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E R Melhem

Publications and source records attributed to E R Melhem.

At least 19 recordsLinked to original sources
PubMed2005

Three-dimensional isotropic contrast-enhanced MR angiography of the carotid artery using sensitivity-encoding and random elliptic centric k-space filling: technique optimization.

We present a study that helped optimize a three-dimensional isotropic contrast-enhanced MR angiographic (CE-MRA) technique, using sensitivity encoding (SENSE) and random elliptic centric k-space filling. Two-dimensional gradient-echo sequence (TR/TE/flip angle 3.4/0.97/40 degrees ) was used to generate time-intensity curves in porcine carotid arteries for a fixed dose of Gd-DTPA (0.02 mmol/kg) at the following intravenous injection rates: 0.1, 0.3, 0.5, 1.0, 1.5, 2.0, and 3.0 ml/s. The time of contrast arrival and time to peak were recorded. Based on the time-intensity curves, three-dimensional high-resolution isotropic (1 mm3) CE-MRA sequence (TR/TE/flip angle: 4.9/2.4/30 degrees ), using SENSE (reduction factor of 2) and random elliptic centric k-space filling, was initiated twice for each of the above injection rates: first at the time of contrast arrival and second at the time of peak contrast. The three-dimensional CE-MRA images were analyzed for artifacts, signal-to-noise ratio, and venous contamination. For the three-dimensional CE-MRA acquisitions that were initiated at the time of contrast arrival, there was a gradual improvement in signal-to-noise ratio (SNR) in the carotid arteries with increasing injection rate. The same trend was not observed for the acquisitions that were initiated at the time of peak contrast. SENSE combined with random elliptic k-space acquisition in CE-MRA allows for higher SNR with fewer ringing artifacts at faster contrast injection rates.

Animals↗
PubMed2003

Analysis of MRI patterns aids prediction of progression in X-linked adrenoleukodystrophy.

BACKGROUND: X-linked adrenoleukodystrophy (X-ALD) has variants with widely different outcomes, hampering clinical counseling and evaluation of therapies. OBJECTIVE: To evaluate the degree to which MRI patterns can predict lesion progression. METHODS: Two hundred six boys and men with cerebral X-ALD (median age 12.2 years, mean age 18.5 years, age range 1.7 to 73.8 years) were studied. In 140 individuals, follow-up MRI were available. Data after bone marrow transplantation (BMT) were excluded. The patterns of MRI abnormalities were subdivided into five groups based on the anatomic location of the initial T2 signal hyperintensity (pattern 1: parieto-occipital white matter, pattern 2: frontal white matter, pattern 3: corticospinal tract, pattern 4: cerebellar white matter, pattern 5: concomitant parieto-occipital and frontal white matter). The X-ALD MRI Severity Scale, a 34-point scale previously described, was used in the analysis. RESULTS: Pattern 1 patients had rapid progression if contrast enhancement was present and if the MRI abnormality manifested at an early age. The latter was also true for pattern 2 patients. Based on these variables, predictive formulas were constructed for these two patterns using multiple regressions. MRI progression was much slower in pattern 3 and 4 patients, whereas in the few pattern 5 patients, it was more rapid than in any other of the patterns. Patterns 1 and 5 occurred mainly in childhood, patterns 2 and 4 in adolescence, and pattern 3 in adults. CONCLUSIONS: MRI progression in X-ALD depends on patient age, initial MRI Severity Scale score, and anatomic location of the lesion. When used in combination, these data aid the prediction of disease course and the selection of patients for BMT.

Adolescent↗
PubMed2003

Correlation of corpus callosal morphometry with cognitive and motor function in periventricular leukomalacia.

PURPOSE: We aim to correlate size and shape of corpus callosum with severity of motor and cognitive impairments in children with periventricular leukomalacia (PVL). METHODS: Children with PVL were stratified based on the severity of their motor and cognitive impairments. An age-matched control group was established. The corpus callosum was identified on mid-sagittal T (1)-weighted spin-echo (TR/TE: 550/15) MR images. The shape characteristics of the corpus callosum were measured with respect to a template via a shape transformation. The degree of callosal-shape transformation was quantified by a deformation function, which in turn was compared, using point-wise T-tests, for controls versus patients, diplegic versus quadriplegic patients, and patients with mild versus severe cognitive impairment. RESULTS: 29 children with spastic cerebral palsy and PVL and 32 age-matched controls were identified. In the PVL group, the entire corpus callosum was significantly smaller than in the control group (p value = 0.001). Significant differences existed in the shape of the corpus callosum between patients with diplegic versus quadriplegic and between patients with severe versus mild cognitive impairment. CONCLUSION: Global and regional corpus callosal morphology can be quantified using deformation functions.

Adolescent↗
PubMed2002

Diffusion tensor imaging of periventricular leukomalacia shows affected sensory cortex white matter pathways.

The authors used diffusion-tensor imaging to examine central white matter pathways in two children with spastic quadriplegic cerebral palsy. Corticospinal tracts projecting from cortex to brainstem resembled controls. In contrast, posterior regions of the corpus callosum, internal capsule, and corona radiata were markedly reduced, primarily in white matter fibers connected to sensory cortex. These findings suggest that the motor impairment in periventricular leukomalacia may, in part, reflect disruption of sensory connections outside classic pyramidal motor pathways.

Brain Mapping↗
PubMed2001

Diffusion tensor brain MR imaging in X-linked cerebral adrenoleukodystrophy.

Brain diffusion tensor MRI of 11 boys with X-linked adrenoleukodystrophy was performed. The authors determined quantitative isotropic apparent diffusion coefficient (ADC(i)) and fractional anisotropy (FA) values in the white matter. ADC(i) and FA values in the affected white matter were significantly different from those in normal-appearing white matter. Zonal ADC(i) and FA gradations, which might originate from well-established histopathologic zonal changes, existed within affected white matter.

Adolescent↗
PubMed2001

Proton magnetic resonance spectroscopy of choroid plexus tumors in children.

A variety of lesions may present as intraventricular masses in children. We report quantitative proton magnetic resonance spectroscopy (MRS) of two intraventricular tumors of the choroid plexus: choroid plexus carcinoma (CPC) and choroid plexus papilloma (CPP). Both lesions were characterized by high levels of choline-containing compounds and a complete absence of creatine and the neuronal/axonal marker N-acetyl aspartate. The CPC showed higher levels of choline compared to the CPP, and it also had elevated lactate. These preliminary results, if confirmed in a larger cohort of patients, indicate that proton MRS may have a role in the presurgical diagnosis of choroid plexus tumors in children, which may also have important implications for therapy and prognosis.

Aspartic Acid↗
PubMed2001

Dysembryoplastic neuroepithelial tumor-like neoplasm of the septum pellucidum: a lesion often misdiagnosed as glioma: report of 10 cases.

The authors report a series of 10 low-grade neoplasms arising in the midline anteriorly in the region of the septum pellucidum with many of the histologic features of dysembryoplastic neuroepithelial tumor (DNT). The patients (five female, five male) ranged in age from 6 to 35 years (mean age, 21.5 years). The most common presenting symptoms were headache, nausea and vomiting, and visual disturbances. Radiographically, the tumors extended into the lateral ventricles from the septal region and obstructed the foramen of Monro. Varying degrees of hydrocephalus were present. The lesions were lobular, well-delineated, hypointense to brain on T1-weighted magnetic resonance imaging, and hyperintense on T2-weighted images. They were uniformly nonenhancing or showed only minimal peripheral enhancement. The tumors, in aggregate, had the histologic features of DNT. These included a mucin-rich background, oligodendrocyte-like cells, "floating neurons," and a "specific glioneuronal element." Seven patients underwent gross total resection and two underwent subtotal resection. No patients received adjuvant chemotherapy or radiotherapy. On follow-up (n = 6; median, 14 months), all tumors had either not recurred or were radiologically stable. On the basis of both neuroimaging and histopathology, DNT-like lesions should be considered in the differential diagnosis of midline intraventricular tumors in children and young adults. Distinction from more aggressive neoplasms is essential because these tumors appear to behave in a benign fashion.

Adolescent↗
PubMed2001

Second surgery for recurrent pilocytic astrocytoma in children.

Pilocytic astrocytoma (PA) is the most common childhood brain tumor. In cases where the tumor progresses or recurs following primary surgical resection, the appropriate treatment is unclear. Options include chemotherapy, radiation therapy, surgical resection or a combination thereof. To analyze the utility of further surgery, we performed a retrospective, single-institution review of pediatric patients with recurrent PAs from 1990 to 1999 who were treated with a second surgical resection. Patients were excluded if they received adjuvant chemotherapy or radiation therapy. Twenty cases were identified. Tumor locations included: cerebral hemisphere (3), cerebellum (7), optic pathway/hypothalamus (5), thalamus (1) and brainstem (4). The indication for 4 surgeries included an enlarging tumor-associated cyst. At second surgery, 10 of 20 patients had a gross total resection (GTR), 2 a near total resection (NTR), and the remaining 8 patients had a subtotal resection (STR). No patients have died. Two of 10 tumors after GTR, 0 of 2 tumors after NTR, and 7 of 8 tumors after STR had second recurrence/progression at a mean of 15 months (range 4-33 months) following second surgery. The remaining 11 patients are recurrence/progression-free at a mean of 40.7 months (range 19-119 months). Surgery for tumors or midline structures rarely resulted in a GTR (1 of 10 cases). Surgery for tumors located in the cerebral hemispheres or cerebellum resulted in GTR or NTR in all cases and can result in long periods of progression-free survival without further adjuvant treatment.

Adolescent↗
PubMed2001

Effect of T1 relaxation time on lesion contrast enhancement in flair MR imaging: a study using computer-generated brain maps.

OBJECTIVE: Using computer-generated brain maps, we aimed to define T1 relaxation time thresholds above which a T2 hyperintense (compared with surrounding white matter) lesion became hypointense on fluid-attenuated inversion recovery (FLAIR) MR imaging. Thresholds were identified for FLAIR MR imaging sequences with different echo times (TEs). CONCLUSION: Thresholds for T1 relaxation times increased as TE increased during FLAIR MR imaging sequences. Such thresholds defined the transition from hyperintense to hypointense lesions.

Adult↗
PubMed2001

Accuracy for detection of simulated lesions: comparison of fluid-attenuated inversion-recovery, proton density--weighted, and T2-weighted synthetic brain MR imaging.

OBJECTIVE: The objective of our study was to determine the effects of MR sequence (fluid-attenuated inversion-recovery [FLAIR], proton density--weighted, and T2-weighted) and of lesion location on sensitivity and specificity of lesion detection. MATERIALS AND METHODS: We generated FLAIR, proton density-weighted, and T2-weighted brain images with 3-mm lesions using published parameters for acute multiple sclerosis plaques. Each image contained from zero to five lesions that were distributed among cortical-subcortical, periventricular, and deep white matter regions; on either side; and anterior or posterior in position. We presented images of 540 lesions, distributed among 2592 image regions, to six neuroradiologists. We constructed a contingency table for image regions with lesions and another for image regions without lesions (normal). Each table included the following: the reviewer's number (1--6); the MR sequence; the side, position, and region of the lesion; and the reviewer's response (lesion present or absent [normal]). We performed chi-square and log-linear analyses. RESULTS: The FLAIR sequence yielded the highest true-positive rates (p < 0.001) and the highest true-negative rates (p < 0.001). Regions also differed in reviewers' true-positive rates (p < 0.001) and true-negative rates (p = 0.002). The true-positive rate model generated by log-linear analysis contained an additional sequence-location interaction. The true-negative rate model generated by log-linear analysis confirmed these associations, but no higher order interactions were added. CONCLUSION: We developed software with which we can generate brain images of a wide range of pulse sequences and that allows us to specify the location, size, shape, and intrinsic characteristics of simulated lesions. We found that the use of FLAIR sequences increases detection accuracy for cortical-subcortical and periventricular lesions over that associated with proton density- and T2-weighted sequences.

Adult↗
PubMed2001

T2 relaxation measurements in X-linked adrenoleukodystrophy performed using dual-echo fast fluid-attenuated inversion recovery MR imaging.

SUMMARY: The purpose of this study was to determine whether dual-echo fast fluid-attenuated inversion recovery MR imaging and corresponding T2 brain maps can show different zones in the affected white matter of patients with cerebral X-linked adrenoleukodystrophy. Ten male patients with cerebral X-linked adrenoleukodystrophy underwent imaging performed using dual-echo fast fluid-attenuated inversion recovery and dual-echo conventional spin-echo MR sequences. Corresponding T2 relaxation maps of the brain were generated. On the basis of dual-echo fast fluid-attenuated inversion recovery images and T2 maps, the affected white matter could be divided into two distinct zones in four patients with cerebral X-linked adrenoleukodystrophy.

Adolescent↗
PubMed2001

Multi-slice proton MR spectroscopy and diffusion-weighted imaging in methylmalonic acidemia: report of two cases and review of the literature.

SUMMARY: Methylmalonic acidemia is an inborn disorder of amino acid metabolism that commonly presents with neurologic deficits. We present the results of multi-slice proton MR spectroscopy and diffusion-weighted imaging of the brain in two patients with methylmalonic acidemia. The findings consisted of restricted diffusion and elevated lactate in the globi pallidi, compatible with acute infarction (patient 1) and elevated lactate in CSF (patient 2).

Adolescent↗
PubMed2001

Time-resolved contrast-enhanced carotid MR angiography using sensitivity encoding (SENSE).

We describe a time-resolved, contrast-enhanced carotid MR angiographic technique using a 3D gradient-echo sequence in combination with a sensitivity-encoding scheme. We delineate the steps involved in generating the dynamic MR angiographic images, discuss issues related to image quality, and outline differences between this technique and recently reported similar methods that implement multiple parallel receivers to reduce imaging time.

Adult↗
PubMed2001

MR imaging of the human brain at 1.5 T: regional variations in transverse relaxation rates in the cerebral cortex.

BACKGROUND AND PURPOSE: Heterogeneity in cortical signal intensity on T2-weighted MR images has been recently documented. Using a whole-brain, multiecho MR imaging technique, we sought to determine the T2 relaxation times of nine predefined regions in the cerebral cortex and one region in the deep gray matter. METHODS: Ten adult volunteers (nine men and one woman; age range, 18-40 y; average age, 30.8 y) underwent whole-brain imaging with an oblique coronal multiecho 3D Carr-Purcell-Meiboom-Gill MR sequence at 1000/25, 50, 75, 100, 125, and 150 (TR/TE). T2 measurements were obtained, with variably sized regions of interest, from the primary auditory cortex, primary visual cortex, caudate nucleus, superior frontal gyrus, inferior temporal gyrus, middle temporal gyrus, superior temporal gyrus, insula cortex, cingulate gyrus, and hippocampus. Repeated-measures analysis of variance was used to assess the existence of differences in T2 measurements among the anatomic locations. RESULTS: On the basis of T2 measurements, the gray matter structures examined could be divided into four statistically different groups. In ascending order of T2 measurements, the first group consisted of the primary auditory cortex and primary visual cortex; the second group, the caudate nucleus, superior frontal gyrus, inferior temporal gyrus, middle temporal gyrus, and superior temporal gyrus; the third group, the insula cortex; and the fourth group, the cingulate gyrus and hippocampus. CONCLUSION: Significant variation in T2 values among the cortical gray matter of the human brain exists.

Adolescent↗
PubMed2000

Cervical spondylosis: contrast-enhanced magnetization transfer prepulsed 3D turbo field echo MR imaging.

Magnetic resonance (MR) imaging of the cervical spine with axial, low flip angle three-dimensional (3D) gradient-echo sequences is limited by long acquisition times and also by increased sensitivity to extrinsic and intrinsic magnetic field inhomogeneity, magnetic susceptibility differences, chemical shifts, and cerebrospinal fluid pulsatility. We attempted to assess the performance of gadolinium-enhanced, magnetization transfer (MT) prepulsed 3D fast gradient-echo sequences in demonstrating spondylotic changes of the cervical spine. Twenty patients with known cervical spine spondylosis were prospectively imaged in the axial plane using two gradient-echo-based MR techniques: 3D fast field echo (FFE) and gadolinium-enhanced, MT prepulsed, segmented turbo field echo (TFE). An average of 58 neural foramina on the 3D FFE images and 47 neural foramina on the contrast-enhanced TFE images were judged to be narrowed. The degree of neural foraminal narrowing was significantly less on the contrast-enhanced TFE images compared with the FFE images (P <0.001). Contrast-enhanced, MT prepulsed, segmented 3D TFE MR imaging has potential for ameliorating some of the limitations encountered in the more widely used gradient-echo techniques.

Cervical Vertebrae↗
PubMed2000

X-Linked adrenoleukodystrophy: overview and prognosis as a function of age and brain magnetic resonance imaging abnormality. A study involving 372 patients.

The phenotypic expression of X-linked adrenoleukodystrophy (X-ALD) ranges from the rapidly progressive childhood cerebral form to the milder adrenomyeloneuropathy (AMN) in adults. It is not possible to predict phenotype by mutation analysis or biochemical assays. This study reports on 372 patients ranging in age from less than 3 years to adulthood, who have been followed at the Kennedy Krieger Institute. With the aim of determining whether a method could be developed to predict clinical course by analysis of data available at time of first contact, the patients were subdivided into 18 subgroups on the basis of age and the extent of brain magnetic resonance (MRI) abnormality utilizing the MRI scoring system devised by Loes et al. Scores to grade degree of neurologic and neuropsychologic impairment were also developed. There was strong correlation between MRI and the neurology and neuropsychology scores at baseline. Information based exclusively on age and MRI score at time of first contact was highly predictive of future clinical course and should aid the evaluation of the effects of bone marrow transplantation and the selection of patients for this procedure, as well as the evaluation of other therapies that may be developed in the future.

Adrenoleukodystrophy↗