BACKGROUND:Many children with heavy exposure to alcohol in utero display characteristic alterations in brain size and structure. However, the long-term effects of low-to-moderate alcohol exposure on these outcomes are unknown. METHODS:Using voxel-based morphometry and region-of-interest analyses, we examined the influence of lower doses of alcohol on gray and white matter composition in a prospectively recruited, homogeneous, well-characterized cohort of alcohol-exposed (n = 11, age 19.5 ± 0.3 years) and control (n = 9, age 19.6 ± 0.5 years) young adults. A large proportion of the exposed individuals were born to mothers whose alcohol consumption during pregnancy was in the low-to-moderate range. RESULTS:There were no differences in total brain volume or total gray or white matter volume between the exposed and control groups. However, gray matter volume was reduced in alcohol-exposed individuals in several areas previously reported to be affected by high levels of exposure, including the left cingulate gyrus, bilateral middle frontal gyri, right middle temporal gyrus, and right caudate nucleus. Notably, this gray matter loss was dose dependent, with higher exposure producing more substantial losses. CONCLUSIONS:These results indicate that even at low doses, alcohol exposure during pregnancy impacts brain development and that these effects persist into young adulthood.

BACKGROUND:Fetal alcohol-related growth restriction persists through infancy, but its impact later in life is less clear. Animal studies have demonstrated important roles for maternal nutrition in fetal alcohol spectrum disorders, but the impact of prenatal maternal body composition has not been studied in humans. This study examined the effects of prenatal alcohol exposure on longitudinal growth from birth through young adulthood and the degree to which maternal weight and body mass index (BMI) moderate these effects.METHODS:Nearly 480 mothers were recruited at their first prenatal clinic visit to overrepresent moderate-to-heavy use of alcohol during pregnancy, including a 5% random sample of low-level drinkers and abstainers. They were interviewed at every prenatal visit about their alcohol consumption using a timeline follow-back approach. Their children were examined for weight, length/height, and head circumference at birth, 6.5 and 13 months, and 7.5, 14, and 19 years.RESULTS:In multiple regression models with repeated measures (adjusted for confounders), prenatal alcohol exposure was associated with longitudinal reductions in weight, height, and weight-for-length/BMI that were largely determined at birth. At low-to-moderate levels of exposure, these effects were more severe in infancy than in later childhood. By contrast, effects persisted among children whose mothers drank at least monthly and among those born to women with alcohol abuse and/or dependence who had consumed ≥ 4 drinks/occasion. In addition, effects on weight, height, and head circumference were markedly stronger among children born to mothers with lower prepregnancy weight.CONCLUSIONS:These findings confirm prior studies demonstrating alcohol-related reductions in weight, height, weight-for-height/BMI, and head circumference that persist through young adulthood. Stronger effects were seen among children born to mothers with smaller prepregnancy weight, which may have been because of attainment of higher blood alcohol concentrations in smaller mothers for a given amount of alcohol intake or to increased vulnerability in infants born to women with poorer nutrition.

E. B. Welch, M. J. Avison, K. D. Niswender, J. Berglund, J. Kullberg, L. Johansson, M. Bruvold, and H. J. Silver Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, School of Medicine, Vanderbilt University, Nashville, TN, United States, Department of Radiology, Uppsala University, Uppsala, Sweden, MR Clinical Science, Philips Healthcare, Best, Netherlands

This study evaluates the intra- and inter-subject variability of digit maps in area 3b of anesthetized squirrel monkeys. Maps were collected using high field blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI). BOLD responses to individual digit stimulations were mapped and their response properties (location, area of activation, % signal change, time to peak response) were compared within and across imaging sessions separated by up to 20 months. During single digit stimulation using a block design, the spatiotemporal response of the BOLD signal for individual runs within and across sessions and animals was well conserved, with a time to peak BOLD response of 20+/-4 s. The variability in the center of BOLD activation in area 3b was 0.41+/-0.24 mm (mean+/-SD) across individual 5-7 min runs within a scanning session and 0.55+/-0.15 mm across sessions. The average signal change across all animals, runs and sessions was 0.62+/-0.38%, and varied 32% within and 40% across sessions. In a comparison of the stability and reproducibility of the area of single digit activation obtained using three approaches, use of a fixed statistical threshold (P<10(-5)) yielded an average area of 4.8+/-3.5 mm(2) (mean+/-SD), adaptive statistical thresholding 1.32+/-1.259 mm(2) (mean+/-SD), and combined fixed statistical and adaptive BOLD signal amplitude 4.4+/-2.5 mm(2) (mean+/-SD) across image runs and sessions. The somatotopic organization was stable within animals across sessions, while across animals, there was some variation in overall activation pattern and inter-digit distances. These results confirm that BOLD activation maps of single digits in area 3b as characterized by activation center, signal amplitudes, and temporal profile are very stable. The activation sizes determined by various criteria are the most variable measure in this preparation, but adaptive statistical thresholding appears to yield the most stable and reproducible maps. This study serves as a baseline assessment of the limits imposed on the detection of plastic changes by experimental variations of the digit BOLD fMRI activation maps in normal animals, and as an indicator of the likely performance limits in human studies.

Introduction Dynamic Shimming (DS) is a technique for obtaining optimal B0 field homogeneity over a volume by updating the shim coil currents for every slice in a multislice acquisition in real time [1, 2]. While DS can theoretically produce better B0 homogeneity for each imaging subvolume than static, global volume shimming methods, its performance may be limited by eddy current fields produced by the switching of 2 and 3 order unshielded shims, especially at ultra-high fields. These time varying eddy fields (which include ‘self’ as well as other spatial harmonics) can cause severe field deviations leading to signal losses, distortion and ghosting in imaging. Traditionally, compensation of eddy currents produced by linear gradients has been achieved using shaped current waveforms, which requires special hardware that is typically not available for higher order shims [3]. In this work, we present a novel method of eddy current compensation (ECC) applied to higher order shim induced eddy currents in a multislice DS experiment. This method does not require the use of extra hardware for ECC and is based on an assumption of reaching an eddy field steady state during an FFE (fast field echo) acquisition. Theory For our method of ECC, we make three assumptions. First, we assume that in a multi slice DS FFE experiment, the time varying eddy fields reach a steady state in which the magnitudes of these fields do not change from shot to shot for the same slice. Secondly, we ignore any change in eddy field magnitude during the FFE data readout window. Thirdly, we assume that the eddy fields produced depend not only on the most recent switch of higher order shim but also on the previous switches. It follows then, that in an n slice DS experiment we can write:

Purpose Large-scale transmit RF field inhomogeneities are often present in ultra-high field human MR images, so there is considerable interest in using accurate B1 + mapping methods for post-acquisition corrections of image intensity as well as for the modeling and design of RF coils and RF pulses. The goal of this study was to compare the accuracy of three widely used B1 + / flip angle mapping techniques and the magnitude of systematic errors inherent in these methods.

Introduction Dynamic Shimming is a technique for obtaining optimal Bo field homogeneity for a multi slice region by updating the shim coil currents for every slice in real time [1]. Dynamic shimming can produce greater field homogeneity within each slice than global volume shimming methods. It can therefore reduce signal losses and geometric distortions due to variations in magnetic susceptibility within the body, and can be especially useful in fast T2* weighted imaging sequences such as EPI. We have implemented first order dynamic shimming on a human 7T system for brain imaging studies. Initial results from the study, and an evaluation of the improvements made, are presented.

N. Zhang, V. A. Fitsanakis, M. Aschner, M. J. Avison, J. C. Gore Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, United States, Physics Department, Vanderbilt University, Nashville, Tennessee, United States, Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States, Department of Pharmacology and the Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee, United States, Neurology Department, Vanderbilt University Medical Center, Nashville, Tennessee, United States

The extent to which the brain regions associated with face processing are selective for that specific function remains controversial. In addition, little is known regarding the extent to which face-responsive brain regions are selective for human faces. To study regional selectivity of face processing, we used functional magnetic resonance imaging to examine whole brain activation in response to human faces, dog faces, and houses. Fourteen healthy right-handed volunteers participated in a passive viewing, blocked experiment. Results indicate that the lateral fusiform gyrus (Brodmann's area 37) responds maximally to both dog and human faces when compared with other sites, followed by the middle/inferior occipital gyrus (BA 18/19). Sites that were activated by houses versus dog and human faces included the medial fusiform gyrus (BA 19/37), the posterior cingulate (BA 30), and the superior occipital gyrus (BA 19). The only site that displayed significant differences in activation between dog and human faces was the lingual/medial fusiform gyrus. In this site, houses elicited the strongest activation, followed by dog faces, while the response to human faces was negligible and did not differ from fixation. The parahippocampal gyrus/amygdala was the sole site that displayed significant activation to human faces, but not to dog faces or houses.

The mechanisms underlying blood-brain barrier (BBB) compromise in human immunodeficiency virus (HIV) infection and the ways in which BBB compromise might impair neurocognitive function remain poorly understood. This study had two aims: (1) to examine the relationship between BBB breakdown, measured using contrast-enhanced magnetic resonance imaging (CE-MRI), plasma viral load, and neurological status; and (2) to examine the influence of highly active antiretroviral therapy (HAART) on the relationship between neuroinflammation using myoinositol/creatine (mI/Cr), a surrogate marker of glial activation as measured by magnetic resonance spectroscopy (MRS), and BBB compromise determined by CE-MRI. In 25 HIV-infected patients, we found that: (1) the severity of neurocognitive impairment correlated with the degree of BBB breakdown in the basal ganglia; (2) for any given degree of BBB compromise, patients with high plasma viral load were more severely impaired; (3) BBB compromise correlated with mI/Cr in the basal ganglia; and (4) for any given level of mI/Cr, the severity of BBB compromise and the severity of neurocognitive impairment were significantly less in patients on HAART than in those who were HAART-naive. These results confirm a role for BBB compromise in the pathogenesis of HIV-associated neurocognitive impairment and suggest that elevated plasma viral load in the presence of BBB compromise may increase the risk for development of HIV-associated dementia (HAD). Additionally, they suggest a salutary effect of HAART on the incidence and severity of HAD, which may, in part, be due to protection of BBB integrity.

HIV dementia (HIVD) is among the most common and most feared neurological complications of AIDS. In vitro studies have identified a constellation of potentially neurotoxic inflammatory and non-inflammatory pathways, one or more of which could underlie HIVD. Magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) studies can distinguish between inflammatory and non-inflammatory pathways in vivo and suggest that either or both might be active in different patients or at different times in the same patient. This could perhaps explain the variability in HIVD development, progression and response to therapy. These findings also suggest that MRI and MRS can identify patients at risk for HIVD and predict response to therapy.