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Background: Standard bolus chase MR angiography (MRA) is increasingly replacing digital subtraction angiography (DSA) in the diagnostic evaluation of peripheral vascular disease. However, a major limitation of bolus chase MRA is the relatively poor visibility of the calf arteries. Purpose: To evaluate the feasibility of visualizing the calf arteries and the visibility quality of an 8-channel cardiac phased array coil using time-resolved imaging of contrast kinetics (TRICKS) MRA compared with standard bolus chase MRA on a 1.5 Tesla MRI scanner. Material and Methods: MRA findings of 59 sequential patients (mean age 57.8 years, range 14-83 years; 41 men) were retrospectively evaluated. All examinations included preliminary TRICKS for the lower leg using a surface 8-channel cardiac coil, followed by a 3-step MRA of the abdominal aorta, thigh, and lower leg using a body coil. Images yielded by both methods were separately evaluated by consensus of two radiologists unaware of the patients' clinical data. Visibility of the calf arteries (popliteal, tibialis anterior, tibialis posterior, tibioperoneal trunk, and peroneal) for both sides was subjectively classified as 'diagnostic' or 'nondiagnostic'. Descriptive statistics for image diagnostic quality were assessed. Results: A total of 575 calf arterial segments were evaluated. Visibility of all calf arteries was significantly better with TRICKS than with the standard bolus chase MRA (P, 0.001). The improvement of calf artery visibility with TRICKS was more pronounced in patients with peripheral vascular disease compared to those with arteritis, vascular malformation and popliteal entrapment syndrome. Conclusion: Using a cardiac coil for MRA of the lower extremities resulted in visibility comparable to that of a dedicated leg coil, with diagnostic superiority for the TRICKS method compared to the standard bolus chase method. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance (MR)-guided vascular interventions are of increasing interest, and, with the use of contrast-enhanced techniques, intraarterial contrast-enhanced MR angiography (ia-ce-MRA) competes with intraarterial digital subtraction angiography (ia-DSA) for the diagnostic evaluation of the infrainguinal vessel tree. Purpose: To assess the diagnostic value of ia-ce-MRA and high-resolution T1-weighted (hr-T1w) imaging compared to the gold-standard ia-DSA for residual stenosis and local dissections after femoropopliteal recanalization in patients with peripheral arterial occlusive disease (PAOD). Material and Methods: Eight patients with PAOD and short vessel occlusion of their femoropopliteal arteries underwent recanalization and balloon positioning under DSA. Patients were transferred to a short-bore MR scanner. Percutaneous transluminal angioplasty (PTA) was accomplished under MR fluoroscopy. Pre- and postinterventional ia-ce three-dimensional (3D) gradient-echo MRA with gadopentate dimeglumine was performed using the intraarterial introducer sheath. Maximum intensity projections (MIP) and multiplanar reconstructions (MPR) were calculated from the data set. High-resolution T1w images of the angioplasty region before and after dilatation were acquired. Control ia-DSA images were obtained. Results: The postinterventional angioplasty results for stenosis grading were comparable in ia-MRA and ia-DSA. Only two of five local dissections in ia-DSA were visualized with the ia-ce-MRA runs including MIPs and MPRs. To clearly depict dissection, hr-T1w images were needed. Conclusion: Grading of stenotic lesions with ia-ce-MRA after PTA is comparable to ia-DSA. Intraarterial ce-MRA with calculated MIPs and MPRs is only partially sufficient to visualize local dissections after PTA. High-resolution T1w images are required for precise diagnosis of dissections in magnetic resonance tomography. [ABSTRACT FROM AUTHOR]

Background: Regions prone to atherosclerosis, such as bends and bifurcations, tend to exhibit a certain degree of non-planarity or curvature, and these geometric features are known to strongly influence local flow patterns. Recently, computational fluid dynamics (CFD) has been used as a means of enhancing understanding of the mechanisms involved in atherosclerotic plaque formation and development. Purpose: To analyze flow patterns and hemodynamic distribution in stenotic carotid bifurcation in vivo by combining CFD with magnetic resonance angiography (MRA). Material and Methods: Twenty-one patients with carotid atherosclerosis proved by digital subtraction angiography (DSA) and/or Doppler ultrasound underwent contrast-enhanced MR angiography of the carotid bifurcation by a 3.0T MR scanner. Hemodynamic variables and flow patterns of the carotid bifurcation were calculated and visualized by combining vascular imaging postprocessing with CFD. Results: In mild stenotic cases, there was much more streamlined flow in the bulbs, with reduced or disappeared areas of weakly turbulent flow. Also, the corresponding areas of low wall shear stress (WSS) were reduced or even disappeared. As the extent of stenosis increased, stronger blood jets formed at the portion of narrowing, and more prominent eddy flows and slow back flows were noted in the lee of the stenosis. Regions of elevated WSS were predicted at the portion of stenosis and in the path of the downstream jet. Areas of low WSS were predicted on the leeward side of the stenosis, corresponding with the location of slowly turbulent flows. Conclusion: CFD combined with MRA can simulate flow patterns and calculate hemodynamic variables in stenotic carotid bifurcations as well as normal ones. It provides a new method to investigate the relationship of vascular geometry and flow condition with atherosclerotic pathological changes. [ABSTRACT FROM AUTHOR]

Background: Contrast-enhanced magnetic resonance angiography (CE-MRA) is less prone to flow-related signal intensity loss than three-dimensional time-of-flight (3D TOF) MRA and may therefore be more sensitive for detection of residual patency in platinum coil-treated intracranial aneurysms. Purpose: To compare MRA and CE-MRA in the follow-up of intracranial aneurysms treated with platinum coils. Material and Methods: CE-MRA and 3D TOF MRA (pre- and postcontrast injection) of the intracranial vasculature was performed at 1.5T in 38 patients (47 aneurysms) referred for DSA in the follow-up of coiled intracranial aneurysms. Results: DSA showed aneurysm patency in 22/47 investigations. Patent aneurysm components were observed with CE-MRA in 18/22 cases, and with 3D TOF MRA in 21/22 cases. There was no significant difference in patent aneurysm component size between CE-MRA and 3D TOF MRA. In addition, CE-MRA showed six, 3D TOF MRA before contrast injection showed seven, and 3D TOF MRA after contrast injection showed eight cases with patent aneurysm components not observed on DSA. Conclusion: 3D TOF MRA was highly sensitive for detection of patent aneurysm components, and at least as sensitive as CE-MRA. Residual aneurysm patency seems to be better visualized with MRA than with DSA in some cases. [ABSTRACT FROM AUTHOR]

Background: Whole-body magnetic resonance angiography (WBMRA) permits noninvasive vascular assessment, which can be utilized in epidemiological studies. Purpose: To assess the relation between a low ankle brachial index (ABI) and high-grade stenoses in the pelvic and leg arteries in the elderly. Material and Methods: WBMRA was performed in a population sample of 306 subjects aged 70 years. The arteries below the aortic bifurcation were graded after the most severe stenosis according to one of three grades: 0-49% stenosis, 50-99% stenosis, or occlusion. ABI was calculated for each side. Results: There were assessable WBMRA and ABI examinations in 268 (right side), 265 (left side), and 258 cases (both sides). At least one ≥50% stenosis was found in 19% (right side), 23% (left side), and 28% (on at least one side) of the cases. The corresponding prevalences for ABI <0.9 were 4.5%, 4.2%, and 6.6%. An ABI cut-off value of 0.9 resulted in a sensitivity, specificity, and positive and negative predictive value of 20%, 99%, 83%, and 84% on the right side, and 15%, 99%, 82%, and 80% on the left side, respectively, for the presence of a ≥50% stenosis in the pelvic or leg arteries. Conclusion: An ABI <0.9 underestimates the prevalence of peripheral arterial occlusive disease in the general elderly population. [ABSTRACT FROM AUTHOR]

Background: A longstanding hypothesis that correlates fluid dynamic forces and atherosclerotic disease has led to numerous analytical, numerical, and experimental studies over the years because it is very difficult to measure the hemodynamic variables of blood in vivo. Purpose: To investigate the technique of visualization and quantitation of hemodynamic variables at carotid artery bifurcation in vivo by combining computational fluid dynamics (CFD) and vascular imaging. Material and Methods: Twenty-six healthy volunteers underwent magnetic resonance (MR) angiography of the bilateral carotid artery by a 3.0T whole-body scanner. Hemodynamic variables at these carotid bifurcations were calculated and visualized by combining vascular imaging post-processing and CFD. Results: The average velocity of the carotid bifurcation in the systolic phase and the diastolic phase was 0.46±0.24 m/s and 0.23±0.05 m/s, respectively. Eddy current and back flows were observed at bifurcation and the lateral part of the proximal internal carotid arteries (ICA) and external carotid arteries (ECA), and the shapes of them changed with phases of the cardiac cycle, which were significant at the middle of the systolic phase and faded out quickly downstream of the ICA and ECA. The average range of wall shear stress (WSS) at the bifurcation was 4.36±1.32 Pa, and the maximum WSS was 18.02±4.11 Pa. The WSS map revealed a large region of low WSS at the carotid bulb and extended to the outer wall in the proximal end of the ICA (the lowest value was below 0.5 Pa), and there was also a small region of low WSS at the outer wall in the proximal end of the ECA. Conclusion: CFD combined with vascular imaging can calculate and visualize hemodynamic variables at carotid bifurcation in vivo individually. [ABSTRACT FROM AUTHOR]

Background: The characterization of brain arteriovenous malformation (AVM) angioarchitecture remains rewarding in planning and predicting therapy. The increased signal-to-noise ratio at higher field strength has been found advantageous in vascular brain pathologies. Purpose: To evaluate whether 3.0T time-of-flight (TOF) magnetic resonance angiography (MRA) is superior to 1.5T TOF-MRA for the characterization of cerebral AVMs. Material and Methods: Fifteen patients with AVM underwent TOF-MRA at 3.0T and 1.5T and catheter angiography (DSA), which was used as the gold standard. Blinded readers scored image quality on a four-point scale, nidus size, and number of feeding arteries and draining veins. Results: Image quality of TOF-MRA at 3.0T was superior to 1.5T but still inferior to DSA. Evaluation of nidus size was equally good at 3.0T and 1.5T for all AVMs. In small AVMs, however, there was a tendency of size overestimation at 3.0T. MRA at 3.0T had increased detection rates for feeding arteries (+21%) and superficial (+13%) and deep draining veins (+33%) over 1.5T MRA. Conclusion: 3.0T TOF-MRA offers superior characterization of AVM angioarchitecture compared with 1.5T TOF-MRA. The image quality of MRA at both 3.0 and 1.5T is still far from equal to DSA, which remains the gold standard for characterization of AVM. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance (MR) permits quantitative flow velocity measurements that could be used to detect changes in the curve profile downstream of a high-grade stenosis. Purpose: To assess whether MR flow measurements can be used to detect iliac artery stenoses. Material and Methods: Contrast-enhanced magnetic resonance angiography (MRA) and quantitative flow measurements in the lower aorta and proximal femoral arteries were performed in 29 patients with suspected iliac artery stenoses. Stenoses were graded into five degrees: 0%, 1-49%, 50-74%, 75-99%, and 100% diameter reduction. The femoral artery waveforms were evaluated qualitatively by two independent reviewers regarding peak systolic velocity (PSV), aortofemoral difference in time-to-peak (ΔTTP), systolic acceleration (SA), curve-shape index (CSI), and the presence of an early diastolic flow reversal. The correlation between these parameters and the degree of stenosis was assessed. Results: A significant correlation with degree of stenosis was observed for the qualitative flow waveform evaluations, with a high degree of interobserver agreement (κ = 0.84). A significant correlation was also found between degree of stenosis and PSV, ΔTTP, SA, CSI, and presence of diastolic flow reversal. The flow velocity pattern, however, remained unchanged, both qualitatively and quantitatively, up to a stenosis degree of at least 75%. Conclusion: Iliac artery stenoses cause femoral artery flow waveform changes that can be detected with MRI, but only at high-grade levels. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the hepatosplenic manifestations and the portal venous system in patients with chronic infection by Schistosoma mansoni. Material and Methods: A cross-sectional observational study was performed in 28 patients with chronic hepatosplenic schistosomiasis submitted to magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the abdomen. Images were interpreted independently by two radiologists to determine the reproducibility of image interpretation and who evaluated the presence of morphological alterations in the liver and spleen, such as hepatosplenomegaly, hepatic fissure widening, periportal fibrosis, and the presence of siderotic nodules. Interobserver and intra-observer agreement were measured with the kappa and intraclass correlation tests. Evaluation of venous collateral pathways and portal and splenic veins was done in consensus by both examiners. Results: Observers identified enlargement of the left lobe (78.5-92.8%) and caudate-to-right-lobe ratio (78.5-92.8%), irregularity of hepatic contours (89.2-96.4%), fissure widening (89.2-100%), and splenic siderotic nodules (84.2%). Splenomegaly, heterogeneity of hepatic parenchyma, peripheral hepatic vessels, and periportal fibrosis were observed in 100% of patients. MRI findings presented almost perfect interobserver (κ = 0.65-1) and intra-observer (κ = 0.73-1 for observer 1, and κ = 0.65-1 for observer 2) agreement for the variables analyzed. MRA showed the presence of collateral pathways in the majority of patients (71.4%) along with widening of portal and splenic veins. Conclusion: Using MRI, hepatosplenic alterations in schistosomiasis are characterized by heterogeneity of hepatic parenchyma, presence of peripheral perihepatic vessels, periportal fibrosis, splenomegaly, siderotic nodules, and the presence of venous collateral pathways. [ABSTRACT FROM AUTHOR]

Purpose: To assess prospectively the agreement of magnetic resonance (MR) pulmonary perfusion with single‐photon emission computed tomography (SPECT) perfusion for perfusion defects down to the subsegmental level in patients with suspected pulmonary embolism (PE).Material and Methods: In 41 patients with suspected PE, contrast‐enhanced MR pulmonary perfusion (3D‐FLASH, TR/TE 1.6/0.6 ms) was compared to SPECT perfusion on a per‐examination basis as well as at the lobar, segmental, and subsegmental level.Results: The MRI protocol was completed in all patients, and mean examination time was 3 min 56 s. MR perfusion showed a very high agreement with SPECT (kappa value per examination 0.98, and 0.98, 0.83, and 0.69 for lobar, segmental, and subsegmental perfusion defects, respectively). Of 15 patients with PE, MR perfusion detected 14 cases.Conclusion: The very high agreement of MR perfusion with SPECT perfusion enables the detection of subtle findings in suspected PE. [ABSTRACT FROM AUTHOR]

Purpose: 1) To compare measurements obtained with MR imaging (MRI)/contrast-enhanced MR angiography (CE MRA) with measurements obtained with angiography (DSA) and CT, for stent-graft sizing of abdominal aortic aneurysms (AAA). 2) To compare MRA measurements obtained with the two post processing techniques MIP (maximum intensity projection) and VRT (3D volume rendering technique).Material and Methods: The prospective study included 20 consecutive patients with AAA identified by DSA and CT as suitable for endovascular repair. For the study, MRI/CE MRA was performed. Five measurement variables for stent-graft sizing were chosen. Comparisons were made between MRI/CE MRA, DSA and CT, and between observers. Comparisons were also made between MIP and VRT.Results: Significantly shorter lengths were obtained with MRA-MIP than with DSA. Three out of six diameter measurements were significantly smaller on MRI/CE MRA than on DSA and CT. No significant differences were found between the observers. One diameter measurement was significantly smaller on MIP than on VRT, while the other measurements showed no significant differences.Conclusion: The length measurements obtained with MRA-MIP were probably more correct than those with DSA. For more reliable diameter measurements with CE MRA, improvements of the technique, including VRT reconstructions and a standardized determination of the vessel boundaries, are needed. [ABSTRACT FROM AUTHOR]

AbstractObjective: To establish in which clinical contexts cerebral MR angiography (MRA) is routinely carried out in a neurological university department and to describe its clinical impact. Material and Methods: Medical records, reports of findings and documentation of imaging examinations carried out in all 69 patients referred to the Department of Radiology from the Department of Neurology between 1995 and 1998 for cerebral MRA were evaluated. The clinical impact of all imaging findings was assessed on the basis of the medical records. Results: Circulatory disturbances in the vertebrobasilar arteries (n=34) were the most frequent indication for investigation. MRA followed CT or duplex sonography in 66 of the 69 patients with a mean delay of 8 days. MRA was considered diagnostically inferior to conventional MR in 11 cases, comparable in 30 and superior in 25. Comparing MRA and duplex sonography, the corresponding figures were 12, 29 and 23. In retrospect, 56 MRAs were judged unnecessary. Conclusion: Controlled clinical studies on optimal use of MRA are needed to avoid wasting resources and to exploit the method's full diagnostic potential in appropriate cases. [ABSTRACT FROM AUTHOR]

Peripheral neuropathy due to vasculitis without any complications of vasculitis in other organs was first reported in 1987. This condition was termed non-systemic vasculitic neuropathy (NSVN). Although vasculitis is believed to develop in small arteries and arterioles in this disease, the level of vascular involvement has not been fully established. We present a case of NSVN followed up by MR angiography, which was thought to be useful to assess the level as well as the state of vascular lesions in this condition. [ABSTRACT FROM AUTHOR]