Contrast-enhanced MR angiography of abdominal vessels: Is there still a role for angiography?

The purpose of this review article is to describe recent advantages in contrast-enhanced (CE) three-dimensional (3D) magnetic resonance angiography (MRA) in comparison with other vascular imaging techniques, and to discuss their current clinical applications for the imaging of abdominal vessels. Principles and technical considerations are presented and clinical applications are reviewed for different vascular diseases. In ruptured aortic aneurysms and acute dissections CT is the method of first choice. Contrast-enhanced 3D MRA can be well used for therapeutic planning and follow-up in patients with stable disease. A comprehensive MR examination including CE 3D MRA, MR urography and MR nephrogram has the potential to replace the conventional studies for the evaluation of renal vascular disease. It is an accurate method for imaging the origins of coeliac and superior mesenteric arteries, although the image resolution is too low for reliable assessment of the inferior mesenteric artery. Contrast-enhanced 3D MRA has emerged as the method of choice for studying the portal venous system in liver transplant recipients, in patients with portal hypertension and in cases with abdominal tumours for preoperative evaluation. Additional non-invasive flow measurements are useful in monitoring portal hypertension. The abdominal veins can be well imaged using unenhanced MR techniques. Imaging may be facilitated with intravascular contrast media. Contrast-enhanced 3D MRA can replace intra-arterial DSA for diagnosis, therapy planning and follow-up in patients with abdominal vascular disease. Catheter-based arteriography will still be used for interventional procedures such as percutaneous transluminal angioplasty, stent placement and embolisation.     

Modern cross-sectional imaging in the diagnosis and follow-up of intracranial aneurysms

Digital subtraction angiography (DSA) is still considered the gold standard for most applications in neurovascular imaging. However, with the ongoing development of cross-sectional imaging modalities DSA is increasingly being replaced by less invasive methods. This contribution describes the diagnostic value and the increasing potential of computed tomography angiography (CTA) and magnetic resonance angiography (MRA) in the diagnosis and follow-up of intracranial aneurysms. The main role of CTA is in the diagnosis and therapy planning of ruptured aneurysms; in contrast, MRA plays an increasingly important role in the screening for asymptomatic aneurysms (especially in cases of familial subarachnoid hemorrhage) and in the follow-up after endovascular therapy with coils and/or intracranial stents. Technical issues concerning examination technique are covered here as well as an approach to advanced postprocessing of the image data. Furthermore, a brief outlook on the impact of new developments (MRA with parallel imaging and at 3.0 T) is given.     

Intracranial vascular malformations

Many efforts and much research have been dedicated to the field of non-invasive angiographic techniques in the past few years. Thanks first to magnetic resonance angiography (MRA) and subsequently to computed tomographic angiography (CTA), very interesting results have been obtained in the diagnosis of cerebrovascular diseases. Neck vessels are most successfully evaluated by both MRA and CTA, and the need for digital subtraction angiography (DSA) examinations in patients at risk for vascular occlusions has significantly decreased. The role and the diagnostic accuracy of these non-invasive modalities in intracranial vascular pathology is still under investigation, and several studies have been and are being performed. Both techniques have a better spatial resolution and sensitivity in detecting cerebrovascular malformations than DSA. In the diagnosis of cerebral aneurysms, both MRA and CTA – due to their high sensitivity – have become screening techniques in the population at risk for subarachnoid hemorrhage, these techniques may become basic diagnostic modalities in treatment planning. The results are less satisfying in the evaluation of brain arteriovenous malformations and in the different steps of pre- and post-therapeutic evaluation. Received 9 February 1998; Accepted 13 February 1998     

Non-invasive assessment of neck-vessel pathology

Clinical trials (NASCET, ECTS) have shown that carotid endarterectomy is protective against stroke in patients with symptomatic severe carotid stenosis. To decrease costs and risks, new diagnostic tools have been developed, such as duplex ultrasound (DUS), magnetic resonance angiography (MRA), and more recently computed tomography angiography (CTA). CTA and MRA provide excellent 3D angiography images of the extracranial vessels, using a volume-rendering technique. Digitally subtracted MRA (DSA-MRA) obtained with high-speed acquisitions during gadolinium injection has also recently become available. These techniques are changing the role of non-invasive assessment of carotid stenosis. Although it is probably too early to assess a definite diagnostic algorithm, the use of DSA as a pre-surgical tool for defining carotid stenosis is rapidly decreasing. Received: 9 February 1998; Accepted: 13 February 1998     

糖尿病下肢血管病变术前MRA诊断进展

糖尿病发病率逐年增高,糖尿病外周血管病变是严重并发症之一,日益威胁着广大患者的肢体健康。外周血管病变的术前影像学评估包括多普勒超声(DUS)、CT血管成像(CTA)、MR血管成像(MRA)、数字减影血管造影(DSA)。在影像设备和影像技术飞速发展的大背景下,本文概述了以上方法的价值、局限性及其进展,并着重总结了MRA在糖尿病下肢血管病变术前诊断方面的价值和进展。文献统计MRA无创而且诊断结果最接近DSA,是术前评价和术后长期随访的理想方法。     

脑动脉瘤的MR血管造影与IA—DSA的对照研究

对经手术证实的２０例脑动脉瘤的ＭＲＡ和ＩＡ－ＤＳＡ的影像进行了对照分析研究，经ＭＲＡ检出１９例（９５％）动脉瘤，１０ｍｍ以下的动脉瘤９例，最小的为４ｍｍ，与ＤＳＡ检出率（１９／２０）相仿。ＭＲＡ的定位符合率为８４％，低于ＤＳＡ（９５％）。１３／１９例（６８％）在ＭＲＡ图象上能显示动脉瘤的瘤颈。作者认为ＭＲＡ是一种新的非侵入性的血管影像方法，可作为脑动脉瘤高危病例的筛选检查，随着ＭＲＡ技术的进一步完善，ＭＲＡ有望在神经外科领域替代部分侵入性血管造影检查。     

Magnetic resonance angiography of intracranial aneurysms: comparison with intra-arterial digital subtraction angiography

Summary Magnetic resonance angiography (MRA) with flow rephased gradient-echo sequences is a new non-invasive method for vascular imaging. We compared MRA and intra-arterial digital subtraction angiography in 18 patients with intracranial aneurysms to test whether MRA presently provides an alternative to cerebral angiography for the diagnosis of these anomalies. MRA showed 19 of the 22 aneurysms detected (86.4%). However, problems, especially with turbulent or slow flow, resulted in 6 studies (27.3%) with limited and 2 with questionable demonstration of an aneurysm, and 1 false negative study. At present, MRA is definitely inferior to angiography for the demonstration of intracranial aneurysms, due to its lower resolution and other limitations.     

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。     

Pseudoaneurysm of the internal carotid artery after shrapnel injury in World War II: demonstration by CT angiography with 3D MIP reconstruction

A case of pseudoaneurysm of the left internal carotid artery (ICA) after shrapnel injury is demonstrated by intra-arterial digital subtraction angiography (DSA) and computed tomography angiography (CTA) with subtraction technique. Although the pseudoaneurysm was well demonstrated by intra-arterial DSA, CTA was the only modality to demonstrate the three-dimensional shape of the perfused part of pseudoaneurysm and the aneurysmal neck, which affected the therapeutic strategy. The CTA technique is useful in the assessment of large pseudoaneurysms and for therapeutic planning. Received: 2 July 1998; Revision received: 5 November 1998; Accepted: 7 December 1998     

Thoracic aortic stent graft: comparison of contrast-enhanced MR angiography and CT angiography in the follow-up: initial results

The objective of this study was to compare contrast-enhanced magnetic resonance angiography (CE MRA) and multislice computed tomographic angiography (MS CTA) in the follow-up of thoracic stent-graft placement. The CE MRA and MS CTA were performed following nitinol stent-graft treatment due to thoracic aneurysm (n=4), intramural bleeding (n=2) and type-B aortic dissection (n=5). Corresponding evaluation of arterial-phase imaging characteristics focused on the stent-graft morphology and leakage assessment. Stent-graft and aneurysm extensions were comparable between both techniques. Complete exclusion (aneurysm, n=4; dissection, n=2) was assessed with high confidence with CE MRA and MS CTA. Incomplete exclusion (intramural bleeding, n=2; dissection, n=3) was assigned to lower confidence scores on CE MRA compared with MS CTA. On CE MRA the stent-graft lumen demonstrated an inhomogeneous signal, the stent struts could not be assessed. The CE MRA can be used as alternative non-invasive imaging for follow-up of nitinol stent grafts. Arterial-phase leak assessment can be less evident in CE MRA compared with MS CTA studies; therefore, the use of late-phase imaging seems to be necessary. The diagnostic gap of stent-graft fracture evaluation using MRA may be filled with plain radiographs.     

The non-invasive detection of intracranial aneurysms: are neuroradiologists any better than other observers?

Can non-neuroradiologists detect intracranial aneurysms as well as neuroradiologists, using CT and MR angiography? Sixty patients undergoing intra-arterial digital subtraction angiography (IADSA) to detect aneurysms also underwent computed tomographic angiography (CTA) and time-of-flight magnetic resonance angiography (MRA). Consensus review of IADSA by two neuroradiologists was the reference standard. Two neuroradiologists, a neurosurgeon, a neuroradiographer and a general radiologist blinded to IADSA, plain CT and clinical data, independently reviewed hard-copy base and reconstructed maximum intensity projection images of the CTA and MRA studies. Thirty patients had a total of 63 aneurysms, 71.4% were 相似文献   

Craniocervical artery dissection: MR imaging and MR angiographic findings

Dissection of the carotid and vertebral arteries is a not so uncommon cause of stroke and has to be considered as a differential diagnosis especially in younger patients. Therapeutic and prognostic implications are different from those in extracranial atherosclerotic disease. Dissection results from hemorrhage into the vessel wall usually between the layers of the media. Digital subtraction angiography (DSA) depicts the resulting luminal compromise that may reveal some typical, but not specific, findings. The same is true for non-invasive angiographic techniques such as time-of-flight magnetic resonance angiography (MRA) and computed tomography angiography (CTA), which have shown accurate results compared with DSA. The main advantage of these techniques is the direct visualization of the vessel wall confirming the intramural hematoma. This is achieved best with MR imaging due to the high signal of blood degradation products on T1- and T2-weighted images. Therefore, MRI in combination with MRA is presently the method of choice for initial diagnosis and follow-up of craniocervical artery dissection (CCAD). In some questionable cases, CTA is a non-invasive alternative that is independent of flow phenomena. Received: 4 May 1998; Revision received: 8 September 1998; Accepted: 10 November 1998     

磁共振血管成像在脑血管病中的诊断价值

目的:探讨三维时间飞跃法MR血管成像(3D TOF MRA)和三维增强MR血管造影(3D CE-MRA)检查技术,评价两种方法对脑血管病的诊断价值。方法:磁共振血管成像检查150例,全部行3D TOF MRA检查;9例进行3D CE-MRA检查,钆对比剂(Gd-DTPA)0.2mmol/kg,注射流率3ml/s,增强前、增强后动脉期及静脉期3次扫描;所有MRA图像进行三维重建,同期12例行DSA检查。常规MRI包括横断面T1WI、T2WI,矢状面T1WI。结果:56例中颅内血管显示正常56例,颅内动脉狭窄或闭塞者46例,颅内动脉瘤22例,颅内动静脉畸形21例,颈内动脉海绵窦瘘3例,烟雾病(moyamoya dis-ease)2例。结论:3D TOF MRA和3D CE-MRA是无创、快速、有效的检查技术,对诊断脑血管病有较高的价值,结合原始图像和常规MRI检查,一次检查即能为临床提供较为全面的信息,可作为脑血管病的筛选和首选诊断方法。     

CT angiography,MR angiography and rotational digital subtraction angiography for volumetric assessment of intracranial aneurysms. An experimental study

The purpose of our experimental study was to assess the accuracy and precision of CT angiography (CTA), MR angiography (MRA) and rotational digital subtraction angiography (DSA) for measuring the volume of an in vitro aneurysm model. A rigid model of the anterior cerebral circulation harbouring an anterior communicating aneurysm was connected to a pulsatile circuit. It was studied using unenhanced 3D time-of-flight MRA, contrast-enhanced CTA and rotational DSA angiography. The source images were then postprocessed on dedicated workstations to calculate the volume of the aneurysm. CTA was more accurate than MRA (P=0.0019). Rotational DSA was more accurate than CTA, although the difference did not reach statistical significance (P=0.1605), and significantly more accurate than MRA (P<0.00001). CTA was more precise than MRA (P=0.12), although this did not reach statistical significance. Rotational DSA can be part of the diagnosis, treatment planning and support endovascular treatment of intracranial aneurysms. The emerging endovascular treatment techniques which consist of using liquid polymers as implants to exclude aneurysms from arterial circulation would certainly benefit from this precise measurement of the volume of aneurysms.     

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。     

64层CTA-MIP、CTA-VR与3D-DSA对颅内动脉瘤诊断价值的对比研究

目的对比评价64层螺旋CT最大密度投影(CTA-MIP),CTA容积再现(CTA-VR)与三维数字血管造影(3D-DSA)对颅内动脉瘤(CA)的诊断价值。资料与方法回顾性分析32例经手术及DSA确诊的CA 64层CT血管成像资料,并与DSA进行对照。结果 32例共40个动脉瘤,CTA-MIP发现35个动脉瘤,CTA-VR发现37个动脉瘤,3D-DSA发现39个动脉瘤。40个动脉瘤中11个位于后交通动脉,16个位于大脑中动脉,4个位于基底动脉,1个位于椎动脉,2个位于大脑前动脉,3个位于大脑后动脉,3个位于颈内动脉。3D-DSA与CTA比较,差异无统计学意义。结论在CA影像学诊断上,CTA-MIP、CTA-VR和3D-DSA各有优势,CTA可作为外科治疗或介入治疗的筛选方法。     

Measurements before endovascular repair of abdominal aortic aneurysms. MR imaging with MRA vs. angiography and CT

Purpose:
1) To compare measurements obtained with MR imaging (MRI)/contrast-enhanced MR angiography (CE MRA) with measurements obtained with angiography (DSA) and CT, for stent-graft sizing of abdominal aortic aneurysms (AAA). 2) To compare MRA measurements obtained with the two post processing techniques MIP (maximum intensity projection) and VRT (3D volume rendering technique). Material and Methods:
The prospective study included 20 consecutive patients with AAA identified by DSA and CT as suitable for endovascular repair. For the study, MRI/CE MRA was performed. Five measurement variables for stent-graft sizing were chosen. Comparisons were made between MRI/CE MRA, DSA and CT, and between observers. Comparisons were also made between MIP and VRT. Results:
Significantly shorter lengths were obtained with MRA-MIP than with DSA. Three out of six diameter measurements were significantly smaller on MRI/CE MRA than on DSA and CT. No significant differences were found between the observers. One diameter measurement was significantly smaller on MIP than on VRT, while the other measurements showed no significant differences. Conclusion:
The length measurements obtained with MRA-MIP were probably more correct than those with DSA. For more reliable diameter measurements with CE MRA, improvements of the technique, including VRT reconstructions and a standardized determination of the vessel boundaries, are needed.     

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     

A practical approach to CT angiography of the neck and brain

Computed tomography angiography (CTA) is a rapidly developing technology with great potential. This is particularly true for evaluating neurovascular disease. Clinical stroke because of atherosclerotic disease of the carotid and vertebral arteries is a common examination indication; areas of stenosis, and soft and calcified plaque along the entire vessel, not only at the carotid bifurcation, permit a full assessment of the patient's disease process. Other diseases including dissection, trauma, intracranial stenosis, thrombosis, and aneurysms can be readily diagnosed. Although duplex ultrasound may be a first line examination in many patients, both magnetic resonance angiography (MRA) and CTA offer distinct advantages over it. CTA and MRA are both highly accurate but CTA has several key advantages. CTA has been advanced by the development of improved multidetector CT (MDCT) and workstations that postprocess the data. Methods to obtain quality CTA images and to rapidly analyze the data for abnormalities are the subject of this chapter. In addition, evolving techniques in future CT scanners and workstations, and developing methods of vulnerable plaque and CT perfusion imaging are discussed.     

Subtraction CT angiography for evaluation of intracranial aneurysms: comparison with conventional CT angiography

The purpose of our study was to compare the diagnostic performance of subtraction computed tomography angiography (CTA) with conventional nonsubtracted CTA and digital subtraction angiography (DSA) for the detection of intracranial aneurysms. A total of 76 patients underwent both subtraction CTA and conventional CTA for the detection and therapy planning of suspected intracranial aneurysms. Subtraction and conventional CTA images were independently assessed by two readers in a blinded manner. The possibility of endovascular treatment or surgical clipping was also assessed based on information provided by CT angiograms alone. In 64 patients, 75 aneurysms were present on DSA. On a per-aneurysm basis, the sensitivity of subtraction CTA was 98.6% for reader 1, and 100% for reader 2. However, sensitivity of conventional CTA was 94.6% for reader 1, and 93.3% for reader 2. Therapeutic decisions could be made regarding 63 patients based on information provided by subtraction CTA images. However, conventional CTA provided sufficient information to make this decision for 55 patients. Conventional CTA has limited sensitivity in detecting very small aneurysms as well as aneurysms adjacent to bone. Subtraction CTA performed on a 64-row multidetector CT is an accurate and promising diagnostic tool that seems to be equivalent to 2D DSA for the detection and pretreatment planning of intracranial aneurysms.