Faculty Bibliography

The volume of temporal lobe structures was examined in twenty-seven older (mean age of 69.2 +/- 8.3 years) and ten younger subjects (mean age of 26.1 +/- 4.1 years) using quantitative magnetic resonance imaging (MRI) methods. Multiple regression analysis, using gender, overall atrophy, and head size as covariates, showed unique contributions of age to variance in both medial and lateral temporal lobe volumes. Temporal lobe subregions that showed the strongest unique age-related reductions were the hippocampus, fusiform gyrus, and parahippocampus. These results suggest age-related reductions in temporal lobe subvolumes

Previously developed design methodology provides a systematic analysis of magnetic structures composed of uniformly magnetized prisms that generate uniform fields. The approach is based on the property of cancellation of field singularities at the interfaces between the media. Applications of this design methodology thus far have been restricted to magnetic structures with concave cavity boundaries. However, convex cavity boundaries may be necessary for C-shaped magnetic structures involved in medical NMR imaging that feature a side opening in addition to openings at both ends. This paper introduces transition structures placed in the region of the magnet opening and analyzes their field properties. The results indicate a remarkable benefit of the transition elements in terms of field uniformity and the size of the imaging region

OBJECTIVE: Positron emission tomography and the fluorodeoxyglucose (FDG) method were used to determine the brain's metabolic response to neuroleptic challenge in a normal, disease-free state. METHOD: FDG measurements were obtained before and 12 hours after administration of 5 mg of haloperidol to 12 young normal men. These values were compared with test-retest FDG measures obtained from nine normal male control subjects who received no drug intervention. RESULTS: After haloperidol administration, the haloperidol subjects showed significantly lower glucose utilization in the neocortex, limbic cortex, thalamus, and caudate nucleus but not in the putamen or cerebellum. After adjustment for global effects, significant reductions were still evident in the frontal, occipital, and anterior cingulate cortex, whereas the putamen and cerebellum showed significant increases. CONCLUSIONS: This study, measuring the brain's metabolic response to acute receptor blockade, is a first step in the development of an assay of CNS pharmacological activity. By determining the response to neuroleptic challenge in a normal state, the study establishes a comparison group for determining response to challenge in various psychiatric conditions

Measurements of hippocampal formation atrophy using MRI have been useful in distinguishing demented patients with a diagnosis of probable Alzheimer's disease from cognitively normal controls. To determine whether there is a similar relationship between hippocampal size and dementia in elderly patients suspected of normal pressure hydrocephalus (NPH), the authors obtained mini-mental status examination (MMSE) scores and MRI measurements of hippocampal size and CSF volume on 16 elderly patients whose severe ventriculomegaly and unexplained gait impairment made NPH a probable diagnosis. Hippocampal size correlated strongly with MMSE score (r = 0.75, p < 0.001); no significant MMSE correlation was found for ventricular CSF volume or extra-ventricular/ventricular CSF ratio. It was concluded that hippocampal atrophy is associated with severe cognitive dysfunction in many elderly patients with a diagnosis of NPH. As a hypothesis for further investigation, the detection of such atrophy may help identify cases where the presence of a pathology of Alzheimer's disease complicates the diagnosis of NPH

Although mild progressive memory impairment is commonly associated with normal human aging, it is unclear whether this phenomenon can be explained by specific structural brain changes. In a research sample of 54 medically healthy and cognitively normal elderly persons (ages 55-87, x = 69.0 +/- 7.9), magnetic resonance imaging (MRI) was used to derive head-size-adjusted measurements of the hippocampal formation (HF) (dentate gyrus, hippocampus proper, alveus, fimbria, subiculum), the superior temporal gyrus (STG), and the subarachnoid cerebrospinal fluid (CSF) (to estimate generalized cerebral atrophy). Subjects were administered tests of primary memory (digit span) and tests of secondary memory with immediate and delayed recall components (paragraph, paired associate, list recall; facial recognition). Separate composite scores for the immediate and delayed components were created by combining, with equal weighting, the subtests of each category. The WAIS vocabulary subtest was used as a control measure for language and intelligence. A highly significant correlation (P < 0.001), independent of age, gender, and generalized cerebral atrophy was found between HF size and delayed memory performance. No significant correlations were found between HF size and primary or immediate memory performance. STG size was not significantly correlated with any of the composite memory variables. These results suggest that HF atrophy may play an important independent role in contributing to the memory loss experienced by many aging adults

This paper discusses a technique for improving the homogeneity of the magnetic field in structures of permanent magnets designed for magnetic resonance imaging, achieved by inserting layers of ferromagnetic plates and permanent magnets along the cavity of the structure. The analysis of the field in the magnet is performed using a boundary integral equation method. An example of optimization of the geometry and the amount of the magnetic material is presented