2D time-of-flight MR angiography using concatenated saturation bands for determining direction of flow in the intracranial vessels

We prospectively studied 15 patients to assess 2D time-of-flight (TOF) magnetic resonance angiography (MRA) with concatenated saturation bands for determining the direction of intracranial blood flow. This MRA sequence was compared to T2-weighted spin-echo MRI, 3D-TOF MRA, and intra-arterial angiography (IAA) as regards demonstration of vessels and determination of the direction of flow in the circle of Willis and its branches. The 2D-TOF MRA sequence demonstrated flow in 98.5 % vessel segments identified on IAA, 3D-TOF demonstrating 92 % and spin-echo images 77 %. The direction of flow shown on the 2D-TOF sequence was correct in 94 % when compared to conventional angiography, the remaining six segments not demonstrating flow. In ten patients, the flow abnormalities demonstrated by this MRA technique provided clinical information similar to that of conventional angiography in nine, but it was incomplete in three, and misleading in one. Slow retrograde flow in ophthalmic artery collaterals and differentiation of arteries and veins presented some problems. 2D-TOF MRA with concatenated saturation bands provides flow direction information using widely available, easily applicable TOF techniques, and can be a useful adjunct to MRI and MRA if information on flow direction is needed. Received: 18 October 1995 Accepted: 16 August 1996     

Acute subarachnoid Haemorrhage: 3D time-of-flight MR angiography versus intra-arterial digital angiography

To evaluate the efficacy and reliability of 3D time-of-flight MR angiography (TOF MRA) as a noninvasive procedure, 27 patients with acute subarachnoid haemorrhage (SAH) were studied with MRA immediately before or after intra-arterial digital subtraction angiography (DSA). 3DTOF MRA was performed with an axial slab of 60 mm centred on the circle of Willis and isotropic voxels. DSA showed 22 aneurysms and 1 dural arteriovenous fistula in 21 patients; the aneurysms ranged in size from 2 to 8 mm. MRA failed to show 2 small aneurysms, at the origin of the posterior and anterior communicating arteries. The 3D display of the intracranial vessels obtained with maximum intensity projection (MIP) or targetted MIP sometimes rendered the aneurysms better than DSA. However, due to its high spatial resolution, DSA more clearly defined the overall anatomy of the walls of the normal and abnormal vessels.1992 Scientific Award of the ESNR     

Three dimensional magnetic resonance angiography of the circle of Willis: Anatomical variations in general Egyptian population

ObjectiveAimed to evaluate the different anatomical variations of the circle of Willis (COW) and determined average vessels diameters in general Egyptian population.Patients and methodsWe retrospectively evaluated the 3D-time of flight (TOF) MR angiogram (MRA) of 250 patients. One hundred and eighty patients out of them had no manifestations of cerebrovascular diseases included in the study. All of them were examined by 3D TOF MRA. The anatomical variants of the anterior and posterior components of the COW were studied. The complete COW were assessed and the diameters of all the components were measured. The correlation between the vessel diameters in relations to age and sex were evaluated.ResultsComplete anterior and complete posterior parts of the COW were seen in 68.3%, and 38.3%, respectively. Entirely complete COW was seen in 46.7%. The prevalence of entirely complete COW was slightly higher in females and young than males and older subjects. The study illustrated that there are statistically significant differences in some vessel diameters according to sex and age.ConclusionThe anatomical variants of the COW and the normal reference values for vessels diameter were determined in general Egyptian population based on measurements in 3DTOF MRA.     

Magnetic resonance angiography compared to intra-arterial digital subtraction angiography in patients with subarachnoid haemorrhage

Summary In order to evaluate the sensitivity and specificity of magnetic resonance angiography (MRA) in spontaneous subarachnoid haemorrhage, 14 patients with recent haemorrhage verified by CT or lumbar puncture were investigated with both selective intra-arterial digital subtraction angiography (IA-DSA) and MRA by two independent teams, each having the same preangiographic information. The results were compared with each other and whenever possible (all positive cases except one) with those of surgical intervention. Seven patients were identified by MRA and IA-DSA as having a single aneurysm on the circle of Willis, 1 an aneurysm of the posterior inferior cerebellar artery 1 an aneurysm of the internal carotid artery (siphon) and 2 patients with two aneurysms on the circle of Willis. MRA and IA-DSA both failed to demonstrate aneurysms in 2 cases. Three patients had negative results on both methods and no surgical intervention was attempted. The aneurysms ranged from 0.3 to 1.5 cm in size. In most cases there was agreement between MRA and DSA, leading us to believe that, if the proper protocols are followed, MRA is a powerful alternative to other established methods in the detection of intracranial aneurysms. At this stage it will not replace IA-DSA prior to surgery, but the ability to obtain various projections using 3D MRA may improve surgical planning.     

Circle of Willis variant analogous to fetal type primitive trigeminal artery

Summary Primitive caroticobasilar anastomoses are uncommon embryonic arterial connections between the carotid (anterior) and vertebrobasilar (posterior) circulations. With the exception of extracranial proatlantal intersegmental arteries, these embryonic arterial anastomoses are named according to the cranial nerves which they parallel. In this report, a previously undescribed variant circle of Willis with supraclinoid caroticobasilar anastomosis, functionally equivalent to a fetal type primitive trigeminal artery, is presented.     

Quantification and visualization of flow in the Circle of Willis: Time‐resolved three‐dimensional phase contrast MRI at 7 T compared with 3 T

The assessment of both geometry and hemodynamics of the intracranial arteries has important diagnostic value in internal carotid occlusion, sickle cell disease, and aneurysm development. Provided that signal to noise ratio (SNR) and resolution are high, these factors can be measured with time‐resolved three‐dimensional phase contrast MRI. However, within a given scan time duration, an increase in resolution causes a decrease in SNR and vice versa, hampering flow quantification and visualization. To study the benefits of higher SNR at 7 T, three‐dimensional phase contrast MRI in the Circle of Willis was performed at 3 T and 7 T in five volunteers. Results showed that the SNR at 7 T was roughly 2.6 times higher than at 3 T. Therefore, segmentation of small vessels such as the anterior and posterior communicating arteries succeeded more frequently at 7 T. Direction of flow and smoothness of streamlines in the anterior and posterior communicating arteries were more pronounced at 7 T. Mean velocity magnitude values in the vessels of the Circle of Willis were higher at 3 T due to noise compared to 7 T. Likewise, areas of the vessels were lower at 3 T. In conclusion, the gain in SNR at 7 T compared to 3 T allows for improved flow visualization and quantification in intracranial arteries. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Nonenhanced ECG-gated time-resolved 4D Steady-state free precession (SSFP) MR angiography (MRA) for assessment of cerebral collateral flow: comparison with digital subtraction angiography (DSA)

Objectives

To evaluate a nonenhanced time-resolved 4D SSFP MRA for dynamic visualization of intracranial collateral blood flow.

Methods

22 patients (59.0?±?11.8 years) with steno-occlusive disease of brain-supplying arteries were included in this study. 4D SSFP MRA of the intracranial arteries was acquired with 15 temporal phases and a temporal resolution of 115 ms using 1.5 T MR. Cerebral DSA served as the reference standard and was available in all patients.

Results

Nonenhanced 4D SSFP MRA allowed for detailed dynamic visualization of blood flow in the circle of Willis and its branches in 21 of 22 (95.5%) patients. Collateral flow was excluded with both 4D SSFP MRA and DSA in 4 patients. In 17 patients, DSA detected anterior collateral flow (n?=?8), posterior collateral flow via the right (n?=?8) and left (n?=?7) posterior communicating artery as well as patent EC-IC bypasses (n?=?8). 29 of 31 collateral flow pathways were visualized by 4D SSFP MRA. As compared to DSA, 4D SSFP MRA showed a high sensitivity (92.3%), specificity (100%), positive predictive value (100%) and negative predictive value (95.2%) for visualization of intracranial collateral flow.

Conclusions

4D SSFP MRA is a promising non-invasive imaging technique for dynamic visualization of intracranial collateral flow.     

Non-invasive assessment of the Circle of Willis using transcranial pulsed Doppler ultrasound with angiographic correlation.

The ability of transcranial pulsed Doppler ultrasound (TCD) to provide a dynamic assessment of the functional capability of the Circle of Willis was assessed using conventional cerebral angiography for anatomic correlation. Eleven patients had normal four-vessel cerebral angiography prior to being investigated with ultrasound. Angiography and ultrasound both demonstrated a functional anterior communicating artery in nine of the eleven patients, giving complete agreement between the two techniques. Posterior communicating arteries were visualized angiographically in all eleven patients. Ultrasound identified bilateral functional vessels in nine, the other two patients having non-functional vessels. In these latter two patients, angiography demonstrated three of the four posterior communicating arteries to be hypoplastic and it was uncertain whether these vessels carried significant blood flow. The fourth posterior communicating artery was shown to have an absent proximal segment of the ipsilateral posterior cerebral artery, with a persistent fetal posterior communicating artery. This anatomical variation is a potential limitation of ultrasound for assessing functional posterior communicating arteries. These preliminary results indicate that a combination of the anatomical (angiographic) and dynamic (ultrasonic) data may prove to be complementary for assessing the Circle of Willis.     

磁共振新技术在颈动脉狭窄诊断中的应用

目的研究增强磁共振血管成像（CE—MRA）技术的成像影响因素,评价MR扫描序列对颈动脉狭窄硬化斑块的应用价值,探讨颈动脉狭窄血流动力学变化与临床症状的联系。方法颈动脉狭窄34例,男22例,女12例。年龄36～78岁,平均56岁。病人首先经多普勒超声（DUS）检查,然后行MRA及CE-MRA。22例同时采用亮血（Bright—blood）、黑血（Black—blood）技术、3例行血流测量分析（Flow measurements）。10例于磁共振检查后1周内接受颈动脉狭窄内膜剥除术。扫描技术：（1）MRA及CE-MRA：MRA：二维时间飞跃法MRA（2D TOF MRA）;CE-MRA：快速梯度回波扫描技术,冠状位采集。最佳扫描延迟时间主要采用造影剂团注试验（test-bolus）法。3例采用时间分辨回波分享血管成像技术（TRATE）。（2）斑块检查序列：亮血与黑血技术及增强前后T1序列。（3）血流测量分析：横断位心电门控2D相位对比序列,Argus系统分析血流方向、流速。结果血管覆盖范围：34例CE-MRA,23例良好显示颈部血管起始段至入颅段。2D TOF法11例。动脉狭窄评估程度：10例手术患者中,CE-MRA正确诊断血管狭窄者9例,低估狭窄程度1例。2D TOF正确诊断血管狭窄程度6例,高估3例,低估1例。22例亮血、黑血技术结合CE—MRA清晰显示血管壁及动脉硬化斑块。颈动脉单独成像24例中,Test—bolus法团注造影剂最佳扫描延迟时间为峰值时间-1s,且监视层面定于主动脉弓者18例。4例眩晕患者,颈动脉狭窄侧后交通动脉（PCOA）显示2例;PCOA粗大1例。狭窄侧未显示PCOA,同侧大脑后动脉主干增粗1例。2例锁骨下动脉窃血综合征血流方向异常,1例无名静脉狭窄,同侧颈静脉血流方向异常。结论（1）CE—MRA能完整、全程显示颈部血管,准确诊断颈动脉、椎动脉狭窄。（2）Test-bolus法确定扫描延迟时间为峰值时间-1s,并将监视层面定于主动脉弓时,可保证造影剂在动脉内达到高峰浓度时采集K空间数据,获得颈动脉单独成像的最佳图像。（3）亮血、黑血技术结合CE-MRA有助于显示颈动脉狭窄硬化斑块。（4）分析、测量颈动脉狭窄的血流动力学变化能全面评价狭窄后血流改变与临床症状的联系。     

后交通动脉变异的MRA研究及其与后循环梗死的相关性

后循环脑梗死日益引起临床的关注。部分后循环脑梗死病人病灶与供血动脉病变不匹配,或血管狭窄的影像表现与临床表现不匹配,提示血管解剖变异或侧支循环影响了脑血流分配代偿。后交通动脉是后循环最重要的侧支动脉,可沟通前后循环的血流,但其常因变异而影响血流代偿,与后循环脑梗死的发生、转归有关。目前有多种磁共振血管成像(MRA)技术可应用于后交通动脉的检查,是活体研究后交通动脉的重要手段。就后交通动脉的MRA以及后交通动脉与后循环脑梗死相关性的研究进行综述,为临床应用MRA筛选潜在高危后循环梗死病人提供参考。     

Transcranial Doppler ultrasound in the evaluation of collateral blood flow in patients with internal carotid artery occlusion: correlation with cerebral angiography.

PURPOSETo determine the accuracy of transcranial Doppler (TCD) ultrasound for evaluation of collateral supply through the circle of Willis in patients with internal carotid artery (ICA) occlusion.METHODSThe evaluation of the collateral pathways through the circle of Willis with TCD ultrasound and with cerebral angiography was compared in 40 patients (30 men, 10 women; mean age, 55 +/- 9 years) in a total of 44 ICA occlusions of which 43 had a suitable ipsilateral temporal bone window for TCD examination.RESULTSBy TCD, a patent anterior communicating artery is indicated by a reversal blood flow in the A1-segment of the anterior cerebral artery or by a prompt fall of blood velocity in the middle cerebral artery after compression of the nonoccluded contralateral carotid artery. In 42 of 43 instances of ICA occlusion, TCD and angiography agreed in the evaluation of a present or absent anterior communicating artery collateral supply. TCD''s sensitivity was 95%, its specificity 100%. A collateral supply through the basilar artery was assumed with TCD when there was: (a) a basilar artery blood velocity of more than 70 cm/s; (b) a marked increase of basilar artery blood velocity after compression of the nonoccluded carotid artery; (c) an evident side-to-side asymmetry of the blood velocity of the posterior cerebral arteries with high blood velocity ipsilateral to the ICA occlusion. For evaluating the collateralization via the basilar artery, TCD and angiography agreed in 37 of 40 ICA occlusions. TCD''s sensitivity was 87%, its specificity 95%.CONCLUSIONSTCD is a reliable tool for the evaluation of the collateral supply in patients with ICA occlusions.     

Transcranial color-coded duplex sonography in unilateral flow-restrictive extracranial carotid artery disease.

PURPOSETo provide transcranial color-coded duplex flow-velocity data for the basal cerebral arteries in patients with unilateral flow-restrictive extracranial carotid artery disease, and to compare these data with the flow velocities obtained in healthy control subjects.METHODSTranscranial color-coded duplex sonography was performed in 78 patients with different patterns of cross flow through the anterior and posterior communicating arteries associated with unilateral obstruction (70% to 100%; 46 stenoses and 32 occlusions) of the internal carotid arteries. Peak systolic, mean, and end diastolic velocities were measured in the anterior, middle, and precommunicating and postcommunicating posterior cerebral arteries. These measurements were compared with the values obtained in 125 age- and sex-matched health control subjects.RESULTSPatients with anterior communicating artery cross flow to the middle cerebral artery (63%) had increased peak velocity in the anterior cerebral artery and decrease peak velocity in the middle cerebral artery on the obstructed (ipsilateral) side, and increased peak velocity in the anterior cerebral artery on unobstructed (contralateral) side. Patients with anterior communicating artery cross flow to the pericallosal artery (19%) had increased contralateral peak systolic velocity and mean anterior cerebral artery velocities. Patients without anterior communicating artery cross flow (18%) had normal peak velocities in the anterior and middle cerebral arteries. Patients with posterior communicating artery cross flow (42%) had ipsilaterally decreased peak systolic and mean middle cerebral artery velocities and increased peak velocities in the precommunicating posterior cerebral artery. Patients without posterior communicating artery cross flow (58%) had ipsilaterally decreased peak systolic and mean middle cerebral artery velocities.CONCLUSIONOur findings suggest that typical abnormalities of basal cerebral artery flow velocities occur in patients with unilateral 70% to 100% obstruction of the internal carotid arteries resulting in different patterns of cross flow through the circle of Willis.     

Circle of Willis in newborns: color Doppler imaging of 53 healthy full- term infants

To establish the usual pattern of flow in the circle of Willis in newborns, the authors scanned 53 healthy full-term infants within 3 days of birth with color Doppler imaging. All examinations were performed and images interpreted by the same experienced individuals. The basilar, internal carotid (ICA), and anterior and middle cerebral arteries were seen in all infants. Vertebral, posterior cerebral, superior cerebellar, and posterior communicating (PCoA) arteries were seen in most infants. PCoA flow was from the ICA toward the posterior cerebral artery in 73 (98.6%) of the 74 vessels that were seen. Flow in the anterior communicating artery was seen in six infants, indicating dependence of an anterior cerebral artery on contralateral ICA perfusion. Two pitfalls involving the distal portion of the ICA were noted: This vessel could be confused with the proximal portion of the anterior cerebral artery or cavernous sinus if real-time images were not interpreted carefully. Variant patterns of flow included tortuous basilar arteries (n = 2), reversed PCoA flow (n = 1), and inferior angulation of the proximal portions of the anterior cerebral arteries (n = 2). Color Doppler imaging allows a detailed analysis of the circle of Willis in newborns and detection of some anatomic variations.     

Computer-assisted 3D reconstruction of the terminal branches of the cerebral arteries

We present a three-dimensional anatomical computer model of the terminal branches of the posterior cerebral artery and circle of Willis, acquired from equidistant serial anatomical slices of three brains. The reconstructions provide a clear picture from all angles of the complicated course of the terminal branches of the cerebral arteries. This can help to identify the arteries in conventional and magnetic resonance angiography. Our rendition of the cerebral arteries can be matched with CT, MR und PET images to indicate the areas of extension of the individual branches, allowing neuromorphological and functional correlations.     

MRI and MR angiography of persistent trigeminal artery

We describe the MRA and MR angiography (MRA) features of persistent trigeminal artery (PTA) found incidentally in eight patients, with special attention to its origin, site and course. The different patterns of posterior communicating arteries were also noted. The PTA were shown on sagittal, coronal and axial MRI and on MRA. In four cases, the PTA arose from the lateral aspect of the intracavernous internal carotid artery, ran caudally, passing round the bottom of the dorsum sellae to join the basilar artery. In the other four cases, it arose from the medial aspect, ran caudally through the sella turcica and pierced the dorsum sellae to join the basilar artery. The posterior communicating arteries were present unilaterally in five cases and bilaterally in one, and absent bilaterally in two. Identification of a PTA with a trans-sellar course is crucial if a trans-sphenoidal surgery is planned. Received: 20 September 1995 Accepted: 20 January 1996     

Willis环磁共振血管成像与血管造影对比研究

目的：对比分析Ｗｉｌｌｉｓ动脉环的ＭＲＡ和ＣＡ表现,探讨ＴＯＦ法ＭＲＡ评价Ｗｉｌｌｉｓ环解剖与功能的价值。材料与方法：选择４３例颅脑血管和肿瘤疾病的ＴＯＦ法ＭＲＡ和ＣＡ资料。ＭＲＡ应用１．０Ｔ超导ＭＲ系统的３Ｄ或２ＤＦＩＳＰ序列扫描,原始血管图像用ＭＩＰ重建。ＣＡ西门子１２５０ｍＡＤＳＡ系统和岛津１０００ｍＡ造影造系统,采用Ｓｅｌｄｉｎｇｅｒ技术导管法股脑血管造（至秒摄取双侧颈动脉和一侧椎动脉造有     

颅颈部血管多层螺旋减影CTA与DSA的比较研究

目的 评价减影CTA对检察颅颈部血管性病变的灵敏度和特异度及其临床应用价值.方法 对76例怀疑颅颈部血管疾病患者施行16层螺旋减影CTA检查,在保证增强前后所采集的数据参数一致的前提下用Neuro-DSA软件进行减影,其中30例与DSA作比较观察.减影CTA图像质量分为优良、一般、差;应用非参数统计检验、计算减影CTA显示病变的灵敏度和特异度.结果 以颈内动脉颅段、前后交通动脉、大脑前中后动脉近段、椎基动脉为观察对象,共观察血管段900段.减影CTA图像质量优良571段,为63.4%,一般有301段,为33.4%.但在显示颅颈部不同段血管的图像质量上有差异;减影CTA检出病变的灵敏度为84.4%,特异度为40%,检出动脉瘤的灵敏度和特异度均为100%.结论 16层螺旋减影CTA无创,快捷,简单易行,能提供较高分辨率的血管图像,可作为一种常规的方法应用于颅颈部血管疾病的筛查和诊断.     

易形成前交通动脉瘤的血管模式再探讨

目的探讨易形成前交通动脉瘤的血管模式。资料与方法将1081份正常磁共振血管成像(MRA)图像定义为一般国人脑血管形态类型,与49例前交通动脉瘤患者脑血管形态类型进行对照。结果49例前交通动脉瘤中一侧A1优势型45例(占87.76%),与正常国人一侧A1优势型和其他类型构成差异有统计学意义(P<0.0001)。其中左侧A1优势型(33例)约为右侧A1优势型(12例)的3倍,与一般人群左侧A1优势型与右侧A1优势型比(11.19%/3.98%)差异无统计学意义(P=0.952)。一侧A1优势型前交通动脉双侧大脑前动脉A2段起始部夹角测量有瘤患者夹角平均值为174.5°,无瘤患者平均值为113.45°,两夹角差异有统计学意义(t=14.198,P=0.002)。结论一侧A1优势供血与前交通动脉瘤的形成相关,造成前交通动脉瘤左右侧差异的原因是一侧A1优势型发育左右侧存在差异,双侧大脑前动脉A2段夹角增大更易形成动脉瘤。对发现的此种血管模式应随访。     

3D-T0F MRA对颅内动脉瘤GDC治疗随访的预期评估

目的：评价磁共振血管成像(MRA)在随访43例病人的45个颅内动脉瘤GDC栓塞后的价值。材料和方法：以数字减影血管造影(DSA)作为诊断的金标准，回顾研究43例病人的45个颅内动脉瘤(前循环34个，后循环11个)MRA检查。所有的病人在GDC栓塞治疗后9个月之内的同一周行DSA和MRA检查，这期间不作处理。分析弹簧圈内残余血流、载瘤动脉和邻近动脉血流，MRA以最大强度投影(MIP)重建和源图像为基础。结果：所有病例中，MRA能提供良好的信息。对于动脉瘤的分析，MRA的敏感性、特征性、阳性预测价值、阴性预测价值，诊断弹簧圈内残余血流分别为87．5％、100％、100％、97％，诊断瘤颈的残余血流分别为90％、100％、100％、97％。对于动脉通畅性分析，MRA的敏感性和阴性预测价值，载瘤动脉分别是90．5％和100％，邻近动脉分别是85．7％和100％。结论：在随访GDC栓塞的动脉瘤中，MRA可以作为一个筛选手段，提高检查效率，减少病人的随访风险。     

Contrast-enhanced MR angiography of the craniocervical vessels: a review

The use of MR angiography (MRA) with injection of contrast medium enables imaging of a large volume with a very short acquisition time, providing angiographic images similar to those obtained with catheter angiography. This makes possible investigation of patients in the acute phase of stroke, with examination of the entire length of the cervical arteries from the aortic arch to the circle of Willis. However, the parameters of the sequence must be carefully chosen to optimise image quality, with a compromise between spatial resolution, acquisition time and image contrast. An overview of the technical aspects is presented, including current developments. Different protocol strategies are discussed, including their advantages and limits. Finally, we review the preliminary results of contrast-enhanced MRA for assessment of atherosclerotic lesions of supra-aortic vessels. Received: 18 June 1999 Accepted: 19 June 1999