Considerations for measuring the fractional anisotropy of metabolites with diffusion tensor spectroscopy.

Diffusion tensor spectroscopy of metabolites in brain is challenging because of their lower diffusivity (i.e. less signal attenuation for a given b value) and much poorer signal-to-noise ratio relative to water.

Spectral editing of weakly coupled spins using variable flip angles in PRESS constant echo time difference spectroscopy: application to GABA.

A general in vivo magnetic resonance spectroscopy editing technique is presented to detect weakly coupled spin systems through subtraction, while preserving singlets through addition, and is applied to the specific brain metabolite gamma-aminobutyric acid (GABA) at 4.7 T. The new method uses double spin echo localization (PRESS) and is based on a constant echo time difference spectroscopy approach employing subtraction of two asymmetric echo timings, which is normally only applicable to strongly coupled spin systems.

Voxel-based morphometry reveals extra-nigral atrophy patterns associated with dopamine refractory cognitive and motor impairment in parkinsonism.

Objectives: To determine overall patterns of brain atrophy associated with memory, executive function (EF) and dopamine non-responsive motor measures in older parkinsonian patients.

Design: Forty-three older PD patients (>or=65 years) and matched controls underwent a neurological examination (Unified Parkinson's Disease Rating Scale, separated into dopamine responsive and dopamine non-responsive signs) and neuropsychological testing (memory: California Verbal Learning Test (CVLT)) and a composite of index of executive function (EF): Stroop Interference, Trail Making Test Part B, and digit ordering. All underwent volumetric MRI scans analyzed using voxel-based morphometry (VBM).

Acute dextro-amphetamine administration does not alter brain myo-inositol levels in humans and animals: MRS investigations at 3 and 18.8 T.

The pathophysiological underpinnings of bipolar disorder are not fully understood. However, they may be due in part to changes in the phosphatidylinositol second messenger system (PI-cycle) generally, or changes in myo-inositol concentrations more specifically. Dextro-amphetamine has been used as a model for mania in several human studies as it causes similar subjective and physiological symptoms.

Anisotropic diffusion of metabolites in peripheral nerve using diffusion weighted magnetic resonance spectroscopy at ultra-high field.

Although the diffusivity and anisotropy of water has been investigated thoroughly in ordered axonal systems (i.e., nervous tissue), there have been very few studies on the directional dependence of diffusion of metabolites.

Diffusion tensor spectroscopy (DTS) of human brain.

The diffusion tensor of N-acetyl aspartate (NAA), creatine and phosphocreatine (tCr), and choline (Cho) was measured at 3T using a diffusion weighted STEAM (1)H-MRS sequence in the healthy human brain in 6 distinct regions (4 white matter and 2 cortical gray matter). The Trace/3 apparent diffusion coefficient (ADC) of each metabolite was significantly greater in white matter than gray matter. The Trace/3 ADC values of tCr and Cho were found to be significantly greater than NAA in white matter, whereas all 3 metabolites had similar Trace/3 ADC in cortical gray matter.

Decreased prefrontal Myo-inositol in major depressive disorder.

Background: Postmortem studies have shown robust prefrontal cortex glial losses and more subtle neuronal changes in major depressive disorder (MDD). Earlier proton magnetic resonance spectroscopy (1H-MRS) studies of the glial marker myo-inositol in MDD were subject to potential confounds. The primary hypothesis of this study was that MDD patients would show reduced prefrontal/anterior cingulate cortex levels of myo-inositol.

Trace apparent diffusion coefficients of metabolites in human brain using diffusion weighted magnetic resonance spectroscopy.

The rotationally invariant trace/3 apparent diffusion coefficients (ADC) of N-acetyl aspartate (NAA), creatine and phosphocreatine (tCr), and choline (Cho) were determined using a diffusion-weighted stimulated echo acquisition mode sequence at 3 T in three separate human brain regions, namely the subcortical white matter, occipital gray matter, and frontal gray matter. The measurement of the mean diffusivity eliminates the dependence of the measured ADC on the direction of the diffusion gradient relative to the tissue microstructure (i.e.