Search

Models of addiction include abnormalities in parts of the brain involving executive function/inhibitory control. Although previous studies have reported evidence of structural abnormalities in cocaine-dependent individuals, none have specifically targeted the homeless. The present preliminary study investigated brain structure in such an understudied group, homeless, crack-cocaine-dependent African American men (n = 9), comparing it to that in healthy controls (n = 8). Structural data were analyzed using voxel based morphometry (VBM) and a regions of interest (ROI) analysis. Homeless cocaine-dependent individuals had smaller gray matter volume in dorsolateral prefrontal cortex, anterior cingulate, the cerebellum, insula, and superior temporal gyrus. Most of these areas subserve executive function or inhibitory control. These results are similar to those found in most previous studies of non-homeless cocaine-dependent individuals. Reduced gray matter in executive function/inhibitory control regions of the brain in cocaine-dependent individuals may be a preexisting risk factor for the development of addiction and/or a consequence of drug abuse.

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. Published online: 25 July 2002

Two end cap designs for bird cage coils for application in nuclear magnetic resonance head imaging are presented. The objectives of the new design are to improve the [B.sub.1] field homogeneity within the coil and to improve the SNR. Design I extends the legs and one end ring of the bird cage coil onto the end cap. The radius of the end ring on the end cap is optimized to maximize the axial field of view with a limited [B.sub.1] field homogeneity. Design II uses a metal disk plate as a mirror placed at one end of the bird cage coil; it is analyzed by using a moment method. The size of the metal plate is optimized. An analysis of the two end cap designs is presented. The results show that in design I the optimal radius of the end ring on the end cap is about 2.5 times smaller than the coil radius; in design II, the inner radius of the disk mirror should be as small as possible and the mirror should be as close as possible to the coil for [B.sub.1] field homogeneity; making the outer radius of the disk larger than the coil radius does not much improve the [B.sub.1] field homogeneity. Index Terms - Birdcage coil, magnetic resonance imaging, method of moment.

Nuclear Overhauser enhancement, used to investigate the cross-relaxation activity of the oyster glycogen protons, revealed a 74% decrease of glycogen H1 following saturation of the H2+H4' resonances of glycogen in D2O. A 60% optimum decrease in H1 intensity occurred after selective reversion of the H2+H4' area and a correct delay for cross-relaxation. These are in agreement with a model in which powerful H1+H2 and H1-H4' dipolar reactions exist.

Glycogen H1 resonance exhibits in vitro relaxation characteristic when the molecular weight of glycogen is low. H-relaxation in glycogen is predominated by certain molecular mechanisms. The H-resonance is subjected to selective, semiselective and nonselective excitation to measure the cross-relaxation observed between hydrogen and other protons. Internal motion is noticed in glycogen solutions due to acute H-resonances.