Gadolinium-enhanced 3D MRA of the aortic arch vessels in the detection of atherosclerotic cerebrovascular occlusive disease

Subclavian Steal Syndrome: Diagnosis with Perfusion Metrics from Contrast-enhanced MR Angiographic Bolus-timing Examination—Initial Experience

PURPOSE

To retrospectively determine whether differential temporal changes in signal intensity of the vertebral arteries, measured at a bolus-timing examination with a test dose of a gadolinium-based contrast agent, are present in patients with subclavian steal syndrome.

MATERIALS AND METHODS

Institutional review board exemption was obtained, and informed consent was not required for this retrospective study. The study complied with the Health Insurance Portability and Accountability Act. Twenty-five patients with known or clinically suspected atherosclerotic disease of the aortic arch and branch vessels underwent breath-hold contrast material-enhanced magnetic resonance (MR) angiography with circulation time derived from a timing examination by using a test bolus of a gadolinium-based contrast agent. Eight patients (three men and five women aged 54-80 years; mean, 70 years) had subclavian stenosis or occlusion with retrograde vertebral artery flow confirmed with time-of-flight MR angiography, nine patients (eight men and one woman aged 31-91 years; mean, 70 years) had mild to severe ostial stenosis of a single vertebral artery, and eight patients (including four men and four women aged 53-86 years; mean, 73 years) had normal vertebral arteries. The difference in time to peak signal intensity between the right and left vertebral arteries was compared among the three groups by using Fisher exact and Cochran-Mantel-Haenszel tests.

RESULTS

The delay in peak enhancement in the ipsilateral vertebral artery ranged from 2 to 4 seconds (mean, 2.5 seconds) in all eight patients with subclavian steal syndrome. In eight of nine patients with ostial vertebral artery stenosis and eight controls, both vertebral arteries filled simultaneously. The presence of unilateral delayed vertebral artery enhancement was significantly associated with retrograde flow in patients with subclavian steal syndrome, compared with patients with normal flow (P < .01) and those with ostial vertebral artery stenosis (P < .01).

CONCLUSION

A bolus-timing examination performed with a test bolus of the gadolinium-based contrast agent via the neck vessels that demonstrates at least a 2-second delay in peak contrast enhancement in the right or left vertebral arteries may, in the appropriate clinical setting, indicate subclavian steal syndrome.

Gadopentetate dimeglumine-enhanced three-dimensional MR-angiography: dosing, safety, and efficacy

Noninvasiveness, inherent three-dimensionality allowing reformations in any desired plane, and safe contrast agents, coupled with high diagnostic accuracy have driven the rise in popularity of contrast-enhanced MR angiography (CE-MRA) within the medical community. Reflecting its dominant market share as a paramagnetic contrast agent, gadopentetate dimeglumine (Gd-DTPA) has been used for the majority of clinically-performed MRA exams. Over the period January 1994 to February 2002, a total of 172 original studies describing the use of gadolinium-enhanced MRA in more than three human subjects were identified. Of these, 117 described the use of Gd-DTPA as the contrast agent for MRA. A total of 4046 subjects who received Gd-DTPA for MRA are described in these studies. Analysis of these data demonstrate Gd-DTPA to be a safe contrast agent for MRA when applied in a dose ranging from 0.1 to 0.3 mmol/kg of bodyweight. The documented clinical results show Gd-DTPA to be efficacious in the assessment of the arterial system. The effectiveness of Gd-DTPA-enhanced MRA extends beyond the detection, localization, and characterization of arterial disease, and encompasses choice and planning of appropriate therapy, as well as evaluation of therapeutic effectiveness.

Evaluation and management of transient ischemic attack and minor cerebral infarction

After immediate intervention for cerebral infarction or transient ischemic attack (TIA), the primary goal is secondary prevention of future cerebral ischemia and prevention of complications related to the initial ischemic event. The goals of the diagnostic evaluation are to (1) determine potential contributing mechanisms (cardioembolic, large-vessel disease of the extracranial and intracranial vessels, small-vessel disease, coagulation defects, and cryptogenic), (2) identify contributing risk factors (hypertension, hyperlipidemia, tobacco use, diabetes), and (3) complete the evaluation in a cost-effective and safe manner. We provide a sequential approach to the diagnostic evaluation of cerebral infarction or TIA to optimize diagnostic yield of testing, minimize cost and potential harm to the patient, and provide information that will change management. This systematic approach focuses on 6 important questions: (1) Are the symptoms consistent with a cerebral infarction or TIA (versus nonischemic pathology)? (2) Where does the ischemic event localize? (3) What etiologies and mechanisms of cerebral infarction and TIA are possible? (4) What is the prevalence of each potential etiology? (5) What treatments are available for this etiology? (6) What tests and studies are useful to evaluate this etiology?

MRA versus DSA in the assessment of occlusive disease in the aortic arch vessels: accuracy in detecting the severity, number, and length of stenoses

PURPOSE

To compare the diagnostic accuracy of contrast-enhanced magnetic resonance angiography (MRA) to that of digital subtraction angiography (DSA) in the detection, grading, and measurement of atherosclerotic stenoses involving the aortic arch arteries.

METHODS

The MRA and DSA studies from 28 patients (16 women; mean age 61.6 years, range 24-83) being evaluated for possible aortic arch vessel disease were examined. The aortic arch vasculature was divided into 9 segments; within each segment, the presence and severity of stenotic or occlusive disease was determined based on a 5-point scale. In addition, stenosis length and distance to the branch were measured in 5-mm increments. Image quality was assessed using a 5-point scale. The accuracy, sensitivity, and specificity values, as well as the positive and negative predictive values in MRA's identification of lesions, were evaluated in comparison to DSA.

RESULTS

In 28 patients, 189 segments were assessed by both methods. Of these, 173 were correctly rated by MRA, resulting in an accuracy of 91.5%. The accuracy dropped slightly to 86.5% when 11 "not assessable" lesions were included. Sensitivity and specificity for severity measurement were 88.5% and 95.6%, respectively. In 39 of 45 lesions, stenosis length measurements were identical by both methods, but there was a difference of 0.5 cm each in 6 lesions.

CONCLUSIONS

MRA as compared to DSA shows high accuracy in the detection and grading of lesions involving the aortic arch vessels. The noninvasive nature of this method recommends its use for screening, treatment planning, and follow-up in known or suspected arterial disease in aortic arch arteries.

On Improving Temporal and Spatial Resolution of 3D Contrast-enhanced Body MR Angiography with Parallel Imaging

Use of a parallel imaging technique to improve temporal and spatial resolution at three-dimensional contrast-enhanced magnetic resonance (MR) angiography was investigated. Thirty experiments were performed in five groups of healthy subjects. In groups 1-3, the technique was used to improve imaging speed by a factor of two or four while maintaining spatial resolution. Contrast agent concentration was two to four times higher than at standard MR angiography, to take advantage of the faster imaging speed. In groups 4 and 5, the technique was used to double spatial resolution in the phase-encoding direction while maintaining imaging speed and contrast agent concentration. At a two to four times faster imaging speed, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) almost equaled those at standard MR angiography, likely a result of increased contrast agent concentration. The use of parallel imaging to achieve higher spatial resolution was also proved feasible, but with substantial reduction in SNR and CNR.

MR angiography of the extracranial circulation

In this article, the authors present a brief history of MR angiography (MRA) of the neck with emphasis on the techniques developed, particularly recent ones, to improve image quality. The goal of MRA is to eventually replace catheter angiography. The use of MRA, particularly contrast enhanced MRA with regards to pathology (atherosclerotic disease/plaque formation, dissection and post-traumatic aneurysm) involving the extra-cranial carotid and vertebral arteries is addressed. The authors also comment on computed tomographic angiography and sonography and how they compare with contrast enhanced MRA when pertinent.

Proximal Great Vessels of Aortic Arch: Comparison of Three-dimensional Gadolinium-enhanced MR Angiography and Digital Subtraction Angiography

PURPOSE

To prospectively compare dynamic three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiography and digital subtraction angiography (DSA) for the detection of ostial stenosis of the craniocervical vessels.

MATERIALS AND METHODS

Thirty-three patients with carotid stenosis of more than 50% at sonography prospectively underwent both MR angiography and DSA. The overall quality of each DSA and MR angiographic study was analyzed. For each craniocervical vessel (brachiocephalic, common carotid, subclavian, and vertebral arteries) (n = 231), ostial stenosis was graded as follows: normal, mild (<50%), moderate to severe (>50%), or occlusion. MR angiographic and DSA results were compared by means of the Spearman rank correlation coefficient (Rs).

RESULTS

The overall diagnostic quality of MR angiography was excellent or adequate. Three studies were inadequate because of a poor signal-to-noise ratio (13 of 231 arteries) or a coverage error (five of 231 arteries). Findings at MR angiography and DSA agreed on the degree of stenosis (Rs = 0.82, P <.001). No cases of stenosis of more than 50% were missed at MR angiography. However, some discrepancies were noted between vertebral arteries and the other craniocervical vessels. The sensitivity and specificity for stenosis of more than 50% in other craniocervical vessels were 100% and 98%, respectively. The sensitivity and specificity for stenosis of more than 50% in the vertebral arteries were 100% and 85%, respectively. Findings at MR angiography tended to result in overestimation of the degree of ostial stenosis, especially in vertebral arteries (10 [15%] of 66 arteries).

CONCLUSION

MR angiography is useful to rule out ostial stenosis of the craniocervical vessels. MR angiography is an adequate diagnostic tool for ostial stenosis, except in the vertebral artery.

Preoperative evaluation of the entire hepatic vasculature in living liver donors with use of contrast-enhanced MR angiography and true fast imaging with steady-state precession

PURPOSE

To preoperatively assess the entire hepatic vasculature in living related liver donors with use of a combination of contrast material-enhanced magnetic resonance (MR) angiography and true fast imaging with steady-state precession (FISP).

MATERIALS AND METHODS

Twenty-five living potential liver donors were examined preoperatively on a 1.5T Siemens Sonata system. Twenty-four underwent surgery and two had catheter angiography performed to delineate complex anatomy. Contiguous 5-mm-thick, sub-second true FISP images of the liver were initially obtained during breath-holding in axial and coronal planes (repetition time [TR]/echo time [TE], 3.2/1.6; flip angle, 70 degrees ). MR angiography was performed with use of a three-dimensional (3D) gradient-echo fast low-angle shot (FLASH) pulse sequence (TR/TE, 3.0/1.2; flip angle, 25 degrees ), with 40 mL of Gadolinium DTPA injected at a rate of 2 mL/sec. One precontrast and two postcontrast coronal 3D volumes were acquired, each in a 20-second breath-hold, and two subtracted 3D sets were calculated. Arterial anatomy was assessed with use of maximum-intensity projection, volume rendering, and multiplanar reformatting algorithms. Hepatic and portal venous anatomy was evaluated with use of the true FISP images and the venous phase of the MR angiogram. Visualization of hepatic arterial branches was noted. Visualization of portal vein branches was scored on a scale of 0-5. The presence of anatomic variants was noted. Vascular anatomy was confirmed at the time of surgery and at catheter angiography.

RESULTS

Segmental branch vessels were visualized on MR angiography in the majority of cases. The segment four branch was identified in 96% patients. Variant arterial anatomy was seen in 50% of patients. MR angiography detected 10 of 11 arterial variants found at surgery and angiography. Visualization of portal vein branches was generally higher with true FISP compared to MR angiography. Twenty-four percent of patients had variant portal venous anatomy. Caudal hepatic veins were identified in 60% of patients, of which eight were significant (>5 mm). Hepatic and portal venous anatomy was accurately predicted by true FISP and MR angiography in all patients who went on to undergo surgery.

CONCLUSION

Preoperative imaging with use of a combination of contrast-enhanced MR angiography and true FISP provides a comprehensive assessment of the entire hepatic vasculature in living liver donors.

Neuroimaging of stroke: a review

Advances in neuroimaging technology during the past 30 years have resulted in a virtual explosion in the amount of pathologic information that can be obtained in the clinical stroke setting. This neuroimaging revolution has led to a much better understanding of cerebrovascular and tissue pathology, creating a wide array of opportunities for acute treatment and secondary prevention. Advances include early and accurate detection of ischemic and infarcted tissue and the ability to reveal hypoperfused tissue at risk. Clinicians are increasingly able to noninvasively detect embolic and atherothrombotic intravascular lesions. Vascular lesions associated with stroke can be characterized through endovascular neuroimaging techniques and repaired by various means. In this article, we provide an overview and update on the various techniques used in the neuroimaging of stroke and intracranial hemorrhage, including computed tomography, magnetic resonance imaging, ultrasound, and catheter angiography. We outline the specific role of each modality in clinical practice.

Thorax: low-dose contrast-enhanced three-dimensional MR angiography with subsecond temporal resolution--initial results

The purpose of the study was to implement a three-dimensional (3D) magnetic resonance (MR) angiographic technique with acquisition times on the order of 800 msec with use of a spoiled gradient-echo pulse sequence (repetition time, 1.60 msec; echo time, 0.65 msec) and bolus intravenous injection of contrast material doses as small as 6 mL. High-spatial-resolution conventional MR angiography performed with 30 mL of gadopentetate dimeglumine was the reference standard. As implemented, subsecond 3D MR angiography allowed temporal sampling that was rapid enough to depict short-lived processes, as illustrated in patients with shunts and dissections. With small contrast material doses and subsecond frame rates, it is also possible to measure pulmonary arteriovenous circulation times with this 3D MR angiographic technique.

Diagnostic imaging of aortic atherosclerosis and its complications

Thoracic aortic atherosclerosis has been shown to be an important cause of severe morbidity and mortality. At the present time, the case of performance, detailed information obtainable, and availability make TEE the procedure of choice for the imaging of thoracic aortic atherosclerosis; however, further technical advances in MR and CT, particularly in MR plaque characterization and the use of plaque specific contrast agents, may allow for a less invasive and more complete evaluation of thoracic aortic atherosclerosis in the near future. Gadolinium-enhanced 3DMRA is the procedure of choice for the noninvasive detection of plaque in the proximal aortic arch vessels. Furthermore, both CT and MRI are better suited to evaluate penetrating atherosclerotic ulcers and their complications such as intramural hematoma, pseudoaneurysm formation, and aortic rupture.

High-resolution, contrast-enhanced magnetic resonance angiography with elliptical centric k-space ordering of supra-aortic arteries compared with selective X-ray angiography

BACKGROUND AND PURPOSE

The objective of this study was to evaluate the relative value of high-resolution, contrast-enhanced MR angiography (CE MRA) with elliptical centric k-space ordering compared with intra-arterial x-ray angiography for imaging carotid stenosis.

METHODS

Thirty patients with suspected stenosis of the carotid arteries were examined with CE MRA (1.5-T scanner) and x-ray angiography (aortic arch survey and selective imaging of both common carotid arteries). For the first time, not only the extracranial carotid bifurcation but all the vessel segments from the aortic arch to the circle of Willis were assessed by independent investigators.

RESULTS

For the internal carotid artery in the region of the extracranial carotid bifurcation, there was a very close correlation between CE MRA and x-ray angiography (sensitivity, 100%; specificity, 92%). The initially suspected overestimation of stenosis on CE MRA in 3 cases was ultimately revealed to be an underestimation on x-ray angiography. CE MRA showed slightly poorer imaging of the basal vessel segments at the level of the aortic arch (because of breathing artifacts) and the intracranial vessel segments (because of small vessel caliber and venous superimposition due to delayed sequence starts).

CONCLUSIONS

The MRA technique described here provides reliable results in the diagnosis of carotid stenosis and is thus suitable for replacing the invasive conventional x-ray angiography method in most cases. Further technical developments with regard to spatial resolution are still required for improved visualization of small vessels (terminal carotid branches and intracranial vessels).

High-resolution breath-hold contrast-enhanced MR angiography of the entire carotid circulation

OBJECTIVE

The purpose of this study was to evaluate the effect of breathing on image quality of the aortic arch and carotid vessels during contrast-enhanced MR angiography and to show that high-resolution breath-hold contrast-enhanced MR angiography combined with a timing-bolus technique can produce high-quality images of the entire carotid circulation.

MATERIALS AND METHODS

Forty patients underwent high-resolution contrast-enhanced MR angiography on a 1.5-T Magnetom Symphony. A coronal three-dimensional (3D) gradient-echo sequence (TR/TE, 4.36/1.64; flip angle, 25 degrees) with asymmetric k-space acquisition was used. The 136 x 512 matrix yielded voxel sizes of 1.33 x 0.64 x 1.0 mm. A timing-bolus acquisition, orientated in the coronal plane to include the aortic arch, was obtained initially during free-breathing. Twenty milliliters of gadopenetate dimeglumine was injected at 2 mL/sec. Unenhanced and enhanced 3D volumes were recorded. A subtracted 3D set was calculated and subjected to a maximum-intensity-projection algorithm. Half of the patients held their breath during angiography and the other half did not. Aortic arch motion was measured on the timing-bolus acquisition as the distance moved by a single pixel in both the x and y directions. Maximum-intensity-projection MR images were assessed independently by two observers, and vessel sharpness was scored on a scale of 1-5. Sharpness was also assessed quantitatively by generating a signal intensity profile across the aortic arch vessel wall and calculating the average of the upslope and downslope at full-width half maximum. Visualization of carotid branch vessels was scored on a scale of 0-5, and venous contamination was scored on a scale of 0-3.

RESULTS

Average in-plane aortic arch movement was 10.3 mm in the x direction and 8.7 mm in the y direction. Quantitative and qualitative sharpness of the aortic arch and great vessel origins was better (p < 0.05) during breath-holding than during non-breath-holding. No difference in the sharpness of the carotid vessels was noted between the two groups. Carotid branch vessels were well visualized from the aortic arch to the intracerebral circulation. The average venous contamination score was 0.56.

CONCLUSION

Breath-holding greatly improves the sharpness of the aortic arch and great vessel origins but has no effect on visualization of the carotid vessels. High-resolution breath-hold contrast-enhanced MR angiography can produce high-quality, artifact-free images of the entire carotid circulation from the aortic arch to the intracerebral circulation.

Angio-RM das artérias carótidas e vertebrais: análise de diferentes técnicas de volume e diluição de contraste em aparelho de 1,0 t e gradiente de 15 mt/m

OBJETIVO: Avaliar as artérias cervicais (carótidas e vertebrais) por meio da angio-RM, utilizando-se diferentes dosagens e diluições de contraste paramagnético. MATERIAIS E MÉTODOS: Estudo prospectivo em 15 pacientes, com análise de 30 artérias carótidas comuns, 30 artérias carótidas internas, 30 artérias carótidas externas e 30 artérias vertebrais, utilizando-se diferentes volumes e dosagens de contraste paramagnético: grupo I <FONT FACE=Symbol>-</FONT> dose única (14 ml de Gd-DTPA); grupo II <FONT FACE=Symbol>-</FONT>dose dupla (28 ml de Gd-DTPA); grupo III <FONT FACE=Symbol>-</FONT> dose única e diluída a 50%. A injeção de contraste foi realizada com a utilização de bomba injetora e com velocidades de injeção de 2 ml/s (grupo I) e 3 ml/s (grupos II e III). Os segmentos arteriais foram analisados por três examinadores em consenso de forma subjetiva, avaliando-se o grau de visibilidade, intensidade de contrastação e definição de seus contornos. RESULTADOS: Em todos os itens analisados os pacientes do grupo II apresentaram melhor resultado (visibilização total, boa contrastação dos vasos e contornos bem definidos). No grupo I houve boa visibilização das artérias carótidas e vertebrais, porém a intensidade de contraste e a definição dos contornos apresentaram variabilidade qualitativa. O grupo III apresentou os piores resultados, com dificuldade de visibilização, intensidade de contrastação baixa e contornos mal definidos. CONCLUSÃO: Entre os grupos analisados, a técnica utilizando dose dupla de gadolínio é a que permite melhor avaliação das artérias cervicais. A utilização de contraste diluído prejudica a avaliação dos vasos do pescoço.

Value of subtraction technique in Gd-DTPA-enhanced magnetic resonance angiography of the thoracic aorta

AIM

To assess routine image subtraction in 3D gadopentate dimeglumine (Gd-DTPA)-enhanced magnetic resonance (MR) angiography of the thoracic aorta.

MATERIALS AND METHODS

This was a prospective study of 22 consecutive patients referred for magnetic resonance imaging (MRI) of the thoracic aorta. All patients had 3D MR aortography (TR/TE/FA; 5/2 ms/25 degrees ) performed before and after bolus intravenous injection of Gd-DTPA. The Gd-DTPA enhanced and unenhanced data sets were subtracted and maximum intensity projections (MIP) projections of the thoracic aorta were performed. The standard unsubtracted MIP images were initially evaluated. These were then reviewed together with the subtracted images to assess for additional diagnostic information. Signal to noise ratios (SNR) and contrast to noise ratios (CNR) were measured.

RESULTS

In four cases there was mild image degradation due to patient movement. In no case did subtraction alter the diagnosis. The mean SNR in the unsubtracted MIP images was 10.8 +/- 4.0 (median 11.1) and on the subtracted images was 21.2 +/- 9.9 (median 20.7;P < 0.0001). The mean aorta-to-mediastinal fat CNR was 3.9 +/- 2.8 (median 3.9) on the unsubtracted images and 15.0 +/- 10.6 (median 13) on the subtracted images (P < 0.0001). The mean aorta-to-vertebral body CNR was 5.2 +/- 3.1 (median 4.4) on the unsubtracted images and 15.1 +/- 9.3 on the subtracted images (P < 0.0001).

CONCLUSION

Image subtraction significantly improved both the SNR and CNR, but did not alter the final diagnosis, and does not appear warranted in routine practice.

Innominate artery atheroma: a lesion seen with gadolinium-enhanced MR angiography and often missed by transesophageal echocardiography

Transesophageal echocardiography (TEE) is the procedure of choice for identifying aortic atheromas, which may result in stroke, transient ischemic attack and peripheral embolization. However, because of anatomic constraints, the innominate artery may not be visualized. We investigated gadolinium-enhanced MR angiography (MRA) as an alternative technique for evaluation of suspected atheromas of the innominate artery. From a retrospective review of 520 examinations, we identified five patients who had innominate artery atheromas diagnosed prospectively with gadolinium-enhanced MRA who also underwent TEE within 1 month. A total of 10 innominate artery atheromas were demonstrated on MRA; none of these were visualized on TEE. One patient had three atheromas, two patients had two atheromas and three patients had one atheroma. They ranged in size from 3 mm to 1.5 cm (mean 6.5 mm). One atheroma was flat, two were filiform, and seven were protruding. Gadolinium-enhanced MRA is superior to TEE for the diagnosis of atheromas of the innominate artery. In the setting of right cerebral or right arm embolization, when no source is seen in the arch on TEE, gadolinium-enhanced MRA should be considered.

Magnetic resonance angiography and evaluation of cervical arteries

Multiple clinical trials have demonstrated the efficacy of endarterectomy in selected groups of patients based primarily on percent diameter stenosis. Although measurement of stenosis in the clinical trials was established by conventional angiography, there is considerable interest in noninvasive alternatives. Magnetic resonance angiography, performed using time-of-flight methods or with contrast enhancement, is one of several alternatives for noninvasive carotid evaluation. Screening examinations are routinely performed for carotid stenosis. Preoperative evaluations based on one or a combination of noninvasive tests have been proposed, although these proposals are the subject of ongoing controversy. Evaluation of the vertebral arteries is more difficult and less well studied: however, the increasing availability of therapies for posterior circulation atherosclerotic narrowing is resulting in increased interest in this problem.

Carotid artery: elliptic centric contrast-enhanced MR angiography compared with conventional angiography

PURPOSE

To determine the accuracy of elliptic centric contrast material-enhanced magnetic resonance (MR) angiography by using conventional angiography as the reference standard.

MATERIALS AND METHODS

Fifty patients were examined prospectively with contrast-enhanced MR angiography and conventional angiography. The two examinations were performed within 1 week of each other. Two patients underwent conventional angiography of only one carotid artery, which yielded 98 arteries for comparison.

RESULTS

With conventional angiography as the reference standard and by using a 70% threshold for internal carotid arterial diameter stenosis, maximum intensity projection (MIP) images had a sensitivity of 93.3%, specificity of 85.1%, and accuracy of 87.6%, whereas reformatted transverse source images had a sensitivity of 83.3%, specificity of 97.0%, and accuracy of 92.8%. Interobserver variability for conventional angiograms was 0.97, for MIP images was 0.91, and for source images was 0.90. The contrast-enhanced MR angiographic technique had a sensitivity of 88.9% and specificity of 58.1% for the presence of irregularity and/or ulceration. All 50 examinations were triggered appropriately so that minimal or no venous signal intensity was depicted.

CONCLUSION

Contrast-enhanced elliptic centric three-dimensional MR angiography offers high-spatial-resolution, venous-suppressed images of the carotid arteries that appear to be adequate to replace conventional angiography in most patients examined prior to carotid endarterectomy.

Contrast-enhanced 3D FISP MR angiography of the aortic arch ostia: preliminary results

PURPOSE

The goal of this work was to evaluate three-dimensional (3D) contrast-enhanced MR angiography (MRA) for the detection of ostial stenoses of the aortic arch.

METHOD

Sixteen patients with suspected carotid atherosclerotic disease prospectively underwent digital subtraction angiography of the aortic arch followed by contrast-enhanced MRA using a 3D fast imaging with steady-state precession (FISP) technique (TR = 5 ms, TE = 2 ms, flip angle = 30 degrees). Three neuroradiologists blindly measured stenoses on the catheter angiograms and MRA. Evaluation included the ostia of the innominate, left carotid, and left subclavian arteries. Any significant disagreement on catheter angiography was resolved by consensus. The MRA grades of each of the three observers were then compared with the consensus grades of the contrast angiogram.

RESULTS

Forty-eight vessels were scored, of which five had significant stenoses. MRA demonstrated 100% sensitivity, 89% specificity, 52% positive predictive value, and 100% negative predictive value. The Bowker test for symmetry indicated no significant difference between conventional angiography and MRA scores (p = 0.32-0.75), and there was good agreement between the three observers (weighted kappa = 0.75-0.86).

CONCLUSION

Contrast-enhanced 3D FISP MRA may be a useful imaging modality for the detection of significant stenoses at the ostia of the major aortic arch branches.

Recent advances in magnetic resonance angiography of carotid and vertebral arteries

New magnetic resonance angiographic sequences using gadolinium infusion allow high-quality images of supra-aortic vessels. Raw data may be obtained in a short scan time of less than 30 s, with a large acquisition volume from the aortic arch to the circle of Willis. After computed reconstruction of the vascular tree, angiograms appear similar to those obtained with conventional catheter angiography. Parameters of the sequence must be carefully chosen, however, with trade-offs between spatial resolution, scan time, acquisition volume and contrast of image. New developments have been proposed to improve the image quality with different acquisition strategies. These recent advances will probably be useful to assess the carotid and the vertebral arteries with more accuracy. They will require high-performance gradient systems and sophisticated software that is not yet available on all machines, however.

Carotid arteries: maximizing arterial to venous contrast in fluoroscopically triggered contrast-enhanced MR angiography with elliptic centric view ordering

PURPOSE

To obtain high-spatial-resolution, venous-suppressed, contrast material-enhanced, three-dimensional (3D) magnetic resonance (MR) angiograms of the carotid arteries and aortic arch by using an elliptic centric view ordering with MR fluoroscopic triggering.

MATERIALS AND METHODS

Forty consecutive patients with cerebrovascular disease in the differential diagnosis were evaluated with fluoroscopically triggered 3D MR angiography (gadoteridol dose range, 0.1-0.3 mmol per kilogram of body weight; mean acquisition time, 40 second +/- 8 [SD]). The contrast-enhanced 3D MR angiograms were evaluated for overall quality, vascular signal intensity, venous suppression, and motion artifact. Twenty patients also underwent two-dimensional (2D) time-of-flight (TOF) MR angiography. The overall quality of the 2D TOF MR angiograms and comparative quality between the 2D TOF and contrast-enhanced 3D MR angiograms were determined.

RESULTS

The contrast-enhanced 3D MR angiograms were of excellent or more than adequate quality for diagnosis in 36 of the 40 studies (90%). In 35 of the 38 contrast-enhanced 3D studies in which the contrast material bolus was detected fluoroscopically, the internal jugular vein signal intensity was either not detectable or barely visible. In 18 of the 20 patients who also underwent 2D TOF MR angiography, the quality of the contrast-enhanced 3D MR angiograms was graded as markedly superior or superior.

CONCLUSION

Contrast-enhanced, elliptic centric 3D MR angiography with real-time MR fluoroscopic triggering offers high-spatial-resolution images of the carotid arteries and aortic arch with reliable venous suppression.