<b><i>Objective:</i></b> To evaluate gestational age-dependent changes in the T2 relaxation time in normal murine placentas in vivo. The role of susceptibility-weighted imaging (SWI) in visualization of the murine fetal anatomy was also elucidated. <b><i>Methods:</i></b> Timed-pregnant CD-1 mice at gestational day (GD) 12 and GD17 underwent magnetic resonance imaging. Multi-echo spin echo and SWI data were acquired. The placental T2 values on GD12 and GD17 were quantified. To account for the influence of systemic maternal physiological factors on placental perfusion, maternal muscle was used as a reference for T2 normalization. A linear mixed-effects model was used to fit the normalized T2 values, and the significance of the coefficients was tested. Fetal SWI images were processed and reviewed for venous vasculature and skeletal structures. <b><i>Results:</i></b> The average placental T2 value decreased significantly on GD17 (40.17 ± 4.10 ms) compared to the value on GD12 (55.78 ± 8.13 ms). The difference in normalized T2 values also remained significant (p = 0.001). Using SWI, major fetal venous structures like the cardinal vein, the subcardinal vein, and the portal vein were visualized on GD12. In addition, fetal skeletal structures could also be discerned on GD17. <b><i>Conclusion:</i></b> The T2 value of a normal murine placenta decreases with advancing gestation. SWI provided clear visualization of the fetal venous vasculature and bony structures.
Chronic cerebrospinal venous insufficiency (CCSVI) is a vascular phenomenon recently described in multiple sclerosis (MS) that is characterized by stenoses affecting the main extracranial venous outflow pathways and by a high rate of cerebral venous reflux that may lead to increased iron deposition in the brain. Aim of this study was to investigate the relationship between CCSVI and iron deposition in the brain of MS patients by correlating venous hemodynamic (VH) parameters and iron concentration in deep-gray matter structures and lesions, as measured by susceptibility-weighted imaging (SWI), and to preliminarily define the relationship between iron measures and clinical and other magnetic resonance imaging (MRI) outcomes.Sixteen (16) consecutive relapsing-remitting MS patients and 8 age- and sex-matched healthy controls (HC) were scanned on a GE 3T scanner, using SWI.All 16 MS patients fulfilled the diagnosis of CCSVI (median VH=4), compared to none of the HC. In MS patients, the higher iron concentration in the pulvinar nucleus of the thalamus, thalamus, globus pallidus, and hippocampus was related to a higher number of VH criteria (P<0.05). There was also a significant association between a higher number of VH criteria and higher iron concentration of overlapping T2 (r=-0.64, P=0.007) and T1 (r=-0.56, P=0.023) phase lesions. Iron concentration measures were related to longer disease duration and increased disability as measured by EDSS and MSFC, and to increased MRI lesion burden and decreased brain volume.The findings from this pilot study suggest that CCSVI may be an important mechanism related to iron deposition in the brain parenchyma of MS patients. In turn, iron deposition, as measured by SWI, is a modest-to-strong predictor of disability progression, lesion volume accumulation and atrophy development in patients with MS.
BACKGROUND AND PURPOSE:To investigate the feasibility of direct magnetic resonance portal vein thrombosis (PVT) visualization with T2*-weighted imaging (T2*WI) without contrast agent.METHODS: Thirty patients with PVT were included in this study.All of them were imaged with contrast-enhanced CT (CE-CT) as well as non-contrast MRI T1, T2 and T2*WI.Imaging data was independently analyzed by two experienced radiologists.T2*WI of all PVT was compared slice-by-slice with each of the comparison sequences (T1WI, T2WI and CE-CT) on the following categories: the location, size, boundary, and conspicuity of thrombus and portal veins. RESULTS:The average score of PVT visualization in T2*WI was higher than T1WI and T2WI in location, size, boundary and conspicuity (t = 7.54 -84.16,P<0.05), and higher than CE-CT in boundary and conspicuity (t = 3.03-6.98,P<0.05).For portal vein visualization, there was no significant score difference in left, middle and right portal veins between CE-CT and T2*WI (t = -1.76-1.35,P>0.05).CONCLUSIONS: Our results suggest T2*WI can characterize PVT accurately with high quality without the use of intravenous contrast agents.
A new technique for detecting vascular malformations, high-resolution BOLD venography (HRBV), is described. This technique relies on the BOLD principle for detecting deoxygenated blood in low-flow malformations. HRBV images are acquired using a modified 3D gradient-echo with voxel volumes of 0.5 x 0.5 x 2 mm3. The magnitude data are masked with the phase images to enhance visibility of the venous structures and are displayed using the minimum intensity projection. Preliminary results for 10 patients show that HRBV is more sensitive in detecting cavernomas than is T2-weighted imaging, and lesions that are presumed to be telangiectasias are detected only with this technique.
Background: Impaired cerebral waste clearance (CWC) has been associated with a broad range of both physiological and pathophysiological neurologic conditions.1,2 Because of the unique anatomy of the brain parenchyma, theoretically, in the brain parenchyma, biochemically inert waste such as magnetic resonance imaging (MRI) contrast agents can only be removed through two possible pathways: cerebrospinal fluid (CSF) pathway, and/or vascular pathway. Despite the controversy, there seems to be a solid consensus on the participation of the CSF pathway in CWC.3 In contrast to the CSF system, the current consensus is that the parenchymal vascular system does not participate in CWC. Considering there is a big difference in flow rate between the blood (2 mL/min) and the CSF (3.7 µL/min) and the brain is the most bioactive, energy-consuming organ (20% nutrition for about 5% of body weight) in the body, it is illogical that the brain would rely on the slow CSF circulation for CWC while less bioactive tissues outside the brain require both the fast vascular and slow lymphatic systems to remove waste in a timely manner.4,5
Methods: Superparamagnetic iron oxide–enhanced susceptibility-weighted imaging (SPIO-SWI) and quantitative susceptibility mapping (QSM) methods were used to simultaneously study 7 T MRI signal changes in parenchymal veins, arteries, and their corresponding para-vascular spaces in 26 rats, following intra-cisterna magna (ICM) infusion of different CSF tracers (FeREX, ferumoxytol, Fe-Dextran) to determine the amount of tracer in the artery and vein quantitatively.
Results: The parenchymal venous system participated in CSF tracer clearance following ICM infusion of different MRI tracers with different concentrations of iron. Parenchymal venous participation was more obvious when 75 μg iron was injected. In the parenchymal veins, the relative mean (±SE) value of the susceptibility increased by 13.5±1.0% at 15 min post-tracer infusion (p<0.01), and 33.6±6.7% at 45 min post-tracer infusion (p=0.01), compared to baseline. In contrast to the parenchymal veins, a negligible amount of CSF tracer entered the parenchymal arteries: 1.3±2.6% at 15 min post-tracer infusion (p=0.6), and 12±19% at 45 min post-tracer infusion (p=0.5), compared to baseline.
Conclusions: MRI tracers can enter the parenchymal vascular system and more MRI tracers were observed in the cerebral venous than arterial vessels, suggesting the direct participation of parenchymal vascular system in CWC.
Methods and materials Carotid arteries of 12 consecutive subjects were imaged with non-contrast multi-detector computed tomography (MDCT) and high resolution 3D susceptibility weighted imaging (SWI) at 3.0 T (MAGNETOM Trio, A Tim System, Siemens AG). Imaging parameters for SWI were optimized to: TE = 15.6 ms; TR = 38 ms (with fat saturation); FA = 10°; BW = 80 Hz/pixel; resolution = 0.5 mm × 0.5 mm × 2.0 mm; coverage: 40 mm, covering the carotid bifurcation. The Head-neck matrix coil was used. MR and CT images were analyzed by two experienced radiologists for the identification of the vessel wall calcification and the measurement of the calcified area, which was determined as high attenuation on CT and high signal intensity on the SWI phase images. SPIN software (Detroit, MI) was used for Phase image review and measurement of the MRI data. Sensitivity and specificity were calculated using CT as the reference standard. Pearson correlation coefficient was determined for the calcified area measurements of the CT and MR images Figure 1.
Describes efficient and robust deformable model based techniques for segmentation of ventricular boundaries in cardiac MR images. Starting with a user specified approximate boundary or an interior point of the left ventricle for one ED slice, the authors' algorithms generate contours for inner and outer walls, and automatically propagate them to other slices in the ED phase (spatial propagation) and to slices in all the phases (temporal propagation) of the cardiac study. The algorithms are based on steepest descent as well as dynamic programming strategies integrated via multiscale analysis. The ventricular boundaries are used to construct a 3-D model for visualization and to compute volume based diagnostic quantities. The algorithms have been incorporated into a user interface which can load, sort, visualize, and analyze a cardiac study an less than 10 minutes. The system has been tested on a dozen volunteers and patients (1000+ images) with excellent results.< >
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