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PubMed2004

Combination of event-related fMRI and diffusion tensor imaging in an infant with perinatal stroke.

Focal ischemic brain injury, or stroke, is an important cause of later handicap in children. Early assessment of structure-function relationships after such injury will provide insight into clinico-anatomic correlation and potentially guide early intervention strategies. We used combined functional MRI (fMRI) with diffusion tensor imaging (DTI) in a 3-month-old infant to explore the structure-function relationship after unilateral perinatal stroke that involved the visual pathways. With visual stimuli, fMRI showed a negative BOLD activation in the visual cortex of the intact right hemisphere, principally in the anterior part, and no activation in the injured hemisphere. The functional activation in the intact hemisphere correlated clearly with the fiber tract of the optic radiation visualized with DTI. DTI confirmed the absence of the optic radiation in the damaged left hemisphere. In addition, event-related fMRI (ER-fMRI) experiments were performed to define the characteristics of the BOLD response. The shape is that of an inverted gamma function (similar to a negative mirror image of the known positive adult BOLD response). The maximum decrease was reached at 5-7 s with signal changes of -1.7 +/- 0.4%.Thus, this report describes for the first time the combined use of DTI and event-related fMRI in an infant and provides insight into the localization of the fMRI visual response in the young infant and the characteristics of the BOLD response.

Asphyxia Neonatorum↗
PubMed2002

Multiparametric MRI ISODATA ischemic lesion analysis: correlation with the clinical neurological deficit and single-parameter MRI techniques.

BACKGROUND AND PURPOSE: The purpose of this study was to show that the computer segmentation algorithm Iterative Self-Organizing Data Analysis Technique (ISODATA), which integrates multiple MRI parameters (diffusion-weighted imaging [DWI], T2-weighted imaging [T2WI], and T1-weighted imaging [T1WI]) into a single composite image, is capable of defining the ischemic lesion in a time-independent manner equally as well as the MRI techniques considered the best for each phase after stroke onset (ie, perfusion weighted imaging [PWI] and DWI for the acute phase and T2WI for the outcome phase). METHODS: We measured MRI parameters of PWI, DWI, T2WI, and T1WI from patients at the acute phase (<30 hours) and DWI, T2WI, and T1WI at the outcome phase (3 months) of ischemic stroke. The clinical neurological deficit was graded with the National Institutes of Health Stroke Scale (NIHSS). We compared the ISODATA lesion size with the PWI, DWI, and T2WI lesion sizes measured within the same slice at each phase. The lesion sizes were also correlated with NIHSS score of each phase. RESULTS: We included 11 patients; 9 (82%) were women, and 7 (64%) were black. The mean+/-SD age was 65.5+/-9.3 years (range, 45 to 82 years). The median NIHSS score was 15 (minimum, 4; maximum, 24)at the acute phase and 3 (minimum, 0; maximum, 22) at the outcome phase. The median time interval from stroke symptom onset to the acute MRI study was 10 hours (range, 6 to 29 hours), and the mean time interval to the outcome study was 93+/-11 days (range, 72 to 106 days). In the acute phase, the ISODATA lesion size had high correlation with the PWI lesion size (r=0.95; 95% CI, 0.89 to 0.98; P<0.0001), DWI lesion size (r=0.83; 95% CI, 0.66 to 0.92; P<0.0001), and T2WI lesion size (r=0.67; 95% CI, 0.39 to 0.84; P=0.008) and moderate correlation with NIHSS score (r=0.59; 95% CI, 0.02 to 0.88; P=0.06). In the outcome phase, the ISODATA lesion size had high correlation with the T2WI lesion size (r=0.97; 95% CI, 0.94 to 0.99; P<0.0001) and NIHSS score (r=0.78; 95% CI, 0.34 to 0.94; P=0.004). CONCLUSIONS: The integrated ISODATA method can identify and characterize the ischemic lesion independently of time elapsed since stroke onset. The ISODATA lesion size highly correlates with the PWI and DWI lesion size in the acute phase and with the T2WI lesion size in the outcome phase of ischemic stroke, as well as with the clinical neurological status of the patient.

Aged↗
PubMed1992

[Malignant lymphoma with subdural effusion].

A 64-year-old woman was admitted for treatment of malignant lymphoma involving the pharynx and abdomen. Lymphoma disappeared after chemotherapy and radiotherapy, but she had central nervous system symptoms; euphorism, left facial nerve palsy, right hemiplesia, and disturbance of micturition. Magnetic resonance imaging (MRI) revealed a diffuse dural thickening and a subdural fluid retention. The subdural fluid was determined to be an exudate, and a biopsy of the dura mater revealed a normal dura and a fibrin clot containing lymphoma cells and neutrophils. MRI can be very useful to detect the meningeal involvement of malignant lymphoma.

Female↗
PubMed2006

Efficient simulation of magnetic resonance imaging with Bloch-Torrey equations using intra-voxel magnetization gradients.

The process of image formation in magnetic resonance imaging (MRI) can be simulated by means of an iterative solution of Bloch-Torrey equations. This is a useful accessory to analyze the influence of sample properties, sequence parameters and hardware specifications on the MRI signal. In this paper, a computer algorithm is presented which is based on calculating partial derivatives of the magnetization vector. This technique allows more efficient simulation than summation of isochromats (the latter being commonly employed for this purpose) and, as a result, the effect of diffusion on the MRI signal can be calculated iteratively. A detailed description of the algorithm is given, and its feasibility for different applications is studied. It is shown that the algorithm is most applicable to simulating the effect of field perturbations, i.e. intra-voxel dephasing, but is also useful for other typical imaging experiments and the simulation of diffusion weighting.

Algorithms↗
PubMed1990

Pelizaeus-Merzbacher disease. Contribution of magnetic resonance imaging to an early diagnosis.

The lesions of the cerebral white matter which characterize Pelizaeus-Merzbacher disease are classically observed at pathological examination. An early diagnosis can now be obtained by magnetic resonance imaging (MRI). In an eutrophic first son born at term, stridor, nystagmus-like eye movements and axial hypotonia were noted immediately after birth and pyramidal signs appeared at 2 months, the only extra-clinical finding at that age being prolonged latencies of evoked visual potentials. An MRI exploration, performed at 3 months, showed that compared with the grey matter the white matter emitted a low-intensity signal on the T1-weighted sequence and a high-intensity signal on the T2-weighted sequence (signal inversion), such diffuse and symmetrical MRI abnormalities being typical of dysmyelination. When combined with suggestive clinical signs, these abnormalities confirm the diagnosis of Pelizaeus-Merzbacher disease, even in the absence of a familial history, and make it possible to warn the parents of the poor prognosis and the risk of recurrence among future sons.

Brain↗
PubMed2003

A phase I trial of etanidazole and hyperfractionated radiotherapy in children with diffuse brainstem glioma.

PURPOSE: To determine the toxicity and maximum tolerated dose of etanidazole administered concurrently with hyperfractionated radiation therapy (HRT) for children with brainstem glioma. METHODS AND MATERIALS: Eighteen patients with brainstem glioma were treated with etanidazole and HRT on a dose escalation protocol (Phase I trial) between 1990 and 1996. All patients had MRI confirmation of diffuse pontine glioma and signs/symptoms of cranial nerve deficit, ataxia, or long tract signs of <6 months' duration. Cervicomedullary tumors were excluded. Patients (median age: 8.5 years; 11 males, 7 females) received HRT to the tumor volume plus a 2-cm margin with parallel-opposed 6-15-MV photons. The total dose was 66 Gy in 44 fractions (1.5 Gy b.i.d., with at least 6 h between fractions) for the first 3 patients and 63 Gy in 42 fractions for the subsequent 15 patients. Etanidazole was administered as a rapid i.v. infusion 30 min before the morning fraction of HRT. Planned doses of etanidazole were 1.8 g/m(2) x 17 doses (30.6 g/m(2)) at Step 1 to a maximum of 2.4 g/m(2) x 21 doses (50.4 g/m(2)) at Step 8. Dose escalation was planned with 3 patients at each of the 8 levels. RESULTS: Three patients were treated at each dose level except Level 2, on which only 1 patient was treated. The highest dose level achieved was Level 7, which delivered a total etanidazole dose of 46.2 g/m(2). Two patients were treated at this level, and both patients experienced Grade 3 toxicity in the form of a diffuse cutaneous rash. Three patients received a lower dose of 42 g/m(2) (dose Level 6) without significant toxicity, and this represents the maximum tolerated dose (MTD). There were 23 cases of Grade 1 toxicity (10 vomiting, 5 peripheral neuropathy, 2 rash, 2 constipation, 1 weight loss, 3 others), 11 cases of Grade 2 toxicity (4 vomiting, 2 skin erythema, 2 constipation, 1 arthralgia, 1 urinary retention, 1 hematologic), and 4 Grade 3 toxicities (2 rash, 1 vomiting, 1 skin desquamation). Grade 2 or 3 peripheral neuropathy was not seen at any dose level. The median survival from the start of treatment was 8.5 months (range: 3-58 months). CONCLUSION: The MTD of etanidazole in children receiving HRT for brainstem glioma is 42 g/m(2), with cutaneous rash as the dose-limiting toxicity. This is in contrast to the adult experience, which demonstrates a 24% lower MTD of 34 g/m(2) limited by peripheral neuropathy.

Adolescent↗
PubMed2006

Diffusion tensor imaging of brain development.

Understanding early human brain development is of great clinical importance, as many neurological and neurobehavioral disorders have their origin in early structural and functional cerebral organization and maturation. Diffusion tensor imaging (DTI), a recent magnetic resonance (MR) modality which assesses water diffusion in biological tissues at a microstructural level, has revealed a powerful technique to explore the structural basis of normal brain development. In fact, the tissue organization can be probed non-invasively, and the age-related changes of diffusion parameters (mean diffusivity, anisotropy) reveal crucial maturational processes, such as white matter myelination. Nevertheless, the developing human brain presents several challenges for DTI applications compared with the adult brain. DTI may further be used to detect brain injury well before conventional MRI, as water diffusion changes are an early indicator of cellular injury. This is particularly critical in infants in the context of administration of neuroprotective therapies. Changes in diffusion characteristics further provide early evidence of both focal and diffuse white matter injury in association with periventricular leukomalacia in the preterm infant. Finally, with the development of 3D fiber tractography, the maturation of white matter connectivity can be followed throughout infant development into adulthood with the potential to study correlations between abnormalities on DTI and ultimate neurologic/cognitive outcome.

Brain↗
PubMed2002

Assessment of infant physiology and neuronal development using magnetic resonance imaging.

Previous work has demonstrated both that there are substantial individual differences in the rate of physiological development,and that infants with risk factors for Sudden Infant Death Syndrome (SIDS) develop more slowly, suggesting that their increased vulnerability may be due to delayed neuronal development associated with compromised development in fetal or early neonatal life. This project aims to test the hypothesis that individual differences in the rate of physiological development of infants correlate with measurable differences in the rate of brain development as assessed by magnetic resonance imaging (MRI). Sixty infants were recruited to this study in three different groups that are known to have differing rates of physiological development. MRI was performed successfully in 49 cases at 6 weeks of age without sedation. Forty-one of these cases had full follow-up (15 normal; 19 IUGR; 11 'high risk'). Postnatal physiological development was assessed by measuring age-related deep body temperature patterns during sleep. Neuronal development was assessed by subjective analysis of MRI images and objective measurements relating to myelination using T1 and diffusion weighted (23 cases) MRI images. As expected the normal group acquired the adult temperature pattern earlier, but this was not statistically significant. All MRI scan appearances were within normal limits. Ranking cases subjectively in order of maturity revealed no significant pattern. The normal group had a significantly higher myelination score than the IUGR and 'high risk' groups (P = 0.001). This trend was also shown by the diffusion weighted myelination score but did not reach statistical significance. No significant differences were seen in both the subjective and objective MRI measurements and development of nocturnal temperature patterns. The results suggest there may be differences in neurodevelopment between the different groups at 6 weeks of age but these are not linked to late development of temperature patterns. It is therefore unlikely that this related to a global delay in maturation.

Brain↗
PubMed1996

The clinical and genetic correlates of MRI findings in myotonic dystrophy.

Amplification of an unstable CTG trinucleotide repeat sequence in a protein kinase gene on chromosome 19 has recently been recognised as the molecular basis of myotonic dystrophy (DM), a multi-system disorder with a wide spectrum of muscular and extramuscular manifestations. The CTG expansion of 40 patients was assessed by direct genotype analysis of the white blood cell DNA and correlated with MRI of the brain and muscles, and with functional clinical data. Cerebral pathology on MRI consisted of diffuse atrophy (68%), subcortical white matter lesions (65%), wide Virchow-Robin spaces (38%) and thickening of the skull (35%). Cerebral atrophy and extent of white matter disease correlated significantly with mental retardation, duration of disease and CTG fragment amplification. MRI of the muscular system showed fatty degeneration of different degrees in neighbouring muscles causing a mosaic pattern of the thigh in 38% and the calf in 44%. Muscular changes on MRI were strongly correlated with muscular impairment but less strongly with CTG expansion. Changes on MRI reflect the stage of development of tissue pathology in DM, modified by defect of the DM gene. Pathology on MRI is strongly correlated with functional deficits.

Adolescent↗
PubMed1996

Acute focal cerebral ischemia in rats studied by diffusion-weighted magnetic resonance imaging--an experimental study.

BACKGROUND: Temporary occlusion of the cerebral artery is occasionally repeated during neurosurgical operations, but the safety of such a procedure remains to be studied further. METHOD: We studied early changes and reversibility of focal cerebral ischemia and the cumulative effects of repeated ischemic insults in rats using magnetic resonance imaging (MRI). RESULTS: Diffusion-weighted magnetic resonance images (DWI) and determination of signal intensity ratio (SIR) proved to be a valuable measure of studying early changes and reversibility of transient focal cerebral ischemia and cumulative adverse effects of repeated ischemic insults. DWIs showed marked intensity changes shortly after focal cerebral ischemia, while T2-weighted images failed to show hyperintensities until 2.5 hours after the onset of permanent ischemia. The critical period of ischemia in this model was 60 minutes. However, 20 minutes ischemia, when repeated twice with 60 minutes reperfusion in between, showed irreversible damage. CONCLUSION: Repeated insults of focal regional cerebral ischemia may cause irreversible tissue damage even if each ischemic period is less than the critical one.

Animals↗
PubMed2004

Primary leptomeningeal sarcomatosis; a pathology proven case with challenging MRI and clinical findings.

A 20-year-old male patient admitted with intractable seizures and progressive dementia is presented. Magnetic resonance imaging (MRI) examinations revealed diffuse leptomeningeal thickening, enhancement especially in the basal cisterns and multiple cystic formations in the brain stem, temporal lobes and basal ganglia. The pathologic examination from the right temporal lobe was consistent with leptomeningeal sarcoma. Marked regression of the symptoms and MRI lesions were detected following radiotherapy.

Adult↗
PubMed2002

Dysmyelination revealed through MRI as increased radial (but unchanged axial) diffusion of water.

Myelin loss and axonal damage are both observed in white matter injuries. Each may have significant impact on the long-term disability of patients. Currently, there does not exist a noninvasive biological marker that enables differentiation between myelin and axonal injury. We describe herein the use of magnetic resonance diffusion tensor imaging (DTI) to quantify the effect of dysmyelination on water directional diffusivities in brains of shiverer mice in vivo. The principal diffusion eigenvalues of eight axonal fiber tracts that can be identified with certainty on DTI maps were measured. The water diffusivity perpendicular to axonal fiber tracts, lambda(perpendicular), was significantly higher in shiverer mice compared with age-matched controls, reflecting the lack of myelin and the increased freedom of cross-fiber diffusion in white matter. The water diffusivity parallel to axonal fiber tracts, lambda(parallel), was not different, which is consistent with the presence of intact axons. It is clear that dysmyelination alone does not impact lambda(parallel). The presence of intact axons in the setting of incomplete myelination was confirmed by electron microscopy. Although further validation is still needed, our finding suggests that changes in lambda(perpendicular) and lambda(parallel) may potentially be used to differentiate myelin loss versus axonal injury.

Animals↗
PubMed2005

Role of MRI in the management of children with diffuse pontine tumors: a study of 15 patients and review of the literature.

BACKGROUND: Pontine tumors carry the worst prognosis of all brain tumors. In most cases, the diagnosis is based solely on MR imaging, without biopsy. OBJECTIVE: To describe the MR findings of pontine tumors at diagnosis and during follow-up and correlate those with prognosis and to assess the value of MR imaging in patient management compared to clinical evaluation. MATERIALS AND METHODS: Ninety-one MR scans of 15 children with diffuse pontine tumors were reviewed at diagnosis and during follow-up. The parameters analyzed were as follows: tumor extent, area, and volume; encasement of the basilar artery; presence of exophytic component; necrosis; cysts; hydrocephalus; and intensity and enhancement. Findings were correlated to length of progression-free and overall survival. Trends of amelioration or worsening on imaging were compared with the clinical findings. RESULTS: Median length of progression-free survival was 10 months, and median survival was 20 months. Only hydrocephalus at presentation was associated with shorter progression-free survival (P=0.02). On the last examination of each patient, the craniocaudal diameter was significantly greater than at diagnosis (P=0.03). The concordance between the imaging and the clinical findings was good. CONCLUSION: MR is the mainstay for the diagnosis and management of pontine tumors. Cranial growth seems to be an ominous sign. However, the prognostic value of MR is limited. MR findings correlate well with the clinical examination.

Adolescent↗
PubMed2005

Differential diagnosis of focal and diffuse neoplastic diseases of bone marrow in MRI.

Magnetic resonance imaging (MRI) has become the preferred imaging modality for the evaluation of malignant disease in the bone marrow. Compared to bone marrow aspiration and biopsy, MRI is noninvasive and provides information by sampling a large volume of bone marrow. Due to disease-related alterations in the composition of bone marrow, MRI provides a very high sensitivity, but lacks specificity for most bone marrow disorders. However, MRI can be a very valuable diagnostic tool properly placed within the clinical context.

Bone Marrow Neoplasms↗
PubMed2000

MRI of small human stroke shows reversible diffusion changes in subcortical gray matter.

Six patients who had suffered small cerebral ischemia affecting subcortical gray matter were examined with diffusion weighted imaging (DWI) and T2-weighted imaging within the first 8 h, during the next 2 days and after 5-16 days. Areas of apparent diffusion coefficient (ADC) decreases were observed acutely and reached the maximum size during the subsequent 2 days. Noticeably, in all subjects, a large portion of the ADC lesion was reversible as judged from the lesion size on final T2 image. The regular reversibility of the ADC decreases in this setting may indicate a hitherto not understood pathophysiological process occurring in small ischemic stroke.

Adult↗
PubMed2004

Mechanism of cerebral edema in children with diabetic ketoacidosis.

OBJECTIVES: Cerebral edema during diabetic ketoacidosis (DKA) has been attributed to osmotic cellular swelling during treatment. We evaluated cerebral water distribution and cerebral perfusion during DKA treatment in children. STUDY DESIGN: We imaged 14 children during DKA treatment and after recovery, using both diffusion and perfusion weighted magnetic resonance imaging (MRI). We assessed the apparent diffusion coefficients (ADCs) and measures reflecting cerebral perfusion. RESULTS: The ADC was significantly elevated during DKA treatment (indicating increased water diffusion) in all regions except the occipital gray matter. Mean reductions in the ADC from initial to postrecovery MRI were: basal ganglia 4.7 +/- 2.5 x 10(-5) mm(2)/s (P=.002), thalamus 3.7 +/- 2.8 x 10(-5) mm(2)/s, (P=.002), periaqueductal gray matter 4.3 +/- 5.1 x 10(-5) mm(2)/s (P=.03), and frontal white matter 2.0 +/- 3.1 x 10(-5) mm(2)/s (P=.03). In contrast, the ADC in the occipital gray matter increased significantly from the initial to postrecovery MRI (mean increase 3.9 +/- 3.9 x 10(-5) mm(2)/s, P=.004). Perfusion MRI during DKA treatment revealed significantly shorter mean transit times (MTTs) and higher peak tracer concentrations, possibly indicating increased cerebral blood flow (CBF). CONCLUSIONS: Elevated ADC values during DKA treatment suggests a vasogenic process as the predominant mechanism of edema formation rather than osmotic cellular swelling.

Adolescent↗
PubMed2000

Normal diffusion-weighted imaging in cerebral air embolism complicating angiography.

We report a case of cerebral air embolism resulting from accidental air infection during cerebral angiography. A 60-year-old man was accidentally injected with air via the left subclavian artery. Angiography demonstrated air within the basilar artery. The patient showed signs of posterior circulation ischaemia (confusion, blindness, gaze palsy and hemiparesis). However, MRI, including diffusion-weighted imaging, showed no abnormality 4 h later. The patient was treated with hyperbaric oxygen within 5 h of the embolism. All symptoms and signs resolved completely within a week.

Brain↗
PubMed1997

Diffusion-weighted magnetic resonance imaging characteristics of hemorrhagic transformation in experimental embolic stroke.

Diffusion-weighted magnetic resonance imaging (MRI) can detect ischemia within minutes of onset, but its ability to reliably detect hyperacute cerebral hemorrhage is unknown. The present study characterized diffusion-weighted, T2-weighted, and contrast-enhanced T1-weighted MRI appearances of hemorrhagic transformation within 5 hours of onset in experimental embolic stroke. Apparent diffusion coefficients and MRI signal characteristics were noted within corresponding regions of hemorrhage observed on gross pathology. Apparent diffusion coefficients were significantly increased within hemorrhagic lesions, but were still within the expected range for bland ischemia. The appearance of the hemorrhagic lesions on diffusion-weighted MRI was also very heterogeneous and not very useful for clinical screening. Other MRI modalities should be investigated, but computed tomography remains the only widely available clinical method of reliably detecting cerebral hemorrhage.

Analysis of Variance↗