Frequency drift in MR spectroscopy at 3T.

Purpose: Heating of gradient coils and passive shim components is a common cause of instability in the B field, especially when gradient intensive sequences are used. The aim of the study was to set a benchmark for typical drift encountered during MR spectroscopy (MRS) to assess the need for real-time field-frequency locking on MRI scanners by comparing field drift data from a large number of sites.

Method: A standardized protocol was developed for 80 participating sites using 99 3T MR scanners from 3 major vendors.

Comparison of Multivendor Single-Voxel MR Spectroscopy Data Acquired in Healthy Brain at 26 Sites.

Background The hardware and software differences between MR vendors and individual sites influence the quantification of MR spectroscopy data. An analysis of a large data set may help to better understand sources of the total variance in quantified metabolite levels. Purpose To compare multisite quantitative brain MR spectroscopy data acquired in healthy participants at 26 sites by using the vendor-supplied single-voxel point-resolved spectroscopy (PRESS) sequence.

Big GABA II: Water-referenced edited MR spectroscopy at 25 research sites.

Accurate and reliable quantification of brain metabolites measured in vivo using H magnetic resonance spectroscopy (MRS) is a topic of continued interest. Aside from differences in the basic approach to quantification, the quantification of metabolite data acquired at different sites and on different platforms poses an additional methodological challenge. In this study, spectrally edited γ-aminobutyric acid (GABA) MRS data were analyzed and GABA levels were quantified relative to an internal tissue water reference.

Resting state cerebral blood flow with arterial spin labeling MRI in developing human brains.

The development of brain circuits is coupled with changes in neurovascular coupling, which refers to the close relationship between neural activity and cerebral blood flow (CBF). Studying the characteristics of CBF during resting state in developing brain can be a complementary way to understand the functional connectivity of the developing brain. Arterial spin labeling (ASL), as a noninvasive MR technique, is particularly attractive for studying cerebral perfusion in children and even newborns.

Big GABA: Edited MR spectroscopy at 24 research sites.

Magnetic resonance spectroscopy (MRS) is the only biomedical imaging method that can noninvasively detect endogenous signals from the neurotransmitter γ-aminobutyric acid (GABA) in the human brain. Its increasing popularity has been aided by improvements in scanner hardware and acquisition methodology, as well as by broader access to pulse sequences that can selectively detect GABA, in particular J-difference spectral editing sequences. Nevertheless, implementations of GABA-edited MRS remain diverse across research sites, making comparisons between studies challenging.

Changes in corticostriatal connectivity during reinforcement learning in humans.

Many computational models assume that reinforcement learning relies on changes in synaptic efficacy between cortical regions representing stimuli and striatal regions involved in response selection, but this assumption has thus far lacked empirical support in humans. We recorded hemodynamic signals with fMRI while participants navigated a virtual maze to find hidden rewards. We fitted a reinforcement-learning algorithm to participants' choice behavior and evaluated the neural activity and the changes in functional connectivity related to trial-by-trial learning variables.

Improving the spectral resolution and spectral fitting of (1) H MRSI data from human calf muscle by the SPREAD technique.

Proton magnetic resonance spectroscopic imaging ((1) H MRSI) has been used for the in vivo measurement of intramyocellular lipids (IMCLs) in human calf muscle for almost two decades, but the low spectral resolution between extramyocellular lipids (EMCLs) and IMCLs, partially caused by the magnetic field inhomogeneity, has hindered the accuracy of spectral fitting. The purpose of this paper was to enhance the spectral resolution of (1) H MRSI data from human calf muscle using the SPREAD (spectral resolution amelioration by deconvolution) technique and to assess the influence of improved spectral resolution on the accuracy of spectral fitting and on in vivo measurement of IMCLs. We acquired MRI and (1) H MRSI data from calf muscles of three healthy volunteers.

Morphological features of the neonatal brain following exposure to regional anesthesia during labor and delivery.

Introduction: Recent animal and human epidemiological studies suggest that early childhood exposure to anesthesia may have adverse effects on brain development. As more than 50% of pregnant women in the United States and one-third in the United Kingdom receive regional anesthesia during labor and delivery, understanding the effects of perinatal anesthesia on postnatal brain development has important public health relevance.

Methods: We used high-resolution magnetic resonance imaging (MRI) to assess the effects of regional anesthesia during labor and delivery as part of a larger study of perinatal exposures on the morphological features of the neonatal brain.

Automated assessment of the quality of diffusion tensor imaging data using color cast of color-encoded fractional anisotropy images.

Diffusion tensor imaging (DTI) data often suffer from artifacts caused by motion. These artifacts are especially severe in DTI data from infants, and implementing tight quality controls is therefore imperative for DTI studies of infants. Currently, routine procedures for quality assurance of DTI data involve the slice-wise visual inspection of color-encoded, fractional anisotropy (CFA) images.

Distinct neural circuits subserve interpersonal and non-interpersonal emotions.

Emotions elicited by interpersonal versus non-interpersonal experiences have different effects on neurobiological functioning in both animals and humans. However, the extent to which the brain circuits underlying interpersonal and non-interpersonal emotions are distinct still remains unclear. The goal of our study was to assess whether different neural circuits are implicated in the processing of arousal and valence of interpersonal versus non-interpersonal emotions.

Neural correlates of reward-based spatial learning in persons with cocaine dependence.

Dysfunctional learning systems are thought to be central to the pathogenesis of and impair recovery from addictions. The functioning of the brain circuits for episodic memory or learning that support goal-directed behavior has not been studied previously in persons with cocaine dependence (CD). Thirteen abstinent CD and 13 healthy participants underwent MRI scanning while performing a task that requires the use of spatial cues to navigate a virtual-reality environment and find monetary rewards, allowing the functional assessment of the brain systems for spatial learning, a form of episodic memory.

Ultra-high-field MR imaging in multiple sclerosis.

In multiple sclerosis (MS), MRI is the most important paraclinical tool used to inform diagnosis and for monitoring disease evolution, either natural or modified by treatment. The increased availability of ultra-high-field magnets (7 Tesla or higher) gives rise to questions about the main benefits of and challenges for their use in patients with MS. The main advantages of ultra-high-field MRI are the improved signal-to-noise ratio, greater chemical shift dispersion, and improved contrast due to magnetic susceptibility variations, which lead to increased sensitivity to the heterogeneous pathological substrates of the disease.

Effects of davunetide on N-acetylaspartate and choline in dorsolateral prefrontal cortex in patients with schizophrenia.

Schizophrenia is associated with extensive neurocognitive and behavioral impairments. Studies indicate that N-acetylaspartate (NAA), a marker of neuronal integrity, and choline, a marker of cell membrane turnover and white matter integrity, may be altered in schizophrenia. Davunetide is a neurotrophic peptide that can enhance cognitive function in animal models of neurodegeneration.

Metabolite Mapping with Extended Brain Coverage Using a Fast Multisection MRSI Pulse Sequence and a Multichannel Coil.

Multisection magnetic resonance spectroscopic imaging is a widely used pulse sequence that has distinct advantages over other spectroscopic imaging sequences, such as dynamic shimming, large region-of-interest coverage within slices, and rapid data acquisition. It has limitations, however, in the number of slices that can be acquired in realistic scan times and information loss from spacing between slices. In this paper, we synergize the multi-section spectroscopic imaging pulse sequence with multichannel coil technology to overcome these limitations.

Multimodal magnetic resonance imaging: The coordinated use of multiple, mutually informative probes to understand brain structure and function.

Differing imaging modalities provide unique channels of information to probe differing aspects of the brain's structural or functional organization. In combination, differing modalities provide complementary and mutually informative data about tissue organization that is more than their sum. We acquired and spatially coregistered data in four MRI modalities--anatomical MRI, functional MRI, diffusion tensor imaging (DTI), and magnetic resonance spectroscopy (MRS)--from 20 healthy adults to understand how interindividual variability in measures from one modality account for variability in measures from other modalities at each voxel of the brain.

An fMRI study of the brain responses of traumatized mothers to viewing their toddlers during separation and play.

This study tested whether mothers with interpersonal violence-related posttraumatic stress disorder (IPV-PTSD) vs healthy controls (HC) would show greater limbic and less frontocortical activity when viewing young children during separation compared to quiet play. Mothers of 20 children (12-42 months) participated: 11 IPV-PTSD mothers and 9 HC with no PTSD. During fMRI, mothers watched epochs of play and separation from their own and unfamiliar children.

Convection-enhanced delivery of topotecan into a PDGF-driven model of glioblastoma prolongs survival and ablates both tumor-initiating cells and recruited glial progenitors.

The contribution of microenvironment to tumor growth has important implications for optimizing chemotherapeutic response and understanding the biology of recurrent tumors. In this study, we tested the effects of locally administered topotecan on a rat model of glioblastoma that is induced by intracerebral injection of PDGF (platelet-derived growth factor)-IRES (internal ribosome entry site)-GFP (green fluorescent protein)-expressing retrovirus, treated the tumors by convection-enhanced delivery (CED) of topotecan (136 μmol/L) for 1, 4, or 7 days, and then characterized the effects on both the retrovirus-transformed tumor cells (GFP(+) cells) as well as the uninfected glial progenitor cells (GFP(-) cells) that are recruited to the tumor. Topotecan treatment reduced GFP(+) cells about 10-fold and recruited progenitors by about 80-fold while providing a significant survival advantage that improved with greater treatment duration.

A virtual reality-based FMRI study of reward-based spatial learning.

Although temporo-parietal cortices mediate spatial navigation in animals and humans, the neural correlates of reward-based spatial learning are less well known. Twenty-five healthy adults performed a virtual reality fMRI task that required learning to use extra-maze cues to navigate an 8-arm radial maze and find hidden rewards. Searching the maze in the spatial learning condition compared to the control conditions was associated with activation of temporo-parietal regions, albeit not including the hippocampus.

Neural systems subserving valence and arousal during the experience of induced emotions.

The circumplex model of affect construes all emotions as linear combinations of 2 independent neurophysiological dimensions, valence and arousal. We used functional magnetic resonance imaging to identify the neural networks subserving valence and arousal, and we assessed, in 10 participants, the associations of the BOLD (blood oxygen level-dependent) response, an indirect index of neural activity, with ratings of valence and arousal during the emotional experiences induced by the presentation of evocative sentences. Unpleasant emotional experience was associated with increased BOLD signal intensities in the supplementary motor, anterior midcingulate, right dorsolateral prefrontal, occipito-temporal, inferior parietal, and cerebellar cortices.

Techniques for in utero, longitudinal MRI of fetal brain development in baboons at 3T.

Magnetic Resonance Imaging (MRI) is a promising tool for the noninvasive, longitudinal study of developing primate brains. We developed a protocol to scan pregnant baboons serially at 3T for up to 3h per session. This protocol includes procedures for animal preparation, anesthesia, MRI scanning, and post-scan animal care.

Computational and experimental optimization of a double-tuned (1)H/(31)P four-ring birdcage head coil for MRS at 3T.

Purpose: To optimize the homogeneity and efficiency of the B(1) magnetic field of a four-ring birdcage head coil that is double-tuned at the Larmor frequencies of both (31)P and (1)H and optimized to acquire magnetic resonance spectroscopy (MRS) data at 3T for the study of infants.

Materials And Methods: We developed a finite difference time domain (FDTD) tool in-house to iteratively compute and seek the range of geometric and electromagnetic parameters of a dual-tuned, four-ring birdcage coil that would produce the desired resonance patterns, optimize homogeneity of the B(1)-field, and maximize efficiency of the coil. To demonstrate the validity of our computational results, we constructed three RF coils: one dual-tuned coil that was based on the calculated optimized parameters and two single-tuned coils that had dimensions similar to those of the dual-tuned coil, but tuned at the Larmor frequencies of both (31)P and (1)H, respectively.

High-field magnetic resonance imaging.

This article explores the role of high-field (HF) MR imaging in medicine. It analyzes advantages of HF MR imaging in application to human subjects and how best they can be used to unravel the secrets of diseases, such as multiple sclerosis. Special emphasis is placed on morphologic imaging to highlight the role of soft tissue contrast, MR spectroscopy to showcase the ability of detecting biochemical information, and functional MR imaging as an emerging technology for assessing tissue function with the possibility of eventual introduction to the clinical arena.

An affective circumplex model of neural systems subserving valence, arousal, and cognitive overlay during the appraisal of emotional faces.

Increasing evidence supports the existence of distinct neural systems that subserve two dimensions of affect--arousal and valence. Ten adult participants underwent functional magnetic resonance imaging during which they were presented a range of standardized faces and then asked, during the scan, to rate the emotional expressions of the faces along the dimensions of arousal and valence. Lower ratings of arousal accompanied greater activity in the amygdala complex, cerebellum, dorsal pons, and right medial prefrontal cortex (mPFC).

The neurophysiological bases of emotion: An fMRI study of the affective circumplex using emotion-denoting words.

Objective: We aimed to study the neural processing of emotion-denoting words based on a circumplex model of affect, which posits that all emotions can be described as a linear combination of two neurophysiological dimensions, valence and arousal. Based on the circumplex model, we predicted a linear relationship between neural activity and incremental changes in these two affective dimensions.

Methods: Using functional magnetic resonance imaging, we assessed in 10 subjects the correlations of BOLD (blood oxygen level dependent) signal with ratings of valence and arousal during the presentation of emotion-denoting words.