Use Of Magnetic Resonance Angiography Research Articles

Diagnostic Strategies Incorporating Computed Tomography Angiography for Pulmonary Embolism

Pulmonary embolism (PE) is a significant cause of morbidity and mortality. The clinical diagnosis of PE can be quite challenging, necessitating a systematic, evidence-based, and cost-effective approach. A sensitive search strategy using keywords associated with PE diagnosis and economic evaluation was conducted. The libraries searched included MEDLINE, EMBASE, Health Technology Assessments, NHS Economic Evaluation Database, and the Cochrane Central Register of Clinical Trials. Studies were required to be a model-based cost-effectiveness analysis (CEA) for PE diagnosis. To be included, studies had to have evaluated both the cost and effectiveness of diagnostic algorithms. In addition, computed tomography (CT) had to have been a component in at least 1 possible algorithm. The characteristics of each CEA were extracted. In addition, the characteristics of CT pulmonary angiography were extracted (sensitivity, specificity, and cost). The most cost-effective strategy and its comparator were presented with the corresponding incremental cost-effectiveness ratio. Thirteen studies met our inclusion criteria. Costs were obtained using a variety of methods. Most studies measured effectiveness using a metric of survival, whereas 3 studies used quality-adjusted life years. Studies varied considerably in terms of the quality of economic evaluation. All but 1 study reported that computed tomographic pulmonary angiography (CTPA)-typically combined with ultrasound or D-dimer-was part of the most cost-effective algorithm. CEA is a useful tool for evaluating potential algorithms for PE diagnosis. Future CEAs would do well to include the use of magnetic resonance angiography and the potential for alternate diagnoses in diagnostic algorithms.

Cerebrovascular stenosis in neurofibromatosis type 1 and utility of magnetic resonance angiography: our experience and literature review

Neurofibromatosis type 1 (NF1) is a multisystem autosomal dominant disorder that primarily involves the skin and the nervous system. Development of cerebral arterial stenosis is a potentially deadly complication of NF1, which is frequently underestimated. The aim of our paper is to report the frequency of this cerebrovascular disease in a series of patients affected by NF1, using magnetic resonance angiography (MRA). A review of the literature was also performed, focused on the usefulness of MRA in NF1 patients. Among 125 patients with NF1 (clinical diagnosis according to the standard National Institutes of Health criteria), 81 (65%) were studied with brain MRI (magnetic resonance imaging) and MRA using a 1.5 T magnet. Multiple intracranial arterial stenoses were found in six patients (7.4%). In our study, MRA proved to be critical, especially for the detection of stenoses in the branches of the Circle of Willis. Few case series have investigated the incidence of vascular complications of NF1, and most of them have used MRI. We suggest adding MRA to the brain imaging of all these patients, as stenoses of the branches of the Circle of Willis are often undetectable by MRI only.

Time spatial labeling inversion pulse magnetic resonance angiography in pregnancy with adenomyosis

Time spatial labeling inversion pulse (Time-SLIP) is a non-contrast magnetic resonance angiography (MRA) technique. No cases in which this technique was used during pregnancy have been reported. We report herein two cases with adenomyosis of the same size and location that underwent Time-SLIP MRA during pregnancy. In case 1, the blood flow within the adenomyosis was poor, and the uterine blood flow toward the placenta was normal, resulting in no fetal growth restriction (FGR). In case 2, the blood flow within the adenomyosis was quite rich, and placental blood flow seemed decreased, resulting in severe FGR. As well as the Doppler ultrasonography, Time-SLIP MRA was useful for evaluating uterine blood flow during pregnancy. This is the first report of the use of Time-SLIP MRA during pregnancy.

Surgical embolectomy for large vessel occlusion of anterior circulation

Object. The aim of this study was to assess the technical details and the efficacy and safety of surgical embolectomy for occlusion of large vessels in the anterior circulation. Methods. Twenty-three consecutive patients with acute ischemic stroke attributed to embolic occlusion of large arteries of the anterior circulation who underwent treatment with surgical embolectomy were retrospectively reviewed. Twenty patients were treated based on data from magnetic resonance angiography (MRA)–diffusion weighted imaging (DWI) mismatch, while three other patients had contraindications to magnetic resonance imaging (MRI) and were treated based on computed tomography (CT) and digital subtraction angiography (DSA) findings. Clinical outcomes, including recanalization rate, recanalization time, complications, modified Rankin Scale (mRS) at 3 months, and National Institute of Health Stroke Scale (NIHSS) score improvement at 1 month, were evaluated. Results. Among the 23 patients (median age, 80 years; median presenting NIHSS score, 21 points), the occlusion site was the internal carotid artery (ICA) terminus in six patients, the M1 segment of the middle cerebral artery (MCA) in 10 patients, and the M2 division of the MCA in seven patients. Final recanalization status was thrombolysis in myocardial infarction (TIMI) 3 in 21 patients (91%). Median recanalization time from symptom onset and from start of surgery was 282 min and 70 min, respectively. One patient (4.3%) had symptomatic haemorrhage. Three patients (13%) had brain oedema due to massive infarction of affected vessel area; two of these patients had undergone embolectomy based on CT findings and had successful recanalization, while one patient underwent embolectomy based on MRI findings and did not have successful recanalization. All 18 patients who underwent embolectomy based on MRA–DWI mismatch and had successful recanalization did not develop additional confluent ischaemic lesion on postoperative DWI. At 3 months, seven patients (30%) had a mRS score of 0–2, eight patients (35%) had a mRS score of 3, and none of the patients had died. Sixteen patients (70%) demonstrated NIHSS score improvement of more than eight points at 1 month. Conclusion. Surgical embolectomy for occlusion of large vessels in the anterior circulation resulted in a high complete recanalization rate with an acceptable safety profile. Use of MRA–DWI mismatch as an indication for surgical embolectomy was associated with a reduced complication rate.

Magnetic Resonance Angiography Evidence of Vasospasm in Children With Suspected Acute Hemiplegic Migraine

Hemiplegic migraine is a rare subtype of migraine that is differentiated by motor weakness in the aura phase. The purpose of this case series was to examine the magnetic resonance angiogram findings of patients suffering from suspected acute hemiplegic migraine. This was a retrospective institutional board review protocol study of 8 patients. All patients received full brain magnetic resonance imaging under a 1.5-T magnet. The scans were subsequently evaluated by a neuroradiologist and 2 neurologists who were blinded to the study. The magnetic resonance angiogram findings of this study showed the presence of vasospasm within the intracranial vasculature during suspected acute hemiplegic migraine. This case series suggests that routine use of magnetic resonance angiography might be beneficial in both managing patients with acute hemiplegic migraine and helping to further understand the pathophysiology of this complicated disease process.

Multimodality Imaging of Lower Extremity Peripheral Arterial Disease

Patients with symptomatic peripheral arterial disease (PAD) affecting the lower extremities are initially evaluated with an ankle-brachial index (ABI) and segmental pressure measurements. An ABI 50% stenosis) with a sensitivity and specificity of 79% and 96%, respectively.1 An ABI between 0.90 and 1.0 is considered borderline. The localization of the stenosis can be inferred by an abnormal decrease (>20 mm Hg) in segmental lower extremity pressures. In the presence of calcified atherosclerosis, arteries may become stiff and noncompressible, which results in a falsely elevated ABI (often >1.3). For patients with suspected PAD and a normal ABI at rest, it is valuable to obtain postexercise ABI measurements, which if <0.85 are consistent with PAD and is an independent predictor of mortality.2 Imaging is then needed to confirm the location and degree of stenosis before revascularization or if the diagnosis of PAD is uncertain. Characterization of PAD can be performed with noninvasive angiography using computed tomography (CTA) or magnetic resonance angiography (MRA), as well as with duplex ultrasonography (US), depending on patient specific characteristics (Table 1). Advances in both CTA and MRA provide clinicians with the opportunity to obtain a high resolution, 3-dimensional (3-D) road map of the peripheral arterial tree in patients, particularly when planning revascularization strategies. Invasive digital subtraction angiography (DSA) has been the accepted standard for evaluation of lower extremity atherosclerosis. Although DSA is a robust technique for diagnosing significant arterial stenosis or obstruction, it provides a 2-D view of the vessels, which may underestimate the degree of stenosis for tortuous vessels.3 Furthermore, there are inherent risks with arterial access, ionizing radiation, and the use of iodinated contrast media (CM).4 View this table: Table 1. Comparison Between CTA, MRA, and Duplex US for Diagnosis of PAD This review aims to deliver a comprehensive, yet concise …

Advances in CT and MR Technology

This article will review recent advances in computed tomography (CT) and magnetic resonance (MR) hardware and software techniques that have dramatically changed the use of CT and MR angiography. For CT angiography, technology has increased the speed of acquisition, reduced the radiation dose necessary to diagnose disease, and simplified the ability to characterize disease. Similarly, advances in MR angiography have focused on safer techniques that do not require the use of intravenous contrast agents, increased the speed of acquisition, and improved spatial resolution. In addition, new MR angiography methods have expanded the use of MR angiography beyond purely anatomical information toward quantitative hemodynamic analyses.

Additional Endovascular Therapy in Patients with Acute Ischemic Stroke Who Are Nonresponsive to Intravenous Tissue Plasminogen Activator: Usefulness of Magnetic Resonance Angiography–Diffusion Mismatch

In patients who are not responsive to intravenous tissue plasminogen activator (IV t-PA), the present study aimed to report recanalization rates, the incidence of hemorrhagic transformation (HT), and clinical outcomes of additional endovascular therapy (AET), and to investigate the usefulness of magnetic resonance angiography-diffusion mismatch (MDM) in a selection of patients eligible for AET. Fifty-eight patients who received IV t-PA therapy because of intracranial major artery occlusion between April 2007 and November 2010 were divided into 2 groups: 18 patients in the AET group and 21 patients in the IV t-PA nonresponders group. The remaining 19 patients were responders to IV t-PA and therefore not eligible for this study. Recanalization rates, HT incidence, and 3-month outcomes were assessed, and the relationship between MDM and clinical outcome was examined. A 3-month modified Rankin Scale (mRS) score of 0 to 3 was seen more frequently in the AET group (72% in the AET group v 29% in the nonresponder group; P = .01). Serious outcomes (3-month mRS of 5-6) were seen significantly less often in the AET group (17%) than in the nonresponder group (57%; P = .019). There were no differences in the incidence of HT. In the AET group, reappraisal considering MDM revealed a significantly higher rate of a 3-month mRS of 0 to 3 in the MDM-positive group compared to the MDM-negative group (86% v 25%, respectively; P = .044). Serious outcomes were observed significantly less frequently in the MDM-positive group compared to the MDM-negative group (0% v 75%, respectively; P = .005). AET for nonresponders to IV t-PA was safe, improved recanalization rates, and led to better prognoses. MDM was a very good predictor of improved prognosis in a selection of eligible patients for AET after IV t-PA.

Abstract No. 412: MRA as a problem-solving tool for identifying and classifying endoleak after EVAR

Review indications, imaging findings, and MR techniques to perform magnetic resonance angiography (MRA) for the evaluation of endoleak (EL) after EVAR. Endovascular repair of aortic aneurysms is increasingly common. Lifetime imaging surveillance is recommended, and EL and continued sac growth are potential issues. Although CTA is the mainstay in EVAR surveillance in our practice, MRA is useful for identifying subtle leaks not detected or well-characterized with CTA. Time-resolved (dynamic) MRA further increases diagnostic accuracy when compared to static MRA by frequently enabling EL-type assessment (15 vs 9, n=23 [65 vs 40%]). Recently TR-MRA has been shown comparable to gold standard DSA for classification of EL type (97% n=30/31), and remains more sensitive than CTA. In our practice, CE-MRA is often performed when routine three-phase CTA (non-contrast, arterial, and delayed) fails to demonstrate the etiology of an expanding, excluded aneurysm sac during EVAR surveillance. We will review potential advantages both of view-shared and non-view-shared TR-MRA with newer contrast agents and parallel imaging techniques and highlight successful use of MRA for endoleak detection, characterization, and treatment planning through clinical examples. 1MRA is extremely helpful for detecting and characterizing endoleaks which are not well seen on CTA.2Higher contrast-to-background ratio, very high combined spatial and temporal resolution, and ability to obtain multiple time-points without exposing the patient to increased ionizing radiation are factors which give MRA an advantage over CTA for detecting and characterizing endoleaks.3MRA should be considered as a first-line or second-line test for problem solving in patients for whom CTA does not provide a definitive diagnosis.

Brain magnetic resonance angiography in splenectomized adults with β-thalassemia intermedia

Hypercoagulability and venous thromboembolism are common in patients with β-thalassemia intermedia (TI), especially in the splenectomized adult. Although arterial involvement is not commonly reported, we have recently observed a high prevalence (60%) of silent brain infarction on brain MRI in 30 splenectomized adults with TI. The pathophysiology of these white matter lesions remains unknown. In this prospective work, we evaluated magnetic resonance angiography (MRA) scans of the same cohort of 30 patients. Data collected were the presence or absence of vascular lesions, their locations, and severity. Correlations between MRA abnormality and patients/disease characteristics were evaluated. Comparisons between MRA and previous MRI findings were made. Of 29 evaluable patients, 8 (27.6%) had evidence of arterial stenosis on MRA. The majority of lesions had mild narrowing and mostly involved the internal carotid artery. Five patients (17.2%) had evidence of aneurysms. Low total hemoglobin and high non-transferrin-bound iron levels independently characterized patients with evidence of stenosis on MRA. Among the 18 patients with silent brain infarction on MRI, three had evidence of stenosis on MRA with only one patient having lesions that could explain the silent infarcts. Cerebral vasculopathy is common in splenectomized adults with TI. However, large-vessel disease does not explain the occurrence of silent brain infarction. The combined use of MRA and MRI better identifies splenectomized TI adults with neuroimaging abnormalities.

Ferumoxytol Use as an Intravenous Contrast Agent for Magnetic Resonance Angiography

To evaluate the efficacy and safety of ferumoxytol for use in magnetic resonance angiography (MRA) of the vasculature. Literature was accessed through MEDLINE (1946-September 2011) and EMBASE (1947-September 2011) using the terms ferumoxytol, magnetic resonance imaging and angiography, blood pool agent, and superparamagnetic iron oxide. Reference citations from identified publications were reviewed for relevant information. All English-language articles and human studies (N = 9) were identified that evaluated ferumoxytol use in magnetic resonance imaging (MRI). Articles that evaluated the use of the drug in first-pass and equilibrium phase imaging of the vasculature were included (n = 4). Contrast agents for MRI improve disease characterization and diagnosis. Ferumoxytol, a medication approved for treatment of iron deficiency anemia in adults with chronic kidney disease, has superparamagnetic properties. As a blood pool agent, ferumoxytol remains primarily in the intravascular space. Therefore, its use in MRI may increase image sensitivity and specificity and have a decreased adverse effect profile compared to other contrast agents. Specifically, ferumoxytol may be an option for MRA, a specific type of MRI that images blood vessels. In the 4 studies evaluated here, ferumoxytol was administered primarily to healthy adults as an accumulative dose of 4 mg Fe/kg injected at 1 mL/sec. Not all studies reported adverse events and addressed safety monitoring. The evaluated studies are limited by small size, open-label design, and noncomparative methodology. Data from small pilot studies suggest that ferumoxytol may improve image quality in MRA; however, further investigation is necessary to establish its efficacy and safety. Large randomized, active-comparator trials are needed to establish optimal dosing, imaging procedures, and safety monitoring.

Classification of persistent primitive trigeminal artery (PPTA): a reconsideration based on MRA

Persistent primitive trigeminal artery (PPTA) is the most common permanent carotid-basilar anastomosis. Magnetic resonance angiography (MRA) has become the primary non-invasive imaging technique for evaluation of cerebral vascular anatomy and can provide detailed 3D imaging of intracranial vessels. To evaluate the usefulness of MRA for the detection of PPTA and to re-classify its variations based on the embryologic types of PcomA and its relationship with the basilar artery and its branches. Of the total 7329 patients who underwent MRA at our institution from March 2008 through November 2010, we retrospectively analyzed the MRAs of 24 patients with a PPTA. Special attention was given to defining the relationship of the PPTA and the basilar artery with PcomA and to determine the site of origin, size, and course of the PPTA. The PPTA classification included five types based on their anatomic relationship to the neighboring arteries. Clinical features and associated vascular anomalies are also described. Twenty-four (17 women and seven men, 34 ~ 81 years of age, mean age 59.67 years) of the 7329 patients had a PPTA (0.33 %). Eleven cases (45.8%) were classified as type 1, three (12.5%) as type 2, five (20.8%) as type 3, one (4.2%) as type 4, and four (16.7%) as type 5b. Fifteen PPTAs (62.5%) were located on the left side and nine were located (37.5%) on the right side. The basilar artery proximal to the insertion of the PPTA showed severe to moderate hypoplasia in 13 cases (54%). Nine intracranial artery aneurysms were detected in seven (29%) of the 24 study patients. This study revealed five types of PPTA and necessitates an adjustment of the previous classification of PPTA on the basis of our MRA examinations. A PPTA should be considered by both the clinician and the radiologist who interpret MR angiography.

Magnetic Resonance Angiography in the Management of Recurrent Hemarthrosis After Total Knee Arthroplasty

Spontaneous hemarthrosis is an infrequent but disabling complication after total knee arthroplasty. The purpose of this case series is to demonstrate the utility of magnetic resonance angiography (MRA) in the evaluation of hemarthrosis after total knee arthroplasty. Patients presenting with hemarthrosis unexplained by trauma, anticoagulation, or a bleeding diathesis were retrospectively identified. Eighteen patients were referred for MRA to evaluate recurrent hemarthrosis after failing conservative therapy (n = 16) or synovectomy (n = 2). Despite artifact caused by the metallic components, diagnostic evaluation of regional vessels was made. In 12 of 13 cases that underwent embolization or synovectomy, a hypertrophic feeding artery (or arteries) was visualized on MRA. One case of negative MRA did not have subsequent surgery, and we are unable to comment on the rate of false-positives because all patients in this case series had evidence of bleeding. By characterizing the vascular anatomy and identifying a dominant artery (or arteries) supplying the hypervascular synovium, MRA can serve as a guide for subsequent embolization or synovectomy, as indicated.

Geographic Variation and Trends in Carotid Imaging Among Medicare Beneficiaries, 2001 to 2006

Diagnostic imaging among Medicare beneficiaries is an important contributor to rising health care costs. We examined temporal trends and geographic variation in the use of carotid ultrasound, carotid magnetic resonance angiography (MRA), and carotid x-ray angiography. Analysis of a 5% national sample of claims from the Centers for Medicare and Medicaid Services for 1999 through 2006. Patients were 65 years or older and underwent carotid ultrasound, carotid MRA, carotid x-ray angiography, or a carotid intervention. The main outcome measures were annual age-adjusted rates of carotid imaging and interventions and factors associated with the use of carotid imaging. Rates of imaging increased by 27%, from 98.2 per 1000 person-years in 2001 to 124.3 per 1000 in 2006. Rates of carotid ultrasound increased by 23%, and rates of MRA increased by 66%. Carotid intervention rates decreased from 3.6 per 1000 person-years in 2001 to 3.1 per 1000 person-years in 2006. In 2006, rates of carotid ultrasound were lowest in the New England, Mountain, and West North Central regions and highest in the Middle Atlantic and South Atlantic regions. Regional differences persisted after adjustment for patient demographic characteristics, history of vascular disease and other comorbid conditions, and study year. From 2001 through 2006, there was substantial growth and variation in the use of carotid imaging, including a marked increase in the use of MRA, and a decrease in the overall rate of carotid intervention.

Dynamic Internal Carotid Artery Dissection Demonstrated by Carotid Duplex Ultrasound

Background Carotid artery dissection is an important cause of stroke in young adults. Because warning signs usually precede stroke, the timely diagnosis of carotid dissection can have a significant clinical impact. We present a case of spontaneous carotid artery dissection with dynamic findings on duplex ultrasound examination. Case Report A 47-year-old man presented with acute neurologic symptoms. Carotid duplex ultrasound demonstrated a high resistive waveform in the right internal carotid artery (RICA) with absent end-diastolic flow (peak-systolic velocity [PSV] = 49 cm/sec, end-diastolic velocity = 0 cm/sec), a narrowing of the lumen in the distal RICA with low velocity flow (PSV = 10 cm/sec), and eventual loss of flow. The right common carotid artery demonstrated a high resistive waveform. The use of magnetic resonance angiography confirmed the presence of distal RICA dissection. The patient was treated with antiplatelet therapy and had marked clinical improvement within 48 hours. A duplex ultrasound study performed 24 hours after the first study demonstrated dramatic restoration of the diastolic flow in the RICA (PSV = 97 cm/sec, EDV = 44 cm/sec) with normalization of the Doppler waveforms. Repeat magnetic resonance angiography demonstrated near complete resolution of the RICA dissection, correlating with the ultrasound findings. Conclusion Our case demonstrates the potentially dynamic nature of carotid artery dissection and the utility of duplex ultrasound as an invaluable tool in the early diagnosis and management of this disorder. In addition, the case demonstrates the importance of carotid Doppler waveform clues as indirect evidence of more distal cerebrovascular disease that warrants further investigation.

Investigation of childhood central nervous system vasculitis: magnetic resonance angiography versus catheter cerebral angiography

We compared the clinical utility of magnetic resonance angiography (MRA) to catheter cerebral angiography (CA) in the investigation of children with suspected central nervous system (CNS) vasculitis. Single-centre retrospective review of children with a suspected diagnosis of CNS vasculitis studied with both MRA and CA. MRA and CA-detected abnormalities (location, multiplicity, and morphology) were compared; sensitivity and specificity were calculated on a per lesion and per patient basis for MRA, with CA as the reference standard. Findings in fourteen patients (median age at presentation of 5 y 10 mo [range 1 y 5 mo-14 y 5 mo]; eight males, six females) relating to sixteen paired studies of MRA and CA were reviewed. CA-detected lesions were commonly bilateral (13/16 studies, p<0.05), and likely to be proximally distributed (15/16 studies, p<0.05).The sensitivity and specificity of MRA for CA lesion detection was 63% (95% confidence interval [CI] 48-78) and 89% (95% CI 81-93), respectively with moderate agreement between the two modalities (kappa=0.51, 95% CI 0.37-0.66). The majority of the false negative observations involved the posterior circulation (9/14). The overall sensitivity for MRA diagnosis of vasculitis per patient was 94% (95% CI 67-99). MRA failed to identify all lesions detected on CA, particularly those in the posterior circulation. MRA is a reasonable initial modality in the investigation of suspected CNS vasculitis but in cases of abnormal parenchymal MRI and normal MRA, CA should be considered.

ORIGINAL ARTICLE: Retrospective audit of the investigation of patients with suspected acute subarachnoid haemorrhage

AbstractIntroduction: Recommended investigational care (RIC) of emergency department (ED) patients with suspected subarachnoid haemorrhage comprises lumbar puncture (LP) to detect xanthochromia if the preceding CT scan is negative.Methods: Retrospective audit of the investigational care of 100 consecutive ED patients presenting with possible subarachnoid haemorrhage.Results: Of the 100 patients, 91 had negative CT, and 36 (39.6%) of these patients had an LP performed to detect xanthochromia (i.e. RIC). Fifty‐five of 91 (60.4%) patients did not receive RIC.Of the 55 patients who did not receive RIC, 25 (45.5%) had a documented senior clinical decision not to perform an LP; 15 (27.3%) had no documented reason; five (9.1%) refused consent; two (3.6%) had an LP but no xanthochromia requested, one patient did not have an LP because of technical issues, six patients underwent CT angiography (CTA), and one patient underwent magnetic resonance angiography (MRA), in the absence of a LP, following a negative CT. Two patients underwent CTA following a negative xanthochromia result. Patients admitted to the emergency extended care unit had 6.85 times the odds of receiving RIC (95% CI 2.20–21.4).Conclusions: Fifty‐five (55) of 91 (60%) ED patients did not receive RIC. Fifteen of the 55 did not have any documented justification for not performing an LP with xanthochromia testing. Admission to an emergency extended care unit was a predictor of receiving RIC. Inappropriate use of CTA and MRA was identified. These findings have important implications for patient safety. Multifaceted strategies are required to close this evidence–practice gap.

DISTAL ABDOMINAL AORTIC THROMBOSIS DIAGNOSED BY THREE‐DIMENSIONAL CONTRAST‐ENHANCED MAGNETIC RESONANCE ANGIOGRAPHY

Contrast enhanced magnetic resonance angiography (MRA) can provide noninvasive relatively rapid three-dimensional high-detailed vascular images over large anatomic areas. There are few descriptions of the use of contrast-enhanced MRA in veterinary patients. This is a report illustrating the use of contrast-enhanced MRA to localize the full extent of distal aortic, external iliac, and femoral artery thrombi confirmed surgically in four dogs. Distal aorta contrast-enhanced MRA was anatomically accurate in detecting the full extent of thrombi involving the aorta, external iliac and femoral arteries in these four canine patients. This procedure can provide important information for surgery.

Use of Magnetic Resonance Angiography to Predict Long-Term Outcomes of Ischemic Stroke Patients with Concurrent Stenoses in Hong Kong

Purpose: To determine the long-term outcome of ischemic stroke patients with concurrent intracranial and extracranial atherosclerosis using magnetic resonance angiography. Methods: A prospective cohort of patients in Hong Kong with acute ischemic stroke was studied with magnetic resonance angiography of the brain and carotid duplex. All patients were followed up regularly for the development of recurrent stroke, cardiac events, or death. Results: Totally 343 patients with acute ischemic stroke were included, of whom 104 (30%) had concurrent intracranial and extracranial lesions. The follow-up period was up to 76 months (mean 44.5 months). Overall, 55 patients (15.5%) died of any cause and 91 patients (26.5%) suffered a further nonfatal vascular event. The overall 5-year cumulative rates of mortality, restroke and poor outcomes (combined death and further vascular events) were 18, 27 and 37%, respectively. In patients with concurrent lesions, these rates were 31, 41 and 51%, respectively. The corresponding rates were 13, 22 and 31% in patients without concurrent lesions. The risks were highest in the first year after stroke. More deaths (log rank, 16.3; p = 0.0001), restrokes (log rank, 9.71; p = 0.002) and poor outcomes (log rank, 13.87; p = 0.0001) were found among patients with concurrent lesions. The presence of concurrent vascular lesions, advanced age, smoking, hyperlipidemia and previous history of stroke were independent predictors of poor outcomes. Conclusions: The long-term prognosis of ischemic stroke patients with concurrent atherosclerosis of intracranial and extracranial vessels is poor. They are at high risk of further vascular events or death.

OBLITERATION DYNAMICS IN CEREBRAL ARTERIOVENOUS MALFORMATIONS AFTER CYBERKNIFE RADIOSURGERY

To investigate the time-dependent obliteration of cerebral arteriovenous malformations (cAVM) after CyberKnife radiosurgery (CKRS) (Accuray, Inc., Sunnyvale, CA) by means of sequential 3-T, 3-dimensional (3D), time-of-flight (TOF) magnetic resonance angiography (MRA), and volumetry of the arteriovenous malformation (AVM) nidus. In this prospective study, 3D TOF MRA was performed on 20 patients with cAVMs treated by single-fraction CKRS. Three-dimensional TOF MRA was performed on a 3-T, 32-channel magnetic resonance scanner (Magnetom TIM Trio; Siemens Medical Solutions, Erlangen, Germany) with isotropic voxel size at a spatial resolution of 0.6 x 0.6 x 0.6 mm3. The time-dependent relative decay of the transnidal blood flow evidenced by 3D TOF MRA was referred to as "obliteration dynamics." Volumetry of the nidus size was performed with OsiriX imaging software (OsiriX Foundation, Geneva, Switzerland). All patients had 3 to 4 follow-up examinations at 3- to 6-month intervals over a minimum follow-up period of 9 months. Subtotal obliteration was determined if the residual nidus volume was 5% or less of the initial nidus volume. Stata/IC software (Version 10.0; Stata Corp., College Station, TX) was used for statistical analysis and to identify potential factors of AVM obliteration. Regarding their clinical status, case history, and pretreatments, the participants of this study represent difficult-to-treat cAVM patients. The median nidus volume was 1.8 mL (range, 0.4-12.5 mL); the median minimum dose prescribed to the nidus was 22 Gy (range, 16-24 Gy) delivered to the 67% isodose line (range, 55-80%). CKRS was well tolerated, with complications in 2 patients. No further hemorrhages occurred after RS, except 1 small and clinically inapparent incident. The median follow-up period after RS was 25.0 months (range, 11.7-36.8 months). After RS, a statistically significant obliteration was observed in all patients. However, the obliteration dynamics of the cAVMs showed a pronounced variability, with 2 types of post-therapeutic behavior identified. cAVMs of Group A showed a faster reduction of transnidal blood flow than cAVMs in Group B. The median time to subtotal obliteration was 23.8 months for all patients, 11.6 months for patients in Group A, and 27.8 months for patients in Group B (P = 0.05). Logistic regression analysis revealed dose homogeneity and the circumscribed isodose to be the only variables (P < 0.01) associated with the obliteration dynamics in this study. The cumulative complete angiographic obliteration rate was 67% (95% confidence interval, 32-95%) 2 years after RS. The use of sequential 3D TOF MRA at 3 T and nidus volumetry enables a noninvasive quantitative assessment of the dynamic obliteration process induced by CKRS in cAVMs. This method may be helpful to identify factors related to AVM obliteration after RS when larger patient cohorts become available.