Gadolinium-enhanced Three-dimensional MR Angiography Research Articles

Mesure des diamètres aortiques dans le suivi IRM des coarctations

Objective During aortic coarctation follow-up, accurate diameter measurements using MRI are required. The purpose of this study was to compare the reproducibility of aortic measurements on axial and sagittal views using black blood (Fast-Spin-Echo) and three-dimensional Gadolinium-enhanced MR angiography. Subjects and methods We studied 34 patients who underwent evaluation after surgical treatment in the first year of life. The aortic measurements were made at six thoraciclevels. We calculated the mean difference between the two sequences, and used Bland and Altman method and the comparison to zero. Results With black blood, either on axial or sagittal views, aortic measurements were in agreement. Between two sequences, we considered as acceptable a mean difference of 0,5 mm with limits of agreement of ± 3 mm. Difficulties were found for proximal ascending aorta measurements on all sequences. Using MR angiography, the highest agreement at the site of repair was on sagittal view, while the highest agreement at other sites was on axial views. Conclusion Black bloodsequence provides a better reproducibility for aortic measurements than native slices of MR angiography.

Zero-Filling Interpolation Processing Technique Can Efficiently Suppress Segmental Stenosis Artifact on Small Arteries of Anatomical Phantoms

The purpose of this study was to evaluate the zero-filling interpolation processing (ZIP) technique for contrast-enhanced MR angiography (CE-MRA). Phantoms of arteries were made with different lumen diameters. Gadolinium-enhanced three-dimensional MR angiography was performed on a GE 1.5T scanner. The parameters of FSPGR pulse sequence were: flip angle 30°, TR 6ms, TE 1.4ms, bandwidth 31.25 kHz, slice thickness 1.2 mm, matrix 256×256. The sequence parameters were kept constant for the studies, whereas four selections were chosen: 1) with ZIP1024 and ZIP×4 techniques; 2) only with ZIP1024 technique; 3) only with ZIP×4 technique; 4) without ZIP technique. For image quality evaluation, MR maximum intensity projection (MIP) images were created. Signal-to-noise ratio (SNR) was measured on MIP images. Vessel edge was determined using full width at half maximum (FWHM) for lumen diameter calculation and results were compared with the actual lumen diameter. The distinctness of the vessel edge and the artifacts on the phantoms were compared for all sequences. Three experienced radiologists made consensus evaluation. The FWHM results of lumen measurements for all the sequences with ZIP techniques were more accurate than that of the sequence without ZIP technique in all phantoms, no matter what the size of the artery. The vessel edge with ZIP1024 technique was more distinct. However, the highest average SNR was obtained with the sequence without ZIP technique. The segmental stenosis artifacts on small artery of phantoms were only efficiently suppressed with the ZIP×4 technique. ZIP technique is excellent for CE-MRA to obtain high quality MR angiography. It not only can improve the spatial resolution and the distinctness of the vessel edge on CE-MRA, but can also efficiently suppress segmental stenosis artifact on small arteries of phantoms.

Vascular complications after living related liver transplantation: evaluation with gadolinium-enhanced three-dimensional MR angiography.

The purpose of this study was to evaluate the efficacy of gadolinium-enhanced three-dimensional (3D) MR angiography for detection of vascular complications in patients who have undergone living related liver transplantation. Seventy-six patients who underwent living related liver transplantation were evaluated with gadolinium-enhanced 3D MR angiography. All MR angiograms were assessed for patency of the hepatic artery and the portal vein using a four-point scale (grades I-IV). The results were correlated with conventional angiography (n = 23) and clinical follow-up with Doppler sonography (n = 53) for more than 6 months. Seventy-three of 76 MR angiography procedures were technically adequate. When grades III (focal narrowing [> 50%] at the anastomotic site) and IV (abrupt cutoff at the anastomotic site with nonvisualization of the right [or left] hepatic artery distal to the anastomosis) were regarded as the diagnostic criteria for hepatic artery stenosis, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MR angiography were 100%, 74%, 29%, 100%, and 77%, respectively. In the portal vein, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MR angiography were 100%, 84%, 35%, 100%, and 85%, respectively, when grades III (narrowing [> 50%] without poststenotic dilatation) and IV (narrowing [> 50%] with poststenotic dilatation) were defined as criteria for portal vein stenosis. MR angiography was sensitive but not specific in the detection of significant vascular stenosis after living related liver transplantation. However, normal MR angiography findings reliably exclude the possibility of significant stenosis.

MR angiography and preoperative evaluation for laparoscopic donor nephrectomy.

The purpose of our study was to evaluate the effectiveness of gadolinium-enhanced MR imaging in imaging arterial, venous, and ureteric anatomy in a group of potential laparoscopic renal donors and to compare our findings with those established at surgery. Sixty-four consecutive patients underwent successful laparoscopic donor nephrectomy. Imaging of the kidneys was performed before surgery with MR imaging and breath-hold three-dimensional gadolinium-enhanced MR angiography. All studies were reviewed prospectively by one of two attending radiologists. Results were compared with findings at the time of laparoscopic nephrectomy. Of the 64 patients, MR imaging and MR angiography identified 30 patients with normal arterial, venous, and ureteric anatomy, and concordance was found at surgery in 29 of these patients. Vascular anomalies were depicted on MR imaging in 34 patients, with complete concordance at surgery in 29 patients. The use of MR angiography for revealing arterial anomalies had a sensitivity of 89.4%, specificity of 94.1%, and accuracy of 90.6%. For venous anomalies, there was a sensitivity of 98.3%, specificity of 100%, and accuracy of 98.4%. No important utereric anomalies were identified at surgery or on MR imaging. Renal MR imaging and gadolinium-enhanced MR angiography provide a safe, accurate, and minimally invasive means of comprehensive assessment of the potential living renal donor.

Evaluation of the Pedal Artery: Comparison of Three-dimensional Gadolinium-Enhanced MR Angiography with Digital Subtraction Angiography

Purpose: To compare the three-dimensional gadolinium-enhanced MR angiography with digital subtraction angiography (DSA) for evaluation of the pedal artery. Materials and Methods: In 12 extremities of 11 patients, both digital subtraction angiography (DSA) and contrast-enhanced MR angiography (CE-MR angiography) were performed during the same week. Among ten of the 11 patients, the following conditions were present: atherosclerosis (n=4), diabetic foot (n=3), Buerger's disease (n=1), calciphylactic arteriopathy (n=1) and arteriovenous malformation of the foot (n=1). The remaining patient underwent angiography prior to flap surgery. For MR angiography, a 1.5T system using an extremity or head coil was used. A three-dimensional FISP (fast imaging with steady state precession) sequence was obtained before enhancement, followed by four sequential acquisitions (scan time, 20 secs; scan interval time, 10 secs) 10 seconds after intravenous bolus injection of normal saline (total 10 cc), following intravenous adminstration of gadolinium (0.02 mmol/kg, 3 ml/sec). Arterial segments of the ankle and foot were classified as the anterior or posterior tibial artery, the distal peroneal artery, the medial or lateral plantar artery, the pedal arch, and the dorsalis pedis artery. Two radiologists independently analysed visualization of each arteraial segment and the mean of visible arterial segments in one extreminty using CE-MR angiography and DSA. Results: Among 84 arterial segments, 16 were invisible at both CE-MR angiography and DSA, while 39 were demonstrated by both modalities. Twenty-six segments were visible only at CE-MR angiography and three only at DSA. CE-MR angiography displayed a higher number of arterial segments than DSA (mean, 5.42 vs. mean 3.50, respectively), a difference which was statistically significant (p

Gadolinium-enhanced three-dimensional MR angiography in jugular phlebectasia and aneurysm

True jugular vein aneurysms and phlebectasias are very rare abnormalities, which are usually discovered in children. Though their ultrasonographic features have been well described, magnetic resonance angiographic appearance of these lesions has not been reported in the radiology literature. We describe gadolinium-enhanced MR angiographic findings in two patients with internal jugular vein phlebectasia and one patient with anterior jugular vein aneurysm. The jugular venous system and its abnormalities were successfully depicted in the coronal plane, much like the images of coronal angiography.

Arterial pseudostenosis on first-pass gadolinium-enhanced three-dimensional MR angiography: new observation of a potential pitfall.

The purpose of this study was to determine the frequency of apparent stenosis of normal aortic branches in patients on first-pass gadolinium-enhanced three-dimensional (3D) MR angiography and to reproduce the same phenomenon in a pulsatile flow phantom model. Apparent stenosis of normal vessels on gadolinium-enhanced 3D MR angiography seen on the first-pass acquisition was observed in only a small proportion (approximately 2%) of our patients. The pseudostenosis was reproducible in the phantom model using rapid injection. A stenosis on first-pass images should be interpreted with caution. Confirmation of the findings on other sequences, such as the second-pass gadolinium-enhanced 3D MR angiography or 3D phase-contrast MR angiography, prevented overdiagnosis of significant stenoses.

MR-Guided PTA in experimental bilateral rabbit renal artery stenosis and MR angiography follow-up versus histomorphometry.

To assess in vivo 1) MR-guided percutaneous transluminal renal angioplasty (PTRA) in experimental bilateral rabbit renal artery stenosis (RAS); 2) postprocedural follow-up by gadolinium-enhanced MR angiography versus histomorphometry. Fifteen male NZW rabbits of mean weight 4.0 kg (range 3.5-4.2 kg) underwent bilateral RAS induction by combined overdilation-deendothelialization with a gadolinium-filled balloon, passively MR-guided by the artifact of a 0.014-inch guidewire. After 4 weeks the rabbits were randomized into two groups: group A (n = 8) underwent right-sided PTRA for treatment of RAS, group B (n = 7) underwent left-sided PTRA. After another 4 weeks the rabbits were killed to assess by histomorphometry recurrent stenosis and contralateral induction injury stenosis lesions. Each step was preceded by gadolinium-enhanced three-dimensional MR angiography, and the cortex-to-aorta (C/A) signal intensity ratio was calculated. RAS induction was successful in all cases. Fourteen arteries developed restenosis and 13 only initial stenosis. MR-guided PTRAs were feasible in 22 arteries (73%). For a successful catheterization of the ostium (20 arteries, 66% success rate), 10-25 steps were required. Five to eight steps were required for balloon localization and inflation for each PTRA. The restenosis effect was reflected by a 16% (12%-27%) decrease in C/A values on MR angiograms (p < 0.05). MR guidance and MR angiography represent a feasible, less invasive alternative for performing and assessing experimental PTRA in RAS.

Pulmonary vein and left atrial invasion by lung cancer: assessment by breath-hold gadolinium-enhanced three-dimensional MR angiography.

The purpose of this work was to evaluate the ability of breath-hold gadolinium-enhanced three-dimensional (3D) MR angiography to assess the invasion of the pulmonary vein and the left atrium by lung cancer. Gadolinium-enhanced 3D MR angiography was performed in 20 consecutive patients with lung cancer. At two sites with left atrial invasion shown by MR angiography, associated partial resection of the left atrium was performed. At five sites with invasion of the proximal pulmonary vein within 1.5 cm from the left atrium on MR, partial resection of the left atrium was performed at one site, and the pulmonary vein was resected at the intrapericardial portion at three sites. At two sites with invasion of the proximal pulmonary vein 1.5 cm more distal to the left atrium, the pulmonary vein was resected at the extrapericardial portion. Breath-hold gadolinium-enhanced 3D MR angiography is suitable for assessing invasion of the pulmonary vein and the left atrium by lung cancer.

Three-dimensional gadolinium-enhanced MR angiography of vascular complications after liver transplantation.

The goal of this study was to evaluate three-dimensional gadolinium-enhanced MR angiography as a tool for examination of liver transplant patients with potential vascular complications. Thirty-eight consecutive three-dimensional gadolinium-enhanced MR angiograms were obtained in 34 patients. Results were retrospectively reviewed and correlated with conventional angiography in 20 of the 38 cases and sonography in 37 of the 38 cases. MR angiograms were evaluated for technical adequacy, vascular patency, and parenchymal abnormalities, and results were compared with angiography and sonography. Conventional angiography and surgery were used as gold standards when available. Thirty-four (90%) of 38 MR angiograms were technically adequate. Vascular abnormalities were identified in 20 patients, and 19 of these patients subsequently underwent angiography, surgery, or both. There were seven cases of hepatic artery thrombosis; all were detected with MR angiography with no false-positive or false-negative interpretations. Seven patients had moderate to severe hepatic artery stenosis (>50% narrowing as determined by conventional angiography). MR angiography revealed this stenosis in six of the seven patients, with one false-negative and three false-positive interpretations. Portal vein thrombosis was detected in three patients, and portal vein stenosis was detected in two patients. Three-dimensional gadolinium-enhanced MR angiography is useful in the examination of liver transplant patients and offers a noninvasive adjunct in patients with difficult or indeterminate sonographic examinations.

Evaluation of dynamic gadolinium-enhanced breath-hold MR angiography in the diagnosis of renal artery stenosis.

The aim of our study was to evaluate a three-dimensional gadolinium-enhanced breath-hold MR angiography sequence using standard MR gradients in detecting renal artery stenosis. Forty-two patients referred for angiography for suspected renal artery stenosis underwent both conventional digital subtraction angiography (DSA) and MR angiography. MR angiography was performed on a 1.5-T scanner with standard gradients. A fast multiplanar spoiled gradient-echo sequence was used with the following parameters: TR/TE, 10.3/1.9; flip angle, 45 degrees; field of view, 36 x 32 cm; matrix size, 256 x 128; one excitation; volume thickness, 70 mm; and partitions, 28. Gadolinium was administered IV as a dynamic bolus of 30-40 ml. Conventional and MR angiographic images were interpreted by two radiologists in consensus. DSA revealed 87 renal arteries, of which 79 were in 35 patients with native kidneys and eight arteries were in seven patients with transplanted kidneys. Gadolinium-enhanced MR angiography showed 85 (98%) of 87 renal arteries. Seventeen patients had 20 significant (>50% stenosis) renal artery stenoses and five patients had five occluded renal arteries revealed by DSA. MR angiography revealed 85 renal arteries (98%), 20 stenoses (100%), and five occlusions (100%). Gadolinium-enhanced MR angiography led to one false-positive interpretation for renal artery stenosis and no false-negative interpretations. Thus, the sensitivity, specificity, and accuracy of MR angiography for renal artery stenosis were 100%, 98%, and 99%, respectively. The MR angiography pulse sequence we used was an effective and reliable technique for the diagnosis of renal artery stenosis. The sequence can be performed on widely available MR equipment that does not require fast gradient hardware.

MRI of acute and chronic aortic pathology: Pre‐operative and postoperative evaluation

With recent advances in the understanding of aortic diseases, both power and versatility have put magnetic resonance imaging (MRI) in the focus of diagnostic work-up in the entire spectrum of clinical aortic pathology. Technical refinements, from classic anatomic imaging to three-dimensional gadolinium-enhanced MR angiography and tissue characterization, have rendered MRI ideal for assessment of acquired disease such as aortic dissection, intramural hematoma, and aneurysm, along with postoperative follow-up evaluation, with better reliability and safety than other imaging modalities. Moreover, congenital pathology of the aorta, including aortic arch anomalies and coarctation, can be non-invasively evaluated by MRI. With spectroscopy and the advent of high-resolution intravascular coils, MRI may even provide histopathologic and potentially prognostic information unparalleled by any other method. J. Magn. Reson. Imaging 1999;10:741–750. © 1999 Wiley-Liss, Inc.

MRI of acute and chronic aortic pathology: pre-operative and postoperative evaluation.

With recent advances in the understanding of aortic diseases, both power and versatility have put magnetic resonance imaging (MRI) in the focus of diagnostic work-up in the entire spectrum of clinical aortic pathology. Technical refinements, from classic anatomic imaging to three-dimensional gadolinium-enhanced MR angiography and tissue characterization, have rendered MRI ideal for assessment of acquired disease such as aortic dissection, intramural hematoma, and aneurysm, along with postoperative follow-up evaluation, with better reliability and safety than other imaging modalities. Moreover, congenital pathology of the aorta, including aortic arch anomalies and coarctation, can be non-invasively evaluated by MRI. With spectroscopy and the advent of high-resolution intravascular coils, MRI may even provide histopathologic and potentially prognostic information unparalleled by any other method. J. Magn. Reson. Imaging 1999;10:741-750.

Gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral arteries: evaluation of a multistation examination using two gadopentetate dimeglumine infusions.

Three-dimensional gadolinium-enhanced MR angiography is a rapid and accurate method that can at times image only a limited amount of anatomy during an examination. We evaluated a technique that doubled the anatomy imaged by obtaining two separate gadolinium-enhanced MR angiograms during a single examination. Twenty-three patients referred for MR evaluation of aortic or peripheral vascular disease underwent two successive gadolinium-enhanced three-dimensional MR angiographic examinations during a single MR examination. An injection of 15 ml of gadopentetate dimeglumine was used for the first MR angiogram, and 25 ml was used for the second MR angiogram. The angiograms were quantitatively and qualitatively evaluated to determine the effect of residual gadolinium from the initial MR angiogram on the second angiogram. The two studies depicted either the entire aorta to the femoral arteries (n = 10) or the distal aorta to the popliteal arteries (n = 13). The total mean gadolinium dose was 0.245 mmol/kg per patient. An average of 15 min elapsed between injections. The value of arterial signal-to-noise ratio (mean, 48.8 versus 56.4) and artery-to-vein contrast-to-noise ratio (mean, 45.5 versus 49.0) increased between the first and second angiograms, respectively. Residual gadolinium elevated the values for venous signal-to-noise ratio (mean, 2.3 versus 7.2) and background-to-muscle signal-to-noise ratio (mean, 5.5 versus 10.1) on the second MR angiogram. Qualitative evaluation by three observers showed no significant differences in diagnostic usefulness or overall image quality between the first and second MR angiograms. The use of two low-dose gadolinium-enhanced three-dimensional MR angiograms during a single examination is a feasible approach to increase anatomic coverage when performing gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral vessels. Although background enhancement is slightly elevated on the second angiogram, such enhancement does not significantly change diagnostic usefulness or overall image quality.

MR ANGIOGRAPHY OF THE AORTIC ARCH VESSELS AND UPPER EXTREMITIES

MR angiography of the aortic arch vessels and upper extremities is a noninvasive alternative to conventional catheter angiography without the risks of stroke or the potential toxicity of iodinated contrast. The use of optimized, breath hold gadolinium-enhanced three-dimensional MR angiography provides excellent image quality with the capability of display options not available with conventional angiography. This article demonstrates the utility of this new technique in the diagnosis of congenital and acquired conditions of the supraaortic vascular system.

Evaluation of renal artery stenosis with dynamic gadolinium-enhanced MR angiography.

The purpose of this study was to compare dynamic gadolinium-enhanced three-dimensional spoiled gradient-recalled MR angiography with conventional arteriography in the evaluation of proximal renal artery stenosis (RAS). MR angiography and conventional arteriographic examinations of 30 patients evaluated for RAS were analyzed retrospectively. Three-dimensional MR angiography was performed with an RF spoiled gradient-recalled imaging sequence acquired during the dynamic i.v. injection of gadolinium (0.2-0.3 mmol/kg), MR data and conventional arteriograms were independently evaluated for the number and location of renal arteries and the degree and location of stenoses. The patients had a mean age of 70 years old and a mean serum creatinine level of 2.9 mg/dl, reflecting a population in whom atherosclerotic RAS was the primary concern. Gadolinium-enhanced MR angiography revealed 100% of main renal arteries. For RAS of 50% or greater occlusion, the technique was 100% sensitive and 71% specific; the negative predictive value was 100%. The technique was 100% sensitive and 71% specific for RAS of 75% or greater occlusion. Dynamic gadolinium-enhanced three-dimensional spoiled gradient-recalled MR angiography has a high sensitivity for revealing proximal RAS and is a quick and reliable technique for obtaining helpful anatomic information.

Breath-hold ultrafast three-dimensional gadolinium-enhanced MR angiography of the renovascular system.

C adolinium-enhanced three-dimensional (3D) MR angiography has been advocated as a potential method for evaluation of the vascular system [ 1-3]. Using a 1.5-T scanner with an enhanced gradient system (Signa; General Electric Medical Systems, Milwaukee, WI) that can reach a maximum gradient strength of 2.3 G/cm in 150 isec, we shortened the acquisition time of this sequence so that it can be performed in a single breath-hold [4, 5]. Our pictorial essay illustrates images obtained with this enhanced breath-hold 3D spoiled gradient-echo sequence in patients with normal main and accessory renal arteries (Figs. 1-3), renal artery stenosis (Figs. 4-7), nonstenotic renal vasculopathies (Figs. 8-10), aortic dissection (Fig. 1 1 ), and renal transplants (Fig. I 2).

Gadolinium-enhanced three-dimensional MR angiography of acquired arch vessel disease.

Gadolinium-enhanced three-dimensional MR angiography of acquired arch vessel disease.

Gadolinium-enhanced three-dimensional MR angiography of the thoracoabdominal aorta

MR angiography (MRA) of the thoracoabdominal aorta is a noninvasive technique that can rapidly acquire a volume of data with the capability of multiplanar reformations (MPR) and “bright blood” maximum intensity projection (MIP) angiographic images. These MIP images can display long tortuous vessels in a single three-dimensional (3D) volume, with excellent delineation of branch vessel disease and without the flow artifacts or long examination times of conventional spin-echo (SE) imaging. Two-dimensional (2D) time-of-flight (TOF) imaging is used most widely because of familiarity and ease of implementation, but this method has limitations in evaluating thoracoabdominal aortic disease. Sequential 2D axial imaging (which maximizes flow-related enhancement) is time consuming, subject to slice-to-slice misregistration, and can be degraded by pulsatile and turbulent flow. Coronal or parasagittal imaging is more time efficient, but image degradation secondary to inplane saturation and stagnant or turbulent flow from aneurysmal disease may lead to nondiagnostic studies. Three-dimensional TOF techniques offer the advantages of higher signal-to-noise ratio, better spatial resolution with near isotropic voxels, and shorter echo times (TEs), which lessen signal loss because of intravoxel phase dispersion. Although these techniques provide excellent image quality in the carotid arteries, they are of limited use in the aorta because of saturation effects. However, the addition of gadolinium chelates shortens the T1 relaxation rate of blood, which obviates the need for flow-related enhancement, allowing for inplane imaging without saturation effects, even in regions of virtually stagnant flow. The enormous signal enhancement of gadolinium chelates enables imaging with high-resolution matrices, providing diagnostic angiograms in as little as 2 minutes. With improved hardware, faster and stronger gradients, and phased-array coils that increase the signal-to-noise ratio, breath-hold gadolinium-enhanced 3D schemes with ultrashort TEs will become the optimal method for imaging the aorta and its branch vessels. Using this technique, the aorta can be imaged in less than 1 minute.

Three-dimensional gadolinium-enhanced MR angiography of the thoracic aorta.

Our objective was to evaluate image quality and preliminary clinical experience with three-dimensional gadolinium-enhanced MR angiography of the thoracic aorta. Ninety patients with suspected thoracic aorta pathology underwent 97 MR examinations at 1.5 T with a 4-min, three-dimensional spoiled gradient-echo techniques. Gadolinium infusion was timed for maximum arterial contrast during acquisition of the central portion of K-space. No ECG gating or breath-holding was used. All MR examinations were evaluated retrospectively for intravascular signal-to-noise ratio (SNR). In 30 of the 90 patients, results from surgery (n = 11), angiography (n = 12), or both (n = 7) were available. Four radiologists who were unaware of the angiographic or surgical findings assessed each of these 30 examinations for three types of pathology: dissection, coarctation, or aneurysm. The observers also assessed aortic branch vessel patency and vascular anomalies in the 19 patients who had angiographic correlation. Image quality (determined as SNR) was highest in the aortic arch, upper descending thoracic aorta, and upper abdominal aorta. We saw a small reduction in the SNR in the ascending aorta and lower descending thoracic aorta (p < .0001), attributable to cardiac and respiratory motion. Image quality was not affected by slow flow. MR imaging correctly diagnosed pathology in all 30 patients with angiographic or surgical correlation, including eight dissections, three coarctations, and 10 aneurysms. The type of the dissection was correctly determined in all eight patients. Stenoses of major branch vessel origins were detected with a sensitivity of 90% (95% bayesian confidence interval, 99-63%) and a specificity of 96% (95% bayesian confidence interval, 99-89%) in the 19 patients with angiographic correlation. Five vascular anomalies, including an aberrant right subclavian artery, a bovine arch, and three accessory renal arteries, were correctly identified. Three-dimensional gadolinium-enhanced MR angiography has the potential to accurately diagnose aortic dissection, coarctation, and aneurysm. It does not require ECG gating or breath-holding and thereby extends the diagnostic utility of MR imaging for the thoracic aorta.