Enhanced Magnetic Resonance Angiography Research Articles

Efficacy of Angiography Examinations using 4D TRAK Contrast Enhancement Techniques

The non-enhanced 3D TOF and the contrast enhancement magnetic resonance angiography (MRA) technique are MRA examination methods used to define the carotid in cerebral vascular examination. Recently, the 4D time-resolved angiography using keyhole(TRAK) technique, which is the combination of the contrast enhancement MRA technique and the keyhole technique, has been used. This study is intended to evaluate its efficacy on the cerebrovascular diagnostic examination by comparing 4D TRAK with the existing contrast enhancement MRA technique. CE Neck MRA was used on 30 patients (15 males and 15 females) who were prescribed a Brain Neck CE MRA after receiving contrast enhancement MRA and 4D TRAK when they entered the emergency room. The same concern sectors were established on the images acquired using each technique after the injection of a contrast medium. The contrast to noise ratio was compared and analyzed through estimated values. According to the results, 4D TRAK showed stronger signal strength than the existing contrast enhancement MRA by 4.38 in CCA, 4.24 in ICA, and 2.94 in VA. The results of the matching sample T-test were statistically significant (p<0.05). When 4D TRAK and the existing contrast enhancement MRA were compared and analyzed in CE Neck MRA examination, 4D TRAK was seen as being more useful at displaying anatomical information about blood vessels and hemodynamics information. These results point towards it being a very useful method for clinical examination

Optimum Refocus Flip Angle of Non-contrast Magnetic Resonance Angiography Using ECG-gated 3D-TSE

In triggered acquisition noncontrast enhancement magnetic resonance angiography using ECG-gated with short-term inversion recovery (STIR-TRANCE), signal intensity and contrast fluctuate according to the value of refocus flip angle (RFA). We believe that we can visualize the pulmonary vascular excellently by optimized RFA which improves the signal intensity of pulmonary vascular and the contrast between pulmonary vascular and lung parenchyma. The purpose of this study is to optimize RFA in pulmonary vascular magnetic resonance angiography (MRA) imaging using STIR-TRANCE. Pulmonary vascular MRA was performed in five normal volunteers. The department's ethics committee approved the study, and informed consent was obtained from all subjects. Before the STIR-TRANCE study, an ECG-gated single shot TSE (SS TSE) scan was performed to determine the timing of diastole. Later, the diastolic STIR-TRANCE imaging using both ECG and respiratory gating was performed with three different RFA (140 degree, 160 degree, and 180 degree). For physical evaluation, we used the signal to noise ratio (SNR) and contrast and for visual evaluation, so we used the Scheffe's method. SNR increases with increasing RFA. The contrast of 160 degree was significantly higher than the contrast of 180 degree. There was no significant difference in visual evaluation. From the perspective of specific absorption rate (SAR) reduction, we concluded that the optimal RFA for pulmonary vascular MRA in this study was 160 degree.

Stable gadolinium based nanoscale lyophilized injection for enhanced MR angiography with efficient renal clearance

There is a great demand to develop high-relaxivity nanoscale contrast agents for magnetic resonance (MR) angiography with high resolution. However, there should be more focus on stability, ion leakage and excretion pathway of the intravenously injected nanoparticles, which are closely related to their clinic potentials. Herein, uniform ultrasmall-sized NaGdF4 nanocrystal (sub-10 nm) was synthesized using a facile high temperature organic solution method, and the nanocrystals were modified by a ligand-exchange approach using PEG-PAA di-block copolymer. The PEG-PAA modified NaGdF4 nanocrystal (denoted as ppNaGdF4 nanocrystal) exhibited a high r1 relaxivity which was twice of commercially used gadopentetate dimeglumine (Gd-DTPA) injection. MR angiography on rabbit using ppNaGdF4 nanocrystal at a low dose showed enhanced vascular details and long circulation time. Lyophilized powder of ppNaGdF4 nanocrystals have been successfully prepared without aggregation or reduction of MR performance, indicating the stability and an effective way to store this nanoscale contrast agent. No haemolysis was induced by ppNaGdF4 nanocrystal, and an extremely low leakage of gadolinium ions was confirmed. Furthermore, efficient renal excretion was one of the clearance pathways of ppNaGdF4 nanocrystal according to both the time dependent distribution data in blood and tissues and MR images. The in vivo toxicity evaluation further validated the great potential as a clinical agent for blood pool imaging.

Segmentation of lumen and outer wall of abdominal aortic aneurysms from 3D black-blood MRI with a registration based geodesic active contour model.

Segmentation of the geometric morphology of abdominal aortic aneurysm is important for interventional planning. However, the segmentation of both the lumen and the outer wall of aneurysm in magnetic resonance (MR) image remains challenging. This study proposes a registration based segmentation methodology for efficiently segmenting MR images of abdominal aortic aneurysms. The proposed methodology first registers the contrast enhanced MR angiography (CE-MRA) and black-blood MR images, and then uses the Hough transform and geometric active contours to extract the vessel lumen by delineating the inner vessel wall directly from the CE-MRA. The proposed registration based geometric active contour is applied to black-blood MR images to generate the outer wall contour. The inner and outer vessel wall are then fused presenting the complete vessel lumen and wall segmentation. The results obtained from 19 cases showed that the proposed registration based geometric active contour model was efficient and comparable to manual segmentation and provided a high segmentation accuracy with an average Dice value reaching 89.79%.

Diagnostic accuracy of contrast enhancement MRI versus CTA in diagnosis of intracranial aneurysm in patients with non-traumatic subarachnoid hemorrhage

Aim of the studyThe most common cause of spontaneous SAH is the rupture of cerebral aneurysm. So it is very important to exclude it from circulation as soon as possible using endovascular therapy. The aim was to determine whether contrast enhancement magnetic resonance angiography (CEMRA) is preferable to computed tomography angiography (CTA) in detection of intracranial aneurysm in patients presenting with non-traumatic subarachnoid hemorrhage (SAH). Patients and methodsTwenty-five patients who presented with non-traumatic SAH underwent CEMRA and CTA for detection of aneurysms. Digital subtraction angiography (DSA) was used as standard of reference. ResultsCEMRA and CTA were done for all patients. A total of 22 aneurysms were detected in 25 patients. 15 patients with single aneurysm, 2 patients with two aneurysms, one patient with 3 aneurysms and in 7 patients no aneurysm was found. CEMRA and CTA angiograms were interpreted for the detection of aneurysms, site and size. ConclusionThe diagnostic performance of CEMRA does not significantly differ from that of CTA in patients presenting with SAH.

MR Imaging of Soft-Tissue Vascular Malformations: Diagnosis, Classification, and Therapy Follow-up

Vascular malformations and tumors comprise a wide, heterogeneous spectrum of lesions that often represent a diagnostic and therapeutic challenge. Frequent use of an inaccurate nomenclature has led to considerable confusion. Since the treatment strategy depends on the type of vascular anomaly, correct diagnosis and classification are crucial. Magnetic resonance (MR) imaging is the most valuable modality for classification of vascular anomalies because it accurately demonstrates their extension and their anatomic relationship to adjacent structures. A comprehensive assessment of vascular anomalies requires functional analysis of the involved vessels. Dynamic time-resolved contrast material-enhanced MR angiography provides information about the hemodynamics of vascular anomalies and allows differentiation of high-flow and low-flow vascular malformations. Furthermore, MR imaging is useful in assessment of treatment success and establishment of a long-term management strategy. Radiologists should be familiar with the clinical and MR imaging features that aid in diagnosis of vascular anomalies and their proper classification. Furthermore, they should be familiar with MR imaging protocols optimized for evaluation of vascular anomalies and with their posttreatment appearances. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.315105213/-/DC1.

The CEMRA findings of brain feeding artery in Transient Ischemic Attack Patients

Objective To evaluate the brain feeding arteries in the patients with transient isehemic attacks(TIA) with contrast enhancement magnetic resonance angiography(MRA).Methods 55 TIA patients were chosen as study subjects,and 48 normal subjects and 46 patients with large area brain infarctions were randomly chosen as control subjects.CEMRA was performed with a superconductive GE 1.5T system.The relationship between TIA and the degree of stenosis of brain feeding arteries were analyzed.Results More lesions were found before the Circle of Willis in normal subjects and the TIA patients,and there were no significant difference between the to groups(P=0.729);More lesions were found behind the Circle of Wims in the patients with brain infarctions,and there were significant difference compared with the former two groups(P＜0.001).There were significant difference among the three groups on the number and the degree of stenosis of the brain feeding artery(P=0.006).TIA and brain infarctions were more prone to have multiple lesions.Conclusion The Circle of Willis had significant compensation for the brain blood-supply.Stenosis or occlusions of brain feeding arteries in patients with TIA might be the risk factors for severe ischemia stroke occurring. Key words: Transient Ischemic Attacks; Contrast Enhancement Magnetic Resonance Angiography; Brain Feeding Artery

Carotid Artery Stenosis: Accuracy of Noninvasive Tests—Individual Patient Data Meta-Analysis

To find clinically relevant estimates of the accuracy of noninvasive imaging-Doppler ultrasonography (US), computed tomographic (CT) angiography, magnetic resonance (MR) angiography, and contrast material-enhanced MR angiography-in diagnosing both severe and moderate symptomatic carotid artery stenosis; to ascertain the effect of prespecified clinical factors and clinical setting on diagnostic accuracy; and to estimate the probability of agreement between two noninvasive tests. Original principal investigators obtained ethics approval for each data set. All data were anonymized. Individual patient data sets (IPDs) for noninvasive imaging tests were used to determine sensitivity, specificity, and agreement between the tests for symptomatic carotid artery stenosis; to compare ipsilateral with contralateral arteries; to compare IPDs with literature estimates; to compare routine audit and research data; and to determine the effect of age and sex on sensitivity and specificity. Contrast-enhanced MR angiography was the most accurate (sensitivity, 0.85 [30 of 35]; 95% confidence interval [CI]: 0.69, 0.93; and specificity, 0.85 [67 of 78]; 95% CI: 0.76, 0.92) for 70%-99% symptomatic stenosis. Sensitivity for a 50%-69% stenosis was poor, although data were limited. Sensitivity and specificity were generally lower in the ipsilateral than in the contralateral artery. IPD estimates were lower than literature values. Results of comparison of research with audit-derived data were inconclusive. Neither age nor sex affected accuracy. Agreement was better between two Doppler US tests and between two contrast-enhanced MR angiographic tests than it was between Doppler US and contrast-enhanced MR angiography, except for a 70%-99% symptomatic stenosis. Primary studies should distinguish ipsilateral from contralateral arteries and carefully describe the patients' characteristics and study environment. The literature overestimates noninvasive imaging accuracy. More data are needed to inform physicians in routine clinical practice.

Supraaortic Arteries: Contrast Material Dose Reduction at 3.0-T High-Spatial-Resolution MR Angiography—Feasibility Study

To evaluate and compare the diagnostic image quality resulting from three contrast agent dose regimens for 3.0-T high-spatial-resolution three-dimensional magnetic resonance (MR) angiography of the supraaortic arteries. Institutional review board approval was obtained; informed consent was waived for this HIPAA-compliant study. One hundred twenty consecutive patients who underwent 3.0-T three-dimensional high-spatial-resolution contrast material-enhanced MR angiography of the supraaortic arteries with an identical acquisition protocol were assigned to either the high-dose (0.154 mmol per kilogram of body weight), intermediate-dose (0.097 mmol/kg), or low-dose (0.047 mmol/kg) group. Two readers evaluated resulting images for arterial definition, venous contamination, and arterial stenosis. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated at six consistent sites. Statistical analysis was performed with the Kruskal-Wallis, Wilcoxon signed rank, and analysis of variance tests and the kappa coefficient. Readers 1 and 2 scored vascular definition as excellent or sufficient for diagnosis in 1311 of 1360 segments and in 1313 of 1360 segments in the high-dose group (kappa = 0.73), in 1321 of 1354 and in 1319 of 1354 segments in the intermediate-dose group (kappa = 0.77), and in 1322 of 1350 and in 1320 of 1350 segments in the low-dose group (kappa= 0.66), respectively. Arterial occlusive disease was detected by reader 1 in 52, 27, and 98 segments in the high-, intermediate-, and low-dose groups, respectively. Arterial occlusive disease was detected by reader 2 in 48, 25, and 100 segments in high-, intermediate-, and low-dose groups, respectively. No significant difference existed among the three groups regarding arterial definition scores (reader 1, P = .21; reader 2, P = .25) and venous contamination scores (reader 1, P = .38; reader 2, P = .35). SNRs and CNRs were lower in the low-dose group (P < .01). At 3.0 T, high-spatial-resolution MR angiography of the supraaortic arteries can be performed with contrast agent doses as low as 0.047 mmol/kg, without compromising image quality, acquisition speed, or spatial resolution. http://radiology.rsnajnls.org/cgi/content/full/249/3/980/DC1http://radiology.rsnajnls.org/cgi/content/full/249/3/980/DC2.

Three-dimensional Reconstructed Contrast–enhanced MR Angiography for Internal Iliac Artery Branch Visualization before Uterine Artery Embolization

To evaluate the feasibility of three-dimensional (3D) reconstructed contrast-enhanced (CE) magnetic resonance (MR) angiography in mapping the pelvic arteries in women before uterine artery embolization (UAE). CE MR angiography studies before UAE in 49 women (age range, 38-57 years; mean, 47.04 y +/- 4.7 [SD]) who underwent UAE for uterine leiomyomas between February 2005 and February 2007 were retrospectively evaluated by two radiologists in consensus. Studies were performed on a 1.5-T MR unit with a 3D fast low-angle shot sequence in the coronal direction. Reconstruction was performed with 3D computed tomographic angiography reconstruction software. In the current study, 98 internal iliac arteries (IIAs) from 49 women were studied. The superior and inferior gluteal arteries were visualized in all cases (N = 98; 100%), the lateral sacral artery in 86 cases (88%), the iliolumbar artery in 84 (86%), the obturator artery in 81 (83%), the internal pudendal artery in 96 (98%), and the uterine artery in 95 (97%). The superior vesical and middle rectal arteries were seen in 21 (21%) and 11 (11%) cases, respectively. The mean length of the uterine artery was 12.56 cm (range, 4.6-22.2 cm), and it showed the longest traceable length among all branches. The uterine artery showed five patterns of origin. The superior gluteal artery showed constant origin from the posterior division of the IIA, whereas the iliolumbar and obturator arteries showed the most variations in origin. Three-dimensional reconstructed CE MR angiography can detect most branches of the IIA in addition to their point of origin. Therefore, it can be used as a mapping tool of the pelvic arterial tree before UAE.

Renal Artery Stenosis Evaluation: Diagnostic Performance of Gadobenate Dimeglumine–enhanced MR Angiography—Comparison with DSA

To prospectively determine diagnostic performance and safety of contrast material-enhanced (CE) magnetic resonance (MR) angiography with 0.1 mmol per kilogram of body weight gadobenate dimeglumine for depiction of significant steno-occlusive disease (> or =51% stenosis) of renal arteries, with digital subtraction angiography (DSA) as reference standard. This multicenter study was approved by local institutional review boards; all patients provided written informed consent. Patient enrollment and examination at centers in the United States complied with HIPAA. Two hundred ninety-three patients (154 men, 139 women; mean age, 61.0 years) with severe hypertension (82.2%), progressive renal failure (11.3%), and suspected renal artery stenosis (6.5%) underwent CE MR angiography with three-dimensional spoiled gradient-echo sequences after administration of 0.1 mmol/kg gadobenate dimeglumine at 2 mL/sec. Anteroposterior and oblique DSA was performed in 268 (91.5%) patients. Three independent blinded reviewers evaluated CE MR angiographic images. Sensitivity, specificity, and accuracy of CE MR angiography for detection of significant steno-occlusive disease (> or =51% vessel lumen narrowing) were determined at segment (main renal artery) and patient levels. Positive and negative predictive values and positive and negative likelihood ratios were determined. Interobserver agreement was analyzed with generalized kappa statistics. A safety evaluation (clinical examination, electrocardiogram, blood and urine analysis, monitoring for adverse events) was performed. Of 268 patients, 178 who were evaluated with MR angiography and DSA had significant steno-occlusive disease of renal arteries at DSA. Sensitivity, specificity, and accuracy of CE MR angiography for detection of 51% or greater stenosis or occlusion were 60.1%-84.1%, 89.4%-94.7%, and 80.4%-86.9%, respectively, at segment level. Similar values were obtained for predictive values and for patient-level analyses. Few CE MR angiographic examinations (1.9%-2.8%) were technically inadequate. Interobserver agreement for detection of significant steno-occlusive disease was good (79.9% agreement; kappa = 0.69). No safety concerns were noted. CE MR angiography performed with 0.1 mmol/kg gadobenate dimeglumine, compared with DSA, is safe and provides good sensitivity, specificity, and accuracy for detection of significant renal artery steno-occlusive disease.

High-Spatial-Resolution Whole-Body MR Angiography with High-Acceleration Parallel Acquisition and 32-Channel 3.0-T Unit: Initial Experience

The purpose of this HIPAA-compliant study was to prospectively evaluate the technical feasibility of a multistation high-spatial-resolution whole-body magnetic resonance (MR) angiography protocol in which high-acceleration parallel imaging (with acceleration factors of three and four) is performed with a 32-channel 3.0-T MR system. After institutional review board approval and written informed consent were obtained, 10 healthy volunteers (four men and six women aged 23-68 years) and four patients (two men and two women aged 56-79 years) suspected of having peripheral vascular disease underwent multistation whole-body contrast material-enhanced MR angiography. Use of multiarray surface coil technology and highly accelerated generalized autocalibrating partially parallel acquisition enabled the acquisition of isotropic high-spatial-resolution three-dimensional data sets for multiple stations. Two radiologists independently evaluated arterial image quality and presence of arterial stenoses. All examinations yielded good or excellent image quality. Interobserver agreement was excellent (kappa = 0.92; 95% confidence interval: 0.86, 0.96). Multistation whole-body MR angiography with high-acceleration parallel acquisition is feasible at 3.0 T. Further clinical studies combined with ongoing optimization of radiofrequency systems and coils seem warranted to advance the potential of this technology.

In Vivo MR Angiographic Quantification of Axial and Twisting Deformations of the Superficial Femoral Artery Resulting from Maximum Hip and Knee Flexion

The goal of this study was to quantify in vivo deformations of the superficial femoral artery (SFA) during maximum knee and hip flexion with use of magnetic resonance (MR) angiography to improve description of the complex, dynamic SFA environment. Contrast medium-enhanced MR angiography was performed on the leg vasculature of eight healthy adults in the supine and fetal positions. The SFA was defined as the centerline path of the iliofemoral segment from the profunda femoris to the descending genicular artery. Deformations that resulted from flexion from the supine position to the fetal position were quantified with the SFA path and its branches. Fourteen SFAs shortened from the supine position to fetal position, whereas two lengthened. Six of eight left SFAs twisted counterclockwise, and seven of eight right SFAs twisted clockwise. Straightness percentages for supine and fetal SFAs were 99.1%+/-0.4% and 98.7%+/-0.6%, respectively. From the supine position to the fetal position, the SFA shortened 13%+/-11% (P<.001) and twisted 60 degrees+/-34 degrees (P<.001). SFA arc length and percent shortening were strongly correlated (r>.8) between left and right limbs; however, no significant correlation existed for SFA twist angle. Complex and varying vascular and muscular anatomy among study participants made SFA lengths and deformations from the supine position to the fetal position unpredictable a priori; however, there were strong symmetries between left and right SFAs in terms of arc length, length change, and direction of twist. The data show that, from the supine position to the fetal position, the SFA tended to shorten and twist substantially, suggesting these as possible fracture mechanisms and also providing important parameters for stent design.

Accuracy of Stepping-Table Lower Extremity MR Angiography with Dual-Level Bolus Timing and Separate Calf Acquisition: Hybrid Peripheral MR Angiography

To retrospectively evaluate the accuracy of hybrid peripheral magnetic resonance (MR) angiography by using conventional digital subtraction angiography (DSA) as the reference standard. This retrospective study protocol received approval from the Office of Sponsored Research at Northwestern University, which included review by the Office for the Protection of Research Subjects. Informed consent was waived for this HIPAA-compliant study. One hundred twenty-one consecutive patients (67 men: mean age, 66 years +/- 12 [standard deviation]; 54 women: mean age, 69 years +/- 14), who were referred for evaluation of peripheral vascular disease, underwent peripheral contrast material-enhanced MR angiography. By using a hybrid technique, two independent timing measurements were performed in the pelvis and calves followed by MR angiography of the calves and, subsequently, a pelvis-thigh stepping-table acquisition. Images were evaluated for extent of disease, on the basis of degree of stenosis; for venous contamination, on the basis of venous signal intensity; and for diagnostic quality, on the basis of diagnostic confidence of the observer. DSA correlation of the extent of vascular disease was available in 45 of these patients, which was used to evaluate the diagnostic power of the hybrid technique. For detection of stenosis greater than 50%, the hybrid technique had 95% sensitivity (P < .05), 95% specificity (P < .05), and 95% accuracy (P < .05). There was no significant venous contamination in any of the examinations performed with this technique. The hybrid peripheral MR angiography technique provides diagnostic-quality examinations and virtually eliminates venous contamination.

Atherosclerotic ischemic renal disease. Diagnosis and prevalence in an hypertensive and/or uremic elderly population.

BackgroundAtherosclerotic ischemic renal disease is a frequent cause of end-stage renal failure leading to dialysis among the elderly; Its prevalence is inferred from autopsy or retrospective arteriographic studies. This study has been conducted on 269 subjects over 50 with hypertension and/or CRF, unrelated to other known causes of renal disease.MethodsAll 269 patients were studied either by color-flow duplex sonography (n = 238) or by renal scintigraphy (n = 224), and 199 of the 269 patients were evaluated using both of these techniques. 40 patients, found to have renal artery stenosis (RAS), were subjected to 3D-contrast enhancement Magnetic Resonance Angiography (MRA) and/or Selective Angiography (SA). An additional 23 cases, negative both to scintigraphy and to ultrasound study, underwent renal angiography (MRA and/or SA).ResultsColor-duplex sonography, carried out in 238 patients, revealed 49 cases of RAS. MR or SA was carried out in 35 of these 49 patients, and confirmed the diagnosis in 33. Color-duplex sonography showed a PPV value of 94.3% and NPV of 87.0% while renal scintigraphy, carried out in 224 patients, had a PPV of 72.2% and a NPV of 29.4%. Patients with RAS showed a higher degree of renal insufficiency compared to non stenotic patients while there were no differences in proteinuria. RAS, based on color-duplex sonography studies, was present in 11% of patients in the age group 50–59, 18% in the 60–69 and 23% at age 70 and above.ConclusionsA relatively large percentage of the elderly population with renal insufficiency and/or hypertension is affected by RAS and is at risk of developing end-stage renal failure. Color-duplex ultrasonography is a valid routine method of investigation of population at risk for renal artery stenosis.

Carotid Artery Stenosis: Prospective Comparison of CT, Three-dimensional Gadolinium-enhanced MR, and Conventional Angiography

To prospectively compare gadolinium-enhanced magnetic resonance (MR) angiography and computed tomographic (CT) angiography with digital subtraction angiography (DSA) for use in detecting atheromatous stenosis and plaque morphology at the carotid bifurcation. Forty-four carotid arteries (in 22 patients) were analyzed by using CT angiography, enhanced MR angiography, and DSA. CT and enhanced MR angiograms were reconstructed with maximum intensity projection and multiplanar volume reconstruction. The following four features were analyzed: degree of stenosis on the basis of North American Symptomatic Carotid Endarterectomy Trial criteria, length of stenosis, luminal surface, and presence of ulcers. There was significant correlation between CT angiography, enhanced MR angiography, and DSA for degree and length of stenosis. With enhanced MR angiography and CT angiography, degree of stenosis was underestimated in two of 44 cases. No case of overestimation with CT angiography was found. Severe internal carotid artery stenoses were detected with high sensitivity and specificity: 100% and 100%, respectively, with CT angiography; 93% and 100%, respectively, with enhanced MR angiography. Luminal surface irregularities were most frequently seen at CT angiography. With CT angiography and enhanced MR angiography, more ulceration was detected than with DSA. There was a significant correlation between CT angiography, enhanced MR angiography, and DSA in evaluation of carotid artery stenosis. Enhanced MR angiography or CT angiography can be used to adequately evaluate carotid stenosis.