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ABSTRACT: INTRODUCTION: 4D phase contrast MR imaging (4D PC MRI) has been introduced for spatiotemporal evaluation of intracranial hemodynamics in various cerebrovascular diseases. However, it still lacks validation with standards of reference. Our goal was to compare blood flow quantification derived from 4D PC MRI with transcranial ultrasound and 2D PC MRI. METHODS: Velocity measurements within large intracranial arteries [internal carotid artery (ICA), basilar artery (BA), and middle cerebral artery (MCA)] were obtained in 20 young healthy volunteers with 4D and 2D PC MRI, transcranial Doppler sonography (TCD), and transcranial color-coded duplex sonography (TCCD). Maximum velocities at peak systole (PSV) and end diastole (EDV) were compared using regression analysis and Bland-Altman plots. RESULTS: Correlation of 4D PC MRI measured velocities was higher in comparison with TCD (r = 0.49-0.66) than with TCCD (0.35-0.44) and 2D PC MRI (0.52-0.60). In mid-BA and ICA C7 segment, a significant correlation was found with TCD (0.68-0.81 and 0.65-0.71, respectively). No significant correlation was found in carotid siphon. On average over all volunteers, PSVs and EDVs in MCA were minimally underestimated compared with TCD/TCCD. Minimal overestimation of velocities was found compared to TCD in mid-BA and ICA C7 segment. CONCLUSION: 4D PC MRI appears as valid alternative for intracranial velocity measurement consistent with previous reference standards, foremost with TCD. Spatiotemporal averaging effects might contribute to vessel size-dependent mild underestimation of velocities in smaller (MCA), and overestimation in larger-sized (BA and ICA) arteries, respectively. Complete spatiotemporal flow analysis may be advantageous in anatomically complex regions (e.g. carotid siphon) relative to restrictions of ultrasound techniques.
Neuroradiology 11/2012; · 2.82 Impact Factor
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ABSTRACT: The persistent trigeminal artery (PTA) is the most common and most cephalad-located embryological anastomosis between the developing carotid artery and vertebrobasilar system to persist into adulthood. As such, it is frequently reported as an incidental finding in computed tomography angiography and magnetic resonance angiography studies. Here, we review the embryology, anatomy, and angiographic imaging findings, including important variants of this commonly encountered cerebrovascular anomaly (reported incidence of PTA/PTA variants ranges from 0.1% to 0.76%). Further, the aim is to present the range of associated arterial anomalies or syndromes, as well as pathologies that are associated with a PTA: aneurysms, trigeminal cavernous fistulas, and trigeminal nerve compression. Besides summarizing the risks and clinical presentation of such pathologies, their management is discussed with endovascular strategies mostly being the primary choice for aneurysms and trigeminal cavernous fistulas. Symptomatic trigeminal nerve compression can be treated with microvascular decompression surgery. As an illustrative example, a case of a trigeminal cavernous fistula on a PTA variant is included, mainly to emphasize the importance of understanding the variant anatomy for treatment planning in such pathologies. Finally, recommendations on how to manage patients with PTA-associated vascular pathologies are advanced.
Neuroradiology 12/2011; · 2.82 Impact Factor
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Mira Katan,
Felix Fluri,
Nils G Morgenthaler,
Philipp Schuetz,
Christian Zweifel,
Roland Bingisser,
Klaus Müller, Stephan Meckel,
Achim Gass,
Ludwig Kappos,
Andreas J Steck,
Stefan T Engelter,
Beat Müller,
Mirjam Christ-Crain
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ABSTRACT: Early prediction of outcome in patients with ischemic stroke is important. Vasopressin is a stress hormone. Its production rate is mirrored in circulating levels of copeptin, a fragment of provasopressin. We evaluated the prognostic value of copeptin in acute stroke patients.
In a prospective observational study, copeptin was measured using a new sandwich immunoassay on admission in plasma of 362 consecutive patients with an acute ischemic stroke. The prognostic value of copeptin to predict the functional outcome (defined as a modified Rankin Scale score of <or=2 or >or=3), mortality within 90 days, was compared with the National Institutes of Health Stroke Scale score and with other known outcome predictors.
Patients with an unfavorable outcomes and nonsurvivors had significantly increased copeptin levels on admission (p <0.0001 and p <0.0001). Receiver operating characteristics to predict functional outcome and mortality demonstrated areas under the curve of copeptin of 0.73 (95% confidence interval [CI], 0.67-0.78) and 0.82 (95% CI, 0.76-0.89), which was comparable with the National Institutes of Health Stroke Scale score but superior to C-reactive protein and glucose (p <0.01). In multivariate logistic regression analysis, copeptin was an independent predictor of functional outcome and mortality, and improved the prognostic accuracy of the National Institutes of Health Stroke Scale to predict functional outcome (combined areas under the curve, 0.79; 95% CI, 0.74-0.84; p <0.01) and mortality (combined areas under the curve, 0.89; 95% CI, 0.84-0.94; p <0.01).
Copeptin is a novel, independent prognostic marker improving currently used risk stratification of stroke patients. Ann Neurol 2009;66:799-808.
Annals of Neurology 12/2009; 66(6):799-808. · 11.09 Impact Factor
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ABSTRACT: To present a novel postprocessing technique for artery/vein separation and background suppression from contrast-enhanced time-resolved magnetic resonance angiography datasets in order to improve the diagnosis of vessel pathologies and arteriovenous fistulas.
Ten normal, two pathologic datasets of the brain, and one hand angiography dataset were postprocessed. Cross-correlation maps between the signal time course of every voxel in the dataset and selected arterial and venous references regions of interest (ROIs) were obtained; these maps were subsequently nonlinearly transformed to obtain two indices representing the likelihood of a voxel belonging to a vessel category. Red-green-blue (RGB) color encoding was utilized to depict synthetic arteriogram and venogram images in a single diagnostically meaningful image.
The technique enabled correct visual separation of vessels on various datasets, as evaluated by two expert neuroradiologists, and also highlighted characteristics of flow in arteriovenous fistulas. A quantitative comparison with existing techniques showed better separation performance on 3 out of 10 normal datasets and higher stability to acquisition characteristics and contrast agent bolus dispersion.
This method can be helpful in the diagnosis of vascular diseases in subjects where bolus dispersion makes it difficult to discriminate between arteries and veins with standard methods (subtraction or correlation analysis).
Journal of Magnetic Resonance Imaging 10/2008; 28(3):646-54. · 2.70 Impact Factor
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ABSTRACT: Blood-flow patterns and wall shear stress (WSS) are considered to play a major role in the development and rupture of cerebral aneurysms. These hemodynamic aspects have been extensively studied in vitro using geometric realistic aneurysm models. The purpose of this study was to evaluate the feasibility of in vivo flow-sensitized 4-D MR imaging for analysis of intraaneurysmal hemodynamics.
Five cerebral aneurysms were examined using ECG-gated, flow-sensitized 4-D MR imaging at 3 T in three patients. Postprocessing included quantification of flow velocities, visualization of time-resolved 2-D vector graphs and 3-D particle traces, vortical flow analysis, and estimation of WSS. Flow patterns were analyzed in relation to aneurysm geometry and aspect ratio.
Magnitude, spatial and temporal evolution of vortical flow differed markedly among the aneurysms. Particularly unstable vortical flow was demonstrated in a wide-necked parophthalmic ICA aneurysm (high aspect ratio). Relatively stable vortical flow was observed in aneurysms with a lower aspect ratio. Except for a wide-necked cavernous ICA aneurysm (low aspect ratio), WSS was reduced in all aneurysms and showed a high spatial variation.
In vivo flow-sensitized 4-D MR imaging can be applied to analyze complex patterns of intraaneurysmal flow. Flow patterns, distribution of flow velocities, and WSS seem to be determined by the vascular geometry of the aneurysm. Temporal and spatial averaging effects are drawbacks of the MR-based analysis of flow patterns as well as the estimation of WSS, particularly in small aneurysms. Further studies are needed to establish a direct link between definitive flow patterns and different aneurysm geometries.
Neuroradiology 07/2008; 50(6):473-84. · 2.82 Impact Factor
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ABSTRACT: Time-resolved (TR) contrast-enhanced 3D MR angiography has recently received considerable attention for the workup of cerebrovascular diseases, foremost dural arteriovenous fistula and arteriovenous malformation, and potentially for the evaluation of dural sinus thrombosis. Thereby, the dynamic visualization of cerebral vessels is enabled similar to the principle of digital subtraction angiography. Yet, its voxel size is relatively large due to an inherent trade-off between the desired spatial and temporal resolutions. The goal of this study was to evaluate whether the limited spatial resolution of TR MR venography (MRV) is sufficient to visualize dural venous sinuses.
The prospective study included 20 patients without compromise of cerebral venous outflow. Two neuroradiologists independently graded the quality of visualization of 11 predefined dural venous sinuses on images of fast TR contrast-enhanced MRV (1.5 s/dataset; voxel size, 2 x 2 x 2.2 mm; acquisition time, 37.5 s) in comparison to time-of-flight (TOF) MRV (voxel size, 0.8 x 0.8 x 4 mm; acquisition time, 3 min 51 s) and steady-state contrast-enhanced 3D (VIBE) MRV (voxel size, 1.1 x 0.9 x 1.5 mm; acquisition time, 2 min 46 s).
The torcular Herophili (p < 0.001), left (p < 0.001) and right (p < 0.01) transverse sinus, and right jugular bulb (p < 0.05) were visualized better at TR MRV than at TOF MRV. For visualization of the small inferior sagittal sinus, TR MRV was inferior to VIBE (p < 0.001) and TOF (p < 0.05) sequences. The visibility of all other dural sinuses was equal.
Despite the inferior spatial resolution, TR MRV depicted some large dural sinuses more clearly than TOF MRV. To overcome the visualization of smaller venous structures, TR MRV can be applied complementarily with high-resolution steady-state contrast-enhanced MRV.
Cerebrovascular Diseases 02/2008; 25(3):217-24. · 2.72 Impact Factor
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ABSTRACT: Recently a new technique for the combined acquisition of multicontrast images, termed "combo acquisition," was introduced. In combo acquisitions, the three concepts of 1) variable acquisition parameters, 2) k-space data sharing, and 3) multicontrast imaging are systematically integrated to reduce MRI scan time and improve data utilization in a clinical setting. In this study, two-contrast and three-contrast spin-echo (SE) and turbo spin-echo (TSE) combo acquisition protocols that were designed and optimized in simulation experiments were implemented on a 1.5 T clinical scanner. Phantom and human brain data from volunteers and patients were acquired. Scan time reductions of 25-52% were achieved compared to standard acquisitions, largely confirming the simulation results. We evaluated the resulting images by quantitatively analyzing the preservation of contrast and the signal-to-noise ratio (SNR). In addition, data sets for 10 clinical cases obtained with TSE combo and corresponding standard acquisitions were graded by two experienced neuroradiologists in terms of the level of artifacts and image quality for comparison. Only minor image degradation with the combo scans was observed, indicating an inherent trade-off between scan time reduction and image quality. The specific aspects of combo acquisitions with respect to motion, flow, and k-space data weighting are discussed.
Magnetic Resonance in Medicine 06/2006; 55(5):1093-105. · 2.96 Impact Factor
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ABSTRACT: For three-dimensional (3D) imaging with magnetic resonance angiography (MRA) of the cerebral and cervical circulation, both a high temporal and a high spatial resolution with isovolumetric datasets are of interest. In an initial evaluation, we analyzed the potential of contrast-enhanced (CE) time-resolved 3D-MRA as an adjunct for neurovascular MR imaging.
In ten patients with various cerebrovascular disorders and vascularized tumors in the cervical circulation, high-speed MR acquisition using parallel imaging with the GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) algorithm on a 1.5-T system with a temporal resolution of 1.5 s per dataset and a nearly isovolumetric spatial resolution was applied. The results were assessed and compared with those from conventional MRA and digital subtraction angiography (DSA).
CE time-resolved 3D-MRA enabled the visualization and characterization of high-flow arteriovenous shunts in cases of vascular malformations or hypervascularized tumors. In steno-occlusive disease, the method provided valuable additional information about altered vessel perfusion compared to standard MRA techniques such as time-of-flight (TOF) MRA. The use of a nearly isovolumetric voxel size allowed a free-form interrogation of 3D datasets. Its comparatively low spatial resolution was found to be the major limitation.
In this preliminary analysis, CE time-resolved 3D-MRA was revealed to be a promising complementary MRA sequence that enabled the visualization of contrast flow dynamics in various types of neurovascular disorders and vascularized cervical tumors.
Neuroradiology 06/2006; 48(5):291-9. · 2.82 Impact Factor
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ABSTRACT: OBJECTIVE: MDCT angiography allows fast imaging of the cerebral vessels, and its potential as a noninvasive technique to detect vascular abnormalities on the basis of morphologic changes is well established. We analyzed vascular enhancement patterns of cerebral venous structures on MDCT angiography, which enabled us to diagnose dural arteriovenous fistula. CONCLUSION: MDCT angiography performed during an early arterial phase showed asymmetrically higher contrast intensity in the transverse or sigmoid sinus, or both, in five patients. In all patients, digital subtraction angiography confirmed the presence of a dural arteriovenous fistula on the side on which the higher contrast intensity appeared. Radiologists should actively look for this sign in the imaging workup of patients presenting with nonspecific symptoms that might be related to a dural arteriovenous fistula.
American Journal of Roentgenology 05/2005; 184(4):1313-6. · 2.78 Impact Factor
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ABSTRACT: To assess and describe post-traumatic articular cartilage injuries isolated to the trochlear groove and provide insight into potential mechanism of injury.
We retrospectively evaluated MR imaging findings of all knee MRIs performed at our institution over the last 2 years (2450). Thirty patients met the criteria of a cartilage injury confined to the trochlear groove. In 15 cases, which were included in our study, arthroscopic correlation was available. Each plane was evaluated and graded for the presence and appearance of articular cartilage defects using a standard arthroscopic grading scheme adapted to MR imaging. Any additional pathological derangement was documented and information about the mechanism of injury was retrieved by chart review.
In all cases the cartilaginous injury was well demonstrated on MRI. In 13 patients additional pathological findings could be observed. The most frequently associated injury was a meniscal tear in nine patients. In eight cases, the arthroscopic grading of the trochlear injury matched exactly with the MRI findings. In the remaining seven cases, the discrepancy between MRI and arthroscopy was never higher than one grade. In 13 out of 15 of patients trauma mechanism could be evaluated. Twelve patients suffered an indirect twisting injury and one suffered a direct trauma to their knee.
The findings of this study demonstrate that MR imaging allows reliable grading of isolated injury to the trochlear groove cartilage and assists in directing surgical diagnosis and treatment. These injuries may be the only hyaline cartilage injury in the knee and meniscal tears are a frequently associated finding. Therefore, it is important to search specifically for cartilage injuries of the trochlear groove in patients with anterior knee pain, even if other coexistent pathology could potentially explain the patient's symptoms.
European Journal of Radiology 02/2005; 53(1):90-5. · 2.61 Impact Factor
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ABSTRACT: To report stent implantation for a malignant obstruction within the pulmonary artery (PA) caused by a recurrent leiomyosarcoma in the pulmonary trunk.
A 62-year-old man with a non-metastatic primary leiomyosarcoma of the right PA underwent pneumectomy of the right lung and postoperative radiotherapy in 1994. Six years later, he presented with symptoms of progressive right ventricular dysfunction. Computed tomography (CT) identified a high-grade stenosis of the left PA due to recurrent tumor within the pulmonary trunk extending into the left PA. Transthoracic ultrasound documented severe pulmonary hypertension with a high pressure gradient across the stenosis. A stent was deployed percutaneously, successfully establishing PA patency. Pressure measurements showed a significantly reduced gradient across the stented area. In follow-up, the patient reported subjective improvement of symptoms; CT scans revealed a fully patent stent. His status remained stable 11 months after stent implantation.
PA leiomyosarcoma is a rare and highly malignant tumor. In most cases, surgery can only prolong survival for the short term. Palliative interventional PA stenting performed under local anesthesia can offer improvement in quality of life by reducing excessive pulmonary hypertension.
Journal of Endovascular Therapy 03/2003; 10(1):141-6. · 2.86 Impact Factor
