Neurosurgeons and neurointerventionists interested in cerebral revascularization to prevent stroke from intracranial atherosclerotic stenoocclusive disease were disappointed in 2011 with the closure of two important negative studies: the... more
Neurosurgeons and neurointerventionists interested in cerebral revascularization to prevent stroke from intracranial atherosclerotic stenoocclusive disease were disappointed in 2011 with the closure of two important negative studies: the Carotid Occlusion Surgery Study (COSS) and Stenting and Aggressive Medical Therapy for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) study. Debates are centered on what causes these failures. While extracranial-intracranial (EC-IC) bypass and neurointervention (angioplasty and/or stenting) cannot be considered a routine intervention for patients presenting with initial ischemic event in the setting of atherosclerotic steno-occlusive disease, selected patients with severe hemodynamic impairment and/or recurrent symptoms despite maximal medical therapy may still benefit from surgery and neurointervention at high-volume centers, which can offer the procedure with low peri-operative morbidity.
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OBJECT The use of digital subtraction angiography (DSA) for semiquantitative cerebral blood flow(CBF) assessment is a new technique. The aim of this study was to determine whether patients with aneurysmal subarachnoid hemorrhage (aSAH)... more
OBJECT The use of digital subtraction angiography (DSA) for semiquantitative cerebral blood flow(CBF) assessment is a new technique. The aim of this study was to determine whether patients with aneurysmal subarachnoid hemorrhage (aSAH) with higher Hunt and Hess grades also had higher angiographic contrast transit times (TTs) than patients with lower grades. METHODS A cohort of 30 patients with aSAH and 10 patients without aSAH was included. Relevant clinical information was collected. A method to measure DSA TTs by color-coding reconstructions from DSA contrast-intensity images was applied. Regions of interest (ROIs) were chosen over major cerebral vessels. The estimated TTs included time-to-peak from 0% to 100% (TTP0-100), TTP from 25% to 100% (TTP25-100), and TT from 100% to 10% (TT100-10) contrast intensities. Statistical analysis was used to compare TTs between Group A (Hunt and Hess Grade I-II), Group B (Hunt and Hess Grade III-IV), and the control group. The correlation coeffi...
Research Interests: Neurosurgery, Diffusion Tensor Imaging, Treatment Outcome, Medicine, Humans, and 14 moreFemale, Male, Glasgow Coma Scale, Subarachnoid hemorrhage, Clinical Sciences, Aged, Middle Aged, Adult, Neurosciences, Intracranial Pressure, Cohort Studies, Cerebral Angiography, anterior cerebral artery, and Digital subtraction angiography
Atherosclerotic vertebrobasilar disease is an important cause of posterior circulation stroke. To examine the role of hemodynamic compromise, a prospective multicenter study, Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic... more
Atherosclerotic vertebrobasilar disease is an important cause of posterior circulation stroke. To examine the role of hemodynamic compromise, a prospective multicenter study, Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS), was conducted. Here, we report clinical features and vessel flow measurements from the study cohort. Patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral or basilar arteries (BA) were enrolled. Large-vessel flow in the vertebrobasilar territory was assessed using quantitative MRA. The cohort (n=72; 44% women) had a mean age of 65.6 years; 72% presented with ischemic stroke. Hypertension (93%) and hyperlipidemia (81%) were the most prevalent vascular risk factors. BA flows correlated negatively with percentage stenosis in the affected vessel and positively to the minimal diameter at the stenosis site (P<0.01). A relative threshold effect wa...
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Background and Purpose— Wall shear stress (WSS) has been implicated as an important stimulus for vascular remodeling. The purpose of this study is to measure WSS in AVM arterial feeders using quantitative magnetic resonance angiography... more
Background and Purpose— Wall shear stress (WSS) has been implicated as an important stimulus for vascular remodeling. The purpose of this study is to measure WSS in AVM arterial feeders using quantitative magnetic resonance angiography pre- and post-embolization/surgery. Methods— Records of patients who underwent AVM embolization and surgical resection at our institution between 2007 and 2013 and had WSS, flow rate, and vessel diameter obtained pre- and post-treatment using quantitative magnetic resonance angiography were retrospectively reviewed. WSS was compared between the feeder and contralateral artery pre- and post-embolization/surgery. Results— Twenty-one patients were included (mean age 34 years, 19% hemorrhagic presentation), with Spetzler–Martin grades 1 to 4. WSS, blood flow, and vessel diameter were assessed in a total of 51 feeder arteries. At baseline, mean WSS was significantly higher compared with the contralateral vessel (29.7±12.0 dynes/cm 2 versus 23.3±11.0 dynes/...
Research Interests: Magnetic Resonance Imaging, Adolescent, Medicine, Stroke, Humans, and 15 moreFemale, Male, Young Adult, Clinical Sciences, Angiography, Middle Aged, Mechanical Stress, Adult, Retrospective Studies, Shear Strength, Intracranial Arteriovenous Malformations, Neurosciences, Embolization, Cardiovascular medicine and haematology, and cerebral arteries
Treatment of dural arteriovenous fistula involving the transverse-sigmoid region with cortical reflux is complex and treatment options may require sacrifice of the fistulous segment of the sinus. To review our results in this subset of... more
Treatment of dural arteriovenous fistula involving the transverse-sigmoid region with cortical reflux is complex and treatment options may require sacrifice of the fistulous segment of the sinus. To review our results in this subset of patients and describe current endovascular decision-making and approaches. We reviewed cases of endovascular sinus sacrifice for dural fistulas at our institution from 2007 to 2012. Demographic, decision-making, technical and outcome data were collected. Seven patients were identified who underwent endovascular sinus sacrifice for treatment of dural fistula during this 4-year period. Determination of the fistulous sinus segment was based on the pattern of cortical drainage. Endovascular access to the sinus was achieved by transarterial, transvenous or via open surgery in one case. Complete cure of the target fistula was obtained in all cases. One patient had transient post-procedure headache. There were no hemorrhages, new neurological deficits or sig...
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Arteriovenous malformation nidus catheterization with a flow-directed catheter at times can be difficult owing to tortuosity of the intracranial vasculature and distal location of the nidus. Since January 1995, hydrophilic wire has been... more
Arteriovenous malformation nidus catheterization with a flow-directed catheter at times can be difficult owing to tortuosity of the intracranial vasculature and distal location of the nidus. Since January 1995, hydrophilic wire has been used in conjunction with the 1.8F flow-directed microcatheter in over 150 vessel embolizations with cyanoacrylate glue for brain and spinal arteriovenous malformations at our institution. This technique has improved our success rate in achieving superselective catheterization of the nidus and has shortened the overall procedure time. To date, only one complication has occurred that was directly related to wire manipulation.
Research Interests: Surgery, Treatment Outcome, Medicine, Catheterization, Complication, and 15 moreHumans, Male, American, Clinical Sciences, Middle Aged, Cyanoacrylate, Adult, Success Rate, Intracranial Arteriovenous Malformations, Neurosciences, Catheter, Magnetic resonance angiography, Cerebral Angiography, Disease Free Survival, and Fatal outcome
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Background and Purpose— The hemodynamic effects of extracranial carotid stenosis on intracranial blood flow are not well characterized. We sought to determine the impact of degree of stenosis, stenosis length, and residual lumen on... more
Background and Purpose— The hemodynamic effects of extracranial carotid stenosis on intracranial blood flow are not well characterized. We sought to determine the impact of degree of stenosis, stenosis length, and residual lumen on intracranial blood flow in patients with extracranial carotid stenosis. Methods— Carotid stenosis patients who had undergone both vessel flow rate measurements using quantitative magnetic resonance angiography and digital subtraction angiography were examined. The impact of the anatomic measurements of the stenosis relative to ipsilateral internal carotid artery (ICA) flow and ipsilateral-to-contralateral middle cerebral artery (MCA) flow ratio were assessed. Results— Forty-four patients (mean age, 67 years; 64% symptomatic) were included. Higher percentage stenosis and smaller residual lumen were associated with a significant decrease in ICA flow ( P <0.01 and 0.04, respectively). On multivariate analysis, percentage stenosis remained as the primary p...
Research Interests: Medicine, Stroke, Humans, Clinical Sciences, Aged, and 12 moreMiddle Aged, Adult, Retrospective Studies, Blood Flow Velocity, Neurosciences, Middle Cerebral Artery, Internal Carotid Artery, Carotid Stenosis, stenosis, Medical and Health Sciences, Cardiovascular medicine and haematology, and Digital subtraction angiography
With recent advancement in medical technology, surgical training has evolved as well. The classical teaching is being challenged by legal and ethical concerns for patient safety, work hour restrictions, and the cost of operating room... more
With recent advancement in medical technology, surgical training has evolved as well. The classical teaching is being challenged by legal and ethical concerns for patient safety, work hour restrictions, and the cost of operating room time. Surgical simulation and skill training offer an opportunity to teach, rehearse, and practice advanced techniques before attempting them on patients. Simulation training available in the neurosurgical field includes the simple straightforward principle of using real instruments and video equipment to manipulate simulated “tissue” in a box trainer, to more advanced computer-based virtual reality (VR) simulators. Early systems have demonstrated their effectiveness and discriminative ability. Newer systems enable the development of comprehensive curricula and full procedural simulations. Surgical organizations are calling for methods to ensure the maintenance of skills, advance surgical training, and credential surgeons as technically competent. The application of VR simulation in neurosurgery training has evolved over the last decade from data visualization, including stereoscopic evaluation, to more complex augmented reality models. With the revolution of computational analysis abilities, fully immersive VR models are currently available in neurosurgery training. Ventriculostomy catheter insertion and endoscopic and endovascular simulations are used in neurosurgical residency training centers across the world. Recent studies have shown the coloration of proficiency with those simulators and levels of experience in the real world.
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Research Interests: Radiology, Surgery, Fistula, Medicine, Case Report, and 3 moreClinical Sciences, Stent, and Neurosciences
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Object The goal of this study was to demonstrate feasibility and evaluate technical aspects of early endovascular access through extracranial-intracranial (EC-IC) bypass grafts. Methods Patients undergoing endovascular interventions... more
Object The goal of this study was to demonstrate feasibility and evaluate technical aspects of early endovascular access through extracranial-intracranial (EC-IC) bypass grafts. Methods Patients undergoing endovascular interventions through the graft in the acute postoperative period following EC-IC bypass are presented. Results, complications, and technical nuances are reviewed. Results Fourteen endovascular procedures were performed in 5 patients after EC-IC bypass for ruptured aneurysms in 4 patients and posterior circulation ischemia in 1 patient. In 2 patients, a saphenous vein graft (SVG) was used to bypass the common carotid artery (CCA) to the middle cerebral artery (MCA). One patient underwent a superficial temporal artery (STA)–MCA bypass, and in 2 other patients the STA stump was connected to the intracranial circulation via an interposition SVG. The interval from surgery to endovascular intervention spanned 2–18 days; the indication was intracranial vasospasm in all pati...
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Object To date, angiography has been the primary modality for assessing graft patency following extracranial–intracranial bypass. The utility of a noninvasive and quantitative method of assessing bypass function postoperatively was... more
Object To date, angiography has been the primary modality for assessing graft patency following extracranial–intracranial bypass. The utility of a noninvasive and quantitative method of assessing bypass function postoperatively was evaluated using quantitative magnetic resonance (MR) angiography. Methods One hundred one cases of bypass surgery performed over a 5.5-year period at a single institution were reviewed. In 62 cases, both angiographic and quantitative MR angiographic data were available. Intraoperative flow measurements were available in 13 cases in which quantitative MR angiography was performed during the early postoperative period (within 48 hours after surgery). There was excellent correlation between quantitative MR angiographic flow and angiographic findings over the mean 10 months of imaging follow up. Occluded bypasses were consistently absent on quantitative MR angiograms (four cases). The flow rates were significantly lower in those bypasses that became stenotic ...
Research Interests: Radiology, Neurosurgery, Magnetic Resonance Imaging, Treatment Outcome, Adolescent, and 15 moreMedicine, Humans, Female, Male, Follow-up studies, Clinical Sciences, Angiography, Aged, Middle Aged, Adult, Retrospective Studies, Reproducibility of Results, Cerebrovascular Disorders, Neurosciences, and Magnetic resonance angiography
Object. Balloon occlusion tests (BOTs) are performed to identify patients who are at risk for ischemia and stroke following permanent internal carotid artery (ICA) occlusion. The object of this work was to determine whether... more
Object. Balloon occlusion tests (BOTs) are performed to identify patients who are at risk for ischemia and stroke following permanent internal carotid artery (ICA) occlusion. The object of this work was to determine whether patient-specific blood flow modeling can be used to identify patients in whom the BOT would not be tolerated. Methods. The test was performed in 16 patients who underwent BOT with continuous neurological and electroencephalographic monitoring, followed by a hypotensive challenge. During hypotension a tracer was injected so that single-photon emission tomography (SPECT) scans could be obtained. Each individual brain circulation was modeled using information gained from phase-contrast magnetic resonance (MR) angiography and digital subtraction (DS) angiography, and the predicted effect of the BOT was evaluated. Six patients did not tolerate the BOT; in these patients, decreases in middle cerebral artery (M1 segment) blood flow of 41 ± 27% (mean ± standard deviation...
Research Interests: Neurosurgery, Medicine, Humans, Computer Simulation, Computer Model, and 15 moreFemale, Male, Clinical Sciences, Aged, Middle Aged, Adult, Blood Flow, Cerebral Blood Flow, Neurosciences, Middle Cerebral Artery, Internal Carotid Artery, Magnetic resonance angiography, Balloon Occlusion, Intracranial aneurysm, and Digital subtraction angiography
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... more
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 fl...
Research Interests: Aging, Adolescent, Medicine, Humans, Hemodynamics, and 15 moreFemale, Male, Clinical Sciences, Aged, Middle Aged, Adult, Cerebral Blood Flow, Blood Flow Velocity, Basilar Artery, Middle Cerebral Artery, Magnetic resonance angiography, Cerebral Angiography, Cardiovascular medicine and haematology, cerebral arteries, and anterior cerebral artery
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Objective: To examine the effect of carotid endarterectomy (CEA) on cerebral hemodynamics using quantitative magnetic resonance angiography (QMRA). Methods: A total of 42 patients with severe carotid artery stenosis were studied (6... more
Objective: To examine the effect of carotid endarterectomy (CEA) on cerebral hemodynamics using quantitative magnetic resonance angiography (QMRA). Methods: A total of 42 patients with severe carotid artery stenosis were studied (6 patients had asymptomatic stenosis). 6 of 42 patients had contralateral carotid artery occlusion. Pre- and post-op blood flow measurements of major cerebral arteries were performed using QMRA (NOVA,Vasol, Inc.). Results: Patients ranged from 39 to 85 (mean 66) years old, 17 female. Ipsilateral carotid artery flow was significantly increased after CEA, 253 ± 110 ml/min compare to 159 ± 79 ml/min (p<0.001). Middle cerebral artery (MCA) flow was not significantly increased (p=0.11), 127 ± 39 ml/min versus pre-op 115 ± 33 ml/min after CEA. Ipsilateral anterior cerebral artery (ACA) flow direction of 6 patients changed to anterograde, 5 patients’ ipsilatral posterior communicating artery (PCOM) flow direction changed to posterior, 1 patient had both flow di...
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Objectives: To determine the effects of extracranial carotid stenting on intracranial blood flow. Methods: Records of patients who underwent stenting for extracranial carotid stenosis at our institution between 2004-2012 and had flow... more
Objectives: To determine the effects of extracranial carotid stenting on intracranial blood flow. Methods: Records of patients who underwent stenting for extracranial carotid stenosis at our institution between 2004-2012 and had flow rates obtained pre and post stenting using quantitative magnetic resonance angiography were retrospectively reviewed. Measurements of degree of stenosis, stenosis length, and residual lumen were made from cerebral angiography images. Results: 18 patients with complete anatomic and flow data were included. Mean age was 66 years with 61% presenting with symptomatic stenosis. Degree of stenosis ranged from 60% to 90%. Internal carotid artery (ICA) mean flow improved significantly post stenting from 174.9 +/- 83.6 mL/min to 250.7 +/- 91.2 mL/min ( P =0.011). Ipsilateral middle cerebral artery (MCA) flow, however, was not significantly altered post stenting (101.8 +/- 47.7 mL/min vs. 111.3 +/- 37.4 mL/min; P =0.15). Multiple regression analysis revealed that...
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The perioperative management of aneurysmal subarachnoidal haemorrhage is challenging and often requires an extensive team work. Unfortunately, there is no uniform system applied for perioperative monitoring of patients with subarachnoid... more
The perioperative management of aneurysmal subarachnoidal haemorrhage is challenging and often requires an extensive team work. Unfortunately, there is no uniform system applied for perioperative monitoring of patients with subarachnoid haemorrhage. The new developing technology enhances our monitoring capability with subsequent impact on patient&#39;s outcome. This article presents a review of current monitoring modalities applicable to patients with subarachnoid haemorrhage with emphasis on the central nervous system and some of the authors&#39; experience.
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These studies were conducted in neurosurgical patients to determine brain tissue nonbicarbonate buffering of pH changes during hypercapnia. Following a craniotomy, a sensor which continuously measures oxygen pressure, carbon dioxide... more
These studies were conducted in neurosurgical patients to determine brain tissue nonbicarbonate buffering of pH changes during hypercapnia. Following a craniotomy, a sensor which continuously measures oxygen pressure, carbon dioxide pressure, pH and temperature was inserted into cortex tissue of nine subjects. Bicarbonate concentration was calculated from the Henderson-Hasselbach equation. Following baseline measures, PaCO2 was increased 10mmHg for 10 min. Tissue pCO2 increased 9 mmHg (p &lt; 0.05) without a change in tissue pO2. In six patients, tissue bicarbonate concentration increased from 18 to 20 meq L-1 (p &lt; 0.05), indicating a 40-50% attenuation of the increase in hydrogen ion (H+) by nonbicarbonate buffering mechanisms. Three patients showed no increase in tissue bicarbonate during hypercapnia; 2 had baseline tissue pH less than 6.5 and one displayed signs of tissue hypoxia during the CO2 challenge. In all patients, increases in tissue H+ during hypercapnia were related to baseline tissue bicarbonate concentration. Marked increases in H+ were seen when baseline bicarbonate decreased below 10 meq L-1. These results suggest that when tissue bicarbonate is depleted, the risk of H+ induced injury during hypercapnia is increased.
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BACKGROUND A double anastomosis using a single superficial temporal artery (STA) donor branch for both a proximal side-to-side (S2S) and a distal end-to-side anastomosis is a novel direct bypass technique for use in selected patients... more
BACKGROUND A double anastomosis using a single superficial temporal artery (STA) donor branch for both a proximal side-to-side (S2S) and a distal end-to-side anastomosis is a novel direct bypass technique for use in selected patients necessitating flow augmentation. OBJECTIVE To describe the single-vessel double anastomosis (SVDA) technique, including its indications, advantages, and limitations, in addition to reporting our cases series of patients who underwent a SVDA bypass surgery. METHODS Patients undergoing a SVDA bypass at a single institution between January 2010 and February 2016 were retrospectively reviewed. Intraoperative flow data was collected, including STA cut-flow, bypass flows, and cut flow index (CFI). Bypass patency was assessed by cerebral angiography and quantitative magnetic resonance angiography with noninvasive optimal vessel analysis. Adverse events occurring during the hospital stay and clinical status at last follow up was recorded. RESULTS Seven patients...
A case of traumatic, direct, carotid cavernous fistula (CCF) associated with Ehlers — Danlos syndrome (EDS) Type IV is reported along with a review of the literature. Excluding the present case, three similar cases associated with... more
A case of traumatic, direct, carotid cavernous fistula (CCF) associated with Ehlers — Danlos syndrome (EDS) Type IV is reported along with a review of the literature. Excluding the present case, three similar cases associated with EDS-TypeIV have already been reported by Gerard M. Debrun et Al1. Despite the risks associated with endovascular manipulation, the fistula was successfully closed by intravascular embolisation but the patient expired a few days later because of underlying disease-associated vascular and visceral complications.
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Computer simulation of the cerebral circulation has been carried out for three decades. We review the developments of cerebral circulation computer models of the last 30 years. Existing models are discussed in terms of fluid dynamics and... more
Computer simulation of the cerebral circulation has been carried out for three decades. We review the developments of cerebral circulation computer models of the last 30 years. Existing models are discussed in terms of fluid dynamics and possible clinical usage. Also the status and new achievements in some related research areas are summarized. Any new achievements in such areas would contribute to the progress of building a better model. A patient specific, highly predictive and reflective model could be a powerful clinical tool which would greatly benefit neurosurgeons and patients.
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Impaired cerebrovascular reserve in chronic steno-occlusive disease has been shown to be associated with poor leptomeningeal collaterals (LMCs) on digital subtraction angiography and increased stroke risk. We examined the relationship... more
Impaired cerebrovascular reserve in chronic steno-occlusive disease has been shown to be associated with poor leptomeningeal collaterals (LMCs) on digital subtraction angiography and increased stroke risk. We examined the relationship between the degree of LMCs and the flow change with Diamox challenge measured using quantitative magnetic resonance angiography (QMRA). Patients with steno-occlusion in the internal carotid artery or middle cerebral artery (MCA) at our institution between 2007 and 2013 were retrospectively studied. Intracranial flows were obtained using QMRA, and flow change with Diamox (QMRAΔd) was calculated as follows: ([flow after Diamox-flow before Diamox]/[flow before Diamox])×100%. Poor LMC was defined as grade 1 or 2, and robust LMC was defined as grade 3 or 4 based on the ASITN/SIR (American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology) grading system on digital subtraction angiography. Thirty-eight patients had ...
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In the 1970's many neurosurgeons gradually adapted microsurgical techniques to spine surgery as the benefits of magnification, illumination and use of fine instruments in cranial surgery became apparent. In the early 1970 s, Robert W.... more
In the 1970's many neurosurgeons gradually adapted microsurgical techniques to spine surgery as the benefits of magnification, illumination and use of fine instruments in cranial surgery became apparent. In the early 1970 s, Robert W. Williams, а neurosurgeon in private practice in Las Vegas, Nevada, independently began to devise spinal microneurosurgical techniques with the goal of improving surgical outcome in lumbar and cervical surgery. Much of his initial work with microlumbar discectomies and microcervical foraminotomies was presented at annual meetings of the American Association of Neurological Surgeons (AANS) and Congress of Neurological Surgeons (CNS) in the 1970's and 1980's. An outsider to organized academic Neurosurgery, Dг. Williams found his work was received cautiously and with significant skepticism. He found the orthopedic spine surgery community and journals more receptive, thus much of his earlier work was published in the orthopedic literature. This ...
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Atherosclerotic vertebrobasilar (VB) occlusive disease is a significant etiology of posterior circulation stroke, with regional hypoperfusion as an important potential contributor to stroke risk. To test the hypothesis that, among... more
Atherosclerotic vertebrobasilar (VB) occlusive disease is a significant etiology of posterior circulation stroke, with regional hypoperfusion as an important potential contributor to stroke risk. To test the hypothesis that, among patients with symptomatic VB stenosis or occlusion, those with distal blood flow compromise as measured by large-vessel quantitative magnetic resonance angiography (QMRA) are at higher risk of subsequent posterior circulation stroke. A prospective, blinded, longitudinal cohort study was conducted at 5 academic hospital-based centers in the United States and Canada; 82 patients from inpatient and outpatient settings were enrolled. Participants with recent VB transient ischemic attack or stroke and 50% or more atherosclerotic stenosis or occlusion in vertebral and/or basilar arteries underwent large-vessel flow measurement in the VB territory using QMRA. Physicians performing follow-up assessments were blinded to QMRA flow status. Follow-up included monthly ...
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Background and Purpose— The pathogenesis of aneurysms associated with cerebral arteriovenous malformation (AVM) feeder vessels is poorly understood. We sought to determine the hemodynamic characteristics of AVM feeder vessels with and... more
Background and Purpose— The pathogenesis of aneurysms associated with cerebral arteriovenous malformation (AVM) feeder vessels is poorly understood. We sought to determine the hemodynamic characteristics of AVM feeder vessels with and without aneurysms. Methods— Patients with AVMs associated with feeder aneurysms who had flow, vessel diameter, and wall shear stress measured before treatment using quantitative magnetic resonance angiography were retrospectively reviewed. Feeders within each AVM were classified into 2 groups based on presence or absence of aneurysms. Hemodynamic parameters were calculated for each arterial feeder and then compared between the 2 groups. Results— Eleven patients had AVMs with feeder aneurysms. Of 35 total feeder arteries, 12 had an aneurysm and 23 feeders did not have any aneurysms. Absolute mean flow was higher (510.2 versus 438.4 mL/min; P =0.53) and vessel diameter was lower (4.0 versus 4.8 mm; P =0.24) in feeders with aneurysms but not significantly...
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The use of digital subtraction angiography (DSA) for semi-quantitative cerebral blood flow (CBF) assessment is a new method. In this report we sought to correlate angiographic transit times (TT) in patients with aneurysmal subarachnoid... more
The use of digital subtraction angiography (DSA) for semi-quantitative cerebral blood flow (CBF) assessment is a new method. In this report we sought to correlate angiographic transit times (TT) in patients with aneurysmal subarachnoid haemorrhage (aSAH) in relation to Hunt &Hess (H&H) grade. A cohort of 28 patients with aSAH were included. Demographic variables, neurological status, and comorbidities were collected. We developed a method to measure CBF by colour-coding reconstruction from DSA contrast intensity. Regions of interest were chosen over major cerebral vessels (see legend Figure 1). The estimated TT included Time-To-Peak (TTP) from 0-100% intensity (TTP-100,), TTP from 25-100% (TTP25--00), and TT from 100--0% (TT100--). Student t-test was used to compare TT between group 1 (H&H 1-2) and 2 (H&H 3-5). There was no difference in demographic factors between groups 1 (n = 10) and 2 (n = 18). The majority of patients in-group 2 (all except 3) had an external ventricular cathet...
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Software tools that utilize haptics for sculpting precise fitting cranial implants are utilized in an augmented reality immersive system to create a virtual working environment for the modelers. The virtual environment is designed to... more
Software tools that utilize haptics for sculpting precise fitting cranial implants are utilized in an augmented reality immersive system to create a virtual working environment for the modelers. The virtual environment is designed to mimic the traditional working environment as closely as possible, providing more functionality for the users. The implant design process uses patient CT data of a defective area. This volumetric data is displayed in an implant modeling tele-immersive augmented reality system where the modeler can build a patient specific implant that precisely fits the defect. To mimic the traditional sculpting workspace, the implant modeling augmented reality system includes stereo vision, viewer centered perspective, sense of touch, and collaboration. To achieve optimized performance, this system includes a dual-processor PC, fast volume rendering with three-dimensional texture mapping, the fast haptic rendering algorithm, and a multi-threading architecture. The syste...
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Ventriculostomy is a neurosurgical procedure that consists of the insertion of a catheter into the ventricles of the brain for relieving the intracranial pressure. A distinct "popping" sensation is felt as the catheter enters... more
Ventriculostomy is a neurosurgical procedure that consists of the insertion of a catheter into the ventricles of the brain for relieving the intracranial pressure. A distinct "popping" sensation is felt as the catheter enters the ventricles. Early ventriculostomy simulators provided some basic audio/visual feedback to simulate the procedure, displaying a 3D virtual model of a human head. Without any tactile feedback, the usefulness of such simulators was very limited. The first generation haptic ventriculostomy simulators incorporated a haptic device to generate a virtual resistance and "give" upon ventricular entry. While this created considerable excitement as a novelty device for cannulating ventricles, its usefulness for teaching and measuring neurosurgical expertise was still very limited. Poor collocation between the haptic device stylus held by the surgeon and the visual representation of the virtual catheter, as well as the lack of a correct viewer-center...
Research Interests: Computer Science, Health Studies, Visual acuity, Virtual Reality, Library and Information Studies, and 15 moreHumans, Computer Simulation, Touch, United States, Audio Visual, Tactile feedback, High Resolution, Visual Representation, Haptic Technology, Public health systems and services research, Hand Tracking, Haptic Device, 3D stereoscopic Display Systems, Ventriculostomy, and Intracranial Pressure
Embolization reduces flow in arteriovenous malformations (AVMs) before surgical resection, but achievement of this goal is determined subjectively from angiograms. Here, we quantify effects of embolization on AVM flow. Records of patients... more
Embolization reduces flow in arteriovenous malformations (AVMs) before surgical resection, but achievement of this goal is determined subjectively from angiograms. Here, we quantify effects of embolization on AVM flow. Records of patients who underwent AVM embolization at our institution between 2007 and 2013 and had flow rates obtained pre- and postembolization using quantitative magnetic resonance angiography were retrospectively reviewed. Total flow was estimated as aggregate flow within primary arterial feeders or flow in single draining veins. Twenty-one patients were included (mean age 35 years, 24% hemorrhagic presentation) with Spetzler-Martin grades 1 to 4. Fifty-four total embolization sessions were performed. The mean AVM flow was 403.4±262.4 mL/min at baseline, 285.3±246.4 mL/min after single session (29% drop, P<0.001), and 102.0±103.3 mL/min after all sessions of embolization (75% drop, P<0.001). Total number of pedicles embolized (P<0.001) and embolization of...
Research Interests: Treatment Outcome, Adolescent, Medicine, Stroke, Humans, and 12 moreHemodynamics, Female, Male, Young Adult, Clinical Sciences, Middle Aged, Adult, Retrospective Studies, Intracranial Arteriovenous Malformations, Neurosciences, Magnetic resonance angiography, and Cardiovascular medicine and haematology
The present technology relates to systems, methods and devices for haptically-enabled virtual reality simulation of cerebral aneurysm clipping, wherein a user uses two physical stations during the simulation. The first station is a haptic... more
The present technology relates to systems, methods and devices for haptically-enabled virtual reality simulation of cerebral aneurysm clipping, wherein a user uses two physical stations during the simulation. The first station is a haptic and augmented reality station, and the second station is a haptic and virtual reality station.
The hemodynamic force of wall shear stress (WSS) has demonstrated a critical role in atherogenesis. To study the effect of age and gender on mean WSS (MWSS) values in major cerebral arteries. Thirteen cerebral arterial location sites in... more
The hemodynamic force of wall shear stress (WSS) has demonstrated a critical role in atherogenesis. To study the effect of age and gender on mean WSS (MWSS) values in major cerebral arteries. Thirteen cerebral arterial location sites in 301 healthy (157 M, 144 F; mean 47 ± 15 years; range 18-84 years old) were studied. Quantitative magnetic resonance angiography was used to obtain volume flow and diameter, and subsequently to calculate MWSS via the Hagen-Poiseuille equation. MWSS decreased significantly with age in all vessels, declining from 9.5 to 5.7 dynes/cm(2) in the neck vessels and from 22.9 to 16.2 dynes/cm(2) in the intracranial vessels. MWSS is significantly higher in females than in males in all six neck vessels. The most significant drop in MWSS occurred between the age groups 48-57 and 58-67 (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .05 for 12 vessels). The overall decline in MWSS observed with age may be due to a decrease in flow. However, the marked drop in MWSS between the 48-57 and 58-67 age groups corresponded with an increase in diameter and systolic blood pressure rather than a significant drop in flow.
Research Interests: Neuroimaging, Aging, Adolescent, Medicine, Humans, and 15 moreFemale, Male, Clinical Sciences, Aged, Middle Aged, Mechanical Stress, Adult, Shear Strength, Reproducibility of Results, Sensitivity and Specificity, Reference Values, Neurosciences, Magnetic resonance angiography, Sex Characteristics, and cerebral arteries
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Research Interests: Neurosurgery, Medical errors, Humans, Computer Simulation, Trigeminal Neuralgia, and 14 moreTouch, Three Dimensional Imaging, Feedback, Rhizotomy, Graduate medical education, Clinical Sciences, Computer User Interface Design, Competency Based Education, Ventriculostomy, Neurosciences, Spinal Fusion, Craniotomy, internship and residency, and vertebroplasty
ABSTRACT