Use Of Magnetic Resonance Angiography Research Articles

MRA for Carotid Artery Stenosis

To the Editor: With interest we read the systematic review and meta-analysis on the diagnostic accuracy of magnetic resonance angiography (MRA) in measuring carotid artery stenosis of Debrey and colleagues.1 In this field with rapid technical developments, such as the increasing use of contrast-enhanced MRA (CE-MRA), a pooled estimate of the diagnostic accuracy is timely and useful. The accuracy of this review is however suboptimal, because the largest …

Clinical utility of magnetic resonance angiography for femoro-popliteal arterial occlusive disease

Magnetic resonance angiography (MRA) has recently become instrumental in the diagnosis of arterial disease and is gaining an important role in the study of plaining revascularization.In this study we present clinical utility of magnetic resonance angiography for femoro-popliteal arterial occlusive disease.

Magnetic Resonance Angiography in the Preoperative Planning of DIEA Perforator Flaps

Sir: Imaging of the abdominal wall vasculature has become an area of growing interest as a tool in preoperative planning for deep inferior epigastric artery (DIEA) perforator flaps for breast reconstruction. Significant variation in individual anatomy necessitates preoperative imaging. Advances in imaging technologies have broadened our means for exploring this anatomy, and further advances are surely pending. Ultrasound, fluoroscopy, and computed tomographic angiography have been described in the literature. Magnetic resonance angiography, an emerging imaging technique, has not yet been described in the literature in the preoperative imaging of DIEA perforator flaps but certainly warrants discussion in this role. Ultrasound has been a useful tool in the preoperative planning of abdominal wall flaps based on the DIEA. Doppler and color duplex sonography have been used to image the DIEA and perforators, but not without significant inconsistencies between imaging and operative findings.1,2 Computed tomographic angiography is a recently described technique used for improved visualization of individual perforators.3 Early studies have shown a degree of high accuracy in displaying the DIEA and perforators and a level of high concordance with operative findings.1,3 As occurred with computed tomographic angiography, the evolution of imaging technologies enhances their application in perforator imaging. The use of magnetic resonance angiography for perforator imaging has not been described in the literature; however, this application intuitively appears appropriate. The use of magnetic resonance angiography for other free flaps has demonstrated high sensitivities and positive predictive values.4 The fact that magnetic resonance angiography is free of ionizing radiation is desirable, as many patients undergoing the procedure are young (and most at risk for radiation exposure). We have begun to explore the use of magnetic resonance angiography in imaging the DIEA, with promising early results. However, the following pitfalls have emerged that should be considered in a discussion of magnetic resonance angiography. Magnetic resonance angiography typically produces images of inferior spatial resolution than computed tomographic angiography, which may make detection of perforators inferior to computed tomographic angiography. Magnetic resonance angiography is similarly less reproducible than computed tomographic angiography. These limitations are largely attributable to timing of the contrast bolus and the intrinsically higher contrast resolution achievable with computed tomographic angiography.5 The financial cost of magnetic resonance angiography is greater than that of computed tomographic angiography in most health systems, with computed tomographic angiography fully reimbursed in our public health system and magnetic resonance angiography fully charged to the patient. The scanning time is also significantly greater with magnetic resonance angiography compared with computed tomographic angiography, a burden on both the patient and the health care system, with magnetic resonance angiography accessibility subsequently limited. In addition, there will be a number of patients unable to undergo magnetic resonance angiography because of safety issues. Despite these limitations of magnetic resonance angiography, the radiation benefit of magnetic resonance angiography will lead to further interest in optimizing the technique. Advances in computed tomographic angiography scanning techniques have already lowered the effective radiation dose to less than that of other abdominal computed tomographic scans, and with continuing modifications, this dose may continue to fall.1,3 There may certainly be a role for selective use of each modality based on preoperative factors. Magnetic resonance angiography is an area of much promise, and preliminary study results are pending. There is no doubt that these issues will continue to arise with future technologies yet to emerge into clinical use. Warren M. Rozen, M.B.B.S., P.G.Dip.Surg.Anat. Jack Brockhoff Reconstructive Plastic Surgery Research Unit University of Melbourne Damien L. Stella, M.B.B.S., F.R.A.N.Z.C.R. Timothy J. Phillips, M.B.B.S., P.G.Dip.Surg.Anat. Department of Radiology Royal Melbourne Hospital Mark W. Ashton, M.B.B.S., M.D. Russell J. Corlett, M.B.B.S., F.R.A.C.S. G. Ian Taylor, M.B.B.S., M.D., A.O. Jack Brockhoff Reconstructive Plastic Surgery Research Unit University of Melbourne Parkville, Victoria, Australia DISCLOSURE The authors declare that there is no source of financial or other support or any financial or professional relationships that might pose a competing interest.

Quantification of blood flow velocity in stenosed arteries by the use of finite elements: an observer-independent noninvasive method

Interventions for peripheral arterial disease should be designed to treat a physiological rather than an anatomic defect. Thus, for vascular surgeons, functional information about stenoses is as important as the anatomic one. In case of finding a stenosis by the use of magnetic resonance angiography, it would be a matter of particular interest to derive automatically and directly objective information about the hemodynamic influence on blood flow, caused by patient-specific stenoses. We developed a methodology to noninvasively perform numerical simulations of a patient's hemodynamic state on the basis of magnetic resonance images and by the means of the finite element method. We performed patient-specific three-dimensional simulation studies of the increase in systolic blood flow velocity due to stenoses using the commercial computational fluid dynamic software package FIDAP 8.52. The generation of a mesh defining the flow domain with a stenosis and some simulation results are shown.

What Causes Nephrogenic Systemic Fibrosis?

What Causes Nephrogenic Systemic Fibrosis?

Abstract No. 243: In Stent Visualization of Balloon Expandable Stents: In Vitro MRI Study

The role of contrast enhanced magnetic resonance angiography (MRA) in the evaluation of stent patency is limited by multiple artifacts. The most dominant artifact is magnetic susceptibility associated with the composition of the stent. This has greatly limited the potential use of MRA for evaluation of luminal patency. The aim of the current study is to evaluate the effect of stent composition and orientation within the magnetic field on the MR signal obtained from blood containing gadolinium chelate.

効果的な塞栓を目的としたＭＲＡによる動脈瘤内ｉｎｆｌｏｗ ｚｏｎｅの同定

It is important to pack the inflow zone of intracerebral aneurysm to prevent coil compaction or recanalization after coil embolization of the aneurysm. In this study, we report the usefulness of magnetic resonance angiography (MRA) to identify the inflow zone of the aneurysm. Between November 2004 and March 2006, 21 patients (IC paraclinoid, 11 cases; BA tip, 3 cases; A-com, 4 cases; IC-top, 2 cases; P1, 1 case) underwent interventional coil embolization for cerebral aneurysms and MRA was used to try to depict the inflow zone of the aneurysm. We designed a 3D time-of-flight MRA technique targeted to the aneurysm with a large flip angle to emphasize the streamline into the aneurysm. We grasped the position of the inflow zone in the aneurysm by MRA before intervention. The inflow zone was packed by coils tightly with balloon neck remodeling technique and/or catheter assist technique, if necessary. The inflow zone was depicted in all 21 cases by MRA. In sidewall type aneurysms, the inflow zone existed beside the distal neck in all cases. In terminal type aneurysms, the inflow zone existed on an extension line from patent artery. Dome filling was not detected in all cases after treatment. Small neck remnant was detected in 6 cases that slightly increased in 4 cases, vanished in 1 case, remained and unchanged in 1 case 6 months after treatment. None of the cases required additional treatment. For effective coil embolization, it is important to grasp the position of the inflow zone of the aneurysm and to pack the point as tightly as possible. Identification of the inflow zone of aneurysm by MRA is useful for coil embolization.

Use of Magnetic Resonance Angiography in Diagnosis and Decision Making of Post-Traumatic, High-Flow Priapism

The ideal imaging modality should demonstrate the presence or absence of a clinically significant, causative vascular lesion that, in high-flow arterial priapism, may need intervention. We report a 22-year-old male with post-traumatic arterial priapism. Color Doppler ultrasound could not reliably identify a significant vascular lesion. Magnetic resonance angiography (MRA) demonstrated the presence of a cavernous artery pseudoaneurysm. Based on this finding, embolization was decided, with a successful outcome. Contrast-enhanced MRA appears to be a useful, noninvasive diagnostic tool for decision making in cases of high-flow priapism.

Ictus and antiphospholipid syndrome: How much is enough?

Herein we report the case of a patient with antiphospholipid Syndrome (APS) and an ischemic stroke suffered while he was anticoagulated, and we discuss the usefulness of magnetic resonance angiography in the early diagnosis of such a complication. We also attempt to emphasize the great value of an individual risk evaluation when warfarin therapy is introduced. In fact, our case supports the importance of high-intensity anticoagulation in patients with multiple thrombotic recurrences, and the exceptional value that strict anticoagulation control has in this kind of patients.

Assessment of brain aneurysms by using high-resolution magnetic resonance angiography after endovascular coil delivery

Digital subtraction (DS) angiography is the current gold standard of assessing intracranial aneurysms after coil placement. Magnetic resonance (MR) angiography offers a noninvasive, low-risk alternative, but its accuracy in delineating coil-treated aneurysms remains uncertain. The objective of this study, therefore, is to compare a high-resolution MR angiography protocol relative to DS angiography for the evaluation of coil-treated aneurysms. In 2003, the authors initiated a prospective protocol of following up patients with coil-treated brain aneurysms using both 1.5-tesla gadolinium-enhanced MR angiography and biplanar DS angiography. Using acquired images, the subject aneurysm was independently scored for degree of remnant identified (complete obliteration, residual neck, or residual aneurysm) and the surgeon's ability to visualize the parent vessel (excellent, fair, or poor). Thirty-seven patients with 42 coil-treated aneurysms were enrolled for a total of 44 paired MR angiography-DS angiography tests (median 9 days between tests). An excellent correlation was found between DS and MR angiography for assessing any residual aneurysm, but not for visualizing the parent vessel (K = 0.86 for residual aneurysm and 0.10 for parent vessel visualization). Paramagnetic artifact from the coil mass was minimal, and in some cases MR angiography identified contrast permeation into the coil mass not revealed by DS angiography. An intravascular microstent typically impeded proper visualization of the parent vessel on MR angiography. Magnetic resonance angiography is a noninvasive and safe means of follow-up review for patients with coil-treated brain aneurysms. Compared with DS angiography, MR angiography accurately delineates residual aneurysm necks and parent vessel patency (in the absence of a stent), and offers superior visualization of contrast filling within the coil mass. Use of MR angiography may obviate the need for routine diagnostic DS angiography in select patients.

Diagnostic tools in the preoperative evaluation of children with anomalous pulmonary venous connections

Pulmonary venous abnormalities are generally diagnosed by echocardiography and often confirmed by cardiac catheterization. Although angiography has been the gold standard for evaluation it carries certain inherent risks, especially in small and sick infants. In this study we retrospectively assessed the utility of magnetic resonance angiography (MRA) and computed tomography angiography (CTA) in the evaluation of pulmonary venous abnormalities in pediatric patients. The results were compared with operative findings. We reviewed nine patients with total APVC and four with partial APVC. Twelve patients were infant (age range: 1 day to 8 months) and the other was 16 years old. MRA and/or CTA clearly visualized the anomalous drainage of pulmonary veins in all patients. Cardiac catheterization was performed five patients with one total anomalous pulmonary venous connection and four with partial anomalous pulmonary venous connection. Ten patients were operated on. Diagnoses of patients were confirmed by operative findings. In Conclusions, MR and CT angiography allow detailed and comprehensive evaluation of the APVC and are good diagnostic modalities for use in the preoperative assessment of the anomaly in pediatric patients.

Usefulness of Magnetic Resonance Angiography in the Evaluation of Complex Congenital Heart Disease in Newborns and Infants

This study evaluated the quality of the visualization of extracardiac thoracic vessels by magnetic resonance angiography (MRA) in young infants with congenital heart disease. Echocardiography is often sufficient in evaluating CHD in young infants. Cardiac catheterization is needed in some instances to evaluate extracardiac thoracic vessels. Extracardiac thoracic vessels can be accurately evaluated using MRA in adults and older children, but image quality in small infants may be limited. Twenty-nine magnetic resonance angiographic scans were performed at a single institution on 28 infants aged <3 months (median 6 days, range 1 to 90 days) with complex CHD in whom imaging was inconclusive by echocardiography. A blinded observer at a different institution graded (from 0 to 3) the quality of the visualization of the main, branch, lobar, and second-generation pulmonary arteries; lobar pulmonary veins; aortopulmonary collaterals; vena cavae; thoracic aorta and its branches; patent ductus arteriosus; and visceral sidedness. The results of MRA were compared with those of x-ray angiography and surgical inspection, when available. The mean image quality grade was >2 for all structures except the second-generation pulmonary arterial branches, for which it was 2. The median total scan duration was 9 minutes (range 3 to 46). Findings were concordant with surgical inspection (n = 25) and cardiac catheterization (n = 8) in all subjects. There were no complications. In conclusion, MRA is excellent for the visualization of extracardiac thoracic vessels in young infants with CHD and can be used as an alternative to cardiac catheterization when echocardiography is inconclusive.

Clinical utility of magnetic resonance angiography (MRA) in the diagnosis and treatment of Takayasu’s arteritis

Dear Editor, The first case of Takayasu’s arteritis (TA) was described in 1908 by Dr. Mikito Takayasu [1] at the Annual Meeting of the Japan Ophthalmology Society. Dr. Takayasu described a peculiar “wreathlike” appearance of blood vessels in the back of the eye (retina). Two Japanese colleagues at the same meeting reported similar eye findings in patients whose wrist pulses were absent. It is now known that TA is a large-vessel vasculitis of unknown etiology that has a predilection for the aorta and its primary branches Figs. 1 and 2. TA has traditionally been divided into an early, “prepulseless” systemic phase and a late occlusive phase. In the early systemic phase, diagnosis is difficult and symptoms are usually nonspecific and constitutional, including fever, myalgias, weight loss, and arthralgias. In the occlusive phase, ischemic symptoms dominate, including angina, claudication, syncope, and visual impairment. Late-phase TA may be further subclassified as classic pulseless disease (type 1), a mixed type (type 2), an atypical coarctation type (type 3), and a dilated type (type 4). The clinical presentation of TA and the results of laboratory tests at the onset of the disease are typically nonspecific, which may lead to delayed diagnosis and most of the patients present with the late-phase disease. Accurate diagnosis virtually always depends on imaging studies; nevertheless, angiography is an invasive method that carries well-known risks of complications resulting from the procedure itself, such as hematoma, arteriovenous fistula, pseudoaneurysm, and vessel thrombosis. The reported overall prevalence of a major vascular complication is 0.02–9% [2]. Magnetic resonance angiography (MRA) advantages include the lack of the need for ionizing radiation and iodinated contrast material; therefore, MRA is ideal for serial evaluation of patients with TA who are undergoing treatment. Furthermore, MRA provides the ability to view vessels in any desired plane, and techniques like cine magnetic resonance imaging (MRI) can detect cardiovascular functional and hemodynamic changes, such as aortic regurgitation, in patients with TA. As with the CT scan, MRI is useful for early diagnosis because of its ability to evaluate wall thickness rather than just the luminal narrowing. In addition, MRA provides detailed information about the location, extent, and degree of vascular involvement. It also provides detailed information about the extent of stenotic lesions, the patency of collateral vessels, and it also seems useful as a follow-up modality to assess the response to treatment [3]. Given the fact that in clinical practice, some patients with TA show normal Erythrocyte sedimentation rate (ESR) at their initial evaluation, and this may give false impression that they Clin Rheumatol (2007) 26:1393–1395 DOI 10.1007/s10067-007-0577-2

Magnet Resonance Angiography versus Conventional Angiography for the Planning of Reconstructive Surgeries.

Assessing the vascular status and anatomy of the lower extremity is of crucial importance when planning the coverage of a tissue defect with a free flap. The standard techniques comprise the clinical examination, Doppler ultrasound and Doppler sonography for healthy patients without suspected direct trauma to the vascular system, and conventional digital subtraction angiography (DSA), respectively, in case of traumatized vessels or patients with peripheral arterial obstructive disease. We have conducted a prospective study for the comparison of the magnetic resonance angiography (MRA) to the conventional DSA. Fourteen patients were examined presurgically by means of both a conventional DSA and an MRA before undergoing planned microvascular coverage of tissue defects of the lower extremity. The surgeon, based on a questionnaire, assessed and compared both examination results according to their information content. Furthermore, the presurgically planned level and localization of the vascular anastomoses and the intraoperative findings were compared postoperatively. The MRA examination yielded sufficient information on the vascular anatomy to enable the surgeon to carry out a detailed presurgical planning. Additionally, the use of MRA showed clear advantages with regard to both patient and user comfort. Taking into account the advantages for the assessment of vessels using MRA, in particular when considering the impact of the frequently varying vascular anatomy of the lower leg on reconstructive surgery, as well as the significantly lower morbidity rate of the examination itself, then the MRA must be regarded as a safe alternative to the DSA.

Nanoshell Magnetic Resonance Imaging Contrast Agents

Nanocontrast agents have great potential in magnetic resonance (MR) molecular imaging applications for clinical diagnosis. We synthesized Au(3)Cu(1) (gold and copper) nanoshells that showed a promising MR contrast effect. For in vitro MR images, the large proton r1 relaxivities brightened T(1)-weighted images. As for the proton-dephasing effect in T(2), Au(3)Cu(1) lightened MR images at the low concentration of 0.125 mg mL(-1) (3.84 x 10(-7) mM), and then the signal continuously decreased as the concentration increased. For in vivo MR imaging, Au(3)Cu(1) nanocontrast agents enhanced the contrast of blood vessels and suggested their potential use in MR angiography as blood-pool agents. We propose that (1) the cooperativity originating from the form of the nanoparticles and (2) the large surface area coordinated to water from their porous hollow morphology are important for efficient relaxivity. In a cytotoxicity and animal survival assay, Au(3)Cu(1) nanocontrast agents showed a dose-dependent toxic effect: the viability rate of experimental mice reached 83% at a dose of 20 mg kg(-1) and as much as 100% at 2 mg kg(-1).

Emerging Vascular Applications of Magnetic Resonance Imaging: A Picture is Worth More than a Thousand Words

Vascular applications of magnetic resonance (MR) imaging are reviewed, with emphasis on algorithms that use nonpictorial information contained in the MR data set. Current clinical vascular practice generally limits use of MR angiography and three-dimensional vessel images to qualitative pictorial rendering without routinely using the available quantitative information contained within the MR data. This review is dedicated to recent advances that include characterization of vessel histology, assessment of carotid plaque vulnerability, characterization of blood flow dynamics, quantitative analysis of disease severity, and prediction of vascular intervention outcome. Examples from histologic preparation, in vitro and in vivo experiments, are discussed, with an emphasis on potential clinical applications and advances in acquisition technology.

Standard-protocol moving-table magnetic resonance angiography for planning of interventional procedures in patients with peripheral vascular occlusive disease

This study aimed to evaluate the usefulness of magnetic resonance angiography (MRA) for the planning of interventional procedures in the lower extremity vascular territory. Patients with peripheral vascular occlusive disease (PVOD) underwent MRA for planning of percutaneous interventional treatment. Digital subtraction angiography was performed in patients scheduled for interventional treatment and served as the standard of reference. In 148 out of 150 cases (98.7%), the necessity for an intervention was recognized correctly; 137 out of 150 interventions (91.3%) were correctly planned based on MRA results. Contrast-enhanced MRA of the lower extremities is a safe, noninvasive tool for preinterventional assessment of patients with PVOD. It allows exact planning of endovascular interventions.

An Evidence-based Review of Magnetic Resonance Angiography for Diagnosing Arterial Thoracic Outlet Syndrome

Arterial thoracic outlet syndrome (TOS) can be difficult to diagnose clinically. Recently, Magnetic Resonance Angiography (MRA) has been used to assist in the diagnosis of arterial TOS. The purpose of this article is to survey the current literature to establish the evidence for or against the use of MRA in the diagnosis of arterial TOS. The evidence-based search was conducted using PubMed, PEDro, Hooked on Evidence, EBM Journals, Ovid, Cochrane, and E medicine. The studies were graded as to the strength of recommendation and to the actual level of evidence. Statistics were calculated when sufficient data were present. The search yielded a total of seven studies. The studies received grades of recommendation that ranged from B to D. The current evidence in support of MRA as a valid test for diagnosing arterial TOS is weak and studies are not based on strong design.

Stereotactic radiosurgery for brain arteriovenous malformations: quantitative MR assessment of nidal response at 1 year and angiographic factors predicting early obliteration

We investigated the role of magnetic resonance angiography (MRA) in the early follow-up of patients after stereotactic radiosurgery (STRS) for cerebral arteriovenous malformations (AVMs) and determined the influence of individual morphological factors of AVMs in early response to treatment. A group of 40 patients (41 AVMs) consented to a dedicated 1.5-T MR protocol 12 months after receiving STRS for a brain AVM. In addition to standard spin echo sequences, 3-D contrast-enhanced sliding interleaved Ky MRA (CE-SLINKY) and dynamic time-resolved subtraction angiography (MR-DSA) were performed. Nidal volumes were calculated using CE-SLINKY data in patients with a persisting arteriovenous shunt. Planning angiographic data was investigated in all 40 patients. The following AVM factors were used in the statistical analysis to determine their role in nidus obliteration: (1) maximum linear dimension, (2) nidal volume, (3) AVM location (4) nidal morphology, (5) venous drainage, (6) "high-flow angiographic change", (7) prior embolization, and (8) dose reduction. Complete nidal obliteration was found in 9 patients, 26 showed greater than 50% nidal reduction and 6 had less than 50%. Two AVM factors, venous drainage and AVM location, were found to significantly correlate with rate of obliteration. We successfully demonstrated the use of MRA to quantitatively assess the response of AVMs to STRS. Two AVM factors, venous drainage and AVM location were found to correlate with rate of obliteration prior to the application of the Bonferroni correction, but if this more rigorous statistical test was applied then none of the factors was found to be significant.

Intracranial aneurysm stenting: Follow‐up with MR angiography

Intracranial stenting is increasingly being used to treat intracranial aneurysms and stenoses. We wanted to assess the utility of magnetic resonance angiography (MRA) in the follow-up of patients treated with various types of intracranial stents and to assess the utility of performing gadolinium-enhanced MRA. A total of 19 patients having undergone intracranial stenting for aneurysms were imaged by MRI at 1.5T. A total of 20 stents were placed in 19 patients. In addition to conventional T2- and diffusion-weighted MRI, 3D time-of-flight MRA was performed before and after contrast administration. In the case of metallic INX stents (N = 7), there was a signal drop at the level of the vessel. which did not allow to evaluating the parent vessel, whereas this was visible in Nitinol stents (N = 8). Additionally a stent with a wire had a small artifact (N = 3). Contrast administration also improved vessel lumen visualization. In the case of Nitinol stents, MRA can be used to reliably demonstrate the vessel lumen after intracranial stenting. The use of postcontrast 3D time-of-flight imaging helps improve the intraluminal definition.