The impact of aortic arch geometry on flow dynamics using a simplified approach with magnetic resonance velocity mapping.

Background: We sought to determine, in vivo, the impact of aortic arch geometry on flow dynamics, which affects overall cardiovascular energetics and has implications for organ perfusion and Doppler flow calculations.

Methods: Twenty-seven patients (13 with left and 14 with right aortic arches) underwent magnetic resonance phase-encoded velocity mapping in the ascending and descending aorta. The cross-sectional area were divided into 4 equal quadrants aligned along the long axis of the aorta for analysis.

Neural correlate of vernier acuity tasks assessed by functional MRI (FMRI).

Vernier acuity refers to the ability to discern a small offset within a line. However, while Vernier acuity has been extensively studied psychophysically, its neural correlates are uncertain. Based upon previous psychophysical and electrophysiologic data, we hypothesized that extrastriate areas of the brain would be involved in Vernier acuity tasks, so we designed event-related functional MRI (fMRI) paradigms to identify cortical regions of the brain involved in this behavior.

Decreased cortical activation in response to a motion stimulus in anisometropic amblyopic eyes using functional magnetic resonance imaging.

Purpose: Motion perception abnormalities and extrastriate abnormalities have been suggested in amblyopia. Functional MRI (fMRI) and motion stimuli were used to study whether interocular differences in activation are detectable in motion-sensitive cortical areas in patients with anisometropic amblyopia.

Methods: We performed fMRI at 1.

Natural history of Canavan disease revealed by proton magnetic resonance spectroscopy (1H-MRS) and diffusion-weighted MRI.

Canavan disease is a childhood leukodystrophy caused by mutations in the gene for human aspartoacylase ( ASPA), which leads to an abnormal accumulation of the substrate molecule N-acetyl-aspartate (NAA) in the brain. This study was designed to model the natural history of Canavan disease using MRI and proton magnetic resonance spectroscopy ( (1)H-MRS). NAA and various indices of brain structure (morphology, quantitative T1, fractional anisotropy, apparent diffusion coefficient) were measured in white and gray matter regions during the progression of Canavan disease.

Fetal posterior fossa volume: assessment with MR imaging.

Purpose: To retrospectively determine the relationship between posterior fossa volume (PFV) and estimated gestational age (EGA) and/or femur length (FL) during pregnancy for the purpose of developing a normal growth curve.

Materials And Methods: Advance institutional review board approval was obtained for this HIPAA-compliant study, and the need for parent informed consent was waived. A cross-sectional retrospective study was performed to measure PFV on in vivo magnetic resonance (MR) images obtained in 76 fetuses of 18-36 weeks gestation who had a morphologically normal CNS.

Spatial and temporal characteristics of physiological noise in fMRI at 3T.

Rationale And Objectives: Physiological noise in blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) has been shown to have characteristics similar to the BOLD signal itself, suggesting that it may have a vascular dependence. In this study, we evaluated the influence of physiological noise in fMRI as revealed by the differences in vasculature sensitivity of gradient-echo echo-planar imaging (GE-EPI) and spin-echo EPI (SE-EPI).

Materials And Methods: The contribution of physiological noise to the fMRI signal during activation of the visual cortex was assessed by comparing its temporal characteristics with respect to echo time (TE), using both GE-EPI and SE-EPI.

Recognition of objects in non-canonical views: a functional MRI study.

Background: The neural correlate of object recognition in non-canonical views is uncertain, but there is evidence for involvement of neural pathways, possibly separate from those used for object recognition in canonical views.

Methods: Boxcar functional MRI (fMRI) techniques were used to detect neural activity while eight normal subjects were instructed to identify digital photographs of objects in non-canonical and canonical orientations.

Results: The right angular gyrus, the left inferior temporal gyrus, and the right cerebellum showed significant fMRI activity during non-canonical as opposed to canonical viewing.

Application of spatial modulation of magnetization (SPAMM) to children: the effect of image resolution on tagging pattern.

Background And Objective: Spatial modulation of magnetization (SPAMM) is a valuable magnetic resonance imaging technique for studying ventricular biomechanics. In order to track the intersection points of the stripes to calculate regional wall motion and strain, the stripe spacing should be at most half the wall thickness, yet sufficiently larger than the image pixel size in order that the stripes be well resolved. These conflicting requirements, that the grid spacing be much smaller than the wall thickness yet much larger than the pixel size, are relatively easy to meet in adult subjects but are difficult in children because of their small size.

Decreased lateral geniculate nucleus activation in retrogeniculate hemianopia demonstrated by functional magnetic resonance imaging at 4 Tesla.

Functional magnetic resonance imaging (fMRI) can detect lateral geniculate nucleus (LGN) activation. We studied LGN function in 5 patients with retrogeniculate homonymous hemianopia using fMRI at 4.0 Tesla during binocular visual stimulation.

Age-related, regional, hemispheric, and medial-lateral differences in myelin integrity in vivo in the normal adult brain.

Background And Purpose: Clinical validation of magnetization transfer (MT) imaging is important for investigating clinical disease and organization of normal brain function. We determined whether an in vivo quantitative measure sensitive to white matter is distributed in functionally important ways.

Methods: Axial 1.

Brain T1 in young children with sickle cell disease: evidence of early abnormalities in brain development.

Measurement of tissue spin lattice relaxation time (T(1)) has been used to characterize brain development in healthy children. Here we report the first study of brain T(1) in young children with sickle cell disease (SCD). The T(1) in 10 tissue samples was measured by established techniques; 46 SCD patients under the age of 4 years were compared to 267 controls, including 55 well children under the age of 4 years.

Direct comparison of two methods to measure T1: in vitro and in vivo values by echo-planar imaging and by segmented k-space imaging.

We test a hypothesis that proton T(1) is accurately measured independent of the physics inherent to the method. We used two well-validated but quite different imaging methods to measure T(1) in phantoms and in humans; an echo-planar imaging T-one measurement (EPITOME) method, and a segmented k-space acquisition precise and accurate inversion recovery (TurboPAIR) method. Agreement between the methods was generally excellent; the square of the correlation coefficient (r(2)) in phantoms was 0.

Acute diffusion abnormalities in the hippocampus of children with new-onset seizures: the development of mesial temporal sclerosis.

We studied the role of early diffusion-weighted imaging DWI in the investigation of children with new-onset prolonged seizures which eventually result in unilateral hippocampal sclerosis (HS). We carried out MRI on five children aged 17 months to 7 years including conventional and diffusion-weighted sequences. We calculated apparent diffusion coefficients (ADC) for the affected and the normal opposite hippocampus.

Diffusion tensor imaging of the hippocampal formation in temporal lobe epilepsy.

Background And Purpose: Diffusion tensor imaging (DTI) is a noninvasive technique that can be used to assess the integrity of cerebral tissue. The purpose of this study was to assess DTI measurements in the hippocampal formation (HF) and to investigate the role of DTI in lateralizing the seizure focus in temporal lobe epilepsy (TLE).

Methods: We evaluated 12 patients with unilateral TLE and 14 healthy subjects.

Pediatric perfusion imaging using pulsed arterial spin labeling.

Purpose: To test the feasibility of pediatric perfusion imaging using a pulsed arterial spin labeling (ASL) technique at 1.5 T.

Materials And Methods: ASL perfusion imaging was carried out on seven neurologically normal children and five healthy adults.

Decreased activation of the lateral geniculate nucleus in a patient with anisometropic amblyopia demonstrated by functional magnetic resonance imaging.

Although postmortem morphological changes in the lateral geniculate nucleus (LGN) have been reported in human amblyopia, LGN function during monocular viewing by amblyopic eyes has not been documented in humans. We used functional magnetic resonance imaging (fMRI) to study monocular visual activation of the LGN in a patient with anisometropic amblyopia. Four normal subjects, a patient with optic neuritis and a patient with anisometropic amblyopia were studied with fMRI at 1.

Diffusion-weighted imaging in acute bacterial meningitis in infancy.

Bacterial meningitis is frequently fatal or leads to severe neurological impairment. Complications such as vasculitis, resulting in infarcts, should be anticipated and dealt with promptly. Our aim was to demonstrate the complications of meningitis by diffusion weighted imaging (DWI) in patients who deteriorated despite therapy.

Flow volume asymmetry in the right aortic arch in children with magnetic resonance phase encoded velocity mapping.

Background: The right aortic arch is not uncommon in pediatrics. Flow dynamics in this type of aortic arch, which is important for cardiac energetics, organ perfusion, and Doppler flow calculations, have not been defined. Although there are complex secondary flow patterns, bulk axial flow makes up most of the energy use.

Functional magnetic resonance imaging and its clinical utility in patients with visual disturbances.

Functional magnetic resonance imaging (fMRI) is a powerful, non-invasive technique for mapping human brain function. Because of the robust signal intensity changes associated with visual stimuli, fMRI is particularly useful for studying visual cortex (including both striate and extrastriate cortex). Also, activation of the lateral geniculate nuclei has been successfully demonstrated by fMRI.

Clinical protocol. Gene therapy of Canavan disease: AAV-2 vector for neurosurgical delivery of aspartoacylase gene (ASPA) to the human brain.

This clinical protocol describes virus-based gene transfer for Canavan disease, a childhood leukodystrophy. Canavan disease, also known as Van Bogaert-Bertrand disease, is a monogeneic, autosomal recessive disease in which the gene coding for the enzyme aspartoacylase (ASPA) is defective. The lack of functional enzyme leads to an increase in the central nervous system of the substrate molecule, N-acetyl-aspartate (NAA), which impairs normal myelination and results in spongiform degeneration of the brain.

Nonuniform flow dynamics in the aorta of normal children: a simplified approach to measurement using magnetic resonance velocity mapping.

Purpose: To determine regional flow dynamics in the normal aorta (Ao) in children. Understanding flow dynamics in children is important in cardiovascular energetics, in designing improved aortic reconstructions by crafting the surgery to mimic normal aortic flow, and in Doppler flow calculations. The objective of this study was to determine regional flow dynamics in the normal Ao in children.

Evaluation of iron overload by single voxel MRS measurement of liver T2.

Purpose: To overcome the difficulty of poor signal-to-noise ratio of magnetic resonance imaging (MRI) in evaluating heavy iron overload by using a single voxel magnetic resonance spectroscopy (MRS) technique.

Materials And Methods: A single voxel STEAM pulse sequence with a minimum TE of 1.5 msec and a sampling volume of 36.

Eye dominance in the visual cortex using functional MRI at 1.5 T: an alternative method.

Purpose: To develop a functional MRI method for producing eye dominance histograms in humans at 1.5 Tesla (T).

Methods: In the first set of experiments, 8 normal persons were tested.

Diffusion imaging in pediatric central nervous system infections.

Our purpose was to investigate the role of diffusion imaging (DI) in central nervous system (CNS) infections in pediatric patients. It was anticipated that DI would be more sensitive than conventional MRI in the detection of the infarctive complications of infection, and possibly, in the detection of the infectious process as well. Seventeen pediatric patients, eight having meningitis,, five with herpes encephalitis, three with brain abscess or cerebritis and one with sepsis, were evaluated at 1.