Yukinao Kambayashi

Determining the Presence of Thin-Walled Regions at High-Pressure Areas in Unruptured Cerebral Aneurysms by Using Computational Fluid Dynamics.

BACKGROUND Thin-walled regions (TWRs) of cerebral aneurysms are at high risk of rupture, and careful attention should be paid during surgical procedures. Despite this, an optimal imaging technique to estimate TWRs has not been established. Previously, pressure elevation at TWRs was reported with computational fluid dynamics (CFD) but not fully evaluated. OBJECTIVE To investigate the possibility of predicting aneurysmal TWRs at high-pressure areas with CFD. METHODS Fifty unruptured middle cerebral artery aneurysms were analyzed. Spatial and temporal maximum pressure (Pmax) areas were determined with a fluid-flow formula under pulsatile blood flow conditions. Intraoperatively, TWRs of aneurysm domes were identified as reddish areas relative to the healthy normal middle cerebral arteries; 5 neurosurgeons evaluated and divided these regions according to Pmax area and TWR correspondence. Pressure difference (PD) was defined as the degree of pressure elevation on the aneurysmal wall at Pmax and was calculated by subtracting the average pressure from the Pmax and dividing by the dynamic pressure at the aneurysm inlet side for normalization. RESULTS In 41 of the 50 cases (82.0%), the Pmax areas and TWRs corresponded. PD values were significantly higher in the correspondence group than in the noncorrespondence group (P = .008). A receiver-operating characteristic curve demonstrated that PD accurately predicted TWRs at Pmax areas (area under the curve, 0.764; 95% confidence interval, 0.574-0.955; cutoff value, 0.607; sensitivity, 66.7%; specificity, 82.9%). CONCLUSION A high PD may be a key parameter for predicting TWRs in unruptured cerebral aneurysms. ABBREVIATIONS CFD, computational fluid dynamicsMCA, middle cerebral arteryPave, average pressurePD, pressure differencePmax, maximum pressureTWR, thin-walled regionWSS, wall shear stress.

Immunohistochemical Analysis of Debris Captured by Filter-Type Distal Embolic Protection Devices for Carotid Artery Stenting

BACKGROUND Little is known about the micro-debris captured in filter-type distal embolic protection devices (EPD) used for carotid stenting (CAS). This study aimed to determine the histological and immunohistochemical characteristics of such debris by using a new liquid-based cytology (LBC) technique. METHODS Fifteen patients who underwent CAS using a filter-type distal EPD (FilterWire EZ; Boston Scientific, Marlborough, MA, USA) were included in the study. After gross inspection of each recovered filter device, micro-debris were collected using a new LBC technique (SurePath; TriPath Imaging, Inc., Burlington, NC). Histological and immunohistochemical analysis of the recovered debris was performed. The pre- and postoperative brain magnetic resonance imaging and neurological status of each patient were also reviewed. RESULTS No patient developed ipsilateral symptomatic stroke due to a thromboembolic event. All 15 patients (100%) had microscopically identifiable debris in the filters, whereas gross inspection detected visible debris only in 5 patients (33.3%). Histological analysis revealed various types of structural components in an advanced atheromatous plaque, including fragments of fibrous cap, calcified plaque, smooth muscle cells, and necrotic tissue fragment infiltrated with monocytes and macrophages. CONCLUSIONS Filter-type EPDs may contribute to reducing the risk of CAS-related embolic events by capturing micro-debris even when gross inspection of the recovered filter shows no visible debris in the device.

High-Resolution C-Arm CT and Metal Artifact Reduction Software: A Novel Imaging Modality for Analyzing Aneurysms Treated with Stent-Assisted Coil Embolization.

BACKGROUND AND PURPOSE: Combination of high-resolution C-arm CT and novel metal artifact reduction software may contribute to the assessment of aneurysms treated with stent-assisted coil embolization. This study aimed to evaluate the efficacy of a novel Metal Artifact Reduction prototype software combined with the currently available high spatial-resolution C-arm CT prototype implementation by using an experimental aneurysm model treated with stent-assisted coil embolization. MATERIALS AND METHODS: Eight experimental aneurysms were created in 6 swine. Coil embolization of each aneurysm was performed by using a stent-assisted technique. High-resolution C-arm CT with intra-arterial contrast injection was performed immediately after the treatment. The obtained images were processed with Metal Artifact Reduction. Five neurointerventional specialists reviewed the image quality before and after Metal Artifact Reduction. Observational and quantitative analyses (via image analysis software) were performed. RESULTS: Every aneurysm was successfully created and treated with stent-assisted coil embolization. Before Metal Artifact Reduction, coil loops protruding through the stent lumen were not visualized due to the prominent metal artifacts produced by the coils. These became visible after Metal Artifact Reduction processing. Contrast filling in the residual aneurysm was also visualized after Metal Artifact Reduction in every aneurysm. Both the observational (P < .0001) and quantitative (P < .001) analyses showed significant reduction of the metal artifacts after application of the Metal Artifact Reduction prototype software. CONCLUSIONS: The combination of high-resolution C-arm CT and Metal Artifact Reduction enables differentiation of the coil mass, stent, and contrast material on the same image by significantly reducing the metal artifacts produced by the platinum coils. This novel image technique may improve the assessment of aneurysms treated with stent-assisted coil embolization.

O-019 4d digital subtraction angiography: the advantages and limitations in the evaluation of brain arteriovenous malformation and brain aneurysms

Purpose To evaluate the potential advantages and limitations of 4D-DSA image acquisition, the acquired images on the patients with arteriovenous malformations (AVMs) and aneurysms were reviewed and analyzed. Methods Brain arteriovenous malformation (AVM) and brain aneurysm patients who underwent 4D-DSA during the pre and post assessment for the endovascular / surgical treatment were included. The obtained source image information of the 4D-DSA was transferred to a dedicated workstation and reconstructed using a software, “Syngo Dyna4D©”. The results were reviewed and interpretation of each image finding was evaluated. The radiation dose required for each examination was calculated, and compared with that required for conventional 5-second 3D-DSA acquisitions. Results 10 aneurysm patients and 4 AVM patients underwent 4D-DSA. One patient had both an intracranial aneurysm and an AVM. 6 aneurysm patients underwent 6-second acquisition protocol. 12-second acquisition was used for all AVM patients as well as 4 aneurysm patients. For aneurysm evaluation, with a temporal sampling of 28.7-volumes/sec and a region of interest (ROI) of 42 cm x× 42 cm, the quality of the image was not sufficient to evaluate contrast flow patterns in the aneurysm although the sizes of all aneurysms were less than 10 mm in the largest diameter. With 12-second acquisition, anatomical information of both arteries and veins were simultaneously obtained in one scan, which was useful for the pre-operative evaluation of surgical clipping. For AVMs, temporal change in the appearance of each feeding artery clearly differentiated the different feeding patterns of each artery to the nidus component. Detailed anatomical structures, e.g. a stenosis in the main drainer which was not detected in the 2D-DSA and difficult to see in the conventional 3D angiogram, were better depicted in the 4D-DSA images. Average surface dose of the radiation was 115 mGy in the 6-second acquisition, 225 mGy in the 12-second acquisition and 105 mGy in the conventional 3D angiogram. Conclusions 4D-DSA provides useful information for the treatment planning of AVM patients by depicting the temporal change in the 3D-DSA. Current temporal resolution was not sufficient for the evaluation of contrast flow patterns in the small aneurysms. The 12-second acquisition which covers the entire arterial phase to the venous phase required approximately double the radiation dose of the conventional 5-second 3D-DSA. However, the dose required for the 6-second acquisition, which mainly covers the arterial phase, was similar to the conventional 3D-DSA.Abstract O-019 Figure 1 Temporal change in the 3D DSA images of an AVM Disclosures I. Yuki: 1; C; Siemens Grant. T. Ishibashi: None. A. Ikemura: 1; C; Siemens Grant. Y. Kambayashi: None. I. Kan: None. Y. Abe: None. C. Dahmani: 5; C; Siemens K. K.. S. Kaku: None. K. Nishimura: None. Y. Murayama: 1; C; Siemens Grant.

Fluid structure interaction analysis reveals facial nerve palsy caused by vertebral-posterior inferior cerebellar artery aneurysm

Cranial nerve palsy caused by aneurysmal compression has not been fully evaluated. The main causes of symptoms are considered to be direct mechanical compression and aneurysm pulsations. Recent studies indicate that nerve dysfunction is mainly induced by pulsation rather than by direct compression, and successful cases of endovascular surgery have been reported. We describe a patient with an unruptured vertebral artery-posterior inferior cerebellar artery (VA-PICA) aneurysm compressing the facial nerve at the root exit zone (REZ). The patient presented with peripheral facial nerve palsy but not hemifacial spasm and was successfully treated by coil embolization. To investigate the mechanisms underlying peripheral facial nerve palsy, fluid structure interaction (FSI) analysis can approximate displacement and the magnitude of aneurysmal wall motion due to hemodynamic forces. In our case, maximum mesh displacement was observed at the aneurysmal wall attached to the facial nerve inside the pons rather than the REZ, which explains the clinical manifestation of facial nerve palsy in the absence of hemifacial spasm. This preliminary report demonstrates the utility of FSI analysis for investigating cranial nerve neuropathy.

O-001 A Novel Metal Artefact Removal Software for C-arm CT; A Novel Imaging Modality to Analyze Aneurysms Treated with Stent Assisted Coil Embolization

Purpose Stent assisted coil embolization recently became a common treatment strategy for the wide neck aneurysms. Normal digital subtraction angiography (DSA), however, does not allow visualization of the deployed stents. With a combination of novel Metal Artefact Removal software (MAR) and C-arm CT, the coil mass, stent, and contrast material can be differentiated. In this study, experimental aneurysms were treated with stent assisted coil embolization and image analysis was performed using the C-arm CT and MAR. I. V. injection of the contrast to obtain the images was also performed. Methods A total of 12 experimental aneurysms were created in 6 swine. The aneurysms were treated with coil embolization using stent assisted technique. High Resolution (HR) C-arm CT with intra-arterial injection of the contrast dye (20%) was performed immediately after the treatment and obtained images were processed with MAR. Intra venous contrast injection (non-diluted) from femoral vein was also performed in 3 swine. Visualization of the residual aneurysms as well as coil loops protruded into the stent lumen was evaluated. Two patients previously treated with stent assisted coil embolization underwent the same image acquisition protocol, and the obtained images were evaluated. Results Coil loops protruded into the stent lumen, which were not visible before the MAR due to the significant metal artefact, were well visualised after the MAR. Likewise, Contrast filling into the residual aneurism was observed after the MAR in every aneurysm. Intravenous injection of the contrast material reproduced similar image quality as compared to the intra arterial injections. The C-arm CT images of the two patients showed remarkable reduction of the metal artefacts after the MAR processing. Conclusions The combination of the C-arm CT and MAR enables the differentiation of the coil mass, stent and contrast material by markedly reducing the metal artefact produced by the coils. This novel image modality may contribute to the evaluation of aneurysms treated with stent assisted coil embolization. Abstract O-001 Figure 1 Disclosures I. Yuki: 1; C; Siemens Grant. Y. Kambayashi: 1; C; Siemens Grant. A. Ikemura: 1; C; Siemens Grant. I. Kan: 1; C; Siemens Grant. Y. Abe: None. A. Mohamed: 5; C; Siemens Japan KK. C. Dahmani: 5; C; Siemens Japan KK. T. Ishibashi: 1; C; Siemens Grant. I. Kajiwara: 1; C; Siemens Grant. K. Nishimura: 1; C; Siemens Grant. Y. Murayama: 1; C; Siemens Grant.

Computational fluid dynamics analysis of tandem carotid artery stenoses: Investigation of neurological complications after carotid artery stenting

BACKGROUND Combined extra- and intracranial carotid artery stenoses, particularly involving multiple lesions, show complex hemodynamic properties and represent a therapeutic dilemma. We used computational fluid dynamics (CFD) to investigate whether insufficient cerebral blood flow (CBF) in a 70-year-old man with tandem stenoses was the cause of aphasia and right hemiparesis after carotid artery stenting (CAS) of the extracranial stenosis. METHOD Three-dimensional digital subtraction angiography (3D-DSA) was performed before and after balloon angioplasty and CAS in the patient. The geometrical and rheological conditions of the carotid arteries were determined, and computational meshes were generated from the patient-specific 3D-DSA datasets. CFD analysis was performed, and hemodynamic parameters such as mass flow, pressure, fractional flow reserve, and streamlines were calculated. RESULTS Post-CAS simulations showed that the percentage of internal carotid artery mass flow from common carotid artery mass flow increased from 9% to 14% and CBF improved by only 5%. CONCLUSIONS CFD analysis suggested that the neurological complications were caused by insufficient CBF rather than embolic events, and in tandem carotid stenoses, CAS for an extracranial lesion alone may not always sufficiently increase CBF. CFD enabled the noninvasive quantitative estimation of the effects of CAS of each stenotic segment on carotid flow.

E-032 Combination of High Resolution Cone-beam CT and 3D DSA for the Evaluation of Intracranial Stents used for Aneurysm Treatment

Purpose Incomplete stent apposition after the treatment of brain aneurysm can increase the risk of thromboembolic complications and remains to be the major concern during the procedure. Utilizing the high resolution cone-beam CT (HR-CBCT) and metal artifact reduction software (MAR), the metal artifact produced by the coil mass is reduced and the visualization of the deployed stent is optimized. After combining with the 3D digital subtraction angiography (3D-DSA), the resulting image is used for the evaluation of the stent apposition in the artery. Initial clinical experience of this novel imaging method is reported. Methods A total of 24 aneurysm patients who underwent the stent assisted coil embolization was selected for this study. All patients were treated using either Neuroform® stent or Enterprise® stent system. Artis PURE® Platform (Siemens) was used in this study. Acquisition protocols are follows. A HR-CBCT acquisition was performed to obtain the image of stent and coil mass. The dataset was then reconstructed using MAR. A 3 D DSA acquisition was performed for the visualization of the vasculature. The two datasets were combined using a dedicated software. A 3D volume rendering (VR) image was created and the stent apposition of each treated patient was evaluated. Results All 24 patients underwent the image acquisition successfully. Relationship between the deployed stent and the wall of the parent artery was well visualized in every patient although partial image defect of the stent due to the metal artifact was observed in the relatively large aneurysms. The incomplete stent apposition was frequently seen near the carotid siphon, especially at the inner curve of the target vessel. Conclusion Combination of high resolution cone-beam CT and 3D DSA for the evaluation of intracranial stents provided sufficient visualization of the deployed stent and parent artery. This imaging method can be used for the evaluation of stent apposition during/after the treatment of brain aneurysms.Abstract E-032 Figure 1 Disclosures I. Yuki: 1; C; Siemens Grant. S. Hataoka: None. T. Ishibashi: 1; C; Siemens Grant. C. Dahmani: 5; C; Employee of Siemens Healthcare. A. Ikemura: None. Y. Kambayashi: None. I. Kan: None. Y. Abe: None. S. kaku: None. K. Nishimura: None. T. Kodama: None. Y. Sasaki: None. Y. Murayama: 1; C; Siemens Grant.