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At least 19 recordsLinked to original sources
PubMed1991

Comparison of magnetic resonance angiography, magnetic resonance imaging and conventional angiography in cerebral arteriovenous malformation.

10 patients with an AVM of the brain were examined by magnetic resonance angiography (MRA), magnetic resonance imaging (MRI) and conventional cerebral angiography (CCA). From MRA in 7/10 patients important information about vascular supply could be provided; in 3 patients, all with small AVM's it could be only suspected. CCA revealed the vascularisation of the AVM's in all patients and showed additional hemodynamic aspects better than MRA. With MRI in all cases the AVM could be diagnosed, but only the involvement of the main cerebral vessels could be demonstrated: however, MRI is superior to MRA and CCA in showing the nidus and the involved brain structures.

Adolescent↗
PubMed1999

Non-invasive assessment of renal artery stenosis: current concepts and future directions in magnetic resonance angiography.

Magnetic resonance angiography is undergoing rapid development as a non-invasive technique to reliably assess renal artery stenosis. Invasive X-ray angiography is currently the gold standard imaging technique and gives excellent spatial resolution. However, its disadvantages include a necessary exposure to radiation and the need for iodinated contrast media. While magnetic resonance angiography does not have these disadvantages, its spatial resolution is inherently lower. On the other hand, magnetic resonance angiography enables true three-dimensional imaging. The use of rapid imaging techniques allows multiple image acquisition within one breath-hold thereby permitting the visualization of distinct vascular phases. The limitation in spatial resolution can be overcome readily by combining morphologic imaging with functional information on the hemodynamic relevance. This can be achieved by means of magnetic resonance phase contrast flow measurements. The use of such a combined approach enables the grading of vascular stenosis based on the combination of morphology and functional information. Magnetic resonance angiography is already able to demonstrate a clinical utility equivalent to that of invasive procedures, indicating that it is likely to become a premier method for the diagnosis and follow up of renovascular disease.

Angiography, Digital Subtraction↗
PubMed1993

Magnetic resonance angiography.

Magnetic resonance angiography is a noninvasive approach to vascular study that recently has become feasible and is quickly proving its usefulness in several areas. Currently, advances are concentrated on evaluation of vessels of the head and neck. Magnetic resonance angiography has also proved valuable in evaluation of the central vasculature, including the heart. Because magnetic resonance angiography is not a single technique and the different techniques of which it is composed have their own strengths and weaknesses, it is important that clinicians, as well as radiologists, be aware of these strengths and weaknesses. Various techniques and their applications and limitations are discussed.

Blood Vessels↗
PubMed2000

[Quantitative assessment of carotid stenosis: comparison between Doppler ultrasound, spiral computed tomography angiography, magnetic resonance angiography and digital angiography].

BACKGROUND: The North American Symptomatic Carotid Endarterectomy Trial has confirmed the benefit of carotid endarterectomy in comparison to medical treatment in stroke prevention in symptomatic patients having a carotid stenosis of 70% or more. The Asymptomatic Carotid Atherosclerosis Study has concluded that the benefit of surgical treatment remains significant in asymptomatic patients with 60% (or more) stenosis of the ipsilateral internal carotid artery, when mortality rate remains inferior to 3%. In these two trials, angiography has been used to quantify the stenosis. Though this test is carrying some neurological and renal risks, replacing the angiography stenosis grading for a non or less invasive test, seems to be permissible. METHODS: In our retroprospective study, the assessments of the carotid stenosis by several non-invasive tests findings were compared to the angiography results. Nineteen carotid arteries of fifteen patients, both symptomatic and asymptomatic, having a carotid stenosis at least 60% or more and being detected by the Doppler ultrasound were explored either by magnetic resonance angiography (MRA), spiral computed tomography angiography (SCTA) and angiography. RESULTS: The ultrasonography and angiography findings were well correlated (r=0,88; p<0.002) according to the Spearman test. The assessments of the MRA were better correlated to the angiography than to the SCTA (respectively r=0.91, p<0.0001 and r=0,68, p<0.001). Using both ultrasonography and MRA as a confirmatory test, the rate of injustified carotid endarterectomy was 25%. And this rate rose up to 33% when the ultrasonography was used with the SCTA. It is noteworthy that negative predictive value of ARM was 100%. To reduce the mortality rate, several surgical teams managed the carotid stenosis without angiography. CONCLUSION: MRA could replace angiography, on condition that the rate of unjustified carotid endarterectomy lowers and becomes acceptable. Far reaching complementary studies are necessary to confirm the fiability of those non-invasive tests. In order to raise the benefit to carotid endarterectomy, the research studies should turn to the predictive score determination of a surgical international risk and towards the "High benefit" patients groups after endarterectomy.

Angiography↗
PubMed1997

Magnetic resonance angiography.

Magnetic resonance angiography (MRA) permits the non-invasive visualization of blood flow through the effects of moving spins on the magnetic resonance signal. MRA techniques can be divided into two main classifications depending upon the primary effect responsible for contrast in the image. Angiograms can be produced using either the time-of-flight (TOF) or phase contrast (PC) methods. Each method has particular advantages and limitations as an angiographic imaging technique and these are reflected in their respective applications. This review article is intended to outline the scientific and technical development of MRA from its basis in the earliest in vitro nuclear magnetic resonance (NMR) experiments, through the implementation of in vivo angiographic techniques on whole body MRI systems, to the recent rapid expansion in MRA acquisition and processing techniques.

Contrast Media↗
PubMed1995

Aneurysmal form of aortoarteritis with aberrant right subclavian artery: diagnosis by Magnetic Resonance Angiography.

Magnetic Resonance Angiography is rapidly advancing as an important imaging modality for vascular disorders. With increasing experience, it bids fair to replace catheter angiography as the diagnostic procedure of choice in select clinical conditions. We report a case of aneurysmal aortoarteritis with renal failure, in which magnetic resonance angiography proved to be a valuable substitute for conventional studies. In addition, the right subclavian artery had an aberrant origin, an unusual association.

Adult↗
PubMed1995

[Principles of magnetic resonance angiography].

Magnetic resonance angiography is a modality of functional imaging which can only be interpreted on the basis of a good understanding of vascular physiology and the physical principles of image acquisition. Magnetic resonance angiography is based on flow-related "artefacts". The oldest method is based on renewal of the image by proton flow: the flight time effect. Dephasing of the protons travelling in magnetic field gradients results in phase-contrast angiography. These two methods of angiography each have respective advantages and disadvantages: they are not mutually exclusive, but complementary.

Hemodynamics↗
PubMed1990

Magnetic resonance angiography.

Magnetic resonance imaging allows the visualization of vascular structures without the use of contrast agents. With three-dimensional imaging techniques, based on gradient echo sequences, up to 128 slices can be acquired within a maximum acquisition time of 21 minutes at a spatial resolution of approximately 1 mm. This allows the carotid arteries and major intracerebral vascular structures to be displayed. From the primary three-dimensional data set, projective images at arbitrary projection angles can be calculated. This technique is extremely helpful for assigning spatially complex vascular structures and identifying vascular disease. As a result of rapid technologic advances in magnetic resonance angiography, it is now necessary to assess its clinical utility for identifying atherosclerotic stenoses, aneurysms, and arteriovenous malformations. Limited experience to date has shown that magnetic resonance angiography, because of its high sensitivity to these vascular diseases, may play a clinically important role as a screening method.

Contrast Media↗
PubMed2004

Peripheral magnetic resonance angiography.

Magnetic Resonance Angiography [MRA] has become a useful imaging modality in the evaluation of vascular anatomy and a variety of vascular disorders in the last several years. Many recent publications have demonstrated that MRA can be an accurate, fast and safe tool in the workup of patients with lower extremity ischemia. It has become a less invasive alternative to catheter angiography, and in some radiology departments MRA has replaced conventional catheter angiography in the initial workup of lower extremity ischemia.

Contrast Media↗
PubMed2002

Semiautomated quantitation of carotid artery stenosis in gadolinium-bolus magnetic resonance angiography.

Magnetic resonance angiography (MRA) has become the standard method for evaluation of carotid occlusive disease. Fast imaging methods combined with bolus intravenous injection of gadolinium contrast have improved the quality of these images. Nevertheless, the gold standard for evaluation was based on projection arterial angiography. The properties of these images are rather different. Whereas most previous evaluations of MRA have used visual assessment of images, we evaluate an algorithm in which a computer algorithm plays the primary role in defining arterial lumen margins, hence, disease. The accuracy of this semiautomated algorithm is shown to compare favorably with gold-standard arteriography in a series of 50 patients.

Algorithms↗
PubMed1996

[Magnetic resonance angiography].

Magnetic resonance angiography (MRA) is a non invasive method for studying the morphology and the hemodynamic of vessels. MRA is becoming well-established for aorta examination and has replaced aortography. MRA is very competitive in screening for renovascular hypertension, intracranial aneurysm, for evaluation of the carotid bifurcation and diagnosis of venous sinus thrombosis. In the future, clinical applications will include pulmonary and coronary arteries.

Humans↗
PubMed1998

[Artifacts in magnetic resonance angiography].

Magnetic resonance angiography (MRA) has become a major tool in the management of vascular diseases. However, many artifacts that may lead to misinterpretations are encountered with this imaging modality. The purpose of this paper was to enumerate, explain and illustrate each kind of artifact encountered with "time of flight" or "phase contrast" imaging methods. For each artifact, we tried to provide one or several techniques to minimize its consequences.

Artifacts↗
PubMedDate not supplied

Instrumentation for magnetic resonance angiography.

Magnetic resonance angiography (MRA) places high demands on instrumentation capabilities. Magnetic gradient strength capabilities, main magnetic field strength and homogeneity, and eddy current compensation all play a role in determining the quality of the flow studies. In addition, radiofrequency coil design and use is governed by the specific vascular territories of interest. Once the instrumentational and pulse sequence considerations have been optimized, the postprocessing and display of the acquired three-dimensional data sets is of key importance. Great strides have been made in addressing instrumentation needs for MRA, but further improvements are anticipated.

Algorithms↗
PubMed1991

[High resolution tridimensional study of the blood vessels of the neck and the intracranial circulation with magnetic resonance angiography].

Magnetic Resonance Angiography (MRA) is a modern vascular imaging technique which allows the noninvasive and direct imaging of vessels. The authors aimed at evaluating the diagnostic accuracy of MRA in the study of pathologic conditions in the neck and intracranial vessels; spatial resolution of the technique was also investigated. Twenty-four healthy volunteers and 82 patients suffering from various diseases of the head and neck vessels were included in the study. First of all, MRA capabilities were investigated in visualizing normal vessels of both neck and intracranial circle. The diagnostic accuracy of the method was then evaluated in the study of vascular diseases, and the results compared with conventional/digital angiographic findings. The comparison demonstrated how stenoses and atherosclerotic plaques tend to be overestimated by MRA because of technical artifacts inherent to the technique itself, whereas vascular ulcerations and aneurysms are frequently underestimated. However, this data was steady and therefore evaluable--the exact knowledge of the artifacts making diagnosis reliable. The diagnostic and technical problems relative to the various vascular diseases are discussed. Finally, several hypotheses of diagnostic iter are suggested.

Angiography, Digital Subtraction↗
PubMed1992

[The stenotic-occlusive anatomy and pathology of the renal arteries. Their evaluation by magnetic resonance angiography].

Magnetic resonance angiography of the renal arteries was performed in 10 healthy subjects, 10 patients with renal artery stenosis and 2 patients with accessory renal artery (1 unilateral, 1 bilateral). All patients selected among 35 subjects with suspected renovascular hypertension had previously undergone digital subtraction angiography. Four patients were studied before and after percutaneous transluminal angioplasty. MRA was performed with time-of-flight technique, with 2D and 3D FISP and 2D FLASH gradient-echo sequences. Digital subtraction angiography demonstrated stenoses ranging 40% to 90% in 10 cases, 7 unilateral (1 transplanted kidney) and 3 bilateral. RA correctly depicted > 90% stenoses in 5 cases, between 50% and 90% stenoses in 2 cases and < 50% in 2 cases. Four stenoses were not properly graded (3 over-graded and 1 not visualized because distal to ostium). Diagnostic accuracy was 71% for unilateral stenoses and 66% for bilateral stenoses (overall accuracy 69.2%).

Adult↗
PubMed1992

Cerebral magnetic resonance angiography.

Magnetic resonance angiography (MRA) is an accurate non-invasive tool for imaging the cerebral vessels. It provides morphologic information about the cerebral vessels relying on blood flow as the physical basis for generating contrast between stationary tissues and moving spins. 'Selective' MRA gives functional information about the cerebrovascular system such as flow direction, origin of flow, and presence or absence of collaterals. Arteries and veins can be imaged selectively due to their usually opposite flow directions. Although at a relatively early stage of development, MRA has already become a widely used tool for the study of the cerebrovascular system.

Arteriovenous Malformations↗
PubMed1991

Technologic advances in magnetic resonance angiography.

Magnetic resonance angiography continues to develop both in technical capabilities and in clinical applications. Head and neck MR angiography is now in common use and is being compared to digital subtraction angiography (DSA) on a daily basis. New approaches to MR angiography in the abdomen and thorax and peripheral areas are making progress. Even coronary angiography is likely to fall prey to MR angiography and the prowess of those designing new techniques. The role of contrast agents in MR angiography is becoming more evident; contrast agents are likely to play an important role in the future. Furthermore, quantitative flow velocity measurements of major vessels are also possible and are of interest to clinicians for blood flow information. This review covers these and other recent developments in MR angiography, including both technical and clinical developments.

Blood Flow Velocity↗
PubMed1993

Cerebrovascular applications of magnetic resonance angiography.

Magnetic resonance angiography (MRA) has been applied to a variety of different manifestations of cerebrovascular disease to date. Practically, the limitations of these techniques must be taken into account such that the appropriate method is applied to answer a specific clinical question and the acquisition parameters are chosen to maximise the sensitivity and specificity of the study. Based upon these results, it must be decided whether the conventional parenchymal MR and MRA evaluations are sufficient in a particular setting or whether it is necessary to commit the patient to a more traditional, invasive angiographic study for a more thorough investigation. Presently, MR angiographic studies and flow measurement techniques serve to compliment the more traditional spin-echo evaluation of patients with small aneurysms, arterial and venous occlusions, vascular malformations and in some cases of neoplastic vascular invasion. With well-trained technicians and carefully prescribed protocols, this new information and improved diagnostic sensitivity can be used routinely with only a minor increase in patient exam time.

Brain↗