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     

MR angiography: supra-aortic vessels

Magnetic resonance angiography (MRA) has become an imaging modality which comprises various techniques based on two concepts: methods relying on the natural flow effects, the time-of-flight and phase-contrast technique, either in two- or three-dimensional acquisition mode, and the more recently developed contrast-enhanced (CE) MRA methods. The main indications for evaluation of the supra-aortic vessels are, firstly, the grading of carotid artery stenoses caused by an atherosclerotic process, and secondly, the evaluation of dissections of the cervical arteries because this disease plays an important role as a cause for stroke especially in younger patients. The various MRA techniques in their application to the main pathologies encountered at the supra-aortic vessels are presented, and recent developments in the promising field of CE MRA are discussed.     

Magnetic resonance angiography (MRA) of the circle of Willis: a prospective comparison with conventional angiography in 54 subjects

We prospectively correlated the findings of magnetic resonance angiography (MRA) with those of transfemoral four-vessel angiography in 54 patients to investigate the direction of flow within the circle of Willis. Our primary goal was to assess the direction of flow using the size of the vessel and signal intensity, without saturation techniques. Analysis of the circle of Willis, especially the communicating arteries, was performed double-blind by two groups of two radiologists. Three types of arteries were identified: high flow or cross-cerebral circulation, patent and nonvisualised arteries. Cerebral angiography was the standard for comparison between the two methods. MRA did not reveal any arteries invisible on angiography, thus providing a specificity of 100%. The sensitivity of MRA was 89.2% for the anterior and 81.3% for the posterior communicating arteries, and 100% for the anterior, middle and posterior cerebral arteries. MRA was shown to be a useful technique for the assessment of patency of the circle of Willis.     

Retrograde flow in the dural sinuses detected by three-dimensional time-of-flight MR angiography

Introduction Retrograde flow in the left dural sinuses is sometimes detected by three-dimensional time-of-flight (3D-TOF) magnetic resonance (MR) angiography. The purpose of this study was to evaluate the incidence of this phenomenon and its characteristic features on 3D-TOF MR angiograms. Methods We retrospectively reviewed cranial MR angiography images of 1,078 patients examined at our institution. All images were obtained by the 3D-TOF technique with one of two 1.5-T scanners. Maximum intensity projection (MIP) images in the horizontal rotation view were displayed stereoscopically. We reviewed the source images, inferosuperior MIP images, and horizontal MIP images and identified retrograde flow in the dural sinuses. Results We found retrograde flow in the dural sinuses of 67 patients on the source images from 3D-TOF MR angiography; the incidence was 6.2%. In 47 of the 67 patients, retrograde flow was identified in the left inferior petrosal sinus, in 13, it was seen in the left sigmoid sinus, and in 6, it was seen in the left inferior petrosal and left sigmoid sinuses. The remaining patient had retrograde flow in the left inferior petrosal and left and right sigmoid sinuses. The mean age of the patients with retrograde flow was slightly greater than that of the patients without this phenomenon (70 years vs 63 years). Conclusion Retrograde flow in the dural sinuses frequently occurs on the left side in middle-aged and elderly patients during 3D-TOF MR angiography performed with the patient in the supine position. This phenomenon should not be misdiagnosed as a dural arteriovenous fistula. This article was presented as an electronic poster paper at the 31st Congress of the ESNR held in Geneva in September 2006.     

Follow-up of intracranial aneurysms treated with detachable coils: comparison of plain radiographs, 3D time-of-flight MRA and digital subtraction angiography

All patients with aneurysms treated with Guglielmi detachable coils (GDC) are undergo angiography to assess long-term stability of aneurysm exclusion or to show recurrence of the aneurysm sac, which may require further treatment. We prospectively compared the plain-film appearance of the coil-mass, 3D time-of-flight MR angiography (TOF MRA) and digital subtraction angiography (DSA) for the detection of aneurysm recanalisation during follow-up. We studied 60 patients with 74 intracranial aneurysms treated with Guglielmi detachable coils. We used the unsubtracted image of the angiograms performed at the completion of any embolisation procedure and at follow-up as the plain radiographs. Recanalisation was considered if loosening, compaction or reorientation of the coil mass was apparent. TOF MRA was performed to assess the presence and size of a neck remnant. DSA was regarded as the definitive investigation. Comparison of the techniques showed good agreement as regards aneurysm recanalisation. MRA was more accurate than plain radiography and could replace DSA for long term follow- up. The initial follow-up examination should, however, include both modalities. In cases of contraindications or limitations to MRA, the interval between follow-up angiographic examinations could be increased if there is no change in the plain-film coil-mass appearances.     

磁共振脑静脉系血管成像技术及其临床应用

目的探讨磁共振脑静脉系血管成像的技术方法和最佳扫描方案，评价磁共振静脉系血管成像技术(MR venography，MRV)对静脉系疾病的诊断价值及临床意义。方法采用二维时间飞跃法MR血管造影(2D-TOF-MRA)、二维相位对比血管造影(2D-PCA)和三维对比增强MR血管造影(3D-CE-MRA)3种血管成像技术分别对20例健康志愿者和20例临床或MRI疑有静脉系疾病的患者行MRV成像，并采用最大强度投影(MIP)、多平面或曲面重建(MPR)及数字减影MRA(DSMRA)技术对图像进行后处理，观察脑静脉系在MRV中的显示情况及脑静脉系疾病在MRV中表现形式，制定脑静脉系成像的最佳方案。结果本组经3D-CE-MRA静脉系成像诊断为13例颅内静脉窦血栓形成(CVST)及7例颅内肿瘤累及静脉系的阳性显示率为100％，均经临床治疗复诊及手术证实。2D-PCA及2D-TOF-MRA对细小引流静脉显示欠佳，且2D-TOF-MRA对复杂区域内静脉血管亦显示欠佳。结论3D-CE-MRA结合2D-PCA及2D-TOF-MRA静脉成像技术形成全脑静脉系成像，为脑静脉系的最佳成像方案，对临床术前评估和指导治疗有极其重要的意义。     

Preliminary evaluation of volume-rendered three-dimensional display of time-of-flight MR angiography in the diagnosis of intracranial aneurysms

We assessed the value of the volume-rendering method of displaying images of three-dimensional (3D) time-of-flight MR angiography (MRA) in the diagnosis of intracranial aneurysms. We obtained three-dimensional volume-rendered MRA from 21 patients with intracranial aneurysms. The images were evaluated in comparison with maximum-intensity-projection images (in 21 patients), conventional angiograms (in 21 ) and CT angiography (in nine). In 17 patients, 3D volume-rendered images were thought to show morphological features most clearly. They were superior to the other methods for demonstrating the precise location of the aneurysm in three patients and in showing the shape of the bleb in another three. 3D volume-rendered MRA can be effectively added to conventional imaging techniques for diagnosis of intracranial aneurysms. Received: 12 October 2000 Accepted: 12 December 2000     

Preliminary experience with dynamic MR projection angiography in the evaluation of cervicocranial steno-occlusive disease

The application of a contrast-enhanced, two-dimensional MR technique, which provides dynamic projection angiograms at a subsecond temporal frame rate for depiction of the cervical and intracranial arteries, was evaluated in three healthy volunteers and seven patients with various cervicocranial steno-occlusive diseases. Intra-arterial digital subtraction angiography (DSA) served as standard of reference for findings in the patients. Magnetic resonance projection angiography (MRPA) was performed on a standard 1.5-T clinical MR imaging system at intravenous injection of a single dose of contrast agent (0.1 mmol/kg GdDTPA-BMA). Sixty consecutive images of the cerebral circulation were acquired at a temporal frame rate of 900 ms per image in the coronal plane. The collateral flow and the perfusion of the compromised vessel territory were readily assessed by MPRA in patients with occlusion of the internal cerebral artery (ICA) or middle cerebral artery (MCA). The leptomeningeal collateralisation of these patients was displayed in a dynamic fashion. Furthermore, quantitative perfusion measurement provided a difference between both MCA territories in the time to peak (ΔDTTP) of the contrast bolus of 1.12 ± 0.28 s in five patients with severe stenosis or occlusion of the ICA (healthy volunteers 0.19 ± 0.05 s). However, important pathological findings, such as the evaluation of carotid artery stenoses and the intracranial collateral flow pattern in patients with severe carotid stenoses, were not sufficiently assessable as compared with DSA. We conclude that the possibility of obtaining simultaneously information about morphology and perfusion dynamics of the cervicocranial vessels is unique in MPRA as compared with other MR techniques. However, in the applied form, the technique is not a reliable tool for the complete evaluation of the cervicocranial vessels in patients with steno-occlusive disease. Received: 27 January 2000/Revised: 11 July 2000/Accepted: 13 July 2000     

三维动态增强MR血管造影对颅内动脉瘤的诊断价值

目的 评价三维动态增强磁共振血管造影(3D DCE-MRA)在颅内动脉瘤诊断中的价值。方法 对54例高度怀疑有颅内动脉瘤的病人行3D DCE-MRA检查，随后行DSA造影及可行的血管内栓塞治疗。3D DCE-MRA用超快速三维梯度回波序列(3D FISP)(钆喷替酸葡甲胺0．2mmol／kg,1次扫描时间10s)，工作站上三维重建，比较3D DCE-MRA及常规DSA在显示动脉瘤、瘤颈及与载瘤动脉关系上的优劣，及对血管内栓塞治疗的价值。结果 39例脑动脉瘤患者共45个动脉瘤，3D DCE-MRA对动脉瘤的敏感度为96％，特异度73％，准确度90％。3D DCE-MRA对动脉瘤细节及瘤颈的显示明显优于常规DSA，尤其是颈内动脉海绵窦部及椎动脉近小脑后下动脉的动脉瘤，可指导DSA显示动脉瘤方向及预先制定治疗方案。但对周边部及动脉分岔处小动脉瘤的诊断应谨慎。结论3D DCE-MRA能无创有效地诊断颅内动脉瘤，所提供的三维信息对治疗方案的制定具有极大帮助。当诊断有怀疑时，应结合DSA检查。     

Improved 2D time-of-flight angiography using a radial-line k-space acquisition

For flow imaging applications, radial-line k-space acquisition methods offer advantages over conventional 2DFT methods. Specifically, radial-line acquisition methods mitigate artifacts resulting from pulsatile flow while offering a potential reduction in scan times. In this paper, radial-line and 2DFT acquisitions are compared in a two-dimensional time-of-flight angiography sequence. The twisting radial-line (TwiRL) trajectory, a variant of 2D projection reconstruction, is used to represent the family of radial-line trajectories. In both phantom and in vivo studies, the TwiRL images demonstrate improved vessel depiction including a more uniform signal intensity and better delineation of the vasculature in comparison with images obtained via the 2DFT method.     

The role of contrast-enhanced MR angiography in the assessment of recently ruptured intracranial aneurysms: a comparative study

We evaluated contrast-enhanced MR angiography (MRA) for the identification of recently ruptured cerebral aneurysms. We studied 23 aneurysms in 18 patients (age range 34–72 years) with aneurysms of the anterior (n=17) and posterior (n=6) circulation by comparing 3D time-of-flight (TOF), contrast-enhanced MRA and digital subtraction angiography (DSA). In four of 23 aneurysms, 3D-TOF did not show the lesion. Contrast-enhanced MRA successfully depicted all aneurysms except one. T1 contamination artefacts from subarachnoid or intraparenchymal haemorrhages were evident on the 3D-TOF images in six cases. The artefacts were completely eliminated on the contrast-enhanced MRA images by subtraction of the pre-contrast images. The diagnostic information in patients with subarachnoid haemorrhages (SAHs) provided by contrast-enhanced MRA was comparable to that provided by DSA.The contents of this article were presented as a poster entitled Contrast-enhanced MR angiography of intracranial aneurysms at the 28th annual meeting of the European Society of Neuroradiology (ESNR), Istanbul, Turkey, 11–14 September 2003     

3.0T时间飞跃法MRA诊断颅内动脉瘤-与DSA对照

目的评价3.0T时间飞跃法磁共振血管成像(3.0TTOFMRA)对颅内动脉瘤的诊断价值。方法对34例临床提示颅内动脉瘤患者前瞻性行3.0TTOFMRA及脑血管DSA检查。所有图像由3名医师分成2组在工作站上进行读片。第1组由2名高年资神经影像组医师分别独立阅读重建的最大密度投影(MIP)图像;第2组由1名高年资神经影像组医师同时阅读MIP和原始数据图像(sourceimage)。以DSA诊断结果作为标准,评价3.0TTOFMRA诊断颅内动脉瘤的灵敏度、特异度及正确率。结果DSA共检测20枚动脉瘤(19例),其中颈内动脉7例,前交通动脉5例,后交通动脉5例,大脑前、中动脉各1例。TOFMRA总体诊断灵敏度、特异度、正确率分别为94.8%、89.4%和91.4%。第2组的诊断有效性最高,两组间诊断阳性率差异无统计学意义(χ2=0.242,P>0.05和χ2=0.172,P>0.05)。结论3.0TTOFMRA作为一种快速、无创的影像检查方法,能够很好显示颅内动脉瘤。MIP结合Source图像可提高3.0TTOFMRA诊断的准确性。     

3D contrast-enhanced MR angiography of the run-off vessels: value of image subtraction

The diagnostic gain associated with image subtractions was assessed regarding contrast-enhanced 3D magnetic resonance angiography (MRA) image sets of the pelvic and lower extremity arteries. The MRA strategy combined a dedicated vascular coil with a single injection, two-station protocol. Voxel-by-voxel signal intensity subtraction was performed on MRA image sets obtained before and during dynamic infusion of a para-magnetic contrast agent. Non-subtracted and subtracted MRA image sets were assessed for the presence of occlusive (four grades) disease, using DSA as the standard of reference. In addition, SNR and CNR were recorded for each vascular segment on both the non-subtracted and subtracted images. While CNR values of subtracted images exceeded those of non-subtracted images (P < 0.05), there was no difference in diagnostic performance. For the detection of hemodynamically significant disease, non-subtracted and subtracted MRA provided overall sensitivity and specificity of 90.2%/90.3% and 95.1%/95.6%, respectively. Concordance between non-subtracted and subtracted MRA was excellent (Kappa = 0.86).     

飞行员颅底动脉环磁共振图像形态的初步分析

目的 调查飞行员颅底动脉环形态的完整性及变异情况. 方法 回顾分析2000年1月1日至2011年1月1日在空军总医院住院、行头颅磁共振血管成像的104例飞行员的病例资料和颅底动脉环图像,排除既往有心脑血管病、高血压、糖尿病病史者,排除有神经功能缺损且头颅MRI有明显异常者.统计颅底动脉环的完整性和变异情况. 结果 51例病历资料完整着入选,均为男性,年龄22～56岁.歼击机飞行员29例,轰炸机或运输机飞行员19例,直升机飞行员3例.飞行时间100～8000 h.41例因病入院,10例改装体检入院.51例中37.3％(19/51)颅底动脉环完整,23.5％(12/51)前交通动脉缺如,7.8％(4/51)A1段发育不良,2.0％(1/51)一侧A1段缺如,51.0％(26/51)后交通动脉缺如,7.8％(4/51)P1段发育不良,3.9％(2/51)一侧或双侧P1段缺如. 结论 本组飞行员颅底动脉环存在变异,有半数以上者不完整,其航空医学意义有待进一步确定.     

旋转式三维数字减影血管造影在脑动脉瘤临床诊断和治疗中的应用价值

目的：探讨旋转式三维数字减影血管造影在脑动脉瘤诊断和治疗中的应用价值，提高诊断水平，增强治疗效果。方法：回顾性分析了213例脑动脉瘤患者的二维、三维数字减影脑血管造影的影像学资料，并对其结果进行了对比分析。结果：213例患者中共检出222枚脑动脉瘤，其中囊性动脉瘤197枚，梭形动脉瘤16枚，夹层动脉瘤9枚；在222枚脑动脉瘤中，小型动脉瘤105枚，中型动脉瘤89枚，大型动脉瘤22枚，巨大型动脉瘤6枚。常规DSA清楚显示的有205枚，17枚显示可疑由三维数字减影脑血管造影进一步证实；对138例脑动脉瘤患者进行手术开颅银夹夹闭治疗，19例进行介入性金属微弹簧圈栓塞治疗。结论：旋转式三维脑血管造影可有效提高脑动脉瘤的诊断准确性和多种治疗方法的安全十牛及疗效。     

Three-dimensional MR digital subtraction angiography using parallel imaging and keyhole data sampling in cerebrovascular diseases: initial experience

We assessed the feasibility of MR digital subtraction angiography (DSA) using parallel imaging and keyhole data sampling in the diagnosis of cerebrovascular diseases (CVDs) in 11 patients. Their diseases included arterial trunk stenosis/occlusion (n=4), aneurysm (n=3), arteriovenous malformation (n=2), venous angioma (n=1), and sinus thrombosis (n=1). The technique depicted not only anatomical features, comparably to MR angiography (n=10/11), but also hemodynamics such as collateral flow at a temporal resolution of 1.68 s/frame. When compared with conventional angiograms (n=7), details were missed in four patients (incomplete demonstration of aneurysmal neck in two and poor separation of AVM components in two). Although inferior to conventional angiography, this technique can provide both anatomical and hemodynamic information of CVDs.     

头颈部血管闭塞性疾病的MRA与DSA对照研究

目的通过与DSA对照,探讨MRA在头颈部血管闭塞性疾病的应用价值与限度。方法回顾性分析头颈部血管检查的病例32例,均进行2D-TOFMRA和DSA检查,检查结果进行对照分析。结果32例经DSA检查8例为正常,余24例中病变血管共38支,其中轻度狭窄12支,中度狭窄8支,重度狭窄8支,闭塞10支;MRA正确诊断26支,总体准确率为约70%。椎动脉假阳性较高,达62.5%。结论MRA可以作为颈动脉和大脑动脉环闭塞性疾病的筛选方法,但不适宜应用于椎动脉。     

Optimized visualization of vessels in contrast enhanced intracranial MR angiography

In this study, the problem of small vessel visualization in magnetic resonance angiography is addressed. The loss of vessel contrast due to slow flow-related signal saturation can be compensated by the T₁ reduction obtained from the use of an MR contrast agent, such as Gd-DTPA. The vesselfbackground signal-difference-to-noise ratio (SDNR) is shown to strongly depend on the imaging parameters, as well as on the time course of the blood T₁ values obtained from the contrast injection. Specifically, it was found that vessel SDNR increases almost linearly with TR, if the sampling bandwidth is reduced proportionately.     

Fast three-dimensional time-of-flight MR angiography of the intracranial vasculature

Magnetic resonance angiography is most commonly performed with the three-dimensional (3D) time-of-flight (TOP) technique. As currently practiced, this requires long image acquisition times (5–10 minutes). The authors show that the acquisition time of 3D TOP images can be reduced to less than 1 minute by using a very short TR (<10msec). Under normal flow conditions, the major vessels of the circle of Willis were consistently well demonstrated on these fast 3D TOP images. Signal saturation was observed in studies of patients with abnormal blood flow. In those cases, it was demonstrated that serial acquisition of fast 3D TOP data during and after contrast agent administration could be used to overcome the saturation effects. Time-resolved fast 3D TOP imaging during and after contrast agent administration can also provide qualitative assessment of flow and may depict other features that cannot be observed in TOP studies with long imaging times.