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1.
Magnetic resonance imaging (MRI) reveals cardiac signal intensity changes in patients with acute myocarditis; however, the
natural history of these changes and their relationship to individual outcomes are unknown. The relationship of MRI findings
to long-term outcome was studied by serial MRI studies in 16 patients with acute myocarditis who were followed for 30±4 (SE)
months. Myocardial contrast enhancement was monitored using contrast-enhanced T1-weighted fast spin-echo images. Left ventricular
ejection fraction was measured with gradient-echo sequences. Clinical symptoms were scored. The results were compared to a
control group of 26 age-matched, healthy volunteers. Myocardial contrast enhancement, which was markedly increased in the
early course of the disease, decreased at 4 weeks and remained within the normal range in most patients after 30 months. Contrast
enhancement 4 weeks after onset of symptoms was predictive for the functional and clinical long-term outcome.
Contrast-enhanced MRI may be a useful, noninvasive tool for long-term follow-up of patients with acute myocarditis. Furthermore,
relatively early MRI findings may predict longer-term outcomes.
Electronic Publication 相似文献
2.
Jeanette Schulz-Menger Oliver Strohm Rainer Dietz Matthias G. Friedrich 《Magma (New York, N.Y.)》2000,11(1):82-83
5. Summary Contrast-enhanced MRI may serve as a sensitive noninvasive tool for the detection and follow-up of myocardial involvement
in patients with systemic sarcoidosis. 相似文献
3.
Heverhagen JT Hahn HK Wegmann M Herz U Shaffer Whitaker CD Matschl V Alfke H 《Magma (New York, N.Y.)》2004,17(2):80-85
Small animal models are widely used to study various pathologies. Magnetic resonance imaging (MRI) allows investigation of these animals in a non-invasive way. Therefore, the aim of our study was to develop and evaluate a low-cost approach to measure lung volumes in small animal MRI using a clinical scanner and a specially designed RF coil. Five mice (three of an established emphysema model and two controls) were investigated in a 1.0-T clinical scanner using a specially built small animal saddle coil and three different three-dimensional sequences; overall imaging time was approximately 16 min. Lung volumes were calculated from these images using an interactive watershed transform algorithm for semi-automatic image segmentation. The gold standard for the volume measurement was water displacement after surgical explantation. MRI measured volumes correlated significantly with ex vivo measurements on the explanted lungs (r = 0.99 to 0.89; p < 0.05). Mean lung volume in emphysema model mice was larger than in controls. High-resolution, small animal MRI using a clinical scanner is feasible for volumetric analysis and provides an alternative to a dedicated small animal scanner. 相似文献
4.
Zhang Z van den Bos EJ Wielopolski PA de Jong-Popijus M Duncker DJ Krestin GP 《Magma (New York, N.Y.)》2004,17(3-6):201-209
Myoblast transplantation is a promising means of restoring cardiac function in infarcted areas. For optimization of transplant protocols, tracking the location and fate of the injected cells is necessary. An attractive imaging modality for this is magnetic resonance imaging (MRI) as it is noninvasive and as iron-labeled myoblasts provide a signal attenuation in T2*-weighted protocols. The aim of this study was to develop an efficient iron-labeling protocol for myoblasts and to visualize single-labeled cells using a clinical 1.5-T scanner. Pig myoblasts were labeled with a superparamagnetic iron oxide (SPIO) agent using a liposome transfection agent. Labeling efficiency, toxicity, cell viability, and proliferative capacity were measured for 10 days. Magnetic resonance (MR) of myoblast cultures used a T2*-weighted three-dimensional protocol with a maximum in-plane resolution of 19.5 × 26.0 m2 and 50 m slices. Use of liposomes improved SPIO labeling efficiency. Labeling did not induce toxicity or affect cell viability or proliferation. The cell distribution as observed with light and fluorescence microscopy matched the signal voids observed in the MRI datasets. Liposomes promote fast, nontoxic and efficient SPIO labeling of myoblasts that can be tracked by MRI microscopy in clinical scanners using susceptibility-weighted protocols. 相似文献
5.
There is great interest in the non-destructive capabilities of magnetic resonance microscopy for studying murine models of
both disease and normal function; however, these studies place extreme demands on the MR hardware, most notably the gradient
field system. We designed, using constrained current minimum inductance methods. and fabricated a complete, unshielded three-axis
gradient coil set that utilizes interleaved, multilayer axes to achieve maximum gradient strengths of over 2000 mT m−1 in rise times of less than 50 μs with an inner coil diameter of 5 cm. The coil was wire-wound using a rectangular wire that
minimizes the deposited power for a given gradient efficiency. Water cooling was also incorporated into the coil to assist
in thermal management. The duty cycle for the most extreme cases of single shot echo planar imaging (EPI) is limited by the
thermal response and expressions for maximum rates of image collection are given for burst and continuous modes of operation.
The final coil is capable of the collection of single shot EPI images with 6 mm field of view and 94 μm isotropic voxels at
imaging rates exceeding 50 s−1. 相似文献
6.
Magnetic resonance imaging of rodent teeth 总被引:1,自引:0,他引:1
In this paper, the anatomical structures of rat jaws are studied using magnetic resonance imaging (MRI) with high spatial
resolution. In vivo microimages of teeth from 3- and 12-week-old (young and adult) rats have been performed. A 2 T nuclear
magnetic resonance microscope was used to collect, with multiple orientations, non-invasive 2D data images using the spin-echo
technique. MRI appears well suited to give images of the oral area and may represent a useful tool for diagnosis of dental
diseases and more particularly of pulp pathologies.
This work was presented at the ESMRMB meeting in Brussels, September 1997. 相似文献
7.
The concept and the implementation of a parallelized and spin-based simulator for magnetic resonance (MR) imaging is presented.
The dynamics of magnetization are modeled using the Bloch equation covering arbitrary radiofrequency (RF) pulses, gradients,
main-field inhomogeneity, and relaxation. A temporal decomposition of a given sequence is introduced, leaning to basic sequence
elements called atoms. A concept of spatial sampling of the object by spins is proposed, in the course of which Shannon's
sampling theorem must be respected. In biomedical MR imaging, spins can be modeled as noninteracting entities, permitting
an efficient parallelization of the simulation. The simulator ParSpin was implemented on a heterogeneous, interconnected cluster
of workstations based on existing message passing libraries. The communication overhead has been kept moderately small. The
aggregate computing performance of many processors enables the research into very complex problems (e.g., three-dimensional
or steady-state MR experiments requiring up to 106 spins). Additionally, ParSpin allows a comprehensive visualization for educational purposes. 相似文献
8.
Detection of myocardial viability in acute infarction using contrast-enhanced <Superscript>1</Superscript>H magnetic resonance imaging 总被引:2,自引:0,他引:2
Hillenbrand HB Sandstede J Lipke C Köstler H Pabst T Werner E Ertl G Hahn D Bauer WR 《Magma (New York, N.Y.)》2003,16(3):129-134
Background Reperfusion strategies salvage myocardium at risk in acute myocardial infarction (MI). This clinical study was performed to
determine whether areas without evidence of delayed MRI contrast enhancement in MI correspond to viability by means of percent
systolic wall thickening (%SWT) and enddiastolic wall thickness (EDWT) in chronic infarction.
Methods Twenty MRI studies were performed in ten patients within 6 days of MI and 3 months post-MI. On a segmental basis the percentage
of viable myocardium as defined by contrast-enhanced MRI (no delayed MRI contrast enhancement) in acute MI was measured and
was compared with %SWT and EDWT in chronic MI.
Results Of the 1718 segments in acute infarction in which the percentage of viable myocardium was measured 1333 were found to be completely
viable by means of contrast-enhanced MRI (no delayed MRI contrast enhancement). All of these segments revealed %SWT on day
90 post-MI, and 97% of segments were viable by means of an EDWT of more than 5.5 mm. In 85 segments the proportion of viable
myocardium was 50–99% (mean 56±8%), with 92% segments found to be viable by means of %SWT and 92% by EDWT, and of 156 segments
with viable myocardium between 1–49% (36±8%) 79% were found to be viable by means of %SWT and 82% by EDWT. Corresponding proportions
of 144 segments with transmural delayed MRI contrast enhancement in acute MI were 45% and 17%.
Conclusions In acute reperfused MI viable myocardium as delineated by contrast-enhanced MRI is correlated with clinical parameters of
viability. Delayed MRI contrast enhancement resolves nontransmural MI and may become a valuable clinical tool when planning
revascularization procedures. 相似文献
9.
Clinical examinations of reptiles are physically limited and therefore usually have to be complemented by other methods. This is especially true for Chelonians. A modern imaging technique like magnetic resonance imaging is well suited for this purpose. Its application and practical experiences with tortoises are presented. 相似文献
10.
A model of transient global brain ischemia consisting of bilateral occlusion of common carotid arteries for 10 min and mild hypoxia (15% O2−85% N2) for 20 min was studied by means of MRI in young and aged Fischer 344 rats (3–4 and 24–26 months, respectively). Ischemia was assessed by full suppression of spontaneous EEG activity, which reappeared and normalized similarly in the two age-groups. The survival of young with respect to aged rats was considerably higher both at 24 h (20/20, i.e. 100% vs 12/16, i.e. 75%) and at 48 h (16/20, i.e. 80% vs 6/16, i.e. 38%). The localisation of brain lesions, their severity and progression were evaluated by a diffusion-weighted MRI (DWI) sequence at 24 and 48 h post-ischemia. There were no DWI-detectable lesions in eight out of 20 young and two out of 12 aged rats. The localisation of DWI-detected lesions was rather similar in rats of the two age-groups. In fact, the cerebral cortex, mainly parietal, occipital and temporal lobes were damaged in 83% of young and 90% of aged rats. The respective percentages for the thalamus were 83 and 60%, for the striatum 58 and 50%, and for the hippocampus 25 and 30%. The lesions present in the cerebral cortex and the thalamus were considerably more severe in aged than in young rats. In conclusion, in spite of similar localisation of ischemic lesions in the two age-groups, their incidence was higher, appearance more rapid and severity more pronounced in aged with respect to young rats. This resulted in a considerably higher mortality of the former. The overall data indicate that the age issue is very important in experimental ischemia research. 相似文献
11.
12.
Botnar R Nagel E Scheidegger MB Pedersen EM Hess O Boesiger P 《Magma (New York, N.Y.)》2000,10(1):18-26
Objectives Magnetic resonance (MRI) velocity mapping was used to evaluate non-invasively the flow profiles of the ascending aorta in
normal volunteers and in patients with an aortic (mechanical) valve prosthesis.
Background In patients with artificial aortic valves the flow profile in the ascending aorta is severely altered. These changes have
been associated with an increased risk of thrombus formation and mechanical hemolysis.
Methods Velocity profiles were determined 30 mm distal to the aortic valve in six healthy volunteers and seven patients with aortic
valve replacement (replacement within the last 2 years) using ECG triggered phase contrast MRI. Peak flow, mean flow and mean
reverse flow were measured in intervals of 25 ms during the entire heart cycle. Systolic reverse flow, end-systolic closing
and diastolic leakage volume were calculated for all subjects.
Results Peak flow velocity during mid-systole was significantly higher in patients with valvular prosthesis than in normals (mean±SD,
1.9±0.4 m/s vs. 1.2±0.03 m/s,P<0.001) with a double peak and a zone of reversed flow close to the inner (left lateral) wall of the ascending aorta of the
patients. Closing volume was significantly larger in patients than in controls (−3.3±1.2 ml/beat vs. −0.9±0.5 ml/beat;P<0.001). There was reverse flow during systole in valvular patients amounting to 15.7±6.7% of total cardiac output compared
to 2.3±1.2% in controls (P<0.001). Diastolic mean flow was negative in patients after valve replacement but not in controls (−11.0±15.2 ml/beat vs.
6.8±3.2 ml/beat;P<0.01).
Conclusions The following three major quantitative observations have been made in the present study: (1) Mechanical valve prostheses have
an increased peak flow velocity with a systolic reverse flow at the inner (left lateral) wall of the ascending aorta. (2)
A double peak flow velocity pattern can be observed in patients with bileaflet (mechanical) prosthesis. (3) The blood volume
required for leaflet closure and the diastolic leakage blood volume are significantly higher for the examined bileaflet valve
than for native heart valves. 相似文献
13.
Accuracy of computed tomography and magnetic resonance imaging in staging bronchogenic carcinoma 总被引:5,自引:0,他引:5
Sixty-three patients with non-small cell bronchogenic carcinoma were prospectively and independently assessed by computed tomography (CT) and magnetic resonance imaging (MRI) before surgery. Images were interpreted by four radiologists who had no knowledge of other imaging studies, except chest x-ray, and were blinded to surgical findings. The data were compared with pathologic and histologic findings. The accuracies of CT and MRI in determining tumor classification and assessing mediastinal and hilar lymph node metastases were compared. Sensitivity of CT in determining T factor was 78%, and specificity was 96%. The values for MRI were 84% and 96%, respectively. There was no significant difference between CT and MRI in staging tumors. MRI is more accurate than CT in diagnosing mediastinal invasion in staging superior sulcus tumors and complex tumors. There was no significant difference between the accuracies of CT and MRI in detecting mediastinal node metastases; the sensitivities were 82% and 90%, respectively, and specificities were 88% and 93%, respectively. 相似文献
14.
The challenges in detection, localization, and staging of prostate cancer have prompted the investigation of the role of various
magnetic resonance (MR) methodologies in a large cohort of men prior to biopsy. The identification of suspicious areas of
malignancy was carried out using magnetic resonance imaging (MRI), magnetic resonance spectroscopic imaging (MRSI) and diffusion-weighted
imaging (DWI). Our data shows that apparent diffusion coefficient (ADC) may be a reliable marker to differentiate normal,
benign, and malignant prostate tissues similar to the metabolite ratio. Also, the combined use of MRSI and DWI improves the
diagnosis of prostate cancer. In this review, we present our experience on the use of MRI, MRSI and DWI methods in the assessment
of prostate cancer in Indian men. Further, analysis of the comparison of the ADC and the metabolite ratio values reported
in the literature across various patient populations are presented.
An erratum to this article can be found at 相似文献
15.
Direct volume rendering is a visualization method that allows display of all information hidden in three-dimensional data
sets of, for example, computed tomography or magnetic resonance imaging (MRI). In contrast to commonly used surface rendering
methods, these algorithms need no preprocessing but suffer from a high computational complexity. A real-time rendering system,
VIRIM (Vitec: Visualization Technology GmbH, Mannheim, Germany), cuts down rendering times of minutes on normal workstations
to an interactive rate of 1 second or less. The immediate visual feedback allows interactive steering of the visualization
process to achieve insight into the internal three-dimensional structure of objects. Additional information is obtained by
using an interactive gray-value segmentation tool that both allows segmentation of the data set according to bone, tissue,
and liquor and display of multifunctional data sets (e.g., functional MRI [fMRI] data sets). Thus, real-time direct volume
rendering allows segmentation and volume data processing of functional and anatomical MR data sets simultaneously. As this
method can be integrated in the clinical routine, it is of great importance for real-time motion artifact detection and the
interpretation of fMRI data acquired during cognitive experiments with normal subjects and psychiatric patients. Because of
the free programmability of VIRIM, more complex matching procedures are currently being investigated for future implementation. 相似文献
16.
Isabelle Mottet Roger Demeure Jean Rataud Michelle Lucas Florence Wahl Vincent Warscotte Jean-Philippe Thiran Jean-François Goudemant Baudouin Maldague Jean-Marie Maloteaux Jean-Marie Stutzmann 《Magma (New York, N.Y.)》1997,5(3):185-191
The aim of this study was to investigate the effects of riluzole on the lesion induced by a permanent middle cerebral artery
occlusion (MCAO) in rats. Riluzole at 4 or 8 mg/kg i.v. significantly reduced the cortical ischemic brain damage. With the
most effective dose of 8 mg/kg, the time evolution of the lesion was assessed by T2-weighted magnetic resonance imaging (MRI) repeated on the same animals after MCAO. MRI obtained at 24, 48, and 72 hours after
MCAO showed a progressive increase of the ischemic lesion, except in the cortex of the riluzole-treated rats (8 mg/kg i.v.).
Furthermore, there was no difference between lesion volumes as measured by MRI or by histology. This study indicates that
MRI may be a valuable method to quantifyin vivo the neuroprotective profile of a drug. 相似文献
17.
Analysis of contrast-enhanced MR images to assess renal function 总被引:1,自引:0,他引:1
Michoux N Vallée JP Pechère-Bertschi A Montet X Buehler L Van Beers BE 《Magma (New York, N.Y.)》2006,19(4):167-179
The image analysis and kinetic modeling methods used in dynamic contrast-enhanced magnetic resonance imaging of the kidney are reviewed. Image analysis includes various techniques of coregistration and segmentation. Few methods have been completely implemented. Nevertheless, the use of coregistration may become a standard to decrease the effect of motion on abdominal images and improve the quality of the renal signals. Kinetic models are classified into three categories: enhancement-based, external and internal representations. Enhancement-based representations are limited to a basic analysis of the tracer concentration curves in the kidneys. Their relationship to the underlying physiology is complex and undefined. However, they can be used to evaluate the split renal function. External representations assess the kidney input and output. An external representation based on the up-slope of the renal enhancement to calculate the renal perfusion is commonly used because of its simplicity. In contrast, external representation based on deconvolution or identification methods remain underexploited. For glomerular filtration, an internal representation based on a two-compartmental model is mostly used. Internal representations based on multi-compartmental models describe the renal function in a more realistic way. Because of their numerical complexity, these models remain rarely used. 相似文献
18.
Yudong Zhang Shuihua Wang Genlin Ji Zhengchao Dong 《IEEJ Transactions on Electrical and Electronic Engineering》2015,10(1):116-117
We propose the use of exponent of wavelet transform (EWT) coefficients as a sparse representation which is combined with the iterative shrinkage/threshold algorithm (ISTA) for the reconstruction of compressed sensing magnetic resonance imaging. In addition, random shifting (RS) is employed to guarantee the translation invariance property of discrete wavelet transform. The proposed method is termed the exponential wavelet iterative shrinkage/threshold algorithm with random shifting (EWISTARS), which takes advantages of the sparse representation of EWT, the simplicity of ISTA, and the translation invariance of RS. Simulation results on brain, vertebrae, and knee MR images demonstrate that EWISTARS is superior to existing algorithms with regard to reconstruction quality and computation time. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
19.
J. Wright V. Adams J. Hykin P. Gowland B. Issa P. Boulby P. Tokarczuk D. Evans R. Spiller P. Mansfield 《Magma (New York, N.Y.)》1994,2(3):467-469
Echo-planar imaging (EPI) can be used to produce snapshot images of the human stomach and antro-pyloro-duodenal segment in real time as an alternative technique to intubation and exposure to ionizing radiation. The method has been further developed to monitor simultaneous gastric motility and gastric emptying of liquid and solid meals. The model has been utilized to study the effects of pharmacological agents on gastric function.Eight normal subjects were imaged in a 0.5-T superconducting magnet for up to 6 h following ingestion of 800 ml tap water, followed by 500 ml porridge test meal + 500 ml tap water. A rapid multislice technique was adopted to image adjacent transverse slices (10 mm thick) through the gastric region. In addition, three subjects were orally dosed with 20 mg of the prokinetic agent Cisapride. Gastric volumes for each slice were calculated and summed to produce a measure of total gastric volume and gastric emptying. Contractile activity at the level of the antro-pyloric segment was detected using sequential 128 ms images at 3 s intervals. Alternate measurements of gastric volume and motility were made for the duration of the study.Gastric emptyingT
1/2's (times to empty 50% of the gastric contents) of 12.9 min for water and 116 min for porridge were in agreement with results obtained by the traditional techniques of gamma scintigraphy and impedance imaging. The frequency of gastric contractions increased from 2.4 contractions per minute (cpm) to 3.2 cpm following water and from 2.9 to 3.2 cpm following porridge. The prokinetic effect of enhanced coordination of antroduodenal contractions was also observed. These studies have demonstrated that EPI can be used to detect and image gastroduodenal function in man, totally noninvasively, and can be used to study the effects of drugs acting on the gastrointestinal tract. 相似文献
20.
Rationale and objectives: To determine the relationship between the lesion and the scar enhancement characteristics in a series of hepatic Focal Nodular
Hyperplasia (FNH) lesions studied with dynamic MR imaging.Methods: Nine patients with FNH were studied. The slice showing the largest scar was selected for the dynamic single slice T1-weighted
Gradient-echo sequence before and after contrast administration (15 images, one every 20 s). Analysis was performed with ROI
measurements in the lesion and the scar. Signal-intensity and enhancement curves were obtained from both structures.Results: Dynamic MRI showed the typical homogeneous early enhancement of the lesion with delayed enhancement of the scar. The scar
enhanced early and vigorously in all cases. Two patterns of enhancement curves were defined. In the parallel pattern, both
curves started early, quickly reaching a plateau maintained over time (77.8%). In the divergent pattern the curve of the scar
was above the curve of the FNH (22.2%). after the maximum slope was reached, with progressive separation of the curves.Conclusion: There is a hypervascular scar enhancement within FNH lesions with either a parallel or divergent course after the maximum
early enhancement. 相似文献