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MRI Data (mri + data)
Selected AbstractsThe Statistical Analysis of Functional MRI Data by LAZAR, N. A.BIOMETRICS, Issue 1 2009Wesley K. Thompson No abstract is available for this article. [source] MRI tumor characterization using Gd-GlyMe-DOTA-perfluorooctyl-mannose-conjugate (Gadofluorine MÔ), a protein-avid contrast agentCONTRAST MEDIA & MOLECULAR IMAGING, Issue 3 2006Hans-Jürgen Raatschen Abstract The rationale and objectives were to define the MRI tumor-characterizing potential of a new protein-avid contrast agent, Gd-GlyMe-DOTA-perfluorooctyl-mannose-conjugate (Gadofluorine MÔ; Schering AG, Berlin, Germany) in a chemically induced tumor model of varying malignancy. Because of the tendency for this agent to form large micelles in water and to bind strongly to hydrophobic sites on proteins, it was hypothesized that patterns of dynamic tumor enhancement could be used to differentiate benign from malignant lesions, to grade the severity of malignancies and to define areas of tumor necrosis. Gadofluorine M, 0.05,mmol,Gd,kg,1, was administered intravenously to 28 anesthetized rats that had developed over 10 months mammary tumors of varying degrees of malignancy as a consequence of intraperitoneal administration of N -ethyl- N -nitrosourea (ENU), 45,250,mg,kg,1. These tumors ranged histologically from benign fibroadenomas to highly undifferentiated adenocarcinomas. Dynamic enhancement data were analyzed kinetically using a two-compartment tumor model to generate estimates of fractional plasma volume (fPV), apparent fractional extracellular volume (fEV*) and an endothelial transfer coefficient (KPS) for this contrast agent. Tumors were examined microscopically for tumor type, degree of malignancy (Scarff,Bloom,Richardson score) and location of necrosis. Eighteen tumor-bearing rats were successfully imaged. MRI data showed an immediate strong and gradually increasing tumor enhancement. KPS and fEV*, but not fPV obtained from tumors correlated significantly (p,<,0.05) with the SBR tumor grade, r,=,0.65 and 0.56, respectively. Estimates for KPS and fEV* but not fPV were significantly lower in a group consisting of benign and low-grade malignant tumors compared with the group of less-differentiated high-grade tumors (1.61,±,0.64 vs 3.37,±,1.49, p,<,0.01; 0.45,±,0.17 vs 0.78,±,0.24, p,<,0.01; and 0.076,±,0.048 vs 0.121,±,0.088, p,=,0.24, respectively). It is concluded that the protein-avid MRI contrast agent Gadofluorine M enhances tumors of varying malignancy depending on the tumor grade, higher contrast agent accumulation for more malignant lesions. The results show potential utility for differentiating benign and low-grade malignant lesions from high-grade cancers. Copyright © 2006 John Wiley & Sons, Ltd. [source] Increased QT variability in young asymptomatic patients with ,-thalassemia majorEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2007Damiano Magrě Abstract Background:, Despite recent progress in iron chelation therapy, sudden cardiac death due to malignant ventricular arrhythmias remains a vexing, clinical problem in patients with ,-thalassemia major (TM). In this study we assessed whether the major indices of QT variability, emerging tools for risk stratification of sudden cardiac death, differ in young asymptomatic patients with TM and healthy persons. Methods: Thirty patients with TM and 30 healthy control subjects underwent a 5-min electrocardiography recording to calculate the following variables: QT variance (QTv), QTv normalized for mean QT (QTVN) and QT variability index (QTVI). All subjects also underwent a two-dimensional and Doppler echocardiography study and magnetic resonance imaging (MRI) to determine cardiac and hepatic T2* values. Results: No differences were observed in clinical and conventional echo-Doppler findings in healthy control subjects and patients with TM whereas QTv, QTVN and QTVI values were significantly higher in patients than those in controls (QTv, P < 0.001; QTVN, P < 0.05 and QTVI, P < 0.001) and cardiac T2* and hepatic MRI T2* values were significantly lower in patients with TM (P < 0.001). The indices of temporal QT variability correlated significantly with MRI data. Conclusions: Young asymptomatic patients with TM have increased cardiac repolarization variability as assessed by QT variability indices, probably due to cardiac iron deposition. These easily assessed, non-invasive markers could be used to identify increased myocardial repolarization lability early in asymptomatic patients with TM. [source] Segmentation of human skull in MRI using statistical shape information from CT dataJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2009Defeng Wang PhD Abstract Purpose To automatically segment the skull from the MRI data using a model-based three-dimensional segmentation scheme. Materials and Methods This study exploited the statistical anatomy extracted from the CT data of a group of subjects by means of constructing an active shape model of the skull surfaces. To construct a reliable shape model, a novel approach was proposed to optimize the automatic landmarking on the coupled surfaces (i.e., the skull vault) by minimizing the description length that incorporated local thickness information. This model was then used to locate the skull shape in MRI of a different group of patients. Results Compared with performing landmarking separately on the coupled surfaces, the proposed landmarking method constructed models that had better generalization ability and specificity. The segmentation accuracies were measured by the Dice coefficient and the set difference, and compared with the method based on mathematical morphology operations. Conclusion The proposed approach using the active shape model based on the statistical skull anatomy presented in the head CT data contributes to more reliable segmentation of the skull from MRI data. J. Magn. Reson. Imaging 2009;30:490,498. © 2009 Wiley-Liss, Inc. [source] Optimum fuzzy filters for phase-contrast magnetic resonance imaging segmentationJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2009Kartik S. Sundareswaran MS Abstract Purpose To develop and validate a multidimensional segmentation and filtering methodology for accurate blood flow velocity field reconstruction from phase-contrast magnetic resonance imaging (PC MRI). Materials and Methods The proposed technique consists of two steps: (1) the boundary of the vessel is automatically segmented using the active contour approach; and (2) the noise embedded within the segmented vector field is selectively removed using a novel fuzzy adaptive vector median filtering (FAVMF) technique. This two-step segmentation process was tested and validated on 111 synthetically generated PC MRI slices and on 10 patients with congenital heart disease. Results The active contour technique was effective for segmenting blood vessels having a sensitivity and specificity of 93.1% and 92.1% using manual segmentation as a reference standard. FAVMF was the superior technique in filtering out noise vectors, when compared with other commonly used filters in PC MRI (P < 0.05). The peak wall shear rate calculated from the PC MRI data (248 ± 39 sec,1), was significantly decreased to (146 ± 26 sec,1) after the filtering process. Conclusion The proposed two-step segmentation and filtering methodology is more accurate compared to a single-step segmentation process for post-processing of PC MRI data. J. Magn. Reson. Imaging 2009;29:155,165. © 2008 Wiley-Liss, Inc. [source] Evaluation of intrarenal oxygenation in mice by BOLD MRI on a 3.0T human whole-body scanner,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2007Lu-Ping Li PhD Abstract Purpose To extend observations on intra-renal oxygenation with blood oxygen level-dependent (BOLD) MRI in human and rats to mouse kidneys imaged with a human whole-body scanner. Materials and Methods Renal BOLD MRI studies were performed on a 3.0T scanner using a multiple gradient-echo (mGRE) sequence with a custom-designed 2.0-cm surface coil to acquire six T2*-weighted images in mice (N = 8) at an in-plane resolution of 156 × 156 ,m2. BOLD MRI data were obtained before and after administration of furosemide (10 mg/kg intravenously [i.v.]). Results The mean weight of eight mice was 24.6 ± 1.0 g. The baseline renal R2* (mean ± standard error [SE]) was 28.6 ± 2.1 seconds,1 in the renal cortex (CO), 35.4 ± 2.2 in the outer medulla (OM), and 21.2 ± 2.1 seconds,1 in the inner medulla (IM). The BOLD response to furosemide (,R2*) was 4.1 ± 1.4 in the CO, 10.1 ± 2.1 seconds,1 in the OM, and 3.4 ± 0.8 seconds,1 in the IM in mice. Conclusion Intrarenal BOLD MR images with sufficiently high resolution can be obtained on a human whole-body scanner when combined with a small receiver coil to allow studies in mice. Both baseline R2* and ,R2* values following administration of furosemide were consistent with previous experience in humans and rats. J. Magn. Reson. Imaging 2007. © 2007 Wiley-Liss, Inc. [source] Reexamining the quantification of perfusion MRI data in the presence of bolus dispersion,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2007Linda Ko BSc Abstract Purpose To determine the true impact of dispersion upon cerebral blood flow (CBF) quantification by removing an algorithm implementation-induced systematic error. Materials and Methods The impact of dispersion on the arterial input function (AIF) between measurement and entry into the tissue of interest on CBF estimates was simulated assuming: 1) contralateral circulation flow that introduces a true arterial tissue delay (ATD)-related dispersive component; and 2) the presence of an arterial stenosis that disperses and shifts the AIF peak entering the tissue; increasing the apparent ATD relative to the original AIF. Results Previously reported CBF estimates for the stenosis dispersion model were found to be a mixture of true dispersive effects and an algorithm implementation-induced systematic error. The true CBFMEASURED/CBFNO-DISPERSION ratios for short mean transit times (MTT) (normal) and long MTT (infarcted) tissue were similar for both dispersion models evaluated; this was an unanticipated result. The CBF quantification inaccuracies induced through the dispersion model truly related to ATD were lower than for the local stenosis-based dispersion for small ATD values. Conclusion Correcting the systematic error present in a previous deconvolution study removes the reported ATD-related impact on CBF quantification. The impact of dispersion was smaller than half that reported in previous simulation studies. J. Magn. Reson. Imaging 2007;25:639,643. © 2007 Wiley-Liss, Inc. [source] MRI measurement of time-resolved wall shear stress vectors in a carotid bifurcation model, and comparison with CFD predictionsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2003Panorea Papathanasopoulou MSc Abstract Purpose To study pulsatile fluid flow in a physiologically realistic model of the human carotid bifurcation, and to derive wall shear stress (WSS) vectors. Materials and Methods WSS vectors were calculated from time-resolved 3D phase-contrast (PC) MRI measurements of the velocity field. The technique was first validated with sinusoidal flow in a straight tube, and then used in a model of a healthy human carotid bifurcation. Velocity measurements in the inflow and outflow regions were also used as boundary conditions for computational fluid dynamics (CFD) calculations of WSS, which were compared with those derived from MRI alone. Results The straight tube measurements gave WSS results that were within 15% of the theoretical value. WSS results for the phantom showed the main features expected from fluid dynamics, notably the low values in the bulb region of the internal carotid artery, with a return to ordered flow further downstream. MRI was not able to detect the high WSS values along the divider wall that were predicted by the CFD model. Otherwise, there was good general agreement between MRI and CFD. Conclusion This is the first report of time-resolved WSS vectors estimated from 3D-MRI data. The technique worked well except in regions of disturbed flow, where the combination with CFD modeling is clearly advantageous. J. Magn. Reson. Imaging 2003;17:153,162. © 2003 Wiley-Liss, Inc. [source] Talairach-Based Parcellation of Neonatal Brain Magnetic Resonance Imaging Data: Validation of a New ApproachJOURNAL OF NEUROIMAGING, Issue 4 2005Haissam Haidar PhD ABSTRACT Background and Purpose. Talairach-based parcellation (TP) of human brain magnetic resonance imaging (MRI) data has been used increasingly in clinical research to make regional measurements of brain structures in vivo. Recently, TP has been applied to pediatric research to elucidate the changes in regional brain volumes related to several neurological disorders. However, all freely available tools have been designed to parcellate adult brain MRI data. Parcellation of neonatal MRI data is very challenging owing to the lack of strong signal contrast, variability in signal intensity within tissues, and the small size and thus difficulty in identifying small structures used as landmarks for TP. Hence the authors designed and validated a new interactive tool to parcellate brain MRI data from newborns and young infants. Methods. The authors' tool was developed as part of a postprocessing pipeline, which includes registration of multichannel MR images, segmentation, and parcellation of the segmented data. The tool employs user-friendly interactive software to visualize and assign the anatomic landmarks required for parcellation, after which the planes and parcels are generated automatically by the algorithm. The authors then performed 3 sets of validation experiments to test the precision and reliability of their tool. Results. Validation experiments of intra-and interrater reliability on data obtained from newborn and 1-year-old children showed a very high sensitivity of >95% and specificity >99.9%. The authors also showed that rotating and reformatting the original MRI data results in a statistically significant difference in parcel volumes, demonstrating the importance of using a tool such as theirs that does not require realignment of the data prior to parcellation. Conclusions. To the authors' knowledge, the presented approach is the first TP method that has been developed and validated specifically for neonatal brain MRI data. Their approach would also be valuable for the analysis of brain MRI data from older children and adults. [source] Effect of aging and degeneration on disc volume and shape: A quantitative study in asymptomatic volunteersJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2006Christian W. A. Pfirrmann Abstract Debate continues on the effect of disc degeneration and aging on disc volume and shape. So far, no quantitative in vivo MRI data is available on the factors influencing disc volume and shape. The objective of this MRI study was to quantitatively investigate changes in disc height, volume, and shape as a result of aging and/or degeneration omitting pathologic (i.e., painful) disc alterations. Seventy asymptomatic volunteers (20,78 years) were investigated with sagittal T1- and T2-weighted MR-images encompassing the whole lumbar spine. Disc height was determined by the Dabbs method and the Farfan index. Disc volume was calculated by the Cavalieri method. For the disc shape the "disc convexity index" was calculated by the ratio of central disc height and mean anterior/posterior disc height. Disc height, disc volume, and the disc convexity index measurements were corrected for disc level and the individuals age, weight, height, and sex in a multilevel regression analysis. Multilevel regression analysis showed that disc volume was negatively influenced by disc degeneration (p,<,0.001) and positively correlated with body height (p,<,0.001) and age (p,<,0.01). Mean disc height and the disc convexity index were negatively influenced by disc degeneration but not by gender, weight, and height. Disc height was positively correlated with age (p,<,0.01). From the results of this study, it can be concluded that disc degeneration generally results in a decrease of disc height and volume as well as a less convex disc shape. In the absence of disc degeneration, however, age tends to result in an inverse relationship on disc height, volume, and shape. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Real-time adaptive sequential design for optimal acquisition of arterial spin labeling MRI dataMAGNETIC RESONANCE IN MEDICINE, Issue 1 2010Jingyi Xie Abstract An optimal sampling schedule strategy based on the Fisher information matrix and the D-optimality criterion has previously been proposed as a formal framework for optimizing inversion time scheduling for multi-inversion-time arterial spin labeling experiments. Optimal sampling schedule possesses the primary advantage of improving parameter estimation precision but requires a priori estimation of plausible parameter distributions that may not be available in all situations. An adaptive sequential design approach addresses this issue by incorporating the optimal sampling schedule strategy into an adaptive process that iteratively updates the parameter estimates and adjusts the optimal sampling schedule accordingly as data are acquired. In this study, the adaptive sequential design method was experimentally implemented with a real-time feedback scheme on a clinical MRI scanner and was tested in six normal volunteers. Adapted schedules were found to accommodate the intrinsically prolonged arterial transit times in the occipital lobe of the brain. Simulation of applying the adaptive sequential design approach on subjects with pathologically reduced perfusion was also implemented. Simulation results show that the adaptive sequential design approach is capable of incorporating pathologic parameter information into an optimal arterial spin labeling scheduling design within a clinically useful experimental time. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] x-f choice: Reconstruction of undersampled dynamic MRI by data-driven alias rejection applied to contrast-enhanced angiographyMAGNETIC RESONANCE IN MEDICINE, Issue 4 2006Shaihan J. Malik Abstract A technique for reconstructing dynamic undersampled MRI data, termed "x-f choice," was developed and applied to dynamic contrast-enhanced MR angiography (DCE-MRA). Regular undersampling in k-t space (a hybrid of k -space and time) creates aliasing in the conjugate x-f space that must be resolved. When regions in the object containing fast dynamic change are sparse, as in DCE-MRA, signal overlap caused by aliasing is often much less than the undersample factor would imply. x-f Choice reconstruction identifies overlapping signals using a model of the full non-aliased x-f space that is automatically generated from the undersampled data, and applies parallel imaging (PI) to separate them. No extra reference scans are required to generate either the model or the coil sensitivity maps. At each location in the reconstructed images, g -factor noise amplification is compared with predicted reconstruction errors to obtain an optimized solution. Acceleration factors greater than the number of receiver coils are possible, but are limited by the sparseness of the dynamic content and the signal-to-noise ratio (SNR) (in DCE-MRA the latter is dominant). Temporal fidelity was validated for up to a factor 10 speed-up using retrospectively undersampled data from a six-coil array. The method was tested on volunteers using fivefold prospective undersampling. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Conventional DTI vs. slow and fast diffusion tensors in cat visual cortexMAGNETIC RESONANCE IN MEDICINE, Issue 5 2003Itamar Ronen Abstract Diffusion tensor imaging (DTI) uses water diffusion anisotropy in axonal fibers to provide a tool for analyzing and tracking those fibers in brain white matter. In the present work, multidirectional diffusion MRI data were collected from a cat brain and decomposed into slow and fast diffusion tensors and directly compared with conventional DTI data from the same imaging slice. The fractional anisotropy of the slow diffusing component (Dslow) was significantly higher than the anisotropy measured by conventional DTI while reflecting a similar directionality and appeared to account for most of the anisotropy observed in gray matter, where the fiber density is notoriously low. Preliminary results of fiber tracking based on the slow diffusion component are shown. Fibers generated based on the slow diffusion component appear to follow the vertical fibers in gray matter. DslowTI may provide a way for increasing the sensitivity to anisotropic structures in cortical gray matter. Magn Reson Med 49:785,790, 2003. © 2003 Wiley-Liss, Inc. [source] Simultaneous echo refocusing in EPIMAGNETIC RESONANCE IN MEDICINE, Issue 1 2002David A. Feinberg Abstract A method to encode multiple two-dimensional Fourier transform (2D FT) images within a single echo train is presented. This new method, simultaneous echo refocusing (SER), is a departure from prior echo planar image (EPI) sequences which use repeated single-shot echo trains for multislice imaging. SER simultaneously acquires multiple slices in a single-shot echo train utilizing a shared refocusing process. The SER technique acquires data faster than conventional multislice EPI since it uses fewer gradient switchings and fewer preparation pulses such as diffusion gradients. SER introduces a new capability to simultaneously record multiple spatially separated sources of physiologic information in subsecond image acquisitions, which enables several applications that are dependent on temporal coherence in MRI data including velocity vector field mapping and brain activation mapping. Magn Reson Med 48:1,5, 2002. © 2002 Wiley-Liss, Inc. [source] Twenty-five pitfalls in the analysis of diffusion MRI data,NMR IN BIOMEDICINE, Issue 7 2010Derek K. Jones Abstract Obtaining reliable data and drawing meaningful and robust inferences from diffusion MRI can be challenging and is subject to many pitfalls. The process of quantifying diffusion indices and eventually comparing them between groups of subjects and/or correlating them with other parameters starts at the acquisition of the raw data, followed by a long pipeline of image processing steps. Each one of these steps is susceptible to sources of bias, which may not only limit the accuracy and precision, but can lead to substantial errors. This article provides a detailed review of the steps along the analysis pipeline and their associated pitfalls. These are grouped into 1 pre-processing of data; 2 estimation of the tensor; 3 derivation of voxelwise quantitative parameters; 4 strategies for extracting quantitative parameters; and finally 5 intra-subject and inter-subject comparison, including region of interest, histogram, tract-specific and voxel-based analyses. The article covers important aspects of diffusion MRI analysis, such as motion correction, susceptibility and eddy current distortion correction, model fitting, region of interest placement, histogram and voxel-based analysis. We have assembled 25 pitfalls (several previously unreported) into a single article, which should serve as a useful reference for those embarking on new diffusion MRI-based studies, and as a check for those who may already be running studies but may have overlooked some important confounds. While some of these problems are well known to diffusion experts, they might not be to other researchers wishing to undertake a clinical study based on diffusion MRI. Copyright © 2010 John Wiley & Sons, Ltd. [source] Ventricular cerebrospinal fluid lactate is increased in chronic fatigue syndrome compared with generalized anxiety disorder: an in vivo 3.0 T 1H MRS imaging study,NMR IN BIOMEDICINE, Issue 3 2009Sanjay J. Mathew Abstract Chronic fatigue syndrome (CFS) is a controversial diagnosis because of the lack of biomarkers for the illness and its symptom overlap with neuropsychiatric, infectious, and rheumatological disorders. We compared lateral ventricular volumes derived from tissue-segmented T1 -weighted volumetric MRI data and cerebrospinal fluid (CSF) lactate concentrations measured by proton MRS imaging (1H MRSI) in 16 subjects with CFS (modified US Centers for Disease Control and Prevention criteria) with those in 14 patients with generalized anxiety disorder (GAD) and in 15 healthy volunteers, matched group-wise for age, sex, body mass index, handedness, and IQ. Mean lateral ventricular lactate concentrations measured by 1H MRSI in CFS were increased by 297% compared with those in GAD (P,<,0.001) and by 348% compared with those in healthy volunteers (P,<,0.001), even after controlling for ventricular volume, which did not differ significantly between the groups. Regression analysis revealed that diagnosis accounted for 43% of the variance in ventricular lactate. CFS is associated with significantly raised concentrations of ventricular lactate, potentially consistent with recent evidence of decreased cortical blood flow, secondary mitochondrial dysfunction, and/or oxidative stress abnormalities in the disorder. Copyright © 2008 John Wiley & Sons, Ltd. [source] Monitoring acute inflammatory processes in mouse muscle by MR imaging and spectroscopy: a comparison with pathological resultsNMR IN BIOMEDICINE, Issue 3 2002Jesús Ruiz-Cabello Abstract We have studied an animal model of acute local inflammation in muscle induced by Aspergillus fumigatus by using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). We have compared our data to those found using histopathology and segmentation maps obtained by the mathematical processing of three-dimensional T2 -weighted MRI data via a neural network. The MRI patterns agreed satisfactorily with the clinical and biological evidence of the phases of acute local infection and its evolution towards chronicity. The MRS results show a statistically significant increase in inorganic phosphate and a significant decrease in phosphocreatine levels in the inflamed region. Image segmentation made with a self-organizing, neural-network map yielded a set of ordered representatives that remained constant for all animals during the inflammatory process, allowing a non-invasive, three-dimensional identification and quantification of the inflamed infected regions by MRI. Copyright © 2002 John Wiley & Sons, Ltd. [source] An fMRI investigation of working memory and sadness in females with bipolar disorder: a brief reportBIPOLAR DISORDERS, Issue 8 2008Thilo Deckersbach Objective:, Functional magnetic resonance imaging (fMRI) studies have documented abnormalities in the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex in bipolar disorder in the context of working memory tasks. It is increasingly recognized that DLPFC regions play a role in mood regulation and the integration of emotion and cognition. The purpose of the present study was to investigate with fMRI the interaction between acute sadness and working memory functioning in individuals with bipolar disorder. Methods:, Nine depressed individuals with DSM-IV bipolar I disorder (BP-I) and 17 healthy control participants matched for age, gender, education, and IQ completed a 2-back working memory paradigm under no mood induction, neutral state, or acute sadness conditions while undergoing fMRI scanning. Functional MRI data were analyzed with SPM2 using a random-effects model. Results:, Behaviorally, BP-I subjects performed equally well as control participants on the 2-back working memory paradigm. Compared to control participants, individuals with BP-I were characterized by more sadness-specific activation increases in the left DLPFC (BA 9/46) and left dorsal anterior cingulate (dACC). Conclusions:, Our study documents sadness-specific abnormalities in the left DLPFC and dACC in bipolar disorder that suggest difficulties in the integration of emotion (sadness) and cognition. These preliminary findings require further corroboration with larger sample sizes of medication-free subjects. [source] Increased rates of white matter hyperintensities in late-onset bipolar disorderBIPOLAR DISORDERS, Issue 7 2008Jaqueline Hatsuko Tamashiro Objectives:, Magnetic resonance imaging (MRI) studies have reported an increased frequency of white matter hyperintensities (WMH) in association with late-onset (LO) depression, and this has supported the notion that vascular-related mechanisms may be implicated in the pathophysiology of LO mood disorders. Recent clinical studies have also suggested a link between LO bipolar disorder (LO-BD) and cerebrovascular risk factors, but this has been little investigated with neuroimaging techniques. In order to ascertain whether there could be a specific association between WMH and LO-BD, we directly compared WMH rates between LO-BD subjects (illness onset , 60 years), early-onset BD subjects (EO-BD, illness onset <60 years), and elderly healthy volunteers. Methods:, T2-weighted MRI data were acquired in LO-BD subjects (n = 10, age = 73.60 ± 4.09), EO-BD patients (n = 49, age = 67.78 ± 4.44), and healthy subjects (n = 24, age = 69.00 ± 7.22). WMH rates were assessed using the Scheltens scale. Results:, There was a greater prevalence of WMH in LO-BD patients relative to the two other groups in the deep parietal region (p = 0.018) and basal ganglia (p < 0.045). When between-group comparisons of mean WMH scores were conducted taking account of age differences (ANCOVA), there were more severe scores in LO-BD patients relative to the two other groups in deep frontal and parietal regions, as well as in the putamen (p < 0.05). Conclusions:, Our results provide empirical support to the proposed link between vascular risk factors and LO-BD. If extended in future studies with larger samples, these findings may help to clarify the pathophysiological distinctions between bipolar disorder emerging at early and late stages of life. [source] Technology preview: X-ray fused with magnetic resonance during invasive cardiovascular proceduresCATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 6 2007Luis F. Gutiérrez PhD Abstract Background: We have developed and validated a system for real-time X-ray fused with magnetic resonance imaging, MRI (XFM), to guide catheter procedures with high spatial precision. Our implementation overlays roadmaps,MRI-derived soft-tissue features of interest,onto conventional X-ray fluoroscopy. We report our initial clinical experience applying XFM, using external fiducial markers, electrocardiogram (ECG)- gating, and automated real-time correction for gantry and table movement. Methods: This prospective case series for technical development was approved by the NHLBI Institutional Review Board and included 19 subjects. Multimodality external fiducial markers were affixed to patients' skin before MRI, which included contrast-enhanced, 3D T1-weighted, or breath-held and ECG-gated 2D steady state free precession imaging at 1.5T. MRI-derived roadmaps were manually segmented while patients were transferred to a calibrated X-ray fluoroscopy system. Image spaces were registered using the fiducial markers and thereafter permitted unrestricted gantry rotation, table panning, and magnification changes. Static and ECG-gated MRI data were transformed from 3D to 2D to correspond with gantry and table position and combined with live X-ray images. Results: Clinical procedures included graft coronary arteriography, right ventricular free-wall biopsy, and iliac and femoral artery recanalization and stenting. MRI roadmaps improved operator confidence, and in the biopsy cases, outperformed the best available alternative imaging modality. Registration errors were increased when external fiducial markers were affixed to more mobile skin positions, such as over the abdomen. Conclusion: XFM using external fiducial markers is feasible during X-ray guided catheter treatments. Multimodality image fusion may prove a useful adjunct to invasive cardiovascular procedures. © 2007 Wiley-Liss, Inc. [source] | |||||||||||||