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     

Non-invasive vascular imaging of peripheral vessels

The purpose of this review is to describe recent advances in non-invasive vascular imaging techniques and to discuss their current clinical applications for imaging of peripheral vessels. Principles for applying ultrasound, CT angiography (CTA), and magnetic resonance angiography (MRA) for non-invasive imaging of peripheral arteries and veins are presented. Clinical applications are reviewed for different vascular diseases, therapy planning, and follow-up studies. Conventional Doppler and color duplex sonography are the most cost-effective procedures to detect or rule out peripheral arterial occlusive disease (PAOD) and to provide specific recommendations for therapy. In the near future, contrast-enhanced MRA (CE MRA) with additional axial two-dimensional time-of-flight studies to search for non-anatomic runoff will replace diagnostic intra-arterial digital subtraction angiography (DSA) for planning of reconstructive surgery with acquisition slabs displaying projections similar to intra-arterial DSA. Color duplex sonography should also be the first non-invasive technique applied for the detection of peripheral aneurysms. Preoperative or preinterventional therapy planning of aneurysms may be performed by CTA or CE MRA. Compression ultrasound is the imaging procedure of choice in deep venous thrombosis (DVT). In the preoperative assessment of venous incompetence, color duplex sonography is the imaging technique which is sufficient in most cases. Received: 5 March 1998; Accepted: 16 March 1998     

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     

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 stenosis and occlusion: comparison of 3D time-of-flight and 3D phase-contrast MR angiography

We compared the value of 3D time-of-flight (TOF) and phase-contrast (PC) MR angiography (MRA) for detection and grading of intracranial vascular steno-occlusive disease. Unenhanced 3D-TOF MRA and 3D-PC MRA (30–60 cm/s velocity encoding) were performed at the level of the circle of Willis in 18 patients, mean age 56 ± 10 years. Postprocessed images using a maximum-intensity projection reconstruction with multiple targetted projections were analysed. A total of 126 vessels was assessed by PC MRA and 143 by TOF MRA, with digital subtraction angiography (DSA) in 15 patients and/or transcranial Doppler sonography (TCD) in 18 as a standard. Two blinded readers reviewed the MRA, DSA and TCD examinations retrospectively. On DSA and/or TCD the two observers found 32 and 28 steno-occlusive lesions. 3D-TOF MRA was more sensitive than 3D-PC MRA (87 % and 86 % vs. 65 % and 60 %) and had a higher negative predictive value (96 % vs. 89 %). Correct grading of stenoses was achieved in 78 % by 3D-TOF and 65 % by 3D-PC MRA. Received: 24 September 1997 Accepted: 27 February 1998     

Preoperative evaluation of living renal donors: value of contrast-enhanced 3D magnetic resonance angiography and comparison of three rendering algorithms

The aim of this study was to assess the value of contrast-enhanced three-dimensional MR angiography (CE 3D MRA) in the preoperative assessment of potential living renal donors, and to compare the accuracy for the depiction of the vascular anatomy using three different rendering algorithms. Twenty-three potential living renal donors were examined with CE 3D MRA (TE/TR=1.3 ms/3.7 ms, field of view 260–320×350 mm, 384–448×512 matrix, slab thickness 9.4 cm, 72 partitions, section thickness 1.3 mm, scan time 24 s, 0.1 mmol/kg body weight gadobenate dimeglumine). Magnetic resonance angiography data sets were processed with maximum intensity projection (MIP), volume rendering (VR), and shaded-surface display (SSD) algorithms. The image analysis was performed independently by three MR-experienced radiologists recording the number of renal arteries, the presence of early branching or vascular pathology. The combination of digital subtraction angiography (DSA) and intraoperative findings served as the gold standard for the image analysis. In total, 52 renal arteries were correspondingly observed in 23 patients at DSA and surgery. Other findings were 3 cases of early branching of the renal arteries, 4 cases of arterial stenosis and 1 case of bilateral fibromuscular dysplasia. With MRA source data all 52 renal arteries were correctly identified by all readers, compared with 51 (98.1%), 51–52 (98.1–100%) and 49–50 renal arteries (94.2–96.2%) with the MIP, VR and SSD projections, respectively. Similarly, the sensitivity, specificity and accuracy was highest with the MRA source data followed by MIP, VR and SSD. Time requirements were lowest for the MIP reconstructions and highest for the VR reconstructions. Contrast-enhanced 3D MRA is a reliable, non-invasive tool for the preoperative evaluation of potential living renal donors. Maximum intensity projection is favourable for the processing of 3D MRA data, as it has minimal time and computational requirements, while having similar or superior accuracy for the depiction of vessel anomalies or pathology compared with VR and SSD, respectively. Electronic Publication     

CTA und MRA bei PAVK – ist die DSA out?

New developments in technique and postprocessing have led to further improvement in diagnosing and evaluating peripheral arterial disease (PAD) by noninvasive computed tomographic angiography (CTA) and magnetic resonance angiography (MRA). Under clinical conditions diagnostic conventional angiography (DSA) will be increasingly replaced by CTA and MRA. The radiologist has to become familiar with the field of indications, the different techniques, postprocessing tools, and effective visualization. In consideration of the current literature some methodological aspects and the role of CTA and MRA in PAD will be discussed.     

The emerging role of multidetector row CT angiography in the diagnosis of cervical arterial dissection: preliminary study

Introduction Cervical artery dissection is an important cause of ischemic stroke, particularly in young patients. The diagnosis can be made with invasive catheter angiography or non-invasive imaging, either with MRI in conjunction with MR angiography (MRA) or CT angiography (CTA). Both modalities have been shown to have a high specificity and sensitivity. New developments such as multi-slice CTA (MSCTA) are emerging as an alternative methods for imaging the cervical and intracranial arteries. However, the contribution of modern MSCTA to carotid artery dissection has not been reported.Methods We present a retrospective series of seven patients in whom both MSCTA and cervical axial T1 MRI and MRA were performed in the acute to subacute setting of internal carotid artery dissection.Results Carotid artery dissection was identified in all seven patients by MSCTA. The combination of MRI and MRA identified dissection in five of the seven patients. Additionally, a pseudoaneurysm was identified by MSCTA that was missed by MRI and MRA.Conclusion Our findings confirm that MSCTA is a complementary technique in comparison to cervical axial T1 MRI and cervical MRA for diagnosing carotid artery dissection, and at times may provide additional information that can impact patient management.     

CTA与MRA诊断动脉瘤及评估动脉瘤破裂风险的比较

 目的 比较CT血管造影术(CT angiography,CTA)与磁共振血管造影(magnetic resonance angiography,MRA)诊断动脉瘤与动脉瘤破裂的风险评估价值。方法 48例高度怀疑为颅内动脉瘤患者随机分为两组,每组24例,记为Ⅰ组和Ⅱ组,其中Ⅰ组行CTA+DSA检查,Ⅱ组行MRA+DSA检查。比较CTA及MRA对颅内动脉瘤的诊断灵敏度、诊断特异性、阳性预测值、阴性预测值及准确率。比较CTA及MRA对5 mm以上动脉瘤的诊断价值。结果 MRA诊断颅内动脉瘤的诊断灵敏度、诊断特异性、阳性预测值、阴性预测值、准确率较CTA稍低,但二者差异无统计学意义。CTA与三维增强MR血管成像(3D CE-MRA)对5 mm以上动脉瘤的诊断能力相当,但与三维时间飞跃法MR血管成像(3D TOF MRA)相比,CTA与CE-MRA的诊断灵敏度、诊断特异性、阳性预测值、阴性预测值、准确率明显较高,差异有统计学意义(P<0.05);CTA能更清楚地显示瘤颈。结论 CTA和MRA可作为诊断动脉瘤与动脉瘤破裂的风险评估的首要手段,CTA诊断的准确率及三维形态高于MRA。     

Pulmonary circulation

Evaluation of the pulmonary vasculature is mainly indicated in patients with suspected pulmonary thromboembolism. The routine procedure so far is ventilation-perfusion scintigraphy alone or in combination with diagnostic assessment of the legs to rule out deep venous thrombosis. The results are still not reliable for the majority of patients. In the case of equivocal diagnosis, invasive conventional angiography is considered the gold standard. With steady improvements in tomographic imaging techniques, such as computed tomography (CT) or magnetic resonance imaging (MRI), non-invasive alternatives to the routine diagnostic work-up are given. Helical CT and CTA techniques are already in clinical use and estimated to sufficiently serve the demands for detection/exclusion of pulmonary thromboembolism. The disadvantages mainly concern peripheral disease and reconstruction artifacts. MRI and MR angiography have been implemented in the diagnosis of pulmonary vascular disease since the introduction of contrast-enhanced MRA. In breath-hold techniques, the entire lung vascularization can be delineated and thromboemboli can be detected. The clinical experience in this field is limited, but MRI has the potential to demonstrate its superiority over CT due to its improved delineation of the vascular periphery and the more comprehensive three-dimensional reconstruction. Received: 20 January 1998; Accepted: 10 February 1998     

脊髓血管畸形的快速增强MRA与DSA诊断的比较研究

目的 评价椭圆形中心顺序(elliptic centric ordered)的快速增强磁共振血管成像(fastcontrast-enhanced MR angiography,CE-MRA)在脊髓血管畸形中的诊断和临床应用价值.方法 25例临床怀疑脊髓血管畸形的患者在1.5T MR机上接受了椭圆形中心顺序的快速CE-MRA检查,所有病例行选择性全脊椎动脉造影,18例施行了外科手术,其中2例术前行血管内栓塞,术后MRA随访了10例;以选择性全脊椎动脉造影为金标准,就病变诊断、供养动脉起源、供养动脉、瘘口或瘤巢、引流静脉和血管的图像质量(包括血管的连续性、强化程度和清晰度)进行MRA和DSA的比较.结果 经外科手术证实18例,包括脊髓动静脉畸形3例、髓周动静脉瘘5例、硬膜动静脉瘘7例、椎旁动静脉瘘1例、自发性椎管内硬膜外血肿2例;MRA显示脊髓血管畸形的诊断、供养动脉起源、供养动脉、瘤巢或瘘口、引流静脉与DSA的符合率分别为93.8%、92%、96.2%、100%和100%,MRA显示血管强化和清晰度类似于DSA(P＞0.05),DSA显示血管的连续性优于MRA(P＜0.05);9例MRA未见椎管内异常血管,与DSA完全符合.术后MRA随访的10例原异常血管未再显示.结论 椭圆形中心顺序的快速CE-MRA能够初步诊断脊髓血管畸形的亚型,能够显示脊髓血管畸形的供养动脉起源、供养动脉、瘤巢或瘘口、引流静脉,能够指导选择性脊椎动脉造影和手术治疗,是脊髓血管畸形术前诊断和术后随访的重要手段.     

Brain arteriovenous malformations: measurement of nidal volume using a combination of static and dynamic magnetic resonance angiography techniques

Arteriovenous malformations of the brain are complex vascular lesions that are an important cause of death and long-term disability. Currently, catheter angiography (CA) is the reference standard procedure for the diagnosis and follow-up of treated arteriovenous malformations (AVMs). This is an invasive procedure with potential risks. Magnetic resonance angiography (MRA) is commonly used in neurovascular imaging as a non-invasive alternative. Various MRA techniques have been used in the diagnosis and follow-up of AVMs but these have suffered from lack of temporal or spatial resolution. In this 60-patient study we describe the combination of two techniques: dynamic magnetic resonance digital subtraction angiography with a high temporal resolution, and a non-dynamic contrast-enhanced time-of-flight sequence with a high spatial resolution technique, in the assessment of AVM. The results showed an excellent correlation between MRA and CA measurement of both maximum linear dimension and AVM nidus volume.     

Contrast-enhanced three-dimensional MR angiography in the assessment of subclavian artery diseases

The purpose of this prospective study was to determine the potential diagnostic value of 3D breath-hold contrast-enhanced MRA (CEMRA) in the evaluation of subclavian artery pathology, and to compare CEMRA and digital subtraction angiography (DSA) findings. The study group included 50 patients with suspicion of subclavian artery pathology: 40 suspected steno-occlusive disease and 10 different vascular anomalies. The MRA examinations were performed on a 1.5-T system using fast 3D sequences. A fixed dose of 40 ml Gd-DTPA was administered at 2 ml/s after previous bolus tracking. Images were analyzed to assess: subclavian depiction; luminal changes; collateral branches; and feeders of arterial venous malformations (AVM). A multireader blinded fashion was used. The CEMRA revealed an optimal agreement with DSA findings in the different types of diseases. Sensitivity and specificity were 90 and 95 %, respectively, in detecting steno-occlusive disease (including functional and arteritic stenoses), and 100 and 100 %, respectively, in cases of vascular anomalies (dilation, kinking, anomalous origin and AVM). Contrast-enhanced MRA can be proposed as a non-invasive, robust technique for imaging subclavian pathologies with high diagnostic performance. Received: 18 May 1999; Revised: 5 January 2000; Accepted: 27 March 2000     

Diagnostic accuracy of colour Doppler ultrasonography, CT angiography and blood-pool-enhanced MR angiography in assessing carotid stenosis: a comparative study with DSA in 170 patients

Purpose

This study was undertaken to prospectively evaluate the diagnostic performance of colour Doppler ultrasonography (CDUS), first-pass (FP) and steady-state (SS) contrast-enhanced magnetic resonance angiography (MRA) and computed tomography angiography (CTA) of the carotid arteries using digital subtraction angiography (DSA) as the reference standard.

Materials and methods

A total of 170 patients with previous cerebrovascular events and suspected carotid artery stenoses underwent CDUS, blood-pool MRA, CTA and DSA. Accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for CDUS, FP MRA, SS MRA and CTA. The McNemar and Wilcoxon tests and receiver operating characteristic (ROC) curve analysis were used to determine significant differences (p<0.05) between the diagnostic performances of the four modalities, and the degree of stenosis was compared using linear regression.

Results

A total of 336 carotid bifurcations were studied. The area under the curve (AUC) for degree of stenosis was: CDUS 0.85±0.02, FP MRA 0.982±0.005, SS MRA 0.994±0.002 and CTA 0.997±0.001. AUC analysis showed no statistically significant difference between CTA and MRA (p=0.0174) and a statistically significant difference between CDUS and the other techniques (p<0.001). Plaque morphology analysis showed no significant difference between CTA and SS MRA; a significant difference was seen between CTA and SS MRA versus FP MRA (p=0.04) and CDUS (p=0.038). Plaque ulceration analysis showed a statistically significant difference between MRA and CTA (0.04< p<0.046) versus CDUS (p=0.019).

Conclusions

CTA is the most accurate technique for evaluating carotid stenoses, with a slightly better performance than MRA (97% vs. 95% for SS MRA and 92% for FP MRA) and a greater accuracy than CDUS (97% vs. 76%). Blood-pool contrast-enhanced SS sequences offer improved evaluation of degree of stenosis and plaque morphology with accuracy substantially identical to CTA.     

Magnetic resonance angiography in suspected cerebral vasculitis

The purpose of this study was to determine the technical capacity and diagnostic accuracy of 3D time-of-flight magnetic resonance angiography (MRA) in suspected cerebral vasculitis in a retrospective analysis of MRA and digital subtraction angiography (DSA) in 14 young patients with clinical and/or radiological suspicion of cerebral vasculitis. A total of nine arteries were evaluated in each patient. Consensus review of DSA by three observers was the reference standard. The sensitivity for detecting a stenosis varied from 62 to 79% for MRA and from 76 to 94% for DSA, depending on the observer. The specificity for detecting a stenosis varied from 83 to 87% for MRA and from 83 to 97% for DSA. Using the criterion more than two stenoses in at least two separate vascular distributions to consider the examination as being true positive, the false-positive rates for MRA and DSA were comparable. MRA plays a role as the first angiographical examination in the diagnostic work-up of suspected cerebral vasculitis. When more than two stenoses in at least two separate vascular distributions are depicted on MRA, DSA is not expected to add a significant diagnostic contribution in a patient with suspected cerebral vasculitis. DSA remains necessary when MRA is normal or when less than three stenoses are seen.     

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。     

Cost analysis of procedures related to the management of renal artery stenosis from various perspectives

To determine the costs associated with the diagnostic work-up and percutaneous revascularization of renal artery stenosis from various perspectives. A prospective multicenter comparative study was conducted between 1998 and 2001. A total of 402 hypertensive patients with suspected renal artery stenosis were included. Costs were assessed of computed tomography angiography (CTA), magnetic resonance angiography (MRA), digital subtraction angiography (DSA), and percutaneous revascularization. From the societal perspective, DSA was the most costly (€1,721) and CTA the least costly diagnostic technique (€424). CTA was the least costly imaging procedure irrespective of the perspective used. The societal costs associated with percutaneous renal artery revascularization ranged from €2,680 to €6,172. Overall the radiology department incurred the largest proportion of the total societal costs. For the management of renal artery stenosis, performing the analysis from different perspectives leads to the same conclusion concerning the least costly diagnostic imaging and revascularization procedure.     

Carotid stenosis: a comparison between MR and spiral CT angiography

We performed a preliminary study comparing three-dimensional time-of-flight (3 D TOF) magnetic resonance angiography (MRA) and spiral CT angiography (SCTA) in the detection and assessment of internal carotid artery stenosis. Digital subtraction angiography (DSA) was the reference examination. We examined 20 patients with signs of cerebrovascular insufficiency, who underwent MRA, SCTA and DSA within a 3 day period. Both internal carotid arteries were assessed by three blinded readers for degree of stenosis at two different levels (bulb and remaining section) giving a total of 80 assessments. Interobserver variability, sensitivity, specificity, diagnostic accuracy, concordance, overestimation and underestimation were assessed. Interobserver variability was not statistically significant. MRA showed higher sensitivity, specificity, diagnostic accuracy and concordance than SCTA (92.0 % vs 80.8 %, 98.2 % vs 96.4 %, 96.3 % vs 91.3 % and 96.0 % vs 88.0 %, respectively). MRA gave rise to a 5.0 % overestimation rate, whereas SCTA occasioned a 7.5 % underestimation rate. These differences are not statistically significant. These results suggest that MRA is a more useful, noninvasive modality for assessment of the internal carotid artery with a more than 70 % stenosis. Received: 8 August 1997 Accepted: 10 October 1997     

多层螺旋CT血管成像与DSA诊断脑动脉瘤的对比研究

目的通过与DSA和外科手术对比评价多层螺旋CT血管成像（CTA）对脑动脉瘤诊断的准确性。方法对471例临床怀疑为脑动脉瘤的患者全部行CTA和DSA检查。所有CTA及DSA图像由两位神经放射科医师独立进行分析评价。以DSA和外科手术结果作为参考标准计算多层螺旋CTA诊断脑动脉瘤的准确性。结果多层螺旋CTA诊断所有动脉瘤的敏感性、特异性和准确性分别是97.0%、98.3%和97.6%,阳性和阴性预测率分别是98.5%和96.6%。多层螺旋CTA对于动脉瘤检出的敏感性与DSA的结果差别没有统计学意义（P〉0.05）。结论多层螺旋CTA对于脑动脉瘤检出具有很高的敏感性、特异性和准确性,它在脑动脉瘤的筛选和诊断可以替代常规DSA检查。     

Intracranial aneurysms: evaluation using CTA and MRA. Correlation with DSA and intraoperative findings

Computed tomographic angiography (CTA) and magnetic resonance angiography (MSA) have been used recently for evaluation of intracranial aneurysms. If they are to replace conventional digital subtraction angiography (DSA), their sensitivity and specificity should be equal to the latter. In order to determine whether computed tomographic angiography and magnetic resonance angiography can provide the necessary information for presurgical evaluation we compared blindly the results of helical CT angiography and MR angiography with the results of digital subtraction angiography and the intraoperative findings. We evaluated 35 patients with the possible clinical diagnosis of intracranial aneurysm. Our data suggest that both CTA and MRA can provide valuable preoperative information concerning the location, the characteristics and the relationships of most intracranial aneurysms. Both original and reconstructed images should be evaluated together for higher accuracy. In addition helical CT, being a fast, inexpensive and noninvasive method, can be used as a reliable alternative to DSA in emergency situations demanding immediate operation.