1) The study analyzed hemodynamic parameters like wall shear stress (WSS) and blood flow rates in brain aneurysms at different locations using computational fluid dynamics on 24 patient-specific aneurysm models.
2) Results found that WSS and flow rates differed significantly between aneurysm locations, with middle cerebral artery aneurysms having higher values and basilar artery and anterior communicating artery aneurysms having lower values.
3) This suggests that aneurysm hemodynamics may be influenced by location, though further studies with larger sample sizes are needed to validate this hypothesis.
Hemodynamics Of Normal Cerebral Arteriesguest629cef
This document compares measurements of blood flow patterns in cerebral arteries from 4D phase-contrast magnetic resonance imaging and computational fluid dynamics simulations in normal subjects. The goal is to assess consistency between the two methods and identify areas of disagreement in order to better interpret the data from each technique. Computational fluid dynamics models were constructed from magnetic resonance images of three subjects. Velocity fields and wall shear stress distributions computed from each method will be qualitatively compared to highlight similarities and differences.
Rupture Risk Based On Anatomical And Morphological Factorsguest629cef
This document summarizes literature on the risk factors for rupture of unruptured intracranial aneurysms. Several studies have found that larger aneurysm size and posterior circulation location are associated with higher rupture risk. However, the data is inconsistent. The aspect ratio of aneurysms, which compares the width to neck size, also differs on average between ruptured and unruptured aneurysms, with higher ratios indicating higher risk. Due to variations in study populations and methods, a definitive meta-analysis is not possible, but these anatomical features provide some guidance on rupture risk assessment.
The study investigated the relationship between dilated Virchow-Robin spaces (VRS) seen on MRI and cerebral microvascular disease in elderly patients with dementia. 75 patients with Alzheimer's disease, ischemic vascular dementia, or frontotemporal dementia underwent MRI and were compared to 35 healthy volunteers. VRS scores were significantly higher in patients with vascular dementia compared to those with Alzheimer's disease, frontotemporal dementia, or healthy volunteers. VRS scores accounted for 29% of the variance in a regression model, more than periventricular hyperintensities, suggesting dilated VRS are a sensitive indicator of cerebral microvascular disease.
1 enfermedad cv ateroesclerótica figura 1 (1)sagita28
This document summarizes recent advances in imaging technologies for detecting and assessing atherosclerotic cardiovascular disease. It discusses how MRI, CT, and molecular imaging techniques can now detect atherosclerosis earlier in its development by imaging plaque composition in arterial walls, in addition to imaging advanced stenosis and its effects. These new imaging approaches may help stratify disease risk, monitor treatment effects, and improve understanding of atherosclerosis biology.
Anestesia para px con aneurisma (colocación de stent)kiria5
This document discusses anesthesia considerations for patients undergoing endovascular stenting for aortic aneurysms. Endovascular stenting carries less risk than open surgery by avoiding aortic dissection, blood loss, and fluid shifts. However, long term outcomes remain uncertain compared to open surgery. Anesthesia aims to properly place the stent graft to seal tears, decompress false lumens, and reduce rupture risk while monitoring for complications. Transesophageal echocardiography is used to guide the procedure and ensure exclusion of lesions. Care is taken to exclude initial intimal tears in dissections. Endovascular stenting is generally preferred over open surgery for patients with multiple comorbidities.
Endovascular and surgical treatments for intracranial aneurysms were compared in an evidence-based review. Single-center studies showed higher rates of aneurysm obliteration but similar or better outcomes after endovascular treatment. Multicenter studies and randomized trials found better outcomes at discharge, 2-6 months, and 1 year after endovascular treatment. For unruptured aneurysms, endovascular treatment had better discharge outcomes and lower costs. More data is still needed, but endovascular treatment appears to provide outcomes comparable or superior to surgery.
2D CFD simulation of intracranial aneurysmwalshb88
This document discusses a computational fluid dynamics (CFD) analysis of intracranial aneurysms. It presents details about two patients, one with a large anterior communicating artery aneurysm and one with an incidental finding. It provides background on intracranial aneurysms, including their prevalence, risk factors for rupture, and typical locations. It also discusses cerebral hemodynamics, the circle of Willis, and prior research using CFD models and imaging to study wall shear stresses and flows within aneurysms.
COMPUTATIONAL ASSESSMENT OF INTRA-CRANIAL ANEURYSMguest629cef
1) The document describes a study analyzing the relationship between intracranial aneurysm height to neck ratio and wall shear stress using computational fluid dynamics models.
2) Five models were developed with increasing height to neck ratios to simulate how changes in aneurysm geometry affect fluid dynamics and wall shear stress.
3) The simulations indicated that wall shear stress increases correspondingly with increasing height to neck ratios, suggesting an association with increased rupture risk.
Hemodynamics Of Normal Cerebral Arteriesguest629cef
This document compares measurements of blood flow patterns in cerebral arteries from 4D phase-contrast magnetic resonance imaging and computational fluid dynamics simulations in normal subjects. The goal is to assess consistency between the two methods and identify areas of disagreement in order to better interpret the data from each technique. Computational fluid dynamics models were constructed from magnetic resonance images of three subjects. Velocity fields and wall shear stress distributions computed from each method will be qualitatively compared to highlight similarities and differences.
Rupture Risk Based On Anatomical And Morphological Factorsguest629cef
This document summarizes literature on the risk factors for rupture of unruptured intracranial aneurysms. Several studies have found that larger aneurysm size and posterior circulation location are associated with higher rupture risk. However, the data is inconsistent. The aspect ratio of aneurysms, which compares the width to neck size, also differs on average between ruptured and unruptured aneurysms, with higher ratios indicating higher risk. Due to variations in study populations and methods, a definitive meta-analysis is not possible, but these anatomical features provide some guidance on rupture risk assessment.
The study investigated the relationship between dilated Virchow-Robin spaces (VRS) seen on MRI and cerebral microvascular disease in elderly patients with dementia. 75 patients with Alzheimer's disease, ischemic vascular dementia, or frontotemporal dementia underwent MRI and were compared to 35 healthy volunteers. VRS scores were significantly higher in patients with vascular dementia compared to those with Alzheimer's disease, frontotemporal dementia, or healthy volunteers. VRS scores accounted for 29% of the variance in a regression model, more than periventricular hyperintensities, suggesting dilated VRS are a sensitive indicator of cerebral microvascular disease.
1 enfermedad cv ateroesclerótica figura 1 (1)sagita28
This document summarizes recent advances in imaging technologies for detecting and assessing atherosclerotic cardiovascular disease. It discusses how MRI, CT, and molecular imaging techniques can now detect atherosclerosis earlier in its development by imaging plaque composition in arterial walls, in addition to imaging advanced stenosis and its effects. These new imaging approaches may help stratify disease risk, monitor treatment effects, and improve understanding of atherosclerosis biology.
Anestesia para px con aneurisma (colocación de stent)kiria5
This document discusses anesthesia considerations for patients undergoing endovascular stenting for aortic aneurysms. Endovascular stenting carries less risk than open surgery by avoiding aortic dissection, blood loss, and fluid shifts. However, long term outcomes remain uncertain compared to open surgery. Anesthesia aims to properly place the stent graft to seal tears, decompress false lumens, and reduce rupture risk while monitoring for complications. Transesophageal echocardiography is used to guide the procedure and ensure exclusion of lesions. Care is taken to exclude initial intimal tears in dissections. Endovascular stenting is generally preferred over open surgery for patients with multiple comorbidities.
Endovascular and surgical treatments for intracranial aneurysms were compared in an evidence-based review. Single-center studies showed higher rates of aneurysm obliteration but similar or better outcomes after endovascular treatment. Multicenter studies and randomized trials found better outcomes at discharge, 2-6 months, and 1 year after endovascular treatment. For unruptured aneurysms, endovascular treatment had better discharge outcomes and lower costs. More data is still needed, but endovascular treatment appears to provide outcomes comparable or superior to surgery.
2D CFD simulation of intracranial aneurysmwalshb88
This document discusses a computational fluid dynamics (CFD) analysis of intracranial aneurysms. It presents details about two patients, one with a large anterior communicating artery aneurysm and one with an incidental finding. It provides background on intracranial aneurysms, including their prevalence, risk factors for rupture, and typical locations. It also discusses cerebral hemodynamics, the circle of Willis, and prior research using CFD models and imaging to study wall shear stresses and flows within aneurysms.
COMPUTATIONAL ASSESSMENT OF INTRA-CRANIAL ANEURYSMguest629cef
1) The document describes a study analyzing the relationship between intracranial aneurysm height to neck ratio and wall shear stress using computational fluid dynamics models.
2) Five models were developed with increasing height to neck ratios to simulate how changes in aneurysm geometry affect fluid dynamics and wall shear stress.
3) The simulations indicated that wall shear stress increases correspondingly with increasing height to neck ratios, suggesting an association with increased rupture risk.
Issues in radiological pathology: Radiological pathology of watershed infarct...Professor Yasser Metwally
The document discusses border zone or watershed infarcts, which occur at the junction between two main arterial territories and constitute approximately 10% of all brain infarcts. There are two types - external (cortical) and internal (subcortical). External infarcts are often embolic in nature while internal infarcts are mainly caused by hemodynamic compromise. Advanced imaging can help identify areas of low perfusion and distinguish the two types. The document then examines the classification, imaging appearance, causal mechanisms, and clinical course of both external and internal border zone infarcts in more detail.
1. The document discusses Chronic Cerebrospinal Venous Insufficiency (CCSVI), a condition linked to multiple sclerosis (MS) where veins draining the brain and spinal cord are narrowed or blocked.
2. It provides details on diagnosing and treating CCSVI using procedures like Doppler ultrasound, MRI, venography, and venous angioplasty to widen blocked veins.
3. While the relationship between CCSVI and MS is still being studied, the document reports that over 600 MS patients treated for CCSVI experienced reduced fatigue, improved quality of life, psychological state, and physical condition based on evaluation scales.
This document discusses cerebral haemorrhage (ICH), which accounts for 10-15% of strokes. ICH can result from several mechanisms, including hypertension (47-66% of cases), cerebral amyloid angiopathy (CAA), and vascular malformations. CAA typically affects the elderly and causes lobar ICH that is often recurrent or involves multiple simultaneous haemorrhages. Vascular malformations like arteriovenous malformations (AVMs) and cavernous angiomas are a common cause of ICH in young, non-hypertensive patients. Imaging techniques like CT and MRI can identify vascular malformations and help determine the underlying cause of ICH.
This case report describes the resection of a large carotid artery aneurysm under cervical epidural anesthesia in a 22-year-old woman. Cervical blockade was not possible due to the location and size of the aneurysm. The patient underwent cervical epidural anesthesia, which allowed for continuous neurological monitoring during the surgery and early detection of any brain ischemia when the carotid artery was clamped. The large aneurysm was successfully resected over the course of a two hour surgery. The patient recovered well with no neurological defects. The report concludes that cervical epidural anesthesia performed by an experienced anesthetist provides safe neurological monitoring and is an acceptable approach for resecting carotid artery aneurysms when other methods are not possible.
This document discusses restenosis of drug-eluting stents. It begins by introducing the topic and defining in-stent restenosis. It then discusses classifications of in-stent restenosis and the underlying mechanisms. Various treatment approaches are mentioned, including medical management, balloon angioplasty, cutting/scoring balloon angioplasty, and drug-eluting balloons. Imaging with IVUS and OCT can help identify factors associated with stent failure. Overall, the document provides an overview of in-stent restenosis and approaches to managing it.
This document describes a bilaterally symmetric form of Hirayama disease observed in some patients. Out of 106 patients studied between 1992-2008, 11 showed nearly symmetric involvement of both upper limbs. The key characteristics of these symmetric cases included onset in teenage years, symmetric or near-symmetric muscle wasting in certain spinal segments, and MRI findings during neck flexion of cord flattening and enhancement of the posterior epidural space in both sides of the cervical spine. This suggests a rarer symmetric form of Hirayama disease can occur in some patients.
This document discusses hybrid operating rooms and procedures that combine endovascular and open surgical techniques. It begins by explaining the rationale for hybrid approaches, which allow treating more complex cardiac conditions while minimizing invasiveness. A hybrid OR has capabilities for both endovascular interventions and open surgery simultaneously. Key components include cath lab and surgical equipment that can be used together. The document discusses examples like using a stent graft with open surgery for aortic aneurysm or replacing valves percutaneously along with coronary artery bypass. It emphasizes teamwork and convergence of specialties to determine the best individualized approach. Hybrid procedures may reduce recovery time compared to traditional open surgery alone.
Cerebral microbleeds are small brain hemorrhages detected by MRI that are caused by leakage of blood from damaged small vessel walls. They are increasingly recognized in patients with cerebrovascular disease, Alzheimer's disease, vascular cognitive impairment, and normal elderly populations. Microbleeds in lobar regions may indicate cerebral amyloid angiopathy and link vascular and amyloid neuropathologies, while deep or infratentorial microbleeds often reflect hypertensive vasculopathy. Detection of microbleeds provides insight into cerebral small vessel disease and its relationship to cognitive impairment and dementia.
- Drug-eluting stents significantly reduced restenosis rates compared to bare-metal stents, but in-stent restenosis still occurs in 5-10% of cases.
- Restenosis can be focal or diffuse and is classified based on its severity and treatment approach. Higher grades of restenosis are associated with poorer outcomes.
- Factors contributing to in-stent restenosis include patient and lesion characteristics, stent design and materials, drug effects, inflammation, neoatherosclerosis, low wall shear stress areas, and potential thrombus formation.
- Earlier and more rapid neoatherosclerosis may occur inside drug-eluting stents compared to bare-metal stents,
This document discusses hybrid coronary revascularization (HCR), which combines coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI). HCR was introduced in 1996 as a treatment for multivessel coronary artery disease. It aims to reduce surgical trauma while preserving long-term survival and minimizing adverse events. The hybrid approach involves using a left internal mammary artery graft for the left anterior descending artery and PCI for other lesions. This takes advantage of the excellent outcomes of the arterial graft and improvements in stents. HCR may provide benefits for higher surgical risk patients and allow shorter recovery times compared to traditional CABG. However, some debate remains around its additional complexity and costs compared to established treatments.
A 57-year-old male patient presented with left lower limb weakness that had progressed over three months. MRI images showed bilateral, symmetrical lesions in the posterior parieto-occipital white matter, which had scalloped margins and did not enhance or cause mass effect. Based on the clinical presentation and MRI findings, the patient was diagnosed with progressive multifocal leukoencephalopathy (PML), a demyelinating disease caused by JC virus reactivation that predominantly affects immunocompromised individuals. PML lesions are typically multifocal and located in the white matter of the brain, most often in the parieto-occipital region.
Cerebral amyloid angiopathy (CAA) refers to the deposition of β-amyloid in the arteries of the cerebral cortex. It is commonly seen in Alzheimer's disease but can also occur in healthy elderly individuals. CAA can cause intracerebral hemorrhage, dementia, or transient neurological symptoms. The deposition damages blood vessels and increases the risk of hemorrhage. Imaging such as CT scans can detect hemorrhages characteristic of CAA, which are often lobar and cortical. Genetic factors like the ApoE genotype can influence the severity and presentation of CAA.
The document discusses in-stent restenosis (ISR), defined as the re-narrowing of a stented coronary artery due to neointimal tissue proliferation. ISR rates range from 3-20% with drug-eluting stents and 16-44% with bare-metal stents, usually occurring 3-20 months after stent placement. Predictors of ISR include patient characteristics like diabetes, lesion characteristics like length, and procedural characteristics like stent undersizing. The main mechanism is neointimal tissue proliferation due to arterial wall damage during stenting. ISR treatment involves revascularization like balloon angioplasty or additional stenting.
Hybrid procedures – from boxing ring to synchronizedArindam Pande
The document discusses various hybrid cardiovascular procedures that combine traditional surgery and percutaneous interventions. It provides details on hybrid CABG/PCI procedures, including advantages of a 1-stop approach over 2-staged, and indications. It also discusses hybrid valve/PCI procedures to allow for minimally invasive valve surgery in patients with coronary artery disease. Finally, it summarizes hybrid approaches for complex thoracic aortic aneurysms/dissections and arrhythmia/AF procedures.
Endovascular Coil Embolization of Dissecting distal MCA Aneurysm with ICH in ...Dr. Shahnawaz Alam
This document discusses a case of a 12-year-old female patient who presented with sudden severe headache and loss of consciousness following a fall in the bathroom. Diagnostic imaging revealed a dissecting aneurysm of the middle cerebral artery (MCA). The patient underwent serial coil embolization of the aneurysm. The document discusses the treatment approach for dissecting MCA aneurysms and reviews similar cases reported in medical literature.
This document contains 3 articles discussing the detection of acute strokes on CT scans:
1) An expert criticizes a previous study's conclusion that a stroke was barely detectable, arguing the hypoattenuation was clearly visible. He questions why this significant finding was missed and how to improve CT interpretation.
2) The authors of the previous study respond, arguing their goal was optimizing detection, not delineation of strokes. They maintain subtle differences can be difficult to see with standard settings.
3) Additional experts discuss the limitations of CT for early stroke detection and the benefits of variable window settings for facilitating rapid identification. Improving detection, even slightly, could significantly impact patient care.
This study describes the experiences of 24 patients treated for complex middle cerebral artery (MCA) aneurysms using bypass surgery combined with parent vessel occlusion. The aneurysms ranged in size from 7-60mm, with most being giant or fusiform. Bypass surgeries included extracranial-intracranial and intracranial-intracranial bypass procedures. Parent vessel occlusion involved partial or total trapping, with or without aneurysm resection. Outcomes were generally good, with 100% aneurysm obliteration and 21 patients (88%) having good functional outcomes, though permanent deficits occurred in 5 patients, most associated with M1 aneurysms. Location of the aneurysm was an important factor in planning treatment
This study developed a binary logistic regression model to predict the probability of intracranial aneurysm rupture using computed tomography angiography data from 279 aneurysms in 217 patients. The model incorporated aneurysm size, shape, location and patient age. When applied to an independent prospective cohort of 49 aneurysms, the model predicted rupture status with 83% sensitivity and 80% accuracy. This validated the model as a potential tool for predicting aneurysm rupture risk to inform treatment decisions.
Computational Fluid Dynamic Evaluation of Intra-Cranial AneurymsChapman Arter
This document describes a study analyzing the relationship between intracranial aneurysm height to neck ratio and wall shear stress using computational fluid dynamics models. The study aims to relate increases in height to neck ratio with increases in wall shear stress and changes in fluid flow patterns. Five models were created with increasing height to neck ratios to simulate how geometry affects vascular fluid dynamics and wall shear stresses. The results indicate that wall shear stress increases correspondingly with increases in height to neck ratio.
Issues in radiological pathology: Radiological pathology of watershed infarct...Professor Yasser Metwally
The document discusses border zone or watershed infarcts, which occur at the junction between two main arterial territories and constitute approximately 10% of all brain infarcts. There are two types - external (cortical) and internal (subcortical). External infarcts are often embolic in nature while internal infarcts are mainly caused by hemodynamic compromise. Advanced imaging can help identify areas of low perfusion and distinguish the two types. The document then examines the classification, imaging appearance, causal mechanisms, and clinical course of both external and internal border zone infarcts in more detail.
1. The document discusses Chronic Cerebrospinal Venous Insufficiency (CCSVI), a condition linked to multiple sclerosis (MS) where veins draining the brain and spinal cord are narrowed or blocked.
2. It provides details on diagnosing and treating CCSVI using procedures like Doppler ultrasound, MRI, venography, and venous angioplasty to widen blocked veins.
3. While the relationship between CCSVI and MS is still being studied, the document reports that over 600 MS patients treated for CCSVI experienced reduced fatigue, improved quality of life, psychological state, and physical condition based on evaluation scales.
This document discusses cerebral haemorrhage (ICH), which accounts for 10-15% of strokes. ICH can result from several mechanisms, including hypertension (47-66% of cases), cerebral amyloid angiopathy (CAA), and vascular malformations. CAA typically affects the elderly and causes lobar ICH that is often recurrent or involves multiple simultaneous haemorrhages. Vascular malformations like arteriovenous malformations (AVMs) and cavernous angiomas are a common cause of ICH in young, non-hypertensive patients. Imaging techniques like CT and MRI can identify vascular malformations and help determine the underlying cause of ICH.
This case report describes the resection of a large carotid artery aneurysm under cervical epidural anesthesia in a 22-year-old woman. Cervical blockade was not possible due to the location and size of the aneurysm. The patient underwent cervical epidural anesthesia, which allowed for continuous neurological monitoring during the surgery and early detection of any brain ischemia when the carotid artery was clamped. The large aneurysm was successfully resected over the course of a two hour surgery. The patient recovered well with no neurological defects. The report concludes that cervical epidural anesthesia performed by an experienced anesthetist provides safe neurological monitoring and is an acceptable approach for resecting carotid artery aneurysms when other methods are not possible.
This document discusses restenosis of drug-eluting stents. It begins by introducing the topic and defining in-stent restenosis. It then discusses classifications of in-stent restenosis and the underlying mechanisms. Various treatment approaches are mentioned, including medical management, balloon angioplasty, cutting/scoring balloon angioplasty, and drug-eluting balloons. Imaging with IVUS and OCT can help identify factors associated with stent failure. Overall, the document provides an overview of in-stent restenosis and approaches to managing it.
This document describes a bilaterally symmetric form of Hirayama disease observed in some patients. Out of 106 patients studied between 1992-2008, 11 showed nearly symmetric involvement of both upper limbs. The key characteristics of these symmetric cases included onset in teenage years, symmetric or near-symmetric muscle wasting in certain spinal segments, and MRI findings during neck flexion of cord flattening and enhancement of the posterior epidural space in both sides of the cervical spine. This suggests a rarer symmetric form of Hirayama disease can occur in some patients.
This document discusses hybrid operating rooms and procedures that combine endovascular and open surgical techniques. It begins by explaining the rationale for hybrid approaches, which allow treating more complex cardiac conditions while minimizing invasiveness. A hybrid OR has capabilities for both endovascular interventions and open surgery simultaneously. Key components include cath lab and surgical equipment that can be used together. The document discusses examples like using a stent graft with open surgery for aortic aneurysm or replacing valves percutaneously along with coronary artery bypass. It emphasizes teamwork and convergence of specialties to determine the best individualized approach. Hybrid procedures may reduce recovery time compared to traditional open surgery alone.
Cerebral microbleeds are small brain hemorrhages detected by MRI that are caused by leakage of blood from damaged small vessel walls. They are increasingly recognized in patients with cerebrovascular disease, Alzheimer's disease, vascular cognitive impairment, and normal elderly populations. Microbleeds in lobar regions may indicate cerebral amyloid angiopathy and link vascular and amyloid neuropathologies, while deep or infratentorial microbleeds often reflect hypertensive vasculopathy. Detection of microbleeds provides insight into cerebral small vessel disease and its relationship to cognitive impairment and dementia.
- Drug-eluting stents significantly reduced restenosis rates compared to bare-metal stents, but in-stent restenosis still occurs in 5-10% of cases.
- Restenosis can be focal or diffuse and is classified based on its severity and treatment approach. Higher grades of restenosis are associated with poorer outcomes.
- Factors contributing to in-stent restenosis include patient and lesion characteristics, stent design and materials, drug effects, inflammation, neoatherosclerosis, low wall shear stress areas, and potential thrombus formation.
- Earlier and more rapid neoatherosclerosis may occur inside drug-eluting stents compared to bare-metal stents,
This document discusses hybrid coronary revascularization (HCR), which combines coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI). HCR was introduced in 1996 as a treatment for multivessel coronary artery disease. It aims to reduce surgical trauma while preserving long-term survival and minimizing adverse events. The hybrid approach involves using a left internal mammary artery graft for the left anterior descending artery and PCI for other lesions. This takes advantage of the excellent outcomes of the arterial graft and improvements in stents. HCR may provide benefits for higher surgical risk patients and allow shorter recovery times compared to traditional CABG. However, some debate remains around its additional complexity and costs compared to established treatments.
A 57-year-old male patient presented with left lower limb weakness that had progressed over three months. MRI images showed bilateral, symmetrical lesions in the posterior parieto-occipital white matter, which had scalloped margins and did not enhance or cause mass effect. Based on the clinical presentation and MRI findings, the patient was diagnosed with progressive multifocal leukoencephalopathy (PML), a demyelinating disease caused by JC virus reactivation that predominantly affects immunocompromised individuals. PML lesions are typically multifocal and located in the white matter of the brain, most often in the parieto-occipital region.
Cerebral amyloid angiopathy (CAA) refers to the deposition of β-amyloid in the arteries of the cerebral cortex. It is commonly seen in Alzheimer's disease but can also occur in healthy elderly individuals. CAA can cause intracerebral hemorrhage, dementia, or transient neurological symptoms. The deposition damages blood vessels and increases the risk of hemorrhage. Imaging such as CT scans can detect hemorrhages characteristic of CAA, which are often lobar and cortical. Genetic factors like the ApoE genotype can influence the severity and presentation of CAA.
The document discusses in-stent restenosis (ISR), defined as the re-narrowing of a stented coronary artery due to neointimal tissue proliferation. ISR rates range from 3-20% with drug-eluting stents and 16-44% with bare-metal stents, usually occurring 3-20 months after stent placement. Predictors of ISR include patient characteristics like diabetes, lesion characteristics like length, and procedural characteristics like stent undersizing. The main mechanism is neointimal tissue proliferation due to arterial wall damage during stenting. ISR treatment involves revascularization like balloon angioplasty or additional stenting.
Hybrid procedures – from boxing ring to synchronizedArindam Pande
The document discusses various hybrid cardiovascular procedures that combine traditional surgery and percutaneous interventions. It provides details on hybrid CABG/PCI procedures, including advantages of a 1-stop approach over 2-staged, and indications. It also discusses hybrid valve/PCI procedures to allow for minimally invasive valve surgery in patients with coronary artery disease. Finally, it summarizes hybrid approaches for complex thoracic aortic aneurysms/dissections and arrhythmia/AF procedures.
Endovascular Coil Embolization of Dissecting distal MCA Aneurysm with ICH in ...Dr. Shahnawaz Alam
This document discusses a case of a 12-year-old female patient who presented with sudden severe headache and loss of consciousness following a fall in the bathroom. Diagnostic imaging revealed a dissecting aneurysm of the middle cerebral artery (MCA). The patient underwent serial coil embolization of the aneurysm. The document discusses the treatment approach for dissecting MCA aneurysms and reviews similar cases reported in medical literature.
This document contains 3 articles discussing the detection of acute strokes on CT scans:
1) An expert criticizes a previous study's conclusion that a stroke was barely detectable, arguing the hypoattenuation was clearly visible. He questions why this significant finding was missed and how to improve CT interpretation.
2) The authors of the previous study respond, arguing their goal was optimizing detection, not delineation of strokes. They maintain subtle differences can be difficult to see with standard settings.
3) Additional experts discuss the limitations of CT for early stroke detection and the benefits of variable window settings for facilitating rapid identification. Improving detection, even slightly, could significantly impact patient care.
This study describes the experiences of 24 patients treated for complex middle cerebral artery (MCA) aneurysms using bypass surgery combined with parent vessel occlusion. The aneurysms ranged in size from 7-60mm, with most being giant or fusiform. Bypass surgeries included extracranial-intracranial and intracranial-intracranial bypass procedures. Parent vessel occlusion involved partial or total trapping, with or without aneurysm resection. Outcomes were generally good, with 100% aneurysm obliteration and 21 patients (88%) having good functional outcomes, though permanent deficits occurred in 5 patients, most associated with M1 aneurysms. Location of the aneurysm was an important factor in planning treatment
This study developed a binary logistic regression model to predict the probability of intracranial aneurysm rupture using computed tomography angiography data from 279 aneurysms in 217 patients. The model incorporated aneurysm size, shape, location and patient age. When applied to an independent prospective cohort of 49 aneurysms, the model predicted rupture status with 83% sensitivity and 80% accuracy. This validated the model as a potential tool for predicting aneurysm rupture risk to inform treatment decisions.
Computational Fluid Dynamic Evaluation of Intra-Cranial AneurymsChapman Arter
This document describes a study analyzing the relationship between intracranial aneurysm height to neck ratio and wall shear stress using computational fluid dynamics models. The study aims to relate increases in height to neck ratio with increases in wall shear stress and changes in fluid flow patterns. Five models were created with increasing height to neck ratios to simulate how geometry affects vascular fluid dynamics and wall shear stresses. The results indicate that wall shear stress increases correspondingly with increases in height to neck ratio.
natural history of brain arteriovenous malformations a systematic reviewPerla Islas Romero
This document summarizes a systematic review of the literature on the natural history of brain arteriovenous malformations (BAVMs). It finds that the incidence of BAVMs is between 1.12-1.42 cases per 100,000 person-years, with 38-68% of new cases presenting with first-ever hemorrhage. The overall annual risk of hemorrhage for untreated BAVMs ranges from 2.10-4.12%. Factors that increase the risk of subsequent hemorrhage include initial hemorrhagic presentation, exclusively deep venous drainage, and deep or infratentorial brain location. The review aims to clarify the natural history of BAVMs to help clinicians counsel patients.
This study investigated factors that influence the need for preoperative vascular imaging before harvesting a vascularized fibular flap. The researchers analyzed 185 angiograms and found significant correlations between lower extremity artery pathology and risk factors like high cholesterol, high blood pressure, coronary heart disease, diabetes, and increased age. Specifically, increased age was the strongest predictor of vessel pathology. The study concludes that preoperative vascular imaging should be performed in patients with medical comorbidities to reduce the risks of flap failure and donor site complications when harvesting a fibular flap.
This document discusses cerebral aneurysms, which are bulges in blood vessel walls in the brain that can fill with blood. While usually asymptomatic, aneurysms can rupture, causing a stroke or pressure on the brain. To treat aneurysms, doctors thread a catheter through arteries to the site and insert platinum coils to block blood flow and cause clotting, supported by a stent. The complex brain vasculature makes this a difficult procedure. Computational fluid dynamics simulations are being used to model blood flow and forces to better understand and treat aneurysms, using open source software to create 3D models from medical images. Results will be compared to experimental and clinical data.
1. Cerebral aneurysms are pathological dilatations of arterial walls that can rupture and cause hemorrhaging.
2. Their formation and progression is driven by a complex interaction of hemodynamic forces on the vessel wall and biological factors within the wall.
3. Abnormal blood flow patterns can lead to endothelial cell damage, inflammation, and wall weakening over time through mechanisms such as increased enzyme activity and smooth muscle cell apoptosis.
3D CFD simulation of intracranial aneurysmwalshb88
1) A CFD study was conducted to analyze the effects of proximal artery occlusion on hemodynamic forces in a giant cerebral aneurysm. Velocity fields, wall shear stress, and pressure distributions were determined for the aneurysm with no occlusion and with each inlet artery occluded.
2) Preliminary results found no conclusive evidence that blocking feeding arteries significantly decreases hemodynamic forces in the aneurysm. Additional patient-specific simulations are needed to determine if changes in vascular anatomy correlate to calculated hemodynamic forces.
3) It remains unclear if proximal artery occlusion is an effective treatment for giant cerebral aneurysms since geometry strongly influences blood flow and blocking arteries may only mitigate forces in some cases.
Evaluation of Occlusive Diseases in Cervical Arteries in Patients of Acute Is...QUESTJOURNAL
This document summarizes a study that evaluated occlusive diseases in cervical arteries of patients with acute ischemic stroke using CT angiography. The study analyzed CTA images of 50 patients to determine the percentage with vascular stenosis or occlusion. It found that 76% of patients showed neck vessel involvement, with 26% having luminal narrowing and 8% having complete occlusion. While many vessels showed atherosclerotic changes, only 45 of 300 total vessels analyzed showed significant luminal narrowing or plaque formation. The study concludes there is a significant correlation between atherosclerotic changes in neck vessels and occurrence of acute ischemic stroke.
1) The document discusses imaging of cerebral ischemia from acute stroke to chronic disorders. Imaging provides valuable information about disease progression, diagnosis, treatment selection and monitoring over time.
2) Several imaging modalities such as CT, MRI, CTA and CTP can be used to evaluate brain parenchyma integrity, vascular disease severity, and changes in tissue metabolism and perfusion over the acute, subacute and chronic phases of ischemia.
3) Choosing the appropriate imaging modality depends on the specific clinical question and can help guide management decisions by providing insight into disease mechanisms and monitoring progression.
This document discusses guidelines and considerations for angiography in patients presenting with subarachnoid hemorrhage (SAH). It notes that angiography should be performed promptly to establish the diagnosis and facilitate timely treatment. It also discusses risks and complications of the procedure, as well as technical aspects such as ensuring adequate patient monitoring and use of specialized projections. The document provides guidance on distinguishing aneurysms, following up on negative studies, and using angiography to assess for cerebral vasospasm.
Présentation du Dr Dake lors du plus grand congrès de cardiologie interventionnelle.
Présentation faite en salle plénière devant plus de 800 personnes.
Aims: Post-mortem pathological studies have shown that a “vulnerable” plaque is the dominant patho-physiological mechanism responsible for acute coronary syndromes (ACS). One way to improve our understanding of these plaques in vivo is by using histological “surrogates” created by intravascular ultrasound derived virtual histology (IVUS-VH). Our aim in this analysis was to determine the relationship between site-specific differences in individual plaque areas between ACS plaques and stable plaques (SP), with a focus on remodelling index and the pattern of calcifying necrosis.
Methods and results: IVUS-VH was performed before percutaneous intervention in both ACS culprit plaques (CP) n=70 and stable disease (SP) n=35. A total of 210 plaque sites were examined in 105 lesions at the minimum lumen area (MLA) and the maximum necrotic core site (MAX NC). Each plaque site had multiple measurements made including some novel calculations to ascertain the plaque calcification equipoise (PCE) and the calcified interface area (CIA). CP has greater amounts of positive remodelling at the MLA (RI@MLA): 1.1 (±0.17) vs. 0.95 (±0.14) (P<0.001);><0.001)>1.12; RI @ MAX NC >1.22; PCE @ MLA <47.1%;><47.3%;>2.6; CIA @ MAX NC >3.1.
Conclusions: Determining the stage of calcifying necrosis, along with the remodelling index can discriminate between stable and ACS related plaques. These findings could be applied in the future to help detect plaques that have a vulnerable phenotype.
This study examined microvascular proliferation (MVP) in neuroblastoma tumors to determine its clinical significance. MVP, including glomeruloid MVP, was significantly associated with poor prognosis in two independent cohorts of neuroblastoma patients. MVP was also significantly associated with the clinically aggressive Schwannian stroma-poor histology of neuroblastomas. These findings provide further evidence that angiogenesis plays an important role in neuroblastoma pathogenesis and behavior, and suggest angiogenesis is regulated differently depending on the amount of Schwannian stroma in the tumor.
Endovascular complications: Antiplatelet management for flow diversionbijnnjournal
Up to 3−5% of the general population is affected by cerebral aneurysms that are associated with both modifiable
as well as non-modifiable risk factors ranging from familial to acquired neurovascular conditions. The initial
treatment option was aneurysm clipping and evolved to including primary or adjuvant endovascular treatment.
Aneurysm re-rupture, although rare, can have devastating consequences such as intracranial bleeding and carotidcavernous fistula. Emergent surgery in view of delayed aneurysm rupture in patients maintained on dual antiplatelet
therapy presents with the need to carefully assess the procedure-related risk factors and evaluate the patients’
platelet function. With the advent of novel technology, flow diverters came into play
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Quantitative Hemodynamic Analysis Of Brain Aneurysm At Different Locations
1. ORIGINAL
Quantitative Hemodynamic Analysis of Brain
RESEARCH Aneurysms at Different Locations
A. Chien BACKGROUND AND PURPOSE: Studies have shown that the occurrence of brain aneurysms and risk of
M.A. Castro rupture vary between locations. However, the reason that aneurysms at different branches of the
cerebral arteries have different clinical presentations is not clear. Because research has indicated that
S. Tateshima
aneurysm hemodynamics may be one of the important factors related to aneurysm growth and
J. Sayre rupture, our aim was to analyze and compare the flow parameters in aneurysms at different locations.
J. Cebral
MATERIALS AND METHODS: A total of 24 patient-specific aneurysm models were constructed by using
F. Vinuela
˜ 3D rotational angiographic data for the hemodynamic simulation. Previously developed computational
fluid dynamics software was applied to each aneurysm to simulate the blood-flow properties. Hemo-
dynamic data at peak pulsatile flow were recorded, and wall shear stress (WSS) and flow rate in the
aneurysms and parent arteries were quantitatively compared. To validate our method, a comparison
with a previously reported technique was also performed.
RESULTS: WSS and flow rate in the aneurysms at the peak of the cardiac cycle were found to differ
in magnitude between different locations. Multiple comparisons among locations showed higher WSS
and flow rate in middle cerebral artery aneurysms and lower WSS and flow rate in basilar artery and
anterior communicating artery aneurysms.
CONCLUSIONS: We observed changes in hemodynamic values that may be related to aneurysm
location. Further study of aneurysm locations with a large number of cases is needed to test this
hypothesis.
B rain aneurysm rupture is one cause of subarachnoid hem-
orrhage and results in substantial rates of morbidity and
mortality. Autopsy studies have reported that intracranial an-
ing, realistic aneurysm geometry and vascular structure can be
incorporated into simulations to perform patient-specific he-
modynamic analysis. This type of image-based hemodynamic
INTERVENTIONAL ORIGINAL RESEARCH
eurysms are common lesions and certain locations tend to research has shown that ruptured aneurysms tend to have a
have a higher rate of incidence.1 Recent international studies more complicated flow pattern.14,17 Using a longitudinal data
have reported that some aneurysm locations have a higher risk base, a recent hemodynamic study of aneurysm growth also
of rupture than others.2-4 Because little is known about the reported that aneurysms are more likely to grow in regions of
cause of brain aneurysms or the process by which they grow low wall shear stress (WSS).18 Although studies have suggested
and rupture, studies of how anatomic location may affect that aneurysms at different locations tend to differ geometri-
brain aneurysms can help further understand this disease.5 cally and clinically,1-4 to our knowledge, whether aneurysms at
Vascular geometry, branching angles, and surrounding an- different locations have different hemodynamic properties has
atomic structures, the features used to identify and specify an not yet been reported. The aim of this study was to examine
aneurysm, have previously been studied to find their relation- the hemodynamic parameters in aneurysms at different
ships with the natural history of aneurysms.6-8 Analyzing dif- locations.
ferences in parent artery geometry revealed that aneurysms
with a large caliber of the proximal artery tended to rupture at
Materials and Methods
a larger size.6 Bifurcations beyond the circle of Willis approx-
imated optimality principles, unlike those within the circle of Data Collection and Imaging Technique
Willis.7 Moreover, the perianeurysmal environment has been Twenty-four aneurysms from 4 of the common locations in cerebral
suggested to influence aneurysm shape and risk of rupture, arteries (anterior communicating artery [AcomA], middle cerebral
especially for locations with unbalanced contact constraint.8 artery [MCA], internal carotid artery [ICA], basilar artery [BA]) were
Intra-aneurysmal hemodynamic characteristics are also selected from the University of California, Los Angeles interventional
believed to be an important factor for aneurysm growth and neuroradiology data base from November 2007 to June 2008. 3D
rupture.9-16 With the help of advancements in medical imag- rotational angiographic (3DRA) images (Integris; Philips Medical
Systems, Best, the Netherlands) obtained before aneurysm emboliza-
Received December 5, 2008; accepted after revision March 1, 2009.
tion were collected and transferred to an Integris workstation (Philips
From the Division of Interventional Neuroradiology (A.C., S.T., F.V.), David Geffen School of
Medicine, University of California Los Angeles, Los Angeles, Calif; Department of Compu-
Medical Systems) for 3D voxel generation. The Table summarizes the
tational Sciences (M.A.C., J.C.), George Mason University, Fairfax, Va; and Department of details of the cases.
Biostatistics (J.S.), School of Public Health, University of California Los Angeles, Los
Angeles, Calif.
Hemodynamic Modeling of Aneurysms
Paper previously presented in part at: Annual Meeting of Society of Neurointerventional
The computational model for each aneurysm was reconstructed by
Surgery, July 28 –August 1, 2008; Lake Tahoe, Calif.
using patient-specific computational fluid dynamics simulation
Please address correspondence to Aichi Chien, PhD, Division of Interventional Neuroradi-
ology, David Geffen School of Medicine at UCLA, 10833 LeConte Ave, Box 951721, Los software developed by George Mason University.14,15,17,19-25 All
Angeles, CA 90095; e-mail: aichi@ucla.edu 3DRA images were denoised and later segmented by using a region-
DOI 10.3174/ajnr.A1600 growing algorithm.14,15,20,24 A volumetric model generated by a 3D
AJNR Am J Neuroradiol 30:1507–12 Sep 2009 www.ajnr.org 1507
2. Summary of aneurysm cases*
Characteristics Group 1 Group 2 Group 3 Group 4 Summary
Age (year)
Mean 65.2 64.2 51.3 57.3 59.5
Range 48–81 42–79 24–70 47–70 24–81
Sex (No. of patients)
Female 5 5 6 3 19
Male 1 1 0 3 5
Unruptured-ruptured aneurysms (No. of patients) 4–2 4–2 4–2 4–2 16–8
Total No. of aneurysms 6 6 6 6 24
Largest diameter of aneurysm (mm)
Mean 5.2 6.25 7.2 11.0 7.4
Range 3.6–8.2 5.1–8.1 5–8 6–15 3.6–15
Diameter of aneurysm neck (mm)
Mean 3.5 3.7 4.4 7.17 4.7
Range 2.3–6.5 3.3–4 2.7–7 4–14.6 2.3–14.6
Size of aneurysm (No. of patients)
7 mm 5 4 2 1 12
7–12 mm 1 2 4 2 9
13–24 mm 0 0 0 3 3
Diameter of parent artery vessel lumen (mm)
Mean 2.1 2.2 3.9 3.4 2.9
Range 1.3–3.2 1.6–2.7 3.4–5.3 2.7–4.4 1.3–4.4
* Groups 1, 2, 3, and 4 are aneurysms located at the AComA, MCA, ICA, and BA, respectively.
advancing front technique was used to define the geometry of the the parent artery— crossing at the proximal end of the aneurysm, the
computational domain. To have the same inflow settings for all the center of the aneurysm, and the distal end of the aneurysm. For an-
aneurysm simulations, aneurysms located at the anterior circulation eurysms located at multi-avenue terminals or bifurcations, 1 region
were all modeled from the ICA cavernous segment, and aneurysms crossed the proximal point of the bifurcation at the main artery and
located at posterior circulation were all modeled from the BA 2 regions crossed the arteries at the distal end of the aneurysm.
segment. Although the 6-region method reduces the complexity of hemo-
Previously reported pulsatile flow profiles for the ICA and BA dynamic results, its consistency with hemodynamic data collected
measured from a healthy subject by using phase-contrast MR imag- from the entire aneurysm dome and parent artery needed to be eval-
ing (Signa 1.5T scanner; GE Healthcare, Waukesha, Wis) were im- uated. Due to the complexity of the data-analysis process, few studies
posed as the inflow for the computational fluid dynamics mod- have detailed the collection of hemodynamic data from the entire
els.14,21,26 The flow profiles were prescribed by using the Womersley aneurysm dome and parent artery. However, one relatively recent
solution for the fully developed pulsatile flow in a rigid straight report by Shojima et al13 extracted data from the entire aneurysm
tube13-15,27 and were scaled according to the cross-sectional area of dome and MCA to study MCA aneurysms. We reproduced their ap-
the inflow vessels for each model.28 Assuming that all the distal vas- proach and compared results collected from the entire dome and
cular beds have similar total resistance to flow, traction-free boundary parent artery with the 6-region method. Because the method of
conditions with the same pressure level were applied to all the model Shojima et al13 was only applicable to study WSS in MCA aneurysms,
outlets. Blood flow was modeled as an incompressible Newtonian 10 MCA aneurysms from the University of California, Los Angeles
fluid. The governing equations were the unsteady Navier-Stokes interventional neuroradiology data base (from November 2007 to
equations in 3D. The blood attenuation was 1.0 g/cm3 and the viscos- June 2008) were selected for the method comparison.
ity was 0.04 poise. Vessel walls were assumed rigid, and no-slip
boundary conditions were applied at the walls. Numeric solutions of Statistical Methods
the Navier-Stokes equations were obtained by using a fully implicit Results were expressed as mean value and SD. Repeated measure-
finite-element formulation. Two cardiac cycles were computed by ments and analysis of variance were used. Multivariate tests and mul-
using 100 steps per cycle, and all the results presented corresponded to tiple comparisons between location groups were performed to see the
the second cardiac cycle.13-15,27 Details of the simulation settings have relationship of hemodynamic properties and locations. The sign
been previously described.14,15,17,19-25 test30 was used for the method comparison. The Spearman rank cor-
relation was used to find the relationship between vessel dimensions
Quantitative Hemodynamic Analysis and Validation and hemodynamic values. The statistical significance level was set
Method at .05.
After the hemodynamic simulation, for each aneurysm, the blood-
flow rate and WSS at the peak of the cardiac cycle were collected both Results
from the aneurysm and the parent artery. We applied a previously
developed technique to perform quantitative analyses by using a pre- Hemodynamic Properties in Aneurysms
defined 6-region method.29 Hemodynamic data were collected from The representative hemodynamic properties of brain aneu-
3 equal sections in the aneurysm dome, with regions defined crossing rysms from different locations are shown in Fig 2. Patient-
the aneurysm dome at the level of the aneurysm neck, middle, and top specific aneurysm models were reconstructed based on the
(Fig 1). Likewise, data in the vessel were recorded from 3 regions of 3DRA images (Fig 2, top row). The instantaneous streamlines
1508 Chien AJNR 30 Sep 2009 www.ajnr.org
3. Fig 1. Schematic representations of regions for hemodynamic data analysis. A, Regions in the arteries of terminal or bifurcation aneurysms. B, Regions in the arteries of sidewall aneurysms.
C, Regions in the aneurysm dome. D and E, Application to patient-specific aneurysm models are shown for a bifurcation aneurysm (D) and a sidewall aneurysm (E ).
Fig 2. Representative hemodynamic results for AcomA (A and B), MCA (C and D ), ICA (E and F ), and BA (G and H ) aneurysms. Top row is the 3DRA images obtained for each aneurysm
during the clinical procedure. A diversity of aneurysms and complicated arterial structures can be observed. The middle row (flow pattern) and the bottom row (WSS) are the hemodynamic
results obtained from the simulation. Flow pattern and WSS show differences among aneurysms, and each one has a unique pattern in the arteries and the aneurysms. WSS is in pascal
units.
at the peak of systole, recorded from the trajectory of the in- we calculated the WSS and flow rate from different regions of
stantaneous 3D velocity field,29 show the flow pattern in aneurysms. The average WSS in the aneurysms, parent arter-
the aneurysms (Fig 2, the second row). The third row is the ies, and the entire aneurysm area (both aneurysm and parent
distribution of WSS for each aneurysm. As previously shown, artery regions) is shown in Fig 3. WSS was found to differ
the patient-specific hemodynamic simulation allowed us to among locations in aneurysms (P .01) and in parent arteries
study flow properties in various aneurysms; however, the re- (P .009). Multiple comparisons showed that the BA aneu-
sults yielded from the simulation can be complicated and dif- rysms had the lowest average WSS, lower than AcomA (P
ficult to compare, especially when studies include a variety of .009), ICA (P .001), and MCA (P .001) aneurysms. WSS
aneurysms. in AcomA aneurysms was lower than that in MCA aneurysms
For quantitative comparison of hemodynamic properties, (P .001).
AJNR Am J Neuroradiol 30:1507–12 Sep 2009 www.ajnr.org 1509
4. Fig 3. WSS in aneurysms at each location. Note the average WSS in arteries and aneurysms and the average WSS in the entire aneurysm area.
Fig 4. Flow rates in aneurysms at different locations. Note the average flow in arteries and aneurysms and the average flow velocity in the entire aneurysm area.
The average blood-flow rate calculated for the aneurysms, shapes and complicated vascular structures. In this study, we
parent arteries, and the entire aneurysm area is shown in Fig 4. quantitatively analyzed hemodynamic data in aneurysms and
We found the trend of flow rate in the parent arteries (P found that there were hemodynamic differences among aneu-
.001) and aneurysms (P .071) also differed among loca- rysms at different locations. Many causes may produce differ-
tions. Aneurysms at the BA had the lowest average flow rate, ences in aneurysmal hemodynamic values among locations:
and multiple comparisons showed that the flow rate in BA aneurysm geometry, vessel geometry, parent artery size and
aneurysms was lower than that in AcomA (P .018), ICA curvature, or blood flow rates. From this study, we were not
(P .001), and MCA (P .001) aneurysms. Flow in AcomA able to determine the reason for such hemodynamic differ-
aneurysms was slower than that in MCA (P .001) and ICA ences because of the small number of cases. Furthermore,
(P .05) aneurysms. many other factors affecting aneurysms were not considered,
including aneurysm size, patient age and sex, and population.
Technique Validation Studies incorporating those groups with more cases are also
Figure 5 shows the average WSS in 10 MCA aneurysms ob- important to find out how hemodynamic changes among lo-
tained by the present method, which collected data from 6 cations are associated with these parameters.
regions, and by the method of Shojima et al,13 which found We found different hemodynamics properties according to
WSS averages in the aneurysm dome and parent artery. The location. The results may not be surprising because different-
average WSS in the aneurysms obtained by the present sized vessels have different flow.31 Such evidence has not yet
method and by Shojima et al were 10.3 5.2 Pa and 11.7 3.6 been shown in human brain aneurysms; instead, many hemo-
Pa, respectively (Fig 5A). The average WSS in the parent arter- dynamic studies have combined aneurysms in various loca-
ies was 19.3 4.6 Pa and 17.4 5.9 Pa, respectively (Fig 5B). tions.14,18,32 Although this is a preliminary study and further
We found that the present method and that of Shojima et al proof of this finding is needed, we think that on the basis of our
yielded similar results and there was no statistical difference results, consideration of hemodynamic variation between lo-
between the techniques (P .344). cations will be important for future studies. Furthermore, in
our cases, no significant correlations were found between par-
Discussion ent artery size and aneurysm WSS ( 0.357; P .086) and
Patient-specific hemodynamic analysis enabled us to simulate flow rate ( 0.286, P .175), suggesting that due to the
intra-aneurysmal flow properties for a diversity of aneurysm complexity of the brain vascular structure, using only the size
1510 Chien AJNR 30 Sep 2009 www.ajnr.org
5. Limitations
We compared hemodynamic properties in aneurysms among
various aneurysm locations; however, even aneurysms at the
same location have anatomic variations that may also affect
the hemodynamic properties. Because of the limited number
of cases, we were not able to compare how these anatomic
differences affect aneurysm hemodynamics. Moreover, the
case selection in this study was not ideal, with, for example,
more large aneurysms in the BA group than in other locations.
This case selection was affected by the patients’ enrollment
patterns in our medical center. Although we found a statisti-
cally significant difference among groups in our cases, these
variations in anatomy and size were included. Further re-
search with more detailed anatomic categorization and com-
bining a multicenter data base would still be needed to provide
thorough understanding of the association among aneurysm
hemodynamics and locations and anatomic variations.
Our hemodynamic study used a human pulsatile profile
with inflow conditions scaled according to the patients’ inflow
vessel sizes. A simulation with patient-specific inflow condi-
tions will be the most ideal flow conditions to use. A recent
study has shown success by using patient-specific blood-flow
information collected from phase-contrast MR imaging to
perform hemodynamic simulations.18 However, obtaining
sufficient aneurysm cases with patients’ intracranial vessel ge-
ometry and flow information is technically challenging. One
of our future tasks will be collecting patient-specific inflow
information to incorporate into the hemodynamic simulation
to test our findings.
In this study, we used the 6-region method to study hemo-
dynamic properties and showed that it was a comparable and
more computationally efficient approach in comparison with
results collected from the entire aneurysm dome and parent
artery. This data-collection method is a useful tool to reduce
Fig 5. A and B, Validation study comparing the hemodynamic results by using 6 regions the amount of data and accelerate the data-collection process,
(solid) and values collected from the entire dome and parent artery (method of Shojima et which is suitable for larger case numbers. However, this is just
al13) (hollow) shows the average WSS in the aneurysms (A ) and the average WSS in the
parent arteries (B). Note in cases 5 and 8 that both methods show the same average WSS
one way to perform data analysis, and efforts to improve the
in the aneurysm. analysis methods for various aneurysms are still needed to
develop accurate and efficient hemodynamic analysis tools for
studies including a large number of cases. In this study, we
of the vessel may not be enough to understand the flow prop- analyzed the hemodynamic value at the peak of systole as our
erties in aneurysms. first step to study aneurysms at different locations. Further
Hemodynamic influences have important effects on vascu- study comparing the entire cardiac cycle with patient-specific
lar diseases.28,33-36 WSS, caused by blood flow, is a tangential flow profiles will be needed to study whether hemodynamic
force acting on the endothelial surface. Studies have shown differences among locations change during the course of the
that though WSS is a small force that is insufficient to tear the cardiac cycle.
vessel wall, it is an important determinant of endothelial cell The current analysis still used hemodynamic simulation
function especially when WSS is low.28,34,35 Recently, studies focused on a particular segment of the artery. Because asym-
evaluated the presence of endothelial cells in human aneu- metric effects may be important to aneurysms within the circle
rysms37,38 and reported that low WSS in aneurysms may relate of Willis,39 future studies with the simulation incorporating
to the risk of rupture and aneurysm growth.13,18 Consistent the entire circle of Willis will facilitate in-depth understanding
with previous studies,13,29 our results showed that WSS was of the influence of location, especially lateral influence.
low in aneurysms, compared with the arteries (P .005).
Moreover, because the low WSS in aneurysms varies among Conclusions
locations, whether this variation associates with the rate of On the basis of the results of this study, our hypothesis is that
endothelium function deterioration or the rate of aneurysm aneurysmal hemodynamic properties may vary according to
growth is a question needing further investigation. Studies location. Consideration of hemodynamic variation among
combining histological findings and flow simulation in aneu- locations may be needed when studying aneurysm hemo-
rysms will be helpful in understanding the meaning of the dynamics, such as aneurysm natural history or aneurysm
different ranges of WSS found in each location. rupture. Further study of aneurysm locations with more cases
AJNR Am J Neuroradiol 30:1507–12 Sep 2009 www.ajnr.org 1511
6. and incorporation of factors such as sex and medical history low wall shear stress: patient-specific correlation of hemodynamics and
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