil embolization: Assessment of brain parenchyma, stents and flow-diverters

PURPOSE Flat panel C-arm CT images acquired in the interventional suite provide valuable information regarding brain parenchyma, vasculature, and device status during the procedure. However, these images often suffer from severe streak artifacts due to the presence of metallic objects such as coils. These artifacts limit the capability to make diagnostic inferences and thus need to be reduced for better image interpretation. The main purpose of this paper is to systematically evaluate the accuracy of one such C-arm CT based metal artifact reduction (MAR) algorithm and to demonstrate its usage in both stent and flow diverter assisted coil embolization procedures. METHODS C-arm CT images routinely acquired in 24 patients during coil embolization procedure (stent-assisted (12) and flow-diverter assisted (12)) were included in this study in a retrospective fashion. These images were reconstructed without and with MAR algorithm on an offline workstation and compared using quantitative image analysis metrics. This analysis was carried out to assess the improvements in both brain parenchyma and device visibility with MAR algorithm. Further, ground truth reference images from phantom experiments and clinical data were used for accurate assessment. RESULTS Quantitative image analysis of brain parenchyma showed uniform distribution of grayscale values and reduced image noise after MAR correction. The line profile plot analysis of device profile in both phantom and clinical data demonstrated improved device visibility with MAR correction. CONCLUSIONS MAR algorithm successfully reduced streak artifacts from coil embolization in all cases, thus allowing more accurate assessment of devices and adjacent brain parenchyma.