摘要:

AbstractJapanese encephalitis (JB) is an acute encephalomyelitis which is a primary viral encephalitis accompanying a viral infection. Clinically, the patient who either resides in an endemic region or who has been exposed to the viral vector (mosquito) may have symptoms including high fever, headache, and impaired consciousness. JE involves many portions of the supratentorial thalamus, basal ganglia, and white matter. Classically MR imaging demonstrates the lesions of JE as hyperintense on T2‐weighted images and hypointense on T1‐weighted images. Hemorrhagic transformations have also been described in JE lesions, with corresponding expected T1 and T2 changes. Differential considerations based on the MRI appearance are somewhat broad, including but not limited to primary viral encephalitis, acute encephalopathy, limbic encephalitis, and acute disseminated encephalomyelitis. The therapy for JE is primarily conservative and supportive since there is no specific treatment for JE, and the disease has a high fatality rate. The prognosis depends on the extent of involvement at primary presentation, and on the autoimmune mechanisms of this dise

ISSN:1053-1807    

DOI:10.1002/jmri.1880080402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThe role of radiological imaging in moyamoya disease includes screening of the disease based on clinical findings, evaluation of the changes in vasculature and brain parenchyma, and clinical follow‐up. The imaging findings in moyamoya disease are classified as primary and secondary. The primary findings essentially consist of occlusion of the circle of Willis and collateral formation, including moyamoya vessel formation. The secondary findings include cerebral infarction, white matter lesions, atrophy, and hemorrhage. For the visualization of the primary and secondary findings as well as postoperative results, MRI and MR angiography are the most reliable methods and play important roles because of their excellent diagnostic yield and noninvasivenes

ISSN:1053-1807    

DOI:10.1002/jmri.1880080403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractIn this study, we investigated differences between gray matter and white matter perfusion in patients with a unilateral occlusion of the internal carotid artery (ICA) with dynamic susceptibility contrast. Seventeen patients and 17 control subjects were studied, using T2*‐weighted gradient echo acquisition. Gray and white matter regions were obtained by segmentation of inversion recovery MRI. Lesions were excluded by segmentation of T2‐weighted MRI. In the symptomatic hemisphere, cerebral blood volume was increased in white matter (P<.05) but not in gray matter. No cerebral blood flow changes were found. All timing parameters (mean transit time [MTT], time of appearance, and time to peak) showed a significant delay for both white and gray matter (P<.05), but the MTT increase of white matter was significantly larger than for gray matter (P<.05). These findings indicate that differentiation between gray and white matter is essential to determine the hemodynamic effects of an ICA occlus

ISSN:1053-1807    

DOI:10.1002/jmri.1880080404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractWe used a numerical simulation of water self‐diffusion among permeable cylinders to predict the dependence of MR‐based apparent diffusion coefficients in white matter on axonal separation, barrier permeability, and diffusion time (T). The transverse apparent diffusion coefficient (tADC), calculated with simulated diffusion‐sensitizing gradients perpendicular to the axon fibers, remains a function of T down to diffusion times as short as .1 μsec for a range of diffusion barrier permeability. As the diffusion time lengthens, the response of tADC depends on axon diameter, with decreases in tADC occurring earliest, and most dramatically, for the smallest fiber diameter simulated (2 μm). For a given axonal separation, asymptotic values of ADC are determined by permeability alone and are the same for 2‐μm and 11‐μm fibers of equal membrane permeability. The effect of increased relative intracellular volume is manifested primarily in a decrease in tADC at short T. Increases in interaxonal spacing increase the tADC at asymptotically long diffusion times and reduce the dependence on permeability. However, at the widest plausible axonal separations, permeability remains an important determinant of tADC. These simulations may enhance interpretation of measured tADC in the context of the underlying physiologic and structural changes at the cellular level that accompany white

ISSN:1053-1807    

DOI:10.1002/jmri.1880080405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to assess the value of dynamic, contrast‐enhanced MRI in patients with malignant glioma (a) to predict before stereotactic radiotherapy local tumor control, (b) to investigate temporal changes in tumor microcirculation after stereotactic radiotherapy, and (c) to analyze whether malignant glioma response may be predicted earlier by alterations in the tissue pharmacokinetics rather than in terms of tumor volume. Ninety MRI studies were performed of 18 patients with malignant glioma before and 6, 18, 26, 52, and 72 weeks after the end of stereotactic radiotherapy. The signal time courses of the contrast‐enhanced tumors were analyzed using a pharmacokinetic two‐compartment model that calculates for the parameterA, reflecting the degree of MRI signal enhancement [no units] and the exchange rate constant k21[min−1]. Before radiotherapy, the amplitudeAwas significantly (P<.05) lower in patients with subsequent local tumor control (n= 8; meanA= .34 ± .15) compared to patients without subsequent local tumor control (n= 10; meanA= .94 ± .71). In the local tumor control group, early after stereotactic radiotherapy (at 6–18 weeks), there was a significant (P<.05) time‐dependent decrease in the parameter k21, whereas there was still no alteration in the tumor volume. A low amplitudeAbefore radiotherapy, combined with an early drop ofk21after stereotactic radiotherapy, reliably characterized the group of patients with subsequent tumor volume decrease. Our preliminary results suggest that two contrast‐enhanced dynamic MR studies, one before and one early after stereotactic radiotherapy, offer important information on local tumor control within the first 6 to 18 weeks after stereotactic radiotherapy. Moreover, this response may be evidenced before tumor volume changes and provides a therapeutic window to broaden treatment options and to improve tr

ISSN:1053-1807    

DOI:10.1002/jmri.1880080406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThis study demonstrates the value of a fast fluid‐attenuated inversion‐recovery (FLAIR) technique in the assessment of primary intraaxial brain tumors. Twenty‐one patients with primary intraaxial brain tumors were examined by T2‐weighted, proton‐density‐weighted fast spin echo, fast FLAIR, and contrast‐enhanced T1‐weighted spin echo using identical slice parameters. The images were evaluated using quantitative and qualitative criteria. Quantitative criteria were tumor‐to‐background and tumor‐to‐cerebrospinal fluid (CSF) contrast and contrast‐to‐noise ratio (CNR). The qualitative evaluation was performed as a multi‐reader analysis concerning lesion detection, lesion delineation, and image artifacts. In the qualitative evaluation, all readers found the fast FLAIR to be superior to fast spin echo in the exact delineation of intraaxial brain tumors (P<.001) and the delineation of enhancing and nonenhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor‐to‐CSF contrast and tumor‐to‐CSF CNR (P<.001). The tumor‐to‐background contrast and tumor‐to‐background CNR of the fast FLAIR images were lower than those of T2‐weighted spin‐echo images but higher than those of proton‐density‐weighted spin‐echo images. FLAIR images had more image artifacts influencing the image interpretation in only two patients. Signal hyperintensities at the ventricular border were present in 92% of the patients. They are common findings in fast FLA

ISSN:1053-1807    

DOI:10.1002/jmri.1880080407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractTo compare the performance of macromolecular albumin gadolinium‐diethylenetriamine pentaacetic acid (Gd‐DTPA)30and low molecular weight gadopentetate dimeglumine for microvessel characterization, we examined an intracranial 9L glioma model in which increased angiogenesis, hypervascularity, and hyperpermeability mimic characteristics of clinical malignant brain tumors. Dynamic MRI data were analyzed using a bidirectional, two‐compartment kinetic model to extract quantitative estimates for fractional blood volume (fBV) and permeability surface area product (PS). Three criteria were used for comparison of contrast agent performance: (a) tumor conspicuity, defined as the contrast‐to‐noise ratio (CNR); (b) dynamic range of differential permeability estimates between tumor and normal brain; (c) reasonableness of blood volume estimates. Gadopentetate was superior to macromolecular albumin‐(Gd‐DTPA)30for detection of 9L brain gliomas and for measurements of hype

ISSN:1053-1807    

DOI:10.1002/jmri.1880080408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractEleven patients with intracranial cystic collections were evaluated in the open‐bore intraoperative MR system. In each case, the cystic collection or the surrounding cerebrospinal fluid (CSF) space was injected with .02 to .5 cc of .5 mol/1 gadopentetate dimeglumine. Serial Imaging was performed using T1‐weighted imaging. In seven patients, free communication was demonstrated between the cystic collection and the surrounding CSF spaces. In four cases, the cyst did not communicate with the CSF; two of these were drained in the intraoperative MR system with reduction in symptoms. One patient developed an aseptic meningitis 10 days after the study, which was successfully treated with steroids; no other complications were noted. We conclude that the communication of intracranial cystic collections with the cisterns and ventricies can be safely and effectively elucidated with gadolinium injection in the intraoperative MR sys

ISSN:1053-1807    

DOI:10.1002/jmri.1880080409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to validate our MR tissue segmentation technique using a hamster brain tumor model and malignant brain tumors in man. We used a multispectral tissue segmentation analysis. Three sets of MRI data were included: proton density, T2‐weighted fast spin echo, and T1‐weighted spin echo, as inputs. Three image preprocessing steps included correcting image nonuniformity, application of an anisotropic diffusion type filter, and data point selection by a qualified observer. We used the k‐Nearest Neighbor segmentation algorithm, which does not require prior knowledge of the sample distribution. This choice allowed us to optimize the different tissue clusters present in three‐dimensional (3D) feature space. In vivo validation of the technique was performed in hamsters harboring tumors induced with JC virus‐transformed HJC‐15 cells, as compared to three control animals. Human brain tumors obtained by stereotactically guided biopsy in six patients were also included in the study. Finally, brain tumors were removed from two patients who underwent conventional craniotomy using segmentation‐derived images as a guide. In the hamsters, 10 tissues were correctly identified by segmentation and were confirmed histologically (P<.02). In the patients, there was also a strong correlation between our segmentation results and the tissue obtained by stereotactic biopsy (P<.01). In one of the two patients who underwent open craniotomy, segmentation images were useful in revealing tumor spread into vital areas of the brain (motor area). In conclusion, the results of segmentation correlate well with the tissues in vivo and thus warrant further clinical utilization a

ISSN:1053-1807    

DOI:10.1002/jmri.1880080410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractHypoxic‐ischemic encephalopathy (HIE) can result from neonatal asphyxia, the pathophysiology of which is poorly understood. We studied the acute evolution of this disease, using magnetic resonance imaging in an established animal model. HIE was induced in neonatal rabbits by a combination of common carotid artery (CCA) ligation and hypoxia. Serial diffusion and perfusion‐weighted magnetic resonance images were acquired before, during, and after the hypoxic interval. Focal areas of decreased apparent diffusion coefficient (ADC) were detected initially in the cortex ipsilateral to CCA ligation within 62 ± 48 min from the onset of hypoxia. Subsequently, these areas of decreased ADC spread to the subcortical white matter, basal ganglia (ipsilateral side), and then to the contralateral side. Corresponding perfusion‐weighted images showed relative cerebral blood volume deficits which closely matched those regions of ADC change. Our results show that MRI diffusion and perfusion‐weighted imaging can detect acute cell swelling post‐hypoxia in this

ISSN:1053-1807    

DOI:10.1002/jmri.1880080411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY