Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Diffusion MRI”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36Linked to original sources
PubMed2001

[Cerebrovascular emergency in neuroradiology].

Common causes to consultate a neuroradiologist in case of emergencies are trauma, brain infarction, or intracranial bleeding. Patients with brain infarction need a rapid assessment of the potentially nonnecrotic area within the ischaemic lesion. If haemorrhage, mostly occurring in the form of subarachnoid bleeding, is suspected, the source of bleeding has to be detected. With cranial computed tomography (CT) a thorough evaluation and staging of ischaemic stroke is possible with respect to thrombolysis. To detect irreversible damage of brain tissue, a combined perfusion-diffusion MRI should be performed.

Brain Infarction↗
PubMed2005

[Cardioembolic stroke due to mitral annular calcification with a mobile component].

We report here a 50-year-old man on maintenance hemodialysis who presents right hemiparesis, aphasia. MRI diffusion weighted image showed an increased signal intensity in the area of the left middle cerebral artery. Transthoracic and transesophageal echocardiography revealed a mitral annular calcification (MAC) with a mobile component. After treated with heparin, follow-up echocardiography demonstrated a decrease in the size of the mobile component, but not disappeared. Intraoperative findings showed calcified attachment on the posterior mitral valve. This patient was diagnosed as having cardioembolic stroke due to a MAC with a mobile component.

Calcinosis↗
PubMed1999

Combined diffusion and perfusion MRI with correlation to single-photon emission CT in acute ischemic stroke. Ischemic penumbra predicts infarct growth.

BACKGROUND AND PURPOSE: More effective imaging methods are needed to overcome the limitations of CT in the investigation of treatments for acute ischemic stroke. Diffusion-weighted MRI (DWI) is sensitive in detecting infarcted brain tissue, whereas perfusion-weighted MRI (PWI) can detect brain perfusion in the same imaging session. Combining these methods may help in identifying the ischemic penumbra, which is an important concept in the hemodynamics of acute stroke. The purpose of this study was to determine whether combined DWI and PWI in acute (<24 hours) ischemic stroke can predict infarct growth and final size. METHODS: Forty-six patients with acute ischemic stroke underwent DWI and PWI on days 1, 2, and 8. No patient received thrombolysis. Twenty-three patients underwent single-photon emission CT in the acute phase. Lesion volumes were measured from DWI, SPECT, and maps of relative cerebral blood flow calculated from PWI. RESULTS: The mean volume of infarcted tissue detected by DWI increased from 46.1 to 75.6 cm(3) between days 1 and 2 (P<0.001; n=46) and to 78.5 cm(3) after 1 week (P<0.001; n=42). The perfusion-diffusion mismatch correlated with infarct growth (r=0. 699, P<0.001). The volume of hypoperfusion on the initial PWI correlated with final infarct size (r=0.827, P<0.001). The hypoperfusion volumes detected by PWI and SPECT correlated significantly (r=0.824, P<0.001). CONCLUSIONS: Combined DWI and PWI can predict infarct enlargement in acute stroke. PWI can detect hypoperfused brain tissue in good agreement with SPECT in acute stroke.

Acute Disease↗
PubMed2006

Impact of diffusion-weighted MRI-measured initial cerebral infarction volume on clinical outcome in acute stroke patients with middle cerebral artery occlusion treated by thrombolysis.

INTRODUCTION: Magnetic resonance imaging (MRI) may help identify acute stroke patients with a higher potential benefit from thrombolytic therapy. The aim of our study was to assess the correlation between initial cerebral infarct (CI) volume (quantified on diffusion-weighted MRI) and the resulting clinical outcome in acute stroke patients with middle cerebral artery (MCA) (M(1-2) segment) occlusion detected on MRI angiography treated by intravenous/intraarterial thrombolysis. METHODS: Initial infarct volume (V(DWI-I) ) was retrospectively compared with neurological deficit evaluated using the NIH stroke scale on admission and 24 h later, and with the 90-day clinical outcome assessed using the modified Rankin scale in a series of 25 consecutive CI patients. The relationship between infarct volume and neurological deficit severity was assessed and, following the establishment of the maximum V(DWI-I) still associated with a good clinical outcome, the patients were divided into two groups (V(DWI-I) < or =70 ml and >70 ml). RESULTS: V(DWI-I) ranged from 0.7 to 321 ml. The 24-h clinical outcome improved significantly (P=0.0001) in 87% of patients with a V(DWI-I) < or =70 ml (group 1) and deteriorated significantly (P=0.0018) in all patients with a V(DWI-I) >70 ml (group 2). The 90-day mortality was 0% in group 1 and 71.5% in group 2. The 90-day clinical outcome was significantly better in group 1 than in group 2 (P=0.026). CONCLUSION: Clinical outcome could be predicted from initial infarct volume quantified by MRI-DWI in acute CI patients with MCA occlusion treated by intravenous/intraarterial thrombolysis. Patients with a V(DWI-I) < or =70 ml had a significantly better outcome.

Diffusion Magnetic Resonance Imaging↗
PubMed1999

The ischemic penumbra: operationally defined by diffusion and perfusion MRI.

BACKGROUND: Identifying tissue at risk for infarction is important in deciding which patients would benefit most from potentially harmful therapies and provides a way to evaluate newer therapies with regard to the amount of ischemic tissue salvaged. OBJECTIVE: To operationally define and characterize cerebral tissue at risk for stroke progression. METHODS: We retrospectively selected 25 patients with an acute onset of a hemispheric stroke from our database who had undergone a combination of two diffusion-weighted MRI studies and a perfusion-weighted MRI study. We applied a logistic regression model using maps of the relative mean transit time and relative cerebral blood flow (rCBF) as well as three different maps of the relative cerebral blood volume (rCBV) to predict an operationally defined penumbra (region of mismatch between the diffusion lesion on day 1 and its extension 24 to 72 hours later). RESULTS: Maps of the rCBF and initial rCBV were significant predictors for identifying penumbral tissue. Our operationally defined penumbral region was characterized by a reduction in the initial rCBV (47% of contralateral control region [CCR]), an increase (163% of CCR) in the total rCBV, and a reduction (37% of CCR) in the rCBF, whereas the operationally defined ischemic core showed a more severe reduction in the rCBF (12% of CCR) and in the initial rCBV (19% of CCR). CONCLUSION: These MR indexes may allow the identification and quantification of viable but ischemically threatened cerebral tissue amenable to therapeutic interventions in the hyperacute care of stroke patients.

Aged↗
PubMedDate not supplied

Diffuse dural gadolinium MRI enhancement associated with bilateral chronic subdural hematomas.

Chronic subdural hematomas (CSDHs) typically present with cognitive dysfunction and a history of trauma. Localized dural enhancement on postcontrast MRI scans associated with the surrounding membrane has been described in CSDH. We present an 83-year-old man with rapidly progressing cognitive dysfunction 4 weeks after head trauma related to a fall. MRI showed CSDHs, which in addition to localized dural gadolinium enhancement, showed a marked diffuse, symmetric, contiguous pachymeningeal enhancement of the supratentorial and infratentorial intracranial dural mater. Meningeal biopsy failed to disclose an infectious or neoplastic cause of the enhancement and instead showed fibrocollagenous change. We conclude that diffuse dural enhancement on MRI scans associated with CSDH cause does not necessarily indicate a superimposed process such as infection or malignancy. CSDH should be considered in the differential diagnosis of diffuse dural enhancement, especially when supported by appropriate clinical findings.

Accidental Falls↗
PubMed2001

Segmenting brain white matter, gray matter and cerebro-spinal fluid using diffusion tensor-MRI derived indices.

Based on its ability to provide quantitative information about tissue microstructure, diffusion tensor magnetic resonance imaging (DT-MRI) might be a valuable approach to improve the reliability of segmentation of the various brain tissues. In this study, a fully automated and easy-to-implement technique based on 2D histogram analysis of DT-MRI derived images was used to segment white and gray matter of the brain from 10 healthy subjects (aged = 27-56 years). The results obtained with this novel segmentation strategy were compared to those achieved by two experienced observers using an operator-dependent segmentation on the dual-echo scans. Visual inspection of the segmented tissues from a third senior observer disclosed that the automated technique worked properly on all images from all subjects and was more accurate than the human raters in defining thalamus white and gray matter portions as well as in tissue classification at the external brain edge. In addition, this segmentation technique resulted in an average gray/white matter ratio similar to that reported by post-mortem assessment. The application of the operator-dependent segmentation strategy was extremely time-consuming and the two observers achieved poorly reproducible results. Segmenting brain white and gray matter using information from DT-MRI proved to be an accurate approach with the potential for improving the understanding of the pathophysiology of many neurologic conditions.

Anisotropy↗
PubMed2005

Intravenous administration of Gd-DTPA prior to DWI does not affect the apparent diffusion constant.

MRI measurements of water diffusion and blood perfusion are increasingly used for the evaluation of organ functionality and tissue viability (e.g., in tumors). While diffusion-weighted imaging is performed without contrast agents, measurement of blood perfusion is normally performed based on the administration of paramagnetic substances such as gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Simultaneous measurements of these two parameters are often preferred. However, it may be argued that Gd-DTPA causes constriction of small blood vessels or alters hemodynamic parameters such as blood viscosity, thereby corrupting subsequent measurements of the apparent diffusion constant (ADC). The objective of the current study was to investigate the possible changes in the ADC in tumors following intravenous administration of 0.2 and 0.4 mmol/kg of Gd-DTPA in mice. The study was conducted with C3H mouse mammary carcinomas inoculated in the right foot of the animal subjects. The results were compared with findings in a sham group, demonstrating that Gd-DTPA had no significant impact on the ADC as measured in a 7-T animal system.

Analysis of Variance↗
PubMed1995

Ischemic and hemorrhagic brain stem lesions mimicking diabetic ophthalmoplegia.

Two patients with diabetes mellitus, one of them with an isolated third cranial nerve palsy and the other with an isolated sixth cranial nerve palsy, are presented. MRI investigations including diffusion-weighted MRI revealed a small ischemic brain stem lesion in the former and a small hemorrhagic brain stem lesion in the latter. In the former case wallerian degeneration of the nerve fascicle within the mesencephalon was also detected. These cases indicate that vascular accidents of the brain stem may masquerade as fascicular or infranuclear disturbance of the oculomotor or abducens nerve; therefore, it is important to include brain stem lesions into the differential diagnosis of isolated ophthalmoplegia. Thorough investigation by MRI including diffusion-weighted MRI is helpful for correct diagnosis.

Abducens Nerve↗
PubMed1995

Minor neurological and perceptuo-motor deficits in children with congenital muscular dystrophy: correlation with brain MRI changes.

Diffuse white matter changes on magnetic resonance imaging (MRI) have been a consistent feature in some children with the "pure" form of congenital muscular dystrophy (CMD) in which there are no structural changes in the brain or severe mental retardation. The aim of this study was to assess fine motor and perceptuo-motor abilities in children with CMD with and without MRI changes. Twenty-two children with "pure" CMD were investigated with a standard neurological examination and a battery of tests (Manual dexterity from the Movement ABC, test of visual-motor integration, Zurich Neuromotor test) which have already been used to detect minor neurological signs related to white matter changes. The cohort was then divided in two groups for analysis depending on the presence or the absence of diffuse white matter changes. A significant difference was found for all the tests between the group of the CMD children with normal MRI and the group with diffuse white matter changes. The manual dexterity and the Zurich Neuromotor tests showed a greater sensitivity than the test of visual-motor integration, which had some false negatives. It is of interest that in the group with diffuse white matter changes the presence of contractures or weakness did not seem to affect the quality of the performance; all these children scored abnormally on the test, irrespective of the severity or the extent of contractures and weakness. In contrast, in children with normal MRI severe contractures and weakness did affect the performances. Our results demonstrate that perceptuo-motor difficulties and minor neurological soft signs are a consistent feature in CMD children with diffuse MRI changes but not with normal MRI.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2005

[Asymmetric cortical high signal on diffusion weighted-MRI in a case of Creutzfeldt-Jakob disease].

High signal in the cerebral cortex and/or basal ganglia on diffusion-weighted magnetic resonance imaging (DW-MRI) has been described as a good diagnostic marker for sporadic Creutzfeldt-Jakob disease (sCJD). We report a case of sCJD with atypical clinical evolution and unusual DW-MRI findings. A 53-year-old man was seen with a 2-year history of a rapidly progressive dementia and cerebellar ataxia. Cerebrospinal fluid analysis, including the test for 14-3-3 protein, was normal. EEG did not show periodic activity. However, DW-MRI showed gyriform hyperintensity involving practically the entire cortical ribbon of the left hemisphere, whilst being limited to the posterior cingulate gyrus in the right hemisphere. DNA analysis showed no mutations or insertions in the prion protein gene, and homozigozity for methionine in codon 129. A subsequent brain biopsy confirmed the diagnosis of CJD. Thus, high signal on DW-MRI may be limited to the cerebral cortex and may present a very asymmetric distribution in sCJD.

Biomarkers↗
PubMed2005

Coregistration of dynamic contrast enhanced MRI and broadband diffuse optical spectroscopy for characterizing breast cancer.

A hand-held scanning probe based on broadband Diffuse Optical Spectroscopy (DOS) was used in combination with dynamic contrast enhanced MRI (DCE-MRI) to quantitatively characterize locally-advanced breast cancers in six patients. Measurements were performed sequentially using external fiducial markers for co-registration. Tumor patterns were categorized according to MRI morphological data, and 3D DCE-MRI slices were converted into a volumetric matrix with isotropic voxels to generate views that coincided with the DOS scanning plane. Tumor volume and depth at each DOS measurement site were determined, and a tissue optical index (TOI) that reflects both angiogenic and stromal characteristics was derived from broadband DOS data. In all six cases, optical scans showed significant TOI contrast corresponding to MRI morphological information. Sharp TOI peaks were recovered for well-circumscribed masses. A reduction in TOI was found inside a tumor with a necrotic center. A broadened peak was observed for a diffuse tumor pattern, and an inflammatory septal case provided two TOI peaks that correlated qualitatively with MRI enhancement. These results provide qualitative confirmation of the common signal origin and complementary information content that can be achieved by combining optical and MR imaging for breast cancer detection and clinical management.

Adult↗
PubMed1998

Diffusion and perfusion MRI, measurements of acute stroke events and outcome: present practice and future hope.

The morphological, metabolic and functional changes of brain ischaemia can be studied using various MRI methods. These are readily available should the early visualisation of affected territories be needed. Morphological changes include the depiction of oedema on T1- and T2-weighted images, and metabolic changes are reflected on magnetic resonance spectroscopy. Functional changes reflect haemodynamic failure seen on diffusion- and perfusion-weighted imaging. Modelling of behaviour of T2 and diffusion changes could predict the histological outcome of affected tissue regarding cell recovery on necrosis. In addition, the combination of diffusion and perfusion MRI offers a potential prognostic value.

Acute Disease↗
PubMed2003

Combined diffusion and strain MRI reveals structure and function of human myocardial laminar sheets in vivo.

The mechanism of ventricular thickening in normal humans was investigated using in vivo MRI. The hypothesis that myocardial laminar sheets contribute to ventricular thickening predominantly via sheet shear and sheet extension, as previously found invasively in canine studies at particular ventricular sites, was tested. In normal human subjects, registered images of myocardial sheet architecture and strain at the mid-left ventricle (mid-LV) at mid-systole were acquired with diffusion and strain MRI. Sheet function was analyzed by computing myocardial strain in the local fiber-sheet coordinates. In general, myocardial sheets contribute to ventricular thickening through all three cross-fiber strain components: sheet shear, sheet extension, and sheet-normal thickening (previously undocumented). Each of these components demonstrated substantial spatial heterogeneity, with sheet shear and sheet extension usually predominant in the anterior free wall, and sheet-normal thickening predominant near the right ventricular (RV) insertions. However, considerable intersubject variability was also found. In all cases, the contributions to thickening of fiber strains were small. Sheet function in normal humans was found to be heterogeneous and variable, contrasting with the uniform and symmetric ventricular patterns of fiber shortening and wall thickening. The study demonstrates that noninvasive NMR imaging is a promising tool for investigations of myocardial sheet architecture and function, and is particularly suited to the evident complexity of this field of study.

Diastole↗
PubMed2005

Diffusion-weighted and perfusion MRI demonstrates parenchymal changes in complex partial status epilepticus.

Diffusion-weighted MRI (DWI) and perfusion MRI (PI) have been mainly applied in acute stroke, but may provide information in the peri-ictal phase in epilepsy patients. Both transient reductions of brain water diffusion, namely a low apparent diffusion coefficient (ADC), and signs of hyperperfusion have been reported in experimental and human epilepsy case studies. We studied 10 patients with complex partial status epilepticus (CPSE) with serial MRI including DWI and PI. All patients showed regional hyperintensity on DWI, and a reduction of the ADC in (i) the hippocampal formation and the pulvinar region of the thalamus (six out of 10 patients), (ii) the pulvinar and cortical regions (two out of 10), (iii) the hippocampal formation only (one out of 10), and (iv) the hippocampal formation, the pulvinar and the cortex (one out of 10). In all patients a close spatial correlation of focal hyperperfusion with areas of ADC/DWI change was present. In two patients hyperperfusion was confirmed in additional SPECT (single photon emission computed tomography) studies. All patients received follow-up MRI examinations showing partial or complete resolution of diffusion and perfusion abnormalities depending on the length of the follow-up interval. The clinical course, EEG and SPECT results all indicate that MRI detected changes related to prolonged epileptic activity. Combined PI and DWI can visualize haemodynamic and tissue changes after CPSE in the hippocampus, thalamus and affected cortical regions.

Adult↗
PubMed2002

Mohr diagram representation of anisotropic diffusion tensor in MRI.

With current approaches, it is difficult to visually comprehend the complete information contained in a diffusion tensor (DT) measured from a microscopically heterogeneous biological tissue. Therefore, in this work the Mohr diagram is introduced to graphically display the key aspects of DTs and to interpret the underlying anisotropy, both qualitatively and quantitatively. Specifically, the mathematical basis for the construction of the Mohr diagram from the elements of DTs is described, the merits of the approach are illustrated with examples of DTs reported for various biological tissues, and the results are discussed in the context of relating the diffusion anisotropy to the tissue structures.

Anisotropy↗
PubMed1996

A serial CT scan and MRI verification of diffuse cerebrospinal gliomatosis: a case report with stereotactic diagnosis and radiological confirmation.

Gliomatosis cerebri is an infrequent tumor of neuroepithelial origin presenting with deterioration of cognitive functions, behavioral and mental changes, motor weakness, headache, and seizures. Laboratory data are unconclusive. MRI appears to be the imaging modality of choice and mainly reveals a bilateral and diffuse infiltration of midline adjacent brain structures whose anatomical configuration remain intact. MRI- or CT-guided stereotactic biopsy is advised as the diagnostic procedure in suspected cases. A 9-year-old girl with diffuse cerebrospinal gliomatosis, investigated with sequential cranial CT scans, and MRI-verified spinal cord involvement is reported, and the corresponding literature is reviewed.

Biopsy↗
PubMed2002

Perfusion MRI abnormalities in the absence of diffusion changes in a case of moyamoya-like syndrome in neurofibromatosis type 1.

We report on a 12-year-old boy with neurofibromatosis type 1 who suffered a transient ischemic attack. Angiography revealed occlusion of intracranial arteries, moyamoya vessels and leptomeningeal collaterals. The conventional T2-weighted and the diffusion-weighted MRI images demonstrated no pathology. Dynamic first-pass postgadolinium T2* perfusion-weighted MRI depicted altered hemodynamics in the vascular territory of the left middle cerebral artery, which defined this region as ischemic tissue at risk. The patient suffered a repeat transient ischemic attack 5 days later.

Cerebral Angiography↗