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 1,513 records · Page 84Linked to original sources
PubMed1997

Spontaneous intracranial hypotension: clinical and magnetic resonance imaging characteristics.

The syndrome of spontaneous intracranial hypotension (SIH) is an uncommon cause of postural headache. We describe three patients with classical low pressure headache associated with low CSF pressure, one of whom presented with sudden deafness and another with a unilateral VIth nerve palsy. Initial magnetic resonance imaging (MRI) scans revealed bilateral diffuse subdural fluid collections in all three cases. Follow up MRI scans performed on two patients at 6 months demonstrated partial resolution of the subdural collections but persistent striking meningeal enhancement despite clinical recovery. These findings differ from previous reported cases wherein clinical resolution of postural symptoms was preceded or closely followed by resolution of the MRI changes.

Adult↗
PubMed1999

Tracking neuronal fiber pathways in the living human brain.

Functional imaging with positron emission tomography and functional MRI has revolutionized studies of the human brain. Understanding the organization of brain systems, especially those used for cognition, remains limited, however, because no methods currently exist for noninvasive tracking of neuronal connections between functional regions [Crick, F. & Jones, E. (1993) Nature (London) 361, 109-110]. Detailed connectivities have been studied in animals through invasive tracer techniques, but these invasive studies cannot be done in humans, and animal results cannot always be extrapolated to human systems. We have developed noninvasive neuronal fiber tracking for use in living humans, utilizing the unique ability of MRI to characterize water diffusion. We reconstructed fiber trajectories throughout the brain by tracking the direction of fastest diffusion (the fiber direction) from a grid of seed points, and then selected tracks that join anatomically or functionally (functional MRI) defined regions. We demonstrate diffusion tracking of fiber bundles in a variety of white matter classes with examples in the corpus callosum, geniculo-calcarine, and subcortical association pathways. Tracks covered long distances, navigated through divergences and tight curves, and manifested topological separations in the geniculo-calcarine tract consistent with tracer studies in animals and retinotopy studies in humans. Additionally, previously undescribed topologies were revealed in the other pathways. This approach enhances the power of modern imaging by enabling study of fiber connections among anatomically and functionally defined brain regions in individual human subjects.

Brain↗
PubMed2000

[Recent progress in diagnostic imaging of cerebrovascular diseases].

The recent development of the neuroimaging modalities has enabled early detection of abnormal cerebral perfusion due to arterial steno-occlusive lesions by means of single photon emission computed tomography (SPECT) and perfusion weighted images of magnetic resonance imaging (MRI), early detection of ischemic brain damage by means of diffusion weighted image of MRI, and lacunar infarction and hemorrhage by means of T 2 * weighted images. These methods are now available for the clinical practice. The imaging technique further visualized various pathological states associated with cerebrovascular disease. The fiber tracts in the white matter and its disruption can be evaluated by anisotropy imaging of MRI. Selective neuronal necrosis after mild ischemia was detected by radioactive tracers specifically bound to neurons. These progress may contribute to uncover the pathophysiology of cerebrovascular diseases and to treat the patients.

Cerebrovascular Circulation↗
PubMed1999

Diffusion-weighted single-shot line scan imaging of the human brain.

Single-shot line scan imaging (LSI) was adapted to diffusion-weighted (DW) MRI by replacing the initial 90 degrees radiofrequency pulse of the underlying high-speed stimulated echo sequence by a DW spin-echo preparation period. Implementation on a 2. 0 T whole-body MRI system yielded DW images of the human brain with b factors of 750 s mm(-2) and total imaging times of about 500 ms either for a single slice at 1.5 x 3.0 x 6 mm(3) resolution or simultaneously for up to seven slices at 3.75 x 3.75 x 8 mm(3) resolution. Isotropic DW images and maps of the trace of the diffusion tensor were calculated from four scans with different combinations of three orthogonal diffusion gradients. DW LSI combines high speed with robustness against image artifacts caused by motion (no phase ghosting) and tissue susceptibility differences (no signal losses, no geometric distortions). Because the latter is an important advantage over echo-planar imaging, DW LSI may find useful applications despite a limited signal-to-noise ratio. Magn Reson Med 42:772-778, 1999.

Brain↗
PubMed1996

[Preoperative diagnosis and surgical treatment for lymph node metastasis in gastric cancer].

In order to clarify the preoperative diagnostic ability for lymph node metastasis, images from magnetic resonance imaging (MRI), computed axial tomography (CT) and ultrasonography (US) were evaluated in 200 gastric cancer patients. The long-term results of 2,000 gastric cancer patients who had undergone gastrectomy were also studied to evaluate the effectiveness of lymphadenectomy. 1) Preoperative diagnosis of lymph node metastasis: The detection rate of lymph nodes around the stomach was 34.1% in MRI, 18.7% in CT and 5.0% in US. The incidence of metastasis was over 80% when the size of lymph node imaged was 1.5 cm and over, against 25% for lymph nodes less than 1.0 cm in size. The detection rate of metastatic lymph node according to the mode of metastasis was 88% for macro-nodular type, 66% for micro-nodular type, 57% for diffuse type in MRI, 70, 41 and 15% in CT, and 38, 3, 0% in US, respectively. Therefore, MRI was most useful for detecting metastatic lymph node preoperatively. 2) Long-term results of gastric cancer with lymph node metastasis: The cumulative 5-year survival rate was 84.2% in n0, 56.1% in n1, 33.7% in n2, 16.5% in n3, and 5.1% in n4 patients. Satisfactory long-term results were obtained for n2 or less patients without serosal invasion. Moreover, by paraaortic lymph node dissection, the cumulative 5-year survival rate in n4 patients was 16.4% (27.8% for cases with radical resection). These results showed the effectiveness of lymph node dissection for gastric cancer.

Follow-Up Studies↗
PubMed2004

Magnetic resonance imaging improves detection of intracerebral hemorrhage over computed tomography after intra-arterial thrombolysis.

BACKGROUND AND PURPOSE: Unenhanced CT is routinely performed after intra-arterial (IA) thrombolysis. The presence of residual contrast causing staining of injured brain may mimic intracerebral hemorrhage (ICH). We evaluated MRI with diffusion-weighted imaging (DWI) and susceptibility-weighted imaging (SWI) for detection of ICH after IA thrombolysis, specifically in equivocal areas of hyperdensity seen on postprocedure CT, to help guide the decision to use anticoagulation or antiplatelet therapy after the IA thrombolysis. METHODS: We performed a retrospective analysis of 15 consecutive patients who underwent IA thrombolysis for acute stroke between September 2000 and March 2003. Inclusion criteria required an immediate postprocedure CT with a questionable hyperdensity and, within the next 48 hours, an MRI with DWI and/or SWI. RESULTS: All patients had CT regions of hyperdensity that were equivocal for the presence of ICH. All patients subsequently underwent DWI, and 11 also underwent SWI. Eleven of 15 patients had magnetic susceptibility-induced hypointensity in DWI hyperintensity regions, signifying the presence of acute deoxyhemoglobin. Nine of these patients also received SWI, which confirmed the presence of blood within these regions. Follow-up CT on all 11 patients confirmed ICH. In the 4 patients without DWI susceptibility change, 0 were found to have ICH on either SWI (performed in 2 patients) or follow-up CT. MRI reliably detected the presence of ICH in all patients, whereas CT failed to differentiate contrast staining from hemorrhage in 4 of the 15 patients. CONCLUSIONS: MRI is an effective means to detect the presence of blood within an equivocal region on post-IA thrombolysis CT. This may influence the decision to use anticoagulation or antiplatelet therapy.

Adult↗
PubMed2003

Effect of incomplete (spontaneous and postthrombolytic) recanalization after middle cerebral artery occlusion: a magnetic resonance imaging study.

BACKGROUND AND PURPOSE: Early reperfusion is one of the best predictors of good outcome after acute middle cerebral artery (MCA) occlusion. The purpose of this study was to analyze the frequency and relevance of incomplete recanalization for tissue and clinical outcome. METHODS: From a larger acute stroke database (Kompetenznetzwerk Schlaganfall B5), all patients (n=82) with MCA main stem occlusion (excluding carotid T-occlusions) were selected. These patients had received a multiparametric stroke MRI protocol including diffusion- and perfusion-weighted imaging (DWI, PWI) and MR angiography (MRA) within 6 hours after symptom onset, at day 1 and after 1 week. Recanalization status was determined with MRA on day 1 (according to Thrombolysis In Myocardial Infarction flow grades) and used to group patients into those with persistent occlusion (0) or minimal (1), partial (2), or complete (3) recanalization. RESULTS: Incomplete recanalization according to MRI criteria was found in 39 patients (grade 1: n=20; grade 2: n=19), complete recanalization in 10, and persistent occlusion in 33. There was no statistically significant difference in any of the clinical (National Institutes of Health Stroke Scale score) or MRI baseline parameters (DWI lesion, PWI deficit, mismatch volume, mismatch ratio). However, lesion growth was smaller in patients with recanalization (even in patients with only minimal recanalization) and outcome was related to the degree of recanalization (mean modified Rankin score at 90 days: 3.36, 2.70, 1.79, and 1.44 for the groups with no, minimal, partial, and complete recanalization, respectively). Both incomplete and complete recanalization was more frequent in patients receiving thrombolysis. CONCLUSIONS: Incomplete recanalization on day 1 is a frequent MR finding after MCA main stem occlusion, indicating a more favorable clinical course than persistent occlusion. MR indicators of early recanalization could be useful surrogates of efficacy in thrombolytic trials.

Adult↗
PubMed2004

Progressive change in primary progressive multiple sclerosis normal-appearing white matter: a serial diffusion magnetic resonance imaging study.

In spite of marked disability, patients with primary progressive multiple sclerosis (PPMS) display smaller lesion volumes on conventional magnetic resonance imaging (MRI) compared with other forms of multiple sclerosis (MS). Hence, damage to the normal-appearing brain tissue (NABT) may play an important role in explaining the pathogenesis of disability in PPMS. Diffusion-weighted MRI (DW-MRI) probes water diffusion in vivo that can be altered by pathologic changes. Using DW-MRI we investigated diffusion in the NABT of 15 patients with PPMS over one year. The average apparent diffusion coefficient (ADCav) was measured in 10 regions of interest located in the normal-appearing thalamus and the normal-appearing white matter (NAWM). Six healthy subjects served as a reference. In contrast to healthy subjects, patients with PPMS showed an increment within 12 months of the ADCav in NAWM which was associated with an increase of the T2- and T1-lesion volumes. The ADCav in frontal NAWM was associated with disability as measured by the MS Functional Composite Measure. Serial DW-MRI depicts progressive changes in the NAWM of patients with PPMS. Our preliminary findings suggest that the processes causing structural damage in NAWM and lesions in patients with PPMS are partially linked and that changes of water diffusion in NAWM depicted by DW-MRI are clinically relevant.

Adult↗
PubMed2001

Diagnostic value of apparent diffusion coefficient hyperintensity in selected patients with acute neurologic deficits.

BACKGROUND AND PURPOSE: A pattern of decreased intensity on apparent diffusion coefficient (ADC) maps is useful in the early detection of ischemic brain injury. Less information exists with regard to patients with acute neurologic deficits in whom there is abnormal conventional magnetic resonance imaging (MRI) and increased ADC intensity. METHODS: The authors identified 13 patients with acute neurologic deficits who underwent diffusion MRI and had calculated ADC maps demonstrating hyper-intensity in regions characterized by computed tomography hypodensity and MRI T2 hyperintensity. The initial and follow-up imaging characteristics and clinical syndromes were recorded. RESULTS: Clinical syndromes included hypertensive encephalopathy, posterior leukoencephalopathy, hyperperfusion following carotid endarterectomy, venous sinus thrombosis, HIV encephalopathy, and brain tumor. Diffusion-weighted imaging (DWI) was hyperintense in 3 of 13 patients, isointense in 4 of 13 patients, heterogeneous in 3 of 13 patients, and hypointense in 3 of 13 patients. The ADC values in these regions were significantly higher than those in control regions (P < .0001). At early follow-up, MRI abnormalities resolved completely in 3 of 13 patients and partially in 9 of 13 patients. MRI abnormalities were unchanged in 1 patient. CONCLUSIONS: In the evaluation of patients with acute neurologic deficits, ADC hyperintensity may identify a subset of patients with vasogenic edema of nonischemic etiology. Frequently, these conditions are potentially reversible if appropriately managed. DWI and conventional images alone are not sufficient to identify these neurologic conditions.

Acute Disease↗
PubMed1995

Leukoencephalopathy with swelling and a discrepantly mild clinical course in eight children.

An identical syndrome of cerebral leukoencephalopathy and megalencephaly with infantile onset was discovered in 8 children, including 2 siblings. Neurological findings were initially normal or near normal, despite megalencephaly and magnetic resonance imaging (MRI) evidence of severe white matter affection. Slowly progressive ataxia and spasticity developed, while intellectual functioning was preserved for years after onset of the disorder. MRI characteristics included diffuse abnormality in signal intensity and swelling of the cerebral hemispheral white matter with cyst-like spaces in the frontoparietal and anterior-temporal subcortical areas. MR spectra were relatively mildly abnormal. Screening for inborn errors, especially those that cause either megalencephaly or white matter disease or both was negative. A distinguishing feature of the present disorder is the apparently severe abnormality of the cerebral white matter as demonstrated by MRI, which contrasts with the remarkably slow course of functional deterioration.

Adolescent↗
PubMed2006

Radiological assessment of Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease is a rare fatal neurodegenerative disorder, characterized by rapidly progressive dementia and neurological signs. There is a need for early and accurate clinical diagnosis in order to exclude any treatable disorder. Additionally, it is of public interest to differentiate the sporadic form of the disease from the variant CJD type (vCJD), which is probably transmitted from cattle infected with bovine spongiform encephalopathy (BSE). High signal in the striatum on T2-weighted, FLAIR and diffusion weighted (DW) MRI as well as cortical high signal in FLAIR and DW MRI are the classical findings in sCJD. The "pulvinar sign", defined as high signal in the pulvinar thalami that is brighter than potential additional high signal in the basal ganglia, is considered pathognomonic for vCJD.

Animals↗
PubMed2000

A case of leukoencephalopathy with vanishing white matter.

A 6-year old Turkish boy with a recently defined entity: "leukoencephalopathy with vanishing white matter" is described. He was born to consanguinous parents. His psychomotor development was normal till he first presented with fever and generalized tonic-clonic seizures at the age of 2.5, followed by rapid motor and mental deterioration. Decerebrate posture and marked spasticity subsequently developed. The initial MRI examination showed diffuse involvement of white matter, including subcortical U-fibers, with signal intensity parallel to CSF on all sequences. The white matter appeared swollen. The ventricles were slightly enlarged and there was cavum septi pellucidi et vergae. The posterior crus of the internal capsule, external and extreme capsules were affected. Cerebellar hemispheres and vermis showed atrophy. The involvement pattern of brainstem was noteworthy in that pontine tegmentum and cruri cerebri were affected. Follow-up MRI obtained after three years did not show any interval change. Brain biopsy showed thinned cortex with relatively preserved cortical layering and neuronal structure. There was rarefaction of the white matter with cystic degeneration. Fibrillary gliosis and increased number of oligodendroglial cells were observed within the cerebral white matter.

Biopsy↗
PubMed2005

Atypical MRI findings in Canavan disease: a patient with a mild course.

Canavan disease is a severe, progressive leukodystrophy with an autosomal recessive inheritance, caused by aspartoacylase (ASPA) deficiency. The characteristic MRI features include diffuse, symmetrical white matter degeneration in the subcortical areas, with bilateral involvement of the globus pallidus. Proton magnetic resonance spectroscopy of the brain shows an increase in the concentration of N-acetylaspartic acid (NAA). The altered NAA metabolism has been traced to mutations in the gene encoding ASPA, located on chromosome 17 (17p13-ter). We present here a patient with a mild form of Canavan disease confirmed with the absent ASPA activity, atypical MRI findings, related to compound heterozygosity for a missense mutation, p.Tyr288Cys, and the known pan-European mutation, the p.Ala305Glu.

Aspartic Acid↗
PubMed2001

Acute stroke patterns in patients with internal carotid artery disease: a diffusion-weighted magnetic resonance imaging study.

BACKGROUND AND PURPOSE: Diffusion-weighted (DW) MRI is a sensitive method that facilitates early stroke pattern identification. There are limited data about the influence of stenosis grade on the development of particular stroke patterns in internal carotid artery (ICA) disease. We therefore investigated the lesion patterns on DW MRI in acute stroke patients with ICA disease. METHODS: DW MRI was analyzed in 102 consecutive acute stroke patients with different degrees of ipsilateral ICA disease. Patients were assigned to 1 of 5 observed lesion patterns: (1) territorial ischemia, (2) subcortical ischemia without or (3) with embolus fragmentation, (4) disseminated lesions in distal cortical regions, and (5) multiple lesions in hemodynamic risk zones. In addition, perfusion-weighted (PW) MRI and MR angiography information was included in the assessment. RESULTS: All patterns were observed in the different stages of ICA disease. Half of the patients with high-grade or subtotal stenosis had lesions in hemodynamic risk zones. Territorial stroke occurred in 47.6% of patients with ICA occlusion. Statistical analysis showed a significant relationship between the degree of stenosis and the observed stroke pattern (P=0.001). In 77.8% of patients exhibiting high-grade ICA stenosis, subtotal stenosis, or occlusion, the perfusion lesion was larger than the diffusion lesion (PW/DW mismatch). CONCLUSIONS: Although in the individual patient any of the infarct patterns may occur, in statistical terms the incidence of a particular stroke pattern is clearly dependent on the degree of stenosis.

Aged↗
PubMed2006

[Diffusion and perfusion MR imaging in cerebral lymphomas].

Because of the increasing incidence of cerebral lymphoma, it is critical for patient management to recognize the MR features of this disease. We present the characteristic morphological and functional MRI features of this tumor. The findings on MRI studies, including morphological, diffusion and perfusion imaging, performed in 9 biopsy-proven cases of cerebral lymphoma with 13 lesions are presented and analyzed, and are discussed in comparison with published literature data. All patients underwent diffusion-weighted imaging with a single shot echo-planar pulse sequence. Dynamic susceptibility-contrast MRI was performed using a T2*-weighted gradient-echo echo-planar sequence after intravenous injection of chelates of gadolinium at the rate of 6 ml/s and a temporal resolution of 1 second. All cases of cerebral lymphoma appeared hypointense or isointense on T1-weighted images and in 75% of cases iso- or hypointense on T2-weighted images. All lesions enhanced except one in a patient receiving steroid therapy. On diffusion-weighted images, tumours were hyperintense with normal or decreased ADC values (0.717+/-0.152.10-3 mm2/sec, range: 0.550-1.014) and an ADC ratio tumour/normal white matter of 0.974+/-0.190 (range: 0.768-1.410). On perfusion, the signal intensity-time curve of each tumour showed a characteristic type of curve with a significant increase of the signal intensity above the baseline and a low maximum relative cerebral blood volume ratio (rCVBmax) of 1.43+/-0.64 (0.55-2.62). Due to their higher cellularity, the lack of neoangiogenesis, and the increased permeability of the blood-brain barrier related to the infiltration of blood vessels wall by lymphomatous cells, cerebral lymphoma presents characteristic diffusion and perfusion MRI features that should be useful for diagnosis and patient follow-up.

Adult↗
PubMed1999

Comparison of multiple sclerosis clinical subgroups using navigated spin echo diffusion-weighted imaging.

The apparent diffusion coefficient (ADC) of tissue provides an indication of the size, shape, and orientation of the water spaces in tissue. Thus, pathologic differences between lesions in multiple sclerosis (MS) patients with different clinical courses may be reflected by changes in ADC measurements in lesions and white matter. Twelve healthy subjects and 35 MS patients with a relapsing-remitting (n = 10), benign (n = 8), secondary progressive (n = 8) and primary progressive (n = 9) clinical course were studied. T2-weighted and post-gadolinium T1-weighted images were obtained using a 1.5 T Signa Echospeed magnetic resonance imaging (MRI) system. Diffusion-weighted imaging was implemented using a pulsed gradient spin echo (PGSE) sequence with diffusion gradients applied in turn along three orthogonal directions in order to obtain the average apparent diffusion coefficient (ADCav). Navigator echo correction and cardiac gating were used to reduce motion artifact. ADC maps were derived using a two point calculation based on the Stejskal-Tanner formula. Diffusion anisotropy was estimated using the van Gelderen formula to calculate an anisotropy index. MS lesions had a higher ADC and reduced anisotropy compared with normal appearing white matter. Highest ADC values were found in gadolinium enhancing lesions and non-enhancing hypointense lesions on T1-weighted imaging. MS white matter had a slightly higher ADC and lower anisotropy than white matter of healthy subjects. Lesion and white matter ADC values did not differ between patients with different clinical courses of MS. There was no correlation between lesion ADC and disability. Diffusion-weighted imaging with measurement of ADC using the PGSE method provides quantitative information on acute edematous MS lesions and chronic lesions associated with demyelination and axonal loss but does not distinguish between clinical subtypes of MS.

Brain↗
PubMed2003

Diffusion-weighted imaging predicts postoperative persistence in meningioma patients with peritumoural abnormalities on magnetic resonance imaging.

OBJECTIVE: While diffusion-weighted magnetic resonance imaging (MRI) has been used to study malignant brain tumours, this modality has not been used to study MRI abnormalities surrounding meningiomas. METHODS: We examined intensity and apparent diffusion coefficient (ADC) on diffusion weighted imaging (DWI) for predicting postoperative persistence of MRI abnormalities surrounding meningiomas as well as characterizing the tumours. RESULTS: Of 36 meningiomas who underwent gross total resection, 27 (75%) showed hyperintensity on DWI at b=1100s/mm2. No atypical meningiomas were hypointense on DWI. Of the 26 supratentorial meningiomas, 18 (69.0%) had associated MRI abnormality. No significant correlation was seen between tumour intensity on DWI and existence of surrounding MRI abnormality. Meningothelial meningiomas showed a relatively low prevalence of MRI abnormalities surrounding tumour (30%). Of 11 patients who underwent sequential MRI, all MRI abnormalities surrounding tumour showing isointensity and high ADC on preoperative DWI disappeared after surgery (from 3 weeks to 10 months). All MRI abnormalities surrounding tumour showing hyperintensity and low ADC on preoperative DWI persisted on final follow-up MRI (from 6 months to 20 months). CONCLUSION: The postoperative course of MRI abnormality surrounding tumour might be predictable from the intensity and ADC on preoperative DWI. Since MRI abnormalities associated with meningiomas can cause preoperative neurologic deficits. We hypothesise that abnormalities with restricted diffusion will be more likely to be associated with a preoperative deficit, and more likely to remain after removal of the causative meningioma.

Adult↗
PubMed2002

CADASIL syndrome in a large Turkish kindred caused by the R90C mutation in the Notch3 receptor.

Mutations in the Notch3 gene are the cause of the autosomal dominant disorder CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). The CADASIL is an adult-onset neurologic disorder (average age of onset is 45 years) characterized by recurrent strokes and dementia. Clinical features combined with cerebral magnetic resonance imaging (MRI), showing a diffuse leukoencephalopathy with subcortical infarcts in the basal ganglia and white matter, are highly contributive to the diagnosis. We present a Turkish family with CADASIL, in which 12 individuals in four generations were affected showing the typical clinical features of recurrent strokes. Mutation analysis of the Notch3 receptor gene identified the recently described R90C mutation in the N-terminal part of the gene in affected individuals. Interestingly, migraine without aura was found as an initial symptom of the disease in two young mutation carriers (22 and 25 years, respectively), who did not show any additional clinical features or any MRI abnormalities. This indicates that migraine without aura in the absence of MRI abnormalities may represent an early initial symptom of CADASIL, which is difficult to diagnose in the absence of molecular diagnosis. Therefore, the used molecular screening method for Notch3 mutations provides a rapid and accurate diagnostic tool in addition to the standard diagnostic procedures.

Brain↗