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PubMed2005

Risk factors for periprocedural complications in carotid artery stenting without filter protection: A serial diffusion-weighted MRI study.

INTRODUCTION: In high-grade stenosis, carotid artery stenting (CAS) may be chosen as an alternative to carotid surgery. Ischemic periprocedural complications may be documented best with diffusion-weighted MRI (DWMRI). In this prospective study serial DW-MRI and color-coded duplex sonography (CCDS) were used to identify carotid stenosis, which is associated with an increased risk of ischemic events due to CAS. METHODS: High resolution DW-MRI were performed in 74 out of 77 patients before and after CAS. All MRI scans were analyzed in a blinded manner. With CCDS each carotid stenosis was evaluated according to the grade, length, echo properties and plaque surface. RESULTS: In 42 out of 74 patients (56.8 %) a total of 188 new procedure- related DWI-lesions could be detected, while in 32 patients MRI-controls remained normal. Of the lesions 79.25 % had a size < 1 cm. In one major and two minor strokes due to CAS (total complication rate 3.9 %) corresponding territorial infarcts could be demonstrated. A highly significant correlation was found between the length of the stenosis and the incidence of new DWI-lesions (p = 0.0141). In contrast, neither the grade of ICA stenosis nor the sonographic plaque morphology or plaque surface correlated with the number of DWI-lesion in postinterventional scans. CONCLUSIONS: The length-and not the degree-of an ICA stenosis seems to be the most decisive sonographic factor for estimating the periprocedural risk of embolism. DWI-lesions are much more frequent than clinical complications and may represent an important surrogate marker for improving the techniques of carotid artery stenting, especially comparing the benefit of different mechanical protection devices.

Aged↗
PubMed2000

Diffusion-weighted MRI for monitoring neurovascular interventions.

Carotid stenting is increasingly considered as treatment for carotid artery disease. A reliable noninvasive method is desirable for assessing the safety of the procedure. Diffusion-weighted MRI (DWI) is sensitive to early brain ischaemia which becoming widely available and might therefore serve this purpose. We prospectively studied 19 patients referred for investigation of carotid artery disease by echo-planar whole-brain DWI before and within 24 h of stenting. The images obtained at a high b value were examined by two independent blinded reviewers for new high-signal areas consistent with ischaemia. We found that 15 patients had no new changes after stenting. One patient showed enlargement of a posterior watershed lesion after the procedure, which correlated with an increase in neurological deficit. Three other patients had presumed small embolic infarcts on DWI; two were asymptomatic and one had weakness at the hand that corresponded to an embolic infarct with a lesion on DWI in the hand notch. There were no false- positive or -negative results on DWI, when compared to clinical findings. DWI is thus a new method that can demonstrate neurologically silent or asymptomatic infants. It can be used to help to assess the safety and efficacy of neurovascular intervention.

Adult↗
PubMed2001

Diffusion-perfusion MRI characterization of post-recanalization hyperperfusion in humans.

BACKGROUND: Animal and human studies have demonstrated that postischemic hyperperfusion may occur both early and late timepoints following acute cerebral ischemia. OBJECTIVE: To use diffusion-perfusion MRI to characterize hyperperfusion in humans following intra-arterial thrombolysis. METHODS: MRI were performed before treatment, several hours following vessel recanalization, and at day 7 in patients successfully recanalized with intra-arterial thrombolytics. RESULTS: Hyperperfusion was visualized in 5 of 12 patients within several hours after recanalization (mean volume, 18 mL; range, 7 to 40 mL), and in 6 of 11 patients at day 7 (mean volume, 28 mL; range, 4 to 45 mL). Within the core region of hyperperfusion, mean cerebral blood flow was 2.1 times greater than in the contralateral homologous region at the early time point, and 3.1 times greater at day 7. Seventy-nine percent of voxels with hyperperfusion at day 7 demonstrated infarction at day 7, whereas only 36% of voxels (within the initial hypoperfusion region) not showing hyperperfusion at day 7 demonstrated infarction at day 7. Mean pretreatment apparent diffusion coefficient (ADC) and perfusion values were more impaired in voxels that subsequently developed hyperperfusion compared with other at-risk voxels (all p values < 0.0001). There were no significant differences in the degree of clinical improvement in patients with regions of hyperperfusion versus those without, although sample size limited power to detect group differences. CONCLUSIONS: Postischemic hyperperfusion, visualized with perfusion MRI in humans following recanalization by intra-arterial thrombolytic therapy, occurred in about 40% of patients within hours and in about 50% of patients at day 7. Hyperperfusion developed mainly in regions that went on to infarction. Compared with other abnormal regions, tissues that developed postischemic hyperperfusion had greater bioenergetic compromise in pretreatment apparent diffusion coefficient values and greater impairment in pretreatment blood flow measures.

Adult↗
PubMed2001

[Diffusion weighted MRI: ischemic and traumatic injuries of the central nervous system].

Diffusion weighted magnetic resonance imaging (DWI) represents a recent development that extends imaging from the depiction of the neuroanatomy into the field of functional and physiologic processes. DWI measures a fundamentally different physiologic parameter than conventional MRI. Image contrast is related to differences in the microscopic motion (diffusion) of water molecules within brain tissue rather than a change in total tissue water. Consequently, DWI can reveal pathology where conventional T1- and T2-weighted MR images are negative. DWI has clinically proven its value in the assessment of acute cerebral stroke and trauma by showing cerebral injury early due to ist ability to discriminate between lesions with cytotoxic edema (decreased diffusion) from lesions with vasogenic edema (increased diffusion). Full tensor DWI allows to calculate a variety of functional maps, the most widely used maps include maps of apparent diffusion coefficients and isotropic diffusion. In addition maps of anisotropic diffusion can be calculated which are believed to give information about the integrity and location of fiber tracts. This functional-anatomical information will most probably play an increasingly important role in the early detection of primary and secondary tissue injury from various reasons and could guide and validate current and future neuroprotective treatments.

Animals↗
PubMed2004

[Diffusion-weighted MRI in the differentiation of brain abscesses and necrotic tumors].

PURPOSE: The differential diagnosis between brain abscesses and necrotic tumors such as glioblastomas and metastases is often difficult by conventional MRI. The goal of our study was to evaluate the ability of the diffusion-weighted (DW) MRI to differentiate these lesions from each other. MATERIALS AND METHODS: MRI was performed in 19 patients (four abscesses, seven glioblastomas, two anaplastic astrocytomas, six metastases). In addition to standard MR sequences, trace DW imaging and apparent diffusion coefficient (ADC) maps were performed. ADC values were calculated for all lesions. For statistical analysis student t-test was used. A p value less than 0.05 indicated a statistically significant difference. RESULTS: The central portion of all six metastases and eight of nine high-grade gliomas showed unrestricted diffusion, whereas all four abscesses showed restricted diffusion (low ADC values) in their cavity. However, restricted diffusion also was found in one glioblastoma. The ADC values of abscesses (0.69-/+0.05 x103 mm2/s) were significantly lower than of 15 malignant necrotic tumors (2.39-/+0.63 x 103 mm2/s). The difference between abscess and necrotic tumors was statistically significant (p<0.001). CONCLUSION: DW MRI can be used to identify a brain abscess and can help to differentiate it from a cystic brain tumor. However, restricted water diffusion is not specific and pathognomonic in the differential diagnosis between abscesses and necrotic tumors.

Adolescent↗
PubMed2004

MRI with diffusion tensor imaging post-mortem at 3.0 T in a patient with frontotemporal dementia.

The formalin-fixed brain of a patient with clinically diagnosed frontotemporal dementia (FTD) was examined post-mortem using magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) at 3.0 T. Frontotemporal atrophy as well as bilateral frontal white matter abnormalities were seen. The white matter changes were slightly more extensive on DTI than on conventional MRI. Correlation with histopathology of the corresponding regions revealed typical frontal lobe degeneration of non-Alzheimer type, with mild frontotemporal degeneration in the outer cortical layers and a moderate frontal white matter gliosis with demyelination. Post-mortem MRI/DTI with histopathologic correlation will enhance our understanding of the basis of white matter changes observed in dementia patients and may improve the in vivo MRI/DTI diagnostic assessment in FTD.

Aged↗
PubMed1998

In vivo 1H MR spectroscopic imaging and diffusion weighted MRI in experimental hydrocephalus.

The severity and progression of ventricular enlargement, the occurrence of cerebral edema, and the localization of ischemic metabolic changes were investigated in a rat model of hydrocephalus, using in vivo 1H MR spectroscopic imaging (SI) and diffusion weighted MRI (DW MRI). Hydrocephalic rats were studied 1, 2, 4, and 8 weeks after injection of kaolin into the cisterna magna. Parametric images of the apparent diffusion coefficient (ADC) revealed a varying degree of ventriculomegaly in all rats, with different time courses of ventricular expansion. Extracellular white matter edema was observed during the early stages of hydrocephalus, most extensively in cases of progressive ventriculomegaly. In gray matter regions, ADC values were not changed, compared with controls. In case of fatal hydrocephalus, high lactate levels were observed throughout the whole brain. In all other rats, at all time points after kaolin injection, lactate was detected only in voxels containing cerebrospinal fluid. This suggests accumulation of lactate in the ventricles, and/or an ongoing periventricular production of lactate as a consequence of cerebral ischemia in experimental hydrocephalus.

Acute Disease↗
PubMed1999

Lack of evidence of acute ischemic tissue change in transient global amnesia on single-shot echo-planar diffusion-weighted MRI.

BACKGROUND AND PURPOSE: There is uncertainty concerning the etiology of transient global amnesia (TGA). Previous CT and MRI studies have indicated that permanent structural abnormality is rare in TGA. Diffusion-weighted (DW) MRI is very sensitive to early ischemic parenchymal changes and has recently demonstrated embolic infarction in the posterior cerebral artery territory in 2 TGA patients. We report the findings of DW MRI in 8 patients in acute stages of TGA. METHODS: Conventional and echo-planar DW MRI was performed in 2 patients in the active phase and 6 patients in the recovery phase (1 to 8 hours after cessation of anterograde memory dysfunction) of spontaneously occurring TGA. RESULTS: None of the patients showed signs of hyperintensity on DW images or hypointensity on quantitative apparent diffusion coefficient (ADC) maps to suggest regional decreases of water mobility or acute T2 changes on transverse or coronal slices. CONCLUSIONS: We were unable to detect ADC or acute T2 changes with echo-planar DW MRI in patients with TGA, which suggests that mechanisms other than ischemic infarction may cause TGA. We did not identify spreading depression-associated changes of the ADC. Further refinement of MRI sequences may be necessary to detect subtle or transient signal change in brain parenchyma.

Aged↗
PubMed1996

Determination of muscle fibre orientation using Diffusion-Weighted MRI.

Biomechanical studies have shown that the distribution of stress and strain in biological tissue is strongly dependent on fibre orientation. Therefore, to analyze the local mechanical load, accurate data on muscle fibre orientation are needed. Traditional techniques to determine fibre orientation are inherently invasive. Here we used Diffusion Weighted MRI to non-invasively determine, in each image voxel of 0.23 x 0.23 mm, the diffusion tensor of water in the cat semimembranosus muscle. The direction corresponding to the largest eigenvector of this tensor was calculated. This direction was found to correspond qualitatively to the muscular fibre direction, as determined by visual inspection.

Animals↗
PubMed2002

Neonatal cerebral infarction diagnosed by diffusion-weighted MRI: pseudonormalization occurs early.

BACKGROUND: Seizures in the neonatal period may be the single symptom of acute ischemic cerebral infarction. It may be difficult to establish the diagnosis in the acute phase by the use of ultrasound, CT, and conventional MRI because of the high water content of the immature brain. Diffusion-weighted (DW) MRI is a very sensitive and fast imaging modality to visualize acute ischemic stroke in infants even before conventional MR images become abnormal. Signal abnormality in DW MRI, however, seems to follow a different time course than in older patients. CASE DESCRIPTION: DW MRI became falsely negative 1 week after stroke (pseudonormalization) in 2 newborn patients during persistence of signal abnormalities on turbo spin-echo images, whereas the so-called pseudonormalization in adults normally occurs within 10 to 14 days. CONCLUSIONS: T2-weighted sequences should supplement DW images to reliably detect subacute ischemic infarctions in the neonatal period.

Cerebral Arteries↗
PubMed2001

Early diagnosis of cerebral fat embolism syndrome by diffusion-weighted MRI (starfield pattern).

BACKGROUND: Cerebral fat embolism syndrome is a rare, but potentially lethal, complication of long bone fractures. Neurological symptoms are variable, and the clinical diagnosis is difficult. The purpose of this case study is to demonstrate the value of diffusion-weighted MRI of the brain for early diagnosis of fat embolism syndrome. Case Description- A non-head-injured 18-year-old woman suffered acute mental status changes 21 hours after an uncomplicated fracture of the left tibia. MRI of the brain was performed 48 hours after injury. T2-weighted images showed multiple nonconfluent areas of high signal intensity, which, on the diffusion-weighted scans, were revealed as bright spots on a dark background ("starfield" pattern). We suggest that this indicates areas of restricted diffusion that are due to cytotoxic edema, resulting from multiple microemboli. CONCLUSIONS: High-intensity lesions in the brain on diffusion-weighted images may serve as an early-appearing and more sensitive indicator of the diagnosis of fat embolism in the clinical context of long bone injury without head trauma.

Accidents, Traffic↗
PubMed2006

Detection of head and neck squamous cell carcinoma with diffusion weighted MRI after (chemo)radiotherapy: correlation between radiologic and histopathologic findings.

PURPOSE: To investigate the value of diffusion weighted magnetic resonance imaging (DW-MRI) in differentiating persistent or recurrent head and neck squamous cell carcinoma (HNSCC) from nontumoral postradiotherapeutic alterations. METHODS AND MATERIALS: In 26 patients with suspicion of persistent or recurrent HNSCC, MRI of the head and neck was performed, including routine turbo spin-echo (TSE) sequences and an additional echo-planar DW-MRI sequence, using a large range of b-values (0-1000 s/mm(2)). Apparent diffusion coefficient (ADC) maps were calculated. In the suspect areas at the primary site and in the suspect lymph nodes, signal intensity was measured on the native b0 and b1000 images and ADC values were calculated for these tissues. The same was done for surrounding irradiated normal tissue. Imaging results were correlated to histopathology. RESULTS: Signal intensity on native b0 images was significantly lower for HNSCC than for nontumoral postradiotherapeutic tissue (p < 0.0001), resulting in a sensitivity of 66.2%, specificity of 60.8%, and accuracy of 62.4%. Signal intensity on native b1000 images was significantly higher for HNSCC than for nontumoral tissue (p < 0.0001), resulting in a sensitivity of 71.6%, specificity of 71.3%, and accuracy of 71.4%. ADC values were significantly lower for HNSCC than for nontumoral tissue (p < 0.0001), resulting in a sensitivity of 94.6%, specificity of 95.9%, and accuracy of 95.5%. When compared with computed tomography, TSE-MRI and fluorodeoxyglucose-positron emission tomography, DW-MRI yielded fewer false-positive results in persistent primary site abnormalities and in persistent adenopathies, and aided in the detection of subcentimetric nodal metastases. CONCLUSIONS: Diffusion weighted-MRI accurately differentiates persistent or recurrent HNSCC from nontumoral tissue changes after (chemo)radiotherapy.

Aged↗
PubMed2004

Diffusion-weighted MRI during early global cerebral hypoxia: a predictor for clinical outcome?

OBJECTIVES: As prognostic assessment of prolonged cerebral hypoxia is often difficult on clinical grounds, a tool for an early prognosis of clinical outcome is desirable. PATIENTS AND METHODS: In a prospective study, we investigated the prognostic value of diffusion-weighted MRI (DWI) in 12 patients within 36 h after global cerebral hypoxia. Results of DWI including apparent diffusion coefficient maps (ADC) were analyzed and related to the clinical outcome after 6 months, in comparison with conventional magnetic resonance imaging (cMRI). RESULTS: Three patients with a short resuscitation time showed normal findings in cMRI and DWI and a good recovery. In seven patients, DWI revealed multiple large hyperintense areas although cMRI was normal. In two patients, large diffuse lesions were observed in DWI which were also found in cMRI. All of these nine patients developed a vegetative state in the follow-up examination. CONCLUSION: Pathological DWI during the early phase after cerebral hypoxia might be superior to cMRI as a predictor of a worse clinical outcome.

Adult↗
PubMed1999

Diffusion-weighted MRI in acute lacunar syndromes. A clinical-radiological correlation study.

BACKGROUND AND PURPOSE: Clinical-radiological correlation studies in lacunar syndromes have been handicapped by the low sensitivity of CT and standard MRI for acute small-vessel infarction and their difficulty in differentiating between acute and chronic lesions. METHODS: We prospectively studied 43 patients presenting with a classic lacunar syndrome using diffusion-weighted MRI, a technique with a high sensitivity and specificity for acute small-vessel infarction. RESULTS: All patients were scanned within 6 days of stroke onset. An acute infarction was identified in all patients. Pure motor stroke was associated with lesions in the posterior limb of the internal capsule (PLIC), pons, corona radiata, and medial medulla; ataxic hemipareses with lesions in the PLIC, corona radiata, pons, and insular cortex; sensorimotor stroke with lesions in the PLIC and lateral medulla; dysarthria-clumsy hand syndrome with lesions in the PLIC and caudate nucleus; and pure sensory stroke with a lesion in the thalamus. Supratentorial lesions extended into neighboring anatomic structures in 48% of the patients. CONCLUSIONS: Lacunar syndromes can be caused by lesions in a variety of locations, and specific locations can cause a variety of lacunar syndromes. Extension of lesions into neighboring structures in patients with lacunar syndromes appears to be more frequent than previously described in studies using CT and standard MRI.

Acute Disease↗
PubMed2006

Peri-infarct reorganization in a patient with corona radiata infarct: a combined study of functional MRI and diffusion tensor image tractography.

PURPOSE: We investigated the motor recovery mechanism of a stroke patient using functional MRI (fMRI) and diffusion tensor image tractography (DTT). METHODS: A 60 year-old woman with right corona radiata infarct presented with complete paralysis of the left upper extremity. The motor function of the affected upper extremity recovered slowly for 6 months to a point of nearly normal function. The motor function of the patient was evaluated by fMRI and DTT at 6 months from the onset. FMRI was performed at 1.5 T with timed hand grasp-release movements. DTT was performed using 1.5 T with a synergy-L Sensitivity Encoding head coil. Three dimensional reconstructions of the fiber tracts were obtained with FA < 0.3, angle > 45 degrees as termination criteria. RESULTS: The contralateral primary sensorimotor cortex (SM1) was activated during both affected (left) and unaffected hand movements. DTT showed that the tracts originated from either SM1; the tracts then descended along the known pathway of the corticospinal tract, with the exception that the tract of the affected (right) hemisphere descended along the posterior portion of the infarcted corona radiata. CONCLUSIONS: It seems that the motor function of the affected upper extremity was reorganized to the posterior portion of the infarcted corona radiata. This finding may reflect functional reorganization of the motor pathway following corticospinal tract damage. This appears to be one motor recovery mechanism of subcortical infarct.

Animals↗
PubMed1999

Usefulness of diffusion-weighted MRI with echo-planar technique in the evaluation of cellularity in gliomas.

The purpose of this study was to evaluate the utility of diffusion-weighted magnetic resonance imaging (MRI) with echo-planar imaging (EPI) technique in depicting the tumor cellularity and grading of gliomas. Twenty consecutive patients (13 men and 7 women, ranging in age from 13 to 69 years) with histologically proven gliomas were examined using a 1.5 T superconducting imager. Tumor cellularity, analyzed with National Institutes of Health Image 1.60 software on a Macintosh computer, was compared with the minimum apparent diffusion coefficient (ADC) and the signal intensity on the T2-weighted images. The relationship of the minimum ADC to the tumor grade was also evaluated. Tumor cellularity correlated well with the minimum ADC value of the gliomas (P = 0.007), but not with the signal intensity on the T2-weighted images. The minimum ADC of the high-grade gliomas was significantly higher than that of the low-grade gliomas. Diffusion-weighted MRI with EPI is a useful technique for assessing the tumor cellularity and grading of gliomas. This information is not obtained with conventional MRI and is useful for the diagnosis and characterization of gliomas.

Adolescent↗
PubMed1999

Diffusion-weighted MRI in cyclosporin A neurotoxicity for the classification of cerebral edema.

Cyclosporin A, an immunosuppressive agent, is known to have neurotoxic effects, but until now, there has not been agreement on the underlying mechanism. Our report suggests, by using diffusion-weighted MRI, that the brain lesions caused by cyclosporin A, are probably related to vasogenic edema. This may explain the complete recovery of the lesions on imaging when cyclosporine therapy is stopped.

Adult↗
PubMed2003

Visualization of the eloquent motor system by integration of MEG, functional, and anisotropic diffusion-weighted MRI in functional neuronavigation.

BACKGROUND: In this study, we visualized the eloquent motor system including the somatosensory-motor cortex and corticospinal tract on a neuronavigation system, integrating magnetoencephalography (MEG), functional magnetic resonance imaging (fMRI), and anisotropic diffusion-weighted MRI (ADWI). METHODS: Four patients with brain lesions adjacent to the eloquent motor system were studied. Motor-evoked responses (MER) by finger-tapping paradigm were acquired with a 1.5-Tesla MR scanner, and somatosensory-evoked magnetic fields (SEF) by median nerve stimulation were measured with a 204-channel MEG system. In the same fMRI examination, ADWI and anatomic three-dimensional T1-weighted imaging (3-D MRI) were obtained. Activated areas of MER, estimated SEF dipoles, and the corticospinal tract on ADWI were coregistered to 3-D MRI, and the combined MR data were transferred to a neuronavigation system (functional neuronavigation). Intraoperative recording of cortical somatosensory-evoked potentials was performed for confirmation of the central sulcus. RESULTS: Combination of fMRI and MEG enabled firm identification of the central sulcus. Functional neuronavigation facilitated extensive tumor resection, having the advantage of sparing the motor cortex and corticospinal tract in all cases. CONCLUSIONS: The proposed functional neuronavigation allows neurosurgeons to perform effective and maximal resection of brain lesions, identifying and sparing eloquent cortical components and their subcortical connections. Potential clinical application of this technique is discussed.

Adolescent↗