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At least 595 records · Page 33Linked to original sources
PubMed2005

Evaluation of the functional diffusion map as an early biomarker of time-to-progression and overall survival in high-grade glioma.

Diffuse malignant gliomas, the most common type of brain tumor, carry a dire prognosis and are poorly responsive to initial treatment. The response to treatment is typically evaluated by measurements obtained from radiographic images several months after the start of treatment; therefore, an early biomarker of tumor response would be useful for making early treatment decisions and for prognostic information. Thirty-four patients with malignant glioma were examined by diffusion MRI before treatment and 3 weeks later. These images were coregistered, and differences in tumor-water diffusion values were calculated as functional diffusion maps (fDM), which were correlated with the radiographic response, time-to-progression (TTP), and overall survival (OS). Changes in fDM at 3 weeks were closely associated with the radiographic response at 10 weeks. The percentage of the tumor undergoing a significant change in the diffusion of water (V(T)) was different between patients with progressive disease (PD) vs. stable disease (SD) (P < 0.001). Patients classified as PD by fDM analysis at 3 weeks were found to have a shorter TTP compared with SD (median TTP, 4.3 vs. 7.3 months; P < 0.04). By using fDM, early patient stratification also was correlated with shorter OS in the PD group compared with SD patients (median survival, 8.0 vs. 18.2 months; P < 0.01). On the basis of fDM, tumor assessment provided an early biomarker for response, TTP, and OS in patients with malignant glioma. Further evaluation of this technique is warranted to determine whether it may be useful in the individualization of treatment or evaluation of the response in clinical protocols.

Adult↗
PubMed2002

Uncinate fasciculus findings in schizophrenia: a magnetic resonance diffusion tensor imaging study.

OBJECTIVE: Disruptions in connectivity between the frontal and temporal lobes may explain some of the symptoms observed in schizophrenia. Conventional magnetic resonance imaging (MRI) studies, however, have not shown compelling evidence for white matter abnormalities, because white matter fiber tracts cannot be visualized by conventional MRI. Diffusion tensor imaging is a relatively new technique that can detect subtle white matter abnormalities in vivo by assessing the degree to which directionally organized fibers have lost their normal integrity. The first three diffusion tensor imaging studies in schizophrenia showed lower anisotropic diffusion, relative to comparison subjects, in whole-brain white matter, prefrontal and temporal white matter, and the corpus callosum, respectively. Here the authors focus on fiber tracts forming temporal-frontal connections. METHOD: Anisotropic diffusion was assessed in the uncinate fasciculus, the most prominent white matter tract connecting temporal and frontal brain regions, in 15 patients with chronic schizophrenia and 18 normal comparison subjects. A 1.5-T GE Echospeed system was used to acquire 4-mm-thick coronal line-scan diffusion tensor images. Maps of the fractional anisotropy were generated to quantify the water diffusion within the uncinate fasciculus. RESULTS: Findings revealed a group-by-side interaction for fractional anisotropy and for uncinate fasciculus area, derived from automatic segmentation. The patients with schizophrenia showed a lack of normal left-greater-than-right asymmetry seen in the comparison subjects. CONCLUSIONS: These findings demonstrate the importance of investigating white matter tracts in vivo in schizophrenia and support the hypothesis of a disruption in the normal pattern of connectivity between temporal and frontal brain regions in schizophrenia.

Adult↗
PubMedDate not supplied

Diffusion magnetic resonance imaging in infantile neuroaxonal dystrophy.

A 7-month-old girl with infantile neuroaxonal dystrophy is reported. In diffusion MRI, the pyramidal tracts and dentate nuclei had high signal on b = 1,000 s/mm2 images and low apparent diffusion coefficient (ADC) values. This pattern likely reflected the presence of abnormal (dystrophic) axons with restricted mobility of water molecules. A reverse pattern was evident in the cerebellar cortex with high ADC values. This was likely a reflection of dysmyelination or lack of myelination.

Brain↗
PubMed2005

Detection of age-dependent changes in healthy adult lungs with diffusion-weighted 3He MRI.

RATIONALE AND OBJECTIVES: To investigate changes in lung microstructure in healthy adult subjects with no smoking history using diffusion-weighted 3He MRI. MATERIALS AND METHODS: Diffusion magnetic resonance imaging using hyperpolarized helium 3 (3He) was applied to healthy volunteers to explore the dependence of lung microstructural changes with age, reflected by changes in the apparent diffusion coefficient (ADC) of 3He in lung air spaces. Data from three sites (University of Virginia (UVa), N = 25; University of Wisconsin (UW), N = 8; University of Nottingham (UN), N = 11) were combined in pooled analysis, including a total of N = 44 subjects (age range, 18-69 years; average age, 41.7 +/- 16.7 years). RESULTS: ADC was found to depend on age at all three sites (UW, R = +0.95, P = .0003; UVa, R = +0.74, P < .0001; UN, R = +0.96, P < .0001). Increases in mean ADCs with age appeared similar across sites (UW, +0.0017 cm2 s(-1) y(-1); UVa, +0.0015 cm2 s(-1) y(-1); pooled, +0.0015 cm2 s(-1) y(-1); P = .71). In a regional analysis performed on UW data, the increase in ADC affected all regions of the lung, but the apical and middle regions showed a greater increase compared with the base of the lung. CONCLUSION: Results suggest the observed age dependence of the ADC may be caused by changes in lung microstructure that increase alveolar volume during the aging process.

Adolescent↗
PubMed2004

[Cerebral abscess: MRI, DWI and MRS features].

Although rare in non immunodeficient patients, the correct diagnosis of brain abscess is essential in order to initiate urgent medical and surgical treatment. We describe the imaging features including spectroscopy and diffusion MRI.

Brain Abscess↗
PubMed2006

Reliable identification of the auditory thalamus using multi-modal structural analyses.

The medial geniculate body (MGB) of the thalamus is a key component of the auditory system. It is involved in relaying and transforming auditory information to the cortex and in top-down modulation of processing in the midbrain, brainstem, and ear. Functional imaging investigations of this region in humans, however, have been limited by the difficulty of distinguishing MGB from other thalamic nuclei. Here, we introduce two methods for reliably delineating MGB anatomically in individuals based on conventional and diffusion MRI data. The first uses high-resolution proton density weighted scanning optimized for subcortical grey-white contrast. The second uses diffusion-weighted imaging and probabilistic tractography to automatically segment the medial and lateral geniculate nuclei from surrounding structures based on their distinctive patterns of connectivity to the rest of the brain. Both methods produce highly replicable results that are consistent with published atlases. Importantly, both methods rely on commonly available imaging sequences and standard hardware, a significant advantage over previously described approaches. In addition to providing useful approaches for identifying the MGB and LGN in vivo, our study offers further validation of diffusion tractography for the parcellation of grey matter regions on the basis of their connectivity patterns.

Adult↗
PubMed2004

Magnetic resonance imaging of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC), the most common primary hepatic malignancy, usually develops in patients with cirrhosis, growing sequentially from low-grade dysplastic nodules to frank malignant HCC. Its recognition is critical because curative treatment and prognosis require early diagnosis. Survival in patients with HCC relates directly to the number, size, and extent of lesions at diagnosis. Imaging of HCC is complicated because the tumor has a varied imaging appearance and frequently coexists with other cirrhotic nodules. Magnetic resonance imaging (MRI), the best available diagnostic technique, offers good contrast resolution and diagnostic sensitivity ranging from 33% to 77%. The main difficulty is not in diagnosing large tumors, but rather small tumors (<2 cm), because of considerable overlap on imaging between benign (regenerative), borderline (dysplastic), and malignant nodules. Increasing degrees of histological malignancy are associated with increasing arterialization and loss of portal blood supply; therefore, recognition of HCC requires dynamic imaging with gadolinium-enhanced T1-weighted sequence. Typically, HCC is a focal lesion with high signal intensity on T2-weighted images, variable signal intensity on T1-weighted images, intense arterial phase enhancement after gadolinium injection, and isointensity or hypointensity at the portal venous phase. The sensitivity of MRI for detecting small lesions is low, and improvement is still needed. Newer contrast agents, higher field strength (3 Tesla) imaging, and perfusion and diffusion MRI techniques possibly will provide greater sensitivity and specificity for detecting small HCCs in the future.

Carcinoma, Hepatocellular↗
PubMed1994

[A case of benign intracranial hypertension associated with systemic lupus erythematosus (SLE) showing diffuse white matter lesions on MRI].

We describe a 35-year-old woman with benign intracranial hypertension (BIH) secondary to systemic lupus erythematosus (SLE). She had low grade fever and skin eruptions, but neurological examination revealed no abnormal findings. Antinuclear and anti ds-DNA antibodies were positive, and complements were decreased. MRI demonstrated diffuse hyperintense white matter lesions on T2-weighted imaging. Mild bilateral papilledemas developed in the fundi, when her headache was exacerbated. The cerebrospinal fluid (CSF) pressure was 550 mmH2O. Cerebral angiography showed no cerebral sinus thrombosis. She was diagnosed as BIH secondary to SLE. Since RI cisternography revealed remarkably delayed absorption of the CSF, it was speculated that the CSF absorption by arachnoid villi would be probably disturbed in association with some autoimmune mechanisms by SLE. The subsequent rise of intraventricular pressure may result in retrograde transependymal flow of the CSF and the diffuse hyperintense white matter lesions on MRI.

Adult↗
PubMed2006

EFNS guideline on neuroimaging in acute stroke. Report of an EFNS task force.

Neuroimaging techniques are necessary for the evaluation of stroke, one of the leading causes of death and neurological impairment in developed countries. The multiplicity of techniques available has increased the complexity of decision making for physicians. We performed a comprehensive review of the literature in English for the period 1965-2005 and critically assessed the relevant publications. The members of the panel reviewed and corrected an initial draft, until a consensus was reached on recommendations stratified according to the European Federation of Neurological Societies (EFNS) criteria. Non-contrast computed tomography (CT) scan is the established imaging procedure for the initial evaluation of stroke patients. However, magnetic resonance imaging (MRI) has a higher sensitivity than CT for the demonstration of infarcted or ischemic areas and depicts well acute and chronic intracerebral hemorrhage. Perfusion and diffusion MRI together with MR angiography (MRA) are very helpful for the acute evaluation of patients with ischemic stroke. MRI and MRA are the recommended techniques for screening cerebral aneurysms and for the diagnosis of cerebral venous thrombosis and arterial dissection. For the non-invasive study of extracranial vessels, MRA is less portable and more expensive than ultrasonography but it has higher sensitivity and specificity for carotid stenosis. Transcranial Doppler is very useful for monitoring arterial reperfusion after thrombolysis, for the diagnosis of intracranial stenosis and of right-to-left shunts, and for monitoring vasospasm after subarachnoid hemorrhage. Currently, single photon emission computed tomography and positron emission tomography have a more limited role in the evaluation of the acute stroke patient.

Humans↗
PubMed2004

Morphological and hemodynamic magnetic resonance assessment of early neonatal brain injury in a piglet model.

PURPOSE: To investigate the utility of functional and morphological magnetic resonance imaging (MRI) to assess the extent of brain injury in a hypoxia-ischemia (HI) piglet model and further to validate that the desired ischemic injury was successfully induced. MATERIALS AND METHODS: MRI was performed at 1.5 T in anesthetized piglets (N = 10, age = 12-36 hours). Relative cerebral blood flow (rCBF), time-to-peak (TTP) contrast, and apparent diffusion coefficient (ADC) were estimated at different time points pre-, during, and post-HI. The effect following bilateral clamping of the carotid arteries was assessed by contrast-enhanced MR angiography (MRA) and phase contrast MR angiography (PCA) (N = 4). RESULTS: A linear correlation was observed between relative cerebral perfusion reduction and cerebral ADC during HI (r(2) = 0.85, P < 0.05). There was no correlation between rCBF reduction during 30 minutes of HI and cerebral ADC after 30 or 150 minutes of reperfusion/reoxygenation (RR). CONCLUSION: The combination of morphological and functional (perfusion and diffusion) MRI enabled consistent assessment of both the presence and absence of complete occlusion as well as the functional significance of the occlusion.

Animals↗
PubMed2003

[Cerebral amyloid angiopathy revealed by transient ischemic events: contribution of MRI to diagnosis and pathophysiology study].

We report the case of a 72-year-old left-handed woman presenting with episodes of paresthesias of the left arm and dysarthria consistent with transient ischemic attacks. The diffusion MRI showed hypersignals of the right corona radiata suggesting recent ischemic process whereas gradient-echo MRI revealed multiple small hypointense regions consistent with petechial hemorrhages restricted to the corticosubcortical regions. Gadolinium-enhanced, T1-weighted MRI showed focal meningeal enhancement. The diagnosis of cerebral amyloid angiopathy was supported by leptomeningeal biopsy. The association of ischemic suffering, petechial haemorrhage and meningeal enhancement as demonstrated by multisequence MRI highly suggest a cerebral amyloid angiopathy.

Aged↗
PubMed2006

Detection of wallerian degeneration in a newborn by diffusion magnetic resonance imaging (MRI).

We present the case of an infant with hypoxic-ischemic encephalopathy in whom wallerian degeneration is demonstrated in white-matter fiber tracts by diffusion magnetic resonance imaging (MRI). MRI was undertaken on days 2 and 9 and then at 9 months of age. On day 2, conventional MRI was normal, but diffusion MRI showed bioccipital abnormalities. On day 9, diffusion MRI showed marked abnormalities in the deep white matter of the occipital regions (left > right), corpus callosum, left posterior limb of the internal capsule, and left cerebral peduncle. Water apparent diffusion coefficient values showed a significant reduction in the left occipital white matter and corpus callosum between days 2 and 9 while demonstrating the expected pseudonormalization in cortical gray matter. Images at 9 months showed left occipital porencephaly and atrophy of the left cerebral peduncle, with the infant displaying right hemiplegia at 18 months of age. In this case, the time course of diffusion changes differed between white and gray matter, with diffusion MRI showing delayed wallerian degeneration of the cerebral white matter. This case characterizes this degeneration with clinical and follow-up MRI at 9 months of age.

Asphyxia Neonatorum↗
PubMed2001

Viability thresholds of ischemic penumbra of hyperacute stroke defined by perfusion-weighted MRI and apparent diffusion coefficient.

BACKGROUND AND PURPOSE: The penumbra of ischemic stroke consists of hypoperfused, but not irreversibly damaged, tissue surrounding the ischemic core. The purpose of this study was to determine viability thresholds in the ischemic penumbra, defined as the perfusion/diffusion mismatch in hyperacute stroke, by the use of diffusion- and perfusion-weighted MRI (DWI and PWI, respectively). METHODS: DWI and PWI were performed in 11 patients </=6 hours after the onset of symptoms of acute ischemic stroke. Regions of interest (ROIs) were placed covering the ischemic core (ROI 1), the penumbra that progressed to infarction on the basis of follow-up scans (ROI 2), and the penumbra that recovered (ROI 3). The ratios of relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), mean transit time (MTT), and apparent diffusion coefficient were calculated as lesion ROIs relative to the contralateral mirror ROIS: RESULTS: The post hoc analysis showed that the penumbra progressed to infarction at the following cutoff values: rCBF <0.59 and MTT >1.63. Higher sensitivity and accuracy in predicting outcome of the penumbra were obtained from the rCBF maps compared with the rCBV and MTT maps. The initial rCBV and apparent diffusion coefficient ratios did not differentiate between the part of the penumbra that recovered and the part that progressed to infarction. The mean rCBF ratio was optimal in distinguishing the parts of the penumbra recovering or progressing to infarction. CONCLUSIONS: The thresholds found in this study by combined DWI/PWI might aid in the selection of patients suitable for therapeutic intervention within 6 hours. However, these hypothesized thresholds need to be prospectively tested at the voxel level on a larger patient sample before they can be applied clinically.

Acute Disease↗
PubMed2004

[Noninvasive measurement of relative cerebral blood flow with the blood bolus MRI arterial spin labeling: basic physics and clinical applications].

Knowledge of tumor blood flow is important for diagnosis and follow-up of brain tumors after therapy, especially to discriminate necrosis from tumor recurrence after radiation or chemotherapy. Meanwhile, perfusion and diffusion MRI, besides MR-angiography, are state of the art in stroke imaging. Until now, perfusion imaging was mostly performed using the first-pass dynamic susceptibility-weighted contrast-enhanced (DSC) MRI. The MRI-based arterial spin labeling technique (ASL) is a novel approach for measuring relative cerebral blood flow (rCBF) without using extrinsic contrast agents, by labeling spins of flowing arterial blood as intrinsic contrast agent. This article describes physical basics of ASL and shows clinical examples in neuroimaging such as in meningeoma, glioblastoma, oligodendroglioma, and cerebral ischemia, using the Q2TIPS ASL technique. Gray matter is clearly visible, while the observed white matter signal obtained by Q2TIPS is only slightly higher than background noise. Venous blood causes artefacts in the sagittal sinus and other large superficial veins in the subarachnoid space. Meningeoma and glioblastoma show elevated rCBF, whereas oligodendroglioma and cerebral ischemia have reduced rCBF values. Arterial-spin-labeling techniques are noninvasive tools for measuring rCBF within 5 min, using a standard MRI scanner.

Blood Flow Velocity↗
PubMed2006

DTI-based assessment of ischemia-reperfusion in mouse skeletal muscle.

Diffusion tensor imaging (DTI) is frequently applied to characterize the microscopic geometrical properties of tissue. To establish whether and how diffusion MRI responds to transient ischemia of skeletal muscle, we studied the effects of ischemia and reperfusion using DTI and T2-weighted MRI before and during ischemia and up to 24 hr after reperfusion. Ischemia was induced by 50 min of hindlimb occlusion with or without dorsal flexor stimulation. During ischemia the apparent diffusion coefficient (ADC) tended to decrease (up to 15%), whereas the fractional anisotropy (FA) and T2 showed a varied response depending on the protocol and muscle type. During reperfusion the ADC and T2 initially increased and subsequently renormalized for the occlusion protocol. For the occlusion plus stimulation (OS) protocol, the FA was decreased by 13% and the ADC and T2 were increased by 20% and 57%, respectively, after 24 hr in the stimulated muscle complex. In the latter tissue the three DTI eigenvalues gradually increased upon reperfusion. The smallest eigenvalue (lambda3) showed the largest relative increase. Changes in DTI indices in the reperfusion phases followed a similar time course as the changes in T2. The changes in MR indices after 24 hr correlated with the tissue damage quantified with histology. The highest correlation was observed for lambda3 (R2 = 0.81). This study shows that DTI can be used to assess ischemia-induced damage to skeletal muscle.

Analysis of Variance↗
PubMed2005

Spontaneous wrist fusion: an unusual complication of Kienböck's disease.

We report a case of spontaneous wrist fusion occurring in a patient with magnetic resonance image (MRI)-proven stage 1 Kienböck's disease. The purpose of this case report is to make hand surgeons aware of this potential finding and to alert hand surgeons and radiologists that diffuse MRI changes of the lunate may not necessarily be pathognomonic for Kienböck's disease.

Adolescent↗
PubMed2001

Use of exponential diffusion imaging to determine the age of ischemic infarcts.

OBJECTIVE: Diffusion-weighted magnetic resonance imaging (DWI) detects acute ischemic infarcts with high lesion conspicuity. Determination of infarct age is difficult on DWI alone because infarct signal intensity (SIinfarct) on DWI is influenced by T2 properties ("T2 shine-through"). Maps of the apparent diffusion coefficient (ADC) reflect pure diffusion characteristics without T2 effects but have low lesion conspicuity. Thus, in clinical practice, combined use of DWI and ADC maps is required. Exponential DWI (eDWI) is an innovative means of MRI-diffusion data analysis that merges the advantages of DWI and ADC maps. The authors hypothesized that SIinfarct on eDWI would correlate with infarct age. The authors studied 114 consecutive patients who had 120 ischemic strokes with clearly determined onset times and who underwent echo-planar DWI. The eDWI were generated by dividing the signal intensity on DWI by that on the corresponding T2 image on a pixel-by-pixel basis. SIinfarct on eDWI was measured in the lesion core and expressed as a percentage of contralateral control tissue. On eDWI, relative SIinfarct changed significantly with infarct age (P < .0001). When patients were sorted in infarct-age groups, no significant differences were found within the first 120 hours. However, for patients studied within 5 days, the mean relative SIinfarct was significantly higher compared with patients studied > or = 8 days after stroke (P < .05). For all infarcts up to 5 days old, the eDWI signal intensity was higher than control tissue (hyperintense appearance). All infarcts > 10 days old had an eDWI signal intensity lower than control tissue (hypointense appearance). The authors concluded that the use of eDWI, as a single set of images, reliably differentiates acute infarcts (< or = 5 days old) from infarcts > 10 days old. This feature would be expected to be helpful when the distinction between acute and nonacute infarction cannot be determined on clinical grounds.

Adolescent↗
PubMed2002

[Cadasil: a case with molecular diagnosis].

CADASIL disease (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) was described in 1991 by Tourmier-Lasserve. Two years later the same authors described its association with chromosome 19; nonetheless, the mutations in gene Notch3 were not described until 1996. Clinical findings depend on the age at onset. The early form of the illness is found in young patients, generally less than 30 years old, and the main clinical manifestation is a migraine headache with subcortical lesions in the white matter, while in the later form ischemic events and behavioral symptoms are predominant. Anatomo-pathological findings in CADASIL include the presence of osmophilic granular deposits in vessel walls, skin, muscles and cerebral arteries. We present a patient with CADASIL and cavernous angioma. We studied a 40-year-old woman who underwent surgery for a left temporal-parietal cavernous angioma, with aphasia as the only symptom, two years before admission. Her family history showed that her father had suffered from vascular dementia. She was admitted to our hospital with right-side hemiparesis and dysarthria. A CT scan showed the presence of ischemic vascular lesions and former surgery sequelae. The duplex scan of the neck vessels and a transesophageal echocardiogram ruled out an embolic source. Laboratory tests including VDRL, HIV, prothrombotic profile and rheumatologic screening tests were normal. An MRI in T2W and FLAIR showed the presence of multiple subcortical cerebral lesions and hyperintensity in the white matter (leukoencephalopaty). We found a left acute putaminal-capsular infarct in the diffusion-MRI. The MRA was normal. Analysis of the cerebrospinal fluid was unremarkable. A molecular DNA test was performed, and a nucleotide substitution in position 583 in exon 4 of gene Notch3 was detected. This mutation was found only in CADASIL patients. The association with cavernous angioma has not been previously reported, and we believe that it was unrelated to CADASIL, either clinically or genetically. To our knowledge, this is the first case of CADASIL diagnosed by molecular DNA test in our country.

Adult↗