Cerebral hemodynamics in Moyamoya disease: correlation between perfusion-weighted MR imaging and cerebral angiography

BACKGROUND AND PURPOSE: In Moyamoya disease, the relationship between cerebral hemodynamics and angiographic findings has not been fully evaluated. The purpose of this study is to evaluate hemodynamics in Moyamoya disease with perfusion-weighted MR imaging (PWI) and cerebral angiography. METHODS: Twenty patients with Moyamoya disease were the subjects. Mean transit time (MTT) derived from PWI was calculated in the medial frontal lobes, the posterior frontal lobes, the occipital lobes, and the basal ganglia. From the angiographies, we classified the degrees of internal carotid artery (ICA) and posterior cerebral artery (PCA) stenoses as well as the degrees of Moyamoya vessels and leptomeningeal anastomosis (LMA). MTT in each region was compared with the angiographic findings. RESULTS: MTT positively correlated with the degree of ICA stenosis in the medial frontal (P < .01), posterior frontal (P < .001), and occipital (P < .001) lobes, as well as in the basal ganglia (P < .001). MTT correlated with the degree of PCA stenosis in the medial frontal (P < .001), posterior frontal (P < .001), and occipital (P < .001) lobes, as well as in the basal ganglia (P < .001). MTT correlated with the degree of Moyamoya vessels in the medial frontal (P < .05) and posterior frontal (P < .01) lobes. A multivariate analysis revealed that ICA and PCA stenoses and Moyamoya vessels were independent factors that prolonged MTT. CONCLUSION: Both ICA and PCA stenoses may influence overall cerebral perfusion in Moyamoya disease. The development of Moyamoya vessels may indicate hemodynamic impairment.     

Proton MR spectroscopy in acute middle cerebral artery stroke.

PURPOSETo investigate the feasibility of performing multisection proton MR spectroscopy in patients with acute stroke, and to determine whether this imaging technique can depict ischemic or infarcted brain regions.METHODSMultisection proton MR spectroscopy, MR imaging, and MR angiography were performed within 24 hours of stroke onset (mean, 12 hours) in 12 patients who had had a stroke of the middle cerebral artery. Spectra were analyzed from brain regions containing T2 hyperintensity abnormalities on MR images, from regions immediately adjacent to these abnormalities, and from anatomically similar contralateral regions. Areas of brain containing lactate were compared with areas of T2 hyperintensities on MR images.RESULTSOne data set was discarded because of excessive artifacts from patient motion. Regions of T2 hyperintensities on MR images were found to contain elevated lactate (all 11 cases) and reduced N-acetyl-aspartate (10 of 11 cases) relative to contralateral measurements. Lactate levels in regions adjacent to T2 hyperintensities were not significantly different from those of infarcted brain. On the other hand, N-acetyl-aspartate was significantly lower in regions of infarction compared with periinfarct tissue. Areas of brain containing elevated lactate significantly exceeded those of T2 abnormality.CONCLUSIONSProton MR spectroscopy is feasible for imaging patients with acute stroke. In the early stages of stroke, tissue containing elevated lactate but no other spectroscopic or MR imaging abnormality can be identified. Such regions may represent an ischemic zone at risk of infarction.     

Vessel enhancement filtering in three-dimensional MR angiography

For a variety of reasons, small vessels have low signal intensity in magnetic resonance angiography. When the vessel signal Intensity is lower than the signal intensity of background tissues, these vessels tend not to be visible on maximum-intensity-projection images. The authors developed a nonlinear second-difference spatial filtering technique that enhances the details of small vessels while suppressing both noise and uniform background tissue. Two similar nonlinear second-difference filters are presented and compared with the linear Laplacian second-difference filter. To evaluate the performance of these filters, they were applied to intracranial three-dimensional time-of-night MR angiographic data and the results compared with the vessel enhancement obtained with a simple second-difference Laplacian filter and with magnetization transfer contrast (MTC) techniques. The comparisons demonstrated that nonlinear filtering and MTC techniques result in similar improvement in small-vessel visibility and apparent continuity. A quantitative comparison demonstrated that the improvement in the contrast-to-noise ratio is much greater with the nonlinear filters than the Laplacian filter.     

Vessel enhancement filtering in three-dimensional MR angiography

For a variety of reasons, small vessels have low signal Intensity in magnetic resonance angiography. When the vessel signal intensity is lower than the signal intensity of background tissues, these vessels tend not to be visible on maximum-intensity-projection images. The authors developed a nonlinear second-difference spatial filtering technique that enhances the details of small vessels while suppressing both noise and uniform background tissue. Two similar nonlinear second-difference filters are presented and compared with the linear Laplacian second-difference filter. To evaluate the performance of these filters, they were applied to intracranial three-dimensional time-of-flight MR angiographic data and the results compared with the vessel enhancement obtained with a simple second-difference Laplacian filter and with magnetization transfer contrast (MTC) techniques. The comparisons demonstrated that nonlinear filtering and MTC techniques result in similar Improvement in small-vessel visibility and apparent continuity. A quantitative comparison demonstrated that the improvement in the contrast-to-noise ratio is much greater with the nonlinear filters than the Laplacian filter.     

MR imaging enhancement patterns as predictors of hemorrhagic transformation in acute ischemic stroke

BACKGROUND AND PURPOSE: Early parenchymal gadolinium enhancement on T1-weighted MR images is predictive of hemorrhagic transformation (HT) in rodent focal ischemia models, but its value in humans is unknown. We sought to investigate gadolinium enhancement in acute ischemic stroke patients to determine their association with subsequent HT. METHODS: We retrospectively examined 22 patients with ischemic stroke who underwent MR imaging within 4.9 hours (+/-1.4) of symptom onset. Patients receiving intravenous tissue plasminogen activator (tPA) (n = 6) were included. Twenty-one patients underwent repeat MR studies at 48 hours, 13 underwent additional MR imaging at 1 week, and one underwent follow-up head CT at 24 hours. Initial images were analyzed for enhancement patterns (vascular, meningeal, parenchymal). Follow-up T2- and T2*-weighted images were evaluated for hemorrhage. RESULTS: In all patients, initial MR images showed vascular enhancement in the vascular territory of the stroke lesion: 19 with vascular enhancement alone and three with vascular and parenchymal enhancement. All three patients with both enhancement patterns had HT: two large and symptomatic, and one asymptomatic (petechial hemorrhage). They received tPA before MR imaging. None of the patients without early parenchymal enhancement developed symptomatic hemorrhage. Six (32%) patients with vascular enhancement alone had petechial hemorrhage at follow-up imaging. In this limited sample, initial mean volumes on diffusion-weighted images, National Institute of Health Stroke Scale scores, and intervals from stroke onset to imaging did not differ between patients with vascular and parenchymal enhancement versus those with vascular enhancement alone. CONCLUSION: Early parenchymal enhancement of stroke lesions may be a good predictor of subsequent symptomatic HT may help identify patients at risk, especially after thrombolytic therapy.     

MR and MR angiography characterization of soft tissue vascular malformations

Hemangioma is an abnormal proliferation of blood vessels that may occur in any vascularized tissue. Different classifications separate vascular lesions of soft tissues into hemangiomas and vascular malformations on the basis of their natural history, location, cellular turnover, and histology. Soft-tissue vascular malformations are relatively common. These lesions can be categorized on MR imaging because of their typical appearance as multiple lobules with fat overgrowth and serpentine channels, depending on the vascular flow. The combination of conventional MR and MR angiography (MRA) enable the differentiation between low-flow and high-flow vascular malformations and allows a noninvasive diagnostic strategy. This article reviews the MR and MRA imaging characteristics of soft-tissue hemangiomas to provide a helpful guide for radiologists to perform a more specific diagnosis and better management of these anomalies.     

急性脑卒中后脑心综合征124例临床分析

目的探讨急性脑卒中后脑心综合征（CCS）的发病率、临床特点、发病机制、防治措施及预后。方法对124例急性脑卒中后脑心综合征患者入院后作心电图（ECG）,心肌酶谱动态观察并结合临床资料进行回顾性分析。结果CCS发生率23．8％,95．2％的患者于脑卒中后数小时至1w内发生,出血性脑卒中CCS发生率远高于缺血性脑卒中（P〈0．01）,位于脑叶的急性啮卒中其CCS的发生率明显低于脑干、丘脑及蛛网膜下腔发生率（P〈0．01）。CCS心电图主要表现为心律失常、心肌缺血和类心肌梗死;心肌酶谱异常率为38．7％,合并低钾血症和（或）低钠血症占28．2％。病死率为20．2％,主要死亡原因为心律失常及心功能衰竭。结论CCS发生与脑卒中类型及部位、低血钾、低血钠等因素有关。死亡原因以心律失常及心功能衰竭为主,发病机制可能为脑卒中直接或间接导致神经体液功能紊乱有关,脑卒中患者须加强心脏功能监护,积极防治脑心综合征。     

急性缺血性脑卒中严重程度与血清sCD40L、PAF相关性研究

目的测定急性缺血性脑卒中患者血可溶性CD40配体(sCD40L)、血小板活化因子(PAF)水平,观察这两个指标与NIHSS评分之间的关系。方法收集经临床及影像学诊断为急性缺血性脑卒中患者50例及正常对照组20例的临床资料,检测其周围血sCD40L、PAF水平,并与入院时NIHSS评分分别作相关性分析。结果急性缺血性脑卒中患者的血sCD40L、PAF水平明显高于正常对照组,且这两种指标的水平与NIHSS评分呈显著正相关,sCD40L与NIHSS评分相关性更大。结论检测血sCD40L、PAF水平可从一定程度上反映急性缺血性脑卒中的严重程度,     

MR angiography of spinal vascular malformations.

PURPOSETo determine the potential and limitations of MR angiography in the evaluation of spinal vascular malformations.METHODSEleven consecutive patients with spinal vascular malformations proved with spinal selective arteriography underwent two-dimensional phase-contrast MR angiography.RESULTSAbnormal vessels within the spinal canal were identified with MR angiography in 10 patients. In 1 patient with a dural arteriovenous fistula no definite vascular abnormality was seen with MR angiography. Correlation of MR angiography with spinal selective arteriography showed that the former allowed identification of the arterial feeder in 3 patients with intramedullary arteriovenous malformations and 2 with perimedullary arteriovenous fistula, whereas the source of intradural draining vein was seen in only 2 of 6 patients with dural arteriovenous fistula.CONCLUSIONMR angiography is a promising complementary tool to MR imaging for detection and characterization of spinal vascular malformations.     

MR angiography in children with cerebral neurovascular diseases: findings in 31 cases.

OBJECTIVE. We evaluated the suitability of MR angiography for routine use in children with suspected intracranial vascular disease. SUBJECTS AND METHODS. Thirty-one children, 6 months to 14 years old, with intracranial lesions or clinically suspected vascular malformations were studied prospectively with conventional MR imaging and time-of-flight MR angiography. In nine cases, MR angiographic findings were verified with digital subtraction angiography or conventional angiography. All MR studies were performed on a 1.5-T MR system using a circularly polarized head coil. RESULTS. Arterial MR angiography, performed in 24 cases, revealed congenital abnormalities of the arterial vessels in 20 cases. Vessel stenosis was observed in nine patients, and displacement of intracranial arteries due to tumors could be seen in 10 patients. Seven children had no abnormal findings. Venous MR angiography was performed in seven children, with depiction of sinus thrombosis in six cases. The comparative analysis of MR angiography and digital subtraction angiography showed equivalent results in nine patients; in one patient the degree of stenosis was overestimated with MR angiography. CONCLUSION. MR angiography, when combined with MR imaging, reveals information about soft-tissue and vascular structures in a single setting. At this point, MR angiography can replace invasive conventional angiography or digital subtraction angiography only in selected cases because of software and hardware limitations. Arterial or venous MR angiography can be helpful as an additional scan in MR examinations of children with suspected cerebral neurovascular diseases, and its noninvasive nature makes it well suited for routine use in children.     

造影增强MR血管成像对急性缺血性中风患者血管状况的评估价值

目的:探讨CE-MRA在急性缺血性中风患者血管状况评估中的可行性。方法:27例大脑中动脉供血区急性缺血性中风患者在发病后6h内进行了TOF-MRA和CE-MRA检查,根据随访结果,对TOF-MRA和CE-MRA在急性缺血性中风患者血管状况的评估价值进行了对比分析。结果:①在27例患者中,有11例患者在TOF-MRA上表现为大脑中动脉完全闭塞而在CE-MRA上仍可见残余血流,随访结果与CE-MRA结果一致;②CE-MRA的扫描时间明显短于TOF-MRA;③CE-MRA可以在不增加扫描时间的情况下对颈部动脉和颅内动脉同时成像。结论:CE-MRA能够及时、准确地对急性缺血性中风患者血管状况进行评估,优于常规的TOF-MRA,由于急性缺血性中风患者需要紧急处理,在应用MR评估血管状况时CE-MRA应为首选。     

Intracranial vascular stenosis and occlusive disease: evaluation with CT angiography, MR angiography, and digital subtraction angiography

BACKGROUND AND PURPOSE: Although digital subtraction angiography (DSA) provides excellent visualization of the intracranial vasculature, it has several limitations. Our purpose was to evaluate the ability of helical CT angiography (CTA) to help detect and quantify intracranial stenosis and occlusion compared with DSA and MR angiography (MRA). METHODS: Twenty-eight patients underwent CTA, DSA, and 3D time-of-flight (TOF) MRA for suspected cerebrovascular lesions. All three studies were performed within a 30-day period. Two readers blinded to prior estimated or calculated stenoses, patient history and clinical information examined 672 vessel segments. Lesions were categorized as normal (0-9%), mild (10-29%), moderate (30-69%), severe (70-99%), or occluded (no flow detected). DSA was the reference standard. Unblinded consensus readings were obtained for all discrepancies. RESULTS: A total of 115 diseased vessel segments were identified. After consensus interpretation, CTA revealed higher sensitivity than that of MRA for intracranial stenosis (98% versus 70%, P < .001) and occlusion (100% versus 87%, P = .02). CTA had a higher positive predictive value than that of MRA for both stenosis (93% versus 65%, P < .001) and occlusion (100% versus 59%, P < .001). CTA had a high interoperator reliability. In 6 of 28 patients (21%), all 6 with low-flow states in the posterior circulation, CTA was superior to DSA in detection of vessel patency. CONCLUSION: CTA has a higher sensitivity and positive predictive value than MRA and is recommended over TOF MRA for detection of intracranial stenosis and occlusion. CTA has a high interoperator reliability. CTA is superior to DSA in the evaluation of posterior circulation steno-occlusive disease when slow flow is present. CTA results had a significant effect on patient clinical management.     

CT angiography and MR angiography in the evaluation of extracranial carotid vascular disease

CTA and MRA techniques likely will continue to increase in use in the evaluation of the extracranial cerebrovascular system. The increasing reliance on noninvasive tests mirrors an overall concern with the risks and costs of more invasive examinations. Given the rapid development of the computer technology, data acquisition, and reconstruction algorithms in the past few years, it is apparent that CTA and MRA also will continue to improve.