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 464 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After making the visualization of the intracranial circulation possible without contrast media, the radiologist is now evaluating the diagnostic role of the different techniques of MRA. Attempts are also being made to characterize the main patterns of intracranial vascular diseases. The authors examined, with 3D TOF MRA, 40 patients presenting with 50 vascular lesions on MRI scans. Twenty of 40 patients were also studied with angiography. Seventeen aneurysms were detected, together with 3 stenoses of the cerebral arteries, 13 arteriovenous malformations, 12 dolichobasilar arteries, 3 postoperative and 2 post-embolization controls. MRI was performed with a superconductive magnet (1.5 T), a dedicated coil and gradient-echo 3D TOF FT sequences. The refocused sequence for flux, FISP 3DFT, required the following parameters: TR = 0.04 s, TE = 10 ms, flip angle = 15 degrees, 256 x 256 matrix, 1 acquisition. The 64-80 mm volume along the axial plane was divided so that an actual 1-mm thickness was excited. In post-processing, the maximum-intensity projection was employed on the axial plane 0 degrees-90 degrees (15 degrees interval). In the various conditions, the results obtained with MRA were correlated and compared with MRI findings. MRA provided useful additional information in 27.4% of cases in the study of aneurysms, arteriovenous malformations, vascular occlusion and dolichobasilar arteries, as well as in the follow-up of these lesions. MRA is currently suggested in the evaluation of cerebral circulation and is considered a complementary technique to MRI. MRA is also to be used preliminary to angiography.
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PMID:[Cerebrovascular pathology. Comparison of magnetic resonance and magnetic resonance angiography]. 176 45

MR angiography of the lumbar venous plexuses (MR venography, MRV) was performed with thirty-one cases using a 1.5 T superconducting MR unit. Two MRV techniques, FISP based subtraction method and FLASH based TOF method were used for this study. After obtaining coronal or axial data acquisition, angiographic images were reconstructed by MIP method. Gd-DTPA was injected in all cases. The over all detectability of the lumbar venous plexuses was more than 77% on coronal data acquisition with subtraction method that better delineated slow-in-plane flow with optimal tissue signal suppression around the vessels. The coronal images were superior to axial ones in terms of wider demonstration of vertebral venous plexuses. Whole lumbar spine can be demonstrated in coronal plane. The use of Gd-DTPA to reduce the saturation effect of venous flow was necessary for better visualization of the lumbar venous plexuses.
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PMID:[2D MR angiography of lumbar venous plexuses]. 812 69

This work was aimed at investigating the value of Gd-DTPA to demonstrate distal renal artery branches with 3D TOF Magnetic Resonance angiography (MRA). Ten volunteers and two patients with proximal-distal renal artery stenoses were studied with MRA; all subjects were studied before and after Gd-DTPA. MRA was performed with a 1.5-T superconductive magnet (Magnetom Siemens); the FISP 3D sequence was used with the following setting: FA 25 degrees, TR 40 ms, TE 6 ms, slice thickness 64 mm with 64 partitions and MA 256 x 256. This setting was not changed from pre- to post-contrast scans. The images acquired on the z axis were rotated, according to the MIP, on the axial and the sagittal axes, from 0 degrees to 180 degrees, with a 15 degrees step. 0.2 ml/kg of Gd-DTPA were injected as bolus during 3D acquisitions; the injection was started half-way through acquisition. To evaluate and compare pre- and post-contrast MRA images, the signal-to-noise (S/N) ratio and the demonstration of the various renal artery segments were studied. Average S/N ratio was 2.3 in the right renal artery and 2.1 in the left renal artery on pre-contrast MRA images, while it was 0.9 in the left renal artery and 0.8 in the right renal artery on post-contrast MRA images. These differences were statistically significant (p < 0.01). As for the demonstration of the distal segments and of the bifurcations, enhanced MRA was no better than unenhanced MRA. As for the demonstration of distal segment stenoses, enhanced MRA proved no better than unenhanced MRA in both patients. To conclude, in our experience MRA after Gd-DTPA failed to allow the systematic demonstration of the distal segments and of the bifurcations of the renal arteries.
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PMID:[Renal arteries: angiography with TOF 3D magnetic resonance with and without contrast media (Gd-DTPA)]. 814 62

The authors report on a diagnostic pitfall which is often observed in magnetic resonance angiography (MRA) of intracranial vessels (time-of-flight 3D)--i.e., the absence of one of the two transverse sinuses. Fifty patients underwent MRA of the intracranial vessels with the TOF 3D (FISP) and the TOF 2D (FISP) techniques. Five patients were affected with sinus stenosis. MRA was performed with a 1.5-T superconductive magnet and a circular head coil. All patients underwent Magnetic Resonance Angiography with FISP 2D sequences (FA 40 degrees, TR 40 ms, TE 12 ms) acquired on coronal plane as well as FISP 3D (FA 15 degrees, TR 30 ms, TE 7 ms) acquired on axial plane. In the patients in whom FISP 2D sequences correctly demonstrated the whole confluence of sinuses, FISP 3D sequences always depicted the upper sagittal sinus, while the right transverse sinus was seen in 84.4% (38/45) of cases and the left transverse sinus in 24.2% (11/45) of cases. In the patients with a stenosis in the confluence of sinuses, FISP 3D sequences demonstrated two false-positive cases with respect to FISP 2D. The statistical analysis (McNemar test) of the results demonstrated the difference between 2D and 3D sequences in the detection of the two transverse sinuses to be statistically significant: p < 0.01 for the right transverse sinus and p < 0.001 for the left transverse sinus. In the study of the intracranial vessels (TOF 3D technique) the absence of one of the two transverse sinuses is suggestive of a diagnostic pitfall; the combination of 3D and 2D sequences answers this diagnostic question.
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PMID:[The torcular Herophili: the diagnostic pitfalls in TOF 3D magnetic resonance angiography]. 819 Sep 27

The diagnostic role of Magnetic Resonance angiography (MRA) was investigated in the study of the abdominal aorta. To obviate the problems relative to motion and respiratory artifacts, the TOF 2D (FISP 2D) technique was employed, together with a superconductive 1.5 T magnet. Fourteen volunteers were studied. The images acquired on the coronal and sagittal planes were processed according to MIP and target MIP, with a rotation on the z axis. The abdominal aorta was clearly demonstrated in 100% of cases, the celiac trunk in 42.8% of cases on coronal and in 100% on sagittal images. The superior mesenteric artery was depicted in 35.7% of cases on coronal and in 100% of subjects on sagittal acquisitions. The renal and iliac arteries were demonstrated in 100% of cases on coronal images only, while dorso-spinal and lumbar arteries were always clearly depicted on sagittal scans only. To evaluate the diagnostic reliability of MRA, 6 patients with abdominal aortic aneurysms were also studied and angiography and surgery were assumed as the gold standard. In all cases MRA yielded similar information to angiography and surgery as to aneurysm extent, vessel involvement and left renal vein course; moreover, MRA allowed the assessment of both the thrombotic and the calcific components of the aneurysm. Unenhanced MRA with the TOF 2D technique allows the detailed depiction of the aorta in about 20 minutes. Our preliminary results in the study of aneurysms are encouraging relative to the future diagnostic role of MRA in the abdominal aorta.
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PMID:[Abdominal aorta: role of angiography with magnetic resonance]. 849 62

The purpose of this study was to investigate capabilities of Magnetic Resonance Angiography (MRA) in delineating neurovascular compression which has emerged as the most frequent etiology in cases of Hemi-Facial Spasm and Trigeminal Neuralgia. MR investigations were carried out at 1.5 t unit (Magnetom Vision, Siemens). The examination consisted of 3D time-of-flight MRA (3d TOF) protocol, with a FISP sequence (Fast Imaging Steady Precession) and magnetization transfer. Imaging parameters were; TR 39 ms, TE 7 ms; MX 256-512; FOV 210-210 mm. Time acquisition is 10 mm 30 s. The axially acquired angiographic slices were reformatted with a multiplanar reconstruction program (MPR) along and across the plane of facial and trigeminal nerves. Then millimetric raw data images were postprocessed with a maximum intensity projection (MIP) technique. 58 patients presented either with hemifacial spasm (36 cases, 16 women, 20 men, mean age: 58.5 y) or trigeminal neuralgia (22 cases, 13 women, 8 men, mean age: 51 y) were compared with 17 patients (9 women, 8 men, mean age: 57.5 y) as references. MRA with MIP and MPR techniques reliably demonstrates neurovascular compression at the root entry zone (REZ), and allows recognition of the implicated vascular loop in 34 the cases of hemifacial spasm investigated. Raw data were post-processed in an axially oblique plane parallel to the acoustico-facial bundle and secondarily reconstructed in coronally obliques views. These reconstructed images clearly delineate the cross-compression of the emerging facial nerve. The neurovascular conflict was related to an arterial loop from the postero-inferior cerebellar artery (PICA, 21 cases, 61%) and the antero-inferior cerebellar artery (AICA, 8 cases, 23%). Vertebral artery is implicated in conflicts in 5 cases. In 2 cases MRA exploration was negative. In HFS group distance between Vth nerve emergency and neuro vascular contact was measured and compared with control group; there is a significative difference (p < 0.01). In case of trigeminal neuralgia, MRA demonstrates neurovascular compression at the root entry zone of the Vth nerve of 16 patients. In theses cases, oblique and coronally reconstructed images are crucial in demonstrating neurovascular contacts. The vessel implicated in conflict is always the superior cerebellar artery (SCA). A supero-medial loop of the superior cerebellar artery was depicted in these 16 cases. Although 3 patients had negative MRA and MR studies, a case of compression of the origin of the Vth nerve by a enlarged draining vein in a case of brainstem arterio-venous malformation, a petrous apex meningioma was incidentally discovered and thoroughly investigated with gadolinium T1 weighted sequences and 1 demyelinating plaques located along the intraaxial course of the Vth nerve were noticed. In control group on 34 explanations only there are only 4 contacts between Vth nerve and SCA. MRA with a 3D-TOF FISP sequence allows recognition of neurovascular conflicts in case of hemifacial spasm and trigeminal neuralgia while MIP helps to characterize the implicated vessel. Sources images need to be carefully assessed in order to depict unsuspected pathology.
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PMID:[The contribution of "time-of-flight" MRI-angiography in the study of neurovascular interactions (hemifacial spasm and trigeminal neuralgia)]. 909 7

Imaging was performed using a 1.0 Tesla superconducting MR system with a body coil. Two-dimensional(2D) turbo FLASH sequence and/or three-dimensional(3D) FISP sequence were carried out in 46 volunteers with 113 pulmonary MRA. The total MRAs were divided into 4 groups and analysed. The results showed: After Gd-DTPA was injected, the signal-to-noise ratio(SNR) of pulmonary 2D- and 3D-TOF MRA was increased in 46 normal pulmonary MR angiography cases(P < 0.01); the number of left and right pulmonary artery divisions identified was much greater than that before Gd-DTPA injection both in 2D- and 3D-MOF(except lingual segment of left lobe). It is suggested that Gd-DTPA may markedly promote the efficiency of pulmonary MRA.
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PMID:[Comparative study of pulmonary magnetic resonance angiography (MRA)]. 1221 14