Faculty Bibliography

BACKGROUND AND PURPOSE: A technique of segmenting total gray matter (GM) and total white matter (WM) in human brain is now available. We investigated the effects of age and sex on total fractional GM (%GM) and total fractional WM (%WM) volumes by using volumetric MR imaging in healthy adults. METHODS: Fifty-four healthy volunteers (22 men, 32 women) aged 20-86 years underwent dual-echo fast spin-echo MR imaging. Total GM, total WM, and intracranial space volumes were segmented by using MR image-based computerized semiautomated software. Volumes were normalized as a percentage of intracranial volume (%GM and %WM) to adjust for variations in head size. Age and sex effects were then assessed. RESULTS: Both %GM and %WM in the intracranial space were significantly less in older subjects (> or =50 years) than in younger subjects (<50 years) (P <.0001 and P =.02, respectively). Consistently, %GM decreased linearly with age, beginning in the youngest subjects. %WM decreased in a quadratic fashion, with a greater rate beginning only in adult midlife. Although larger GM volumes were observed in men before adjustments for cranium size, no significant differences in %GM or %WM were observed between the sexes. CONCLUSION: GM volume loss appears to be a constant, linear function of age throughout adult life, whereas WM volume loss seems to be delayed until middle adult life. Both appear to be independent of sex. Quantitative analysis of %GM and %WM volumes can improve our understanding of brain atrophy due to normal aging; this knowledge may be valuable in distinguishing atrophy of disease patterns from characteristics of the normal aging process

BACKGROUND AND PURPOSE: The magnetization transfer ratio (MTR) is a sensitive and quantitative identifier of underlying structural changes in the brain. We quantitatively evaluated age- and sex-related MTR changes in global gray matter (GM) and global white matter (WM) in healthy adults. METHODS: Fifty-two healthy volunteers (21 men, 31 women) aged 20-86 years underwent dual-echo fast spin-echo and magnetization transfer imaging performed with and then without a saturation pulse. GM and WM were distinguished by using a computer-assisted semiautomated segmentation technique. MTR histograms were generated for each segmented tissue in each subject and compared among age and sex groups. RESULTS: The mean, median, first quartile, and peak height of the MTR histogram were significantly lower in the older group (> or =50 years) than those in the younger group (<50 years) for both GM and WM. The age dependency of these values can be expressed in a quadratic fashion over the entire span of adulthood. The MTRs started to decline only after the age of approximately 40 years in both tissues. No statistically significant differences in MTR histogram measurements between the sexes were observed. CONCLUSION: The different MTR values for both GM and WM in the two age groups suggest that notable microscopic changes occur in GM and WM with advancing age, yet no significant sex-related variations in MTR measurements were found in these neurologically healthy adults. Such normative data based on the inherent contrast in MTRs are essential in studies of specific disorders of aging, and they may have implications for our understanding of the gross structural changes in both GM and WM in the aging brain

On June 24-26, 2001, the first meeting of the White Matter Study Group (WMSG) of the International Society for Magnetic Resonance in Medicine (ISMRM) was held in Bordeaux, France. This paper is the report of the consensus reached among the delegates of the meeting on how to use magnetic resonance imaging (MRI) to make an early diagnosis of multiple sclerosis (MS), to measure MS activity accurately and reliably, and to monitor the effect of treatment on disease evolution

We report a case of a patient who developed a left posterior cerebral artery aneurysm 5 years after balloon occlusion of the right internal carotid artery for a giant cavernous aneurysm. The location of the new aneurysm was outside of the primary collateral pathways to the contralateral, proximally occluded, anterior circulation, illustrating the complexity of hemodynamic factors contributing to the development of intracranial saccular aneurysms. The appearance of an aneurysm in this setting supports the hypothesis that degenerative factors and hemodynamic stresses are important in the etiology of intracranial aneurysms

Conventional MRI (cMRI) is limited in its ability to provide specific information about pathology in MS. Measures commonly derived from cMRI include T2 lesions, T1-enhanced lesions, atrophy, and possibly T1-hypointense lesions, which have been extensively investigated in many clinical trials. Better MRI measures are needed to advance our understanding of MS and design ideal clinical trials. This article reviews the strengths and weaknesses of the major MRI-based methods used to monitor MS evolution and submits that 1) metrics derived from magnetization transfer MRI, diffusion-weighted MRI, and proton MRS should be implemented to achieve reliable specific in vivo quantification of MS pathology; 2) targeted multiparametric MRI protocols rather than generic application of cMRI should be used in all possible clinical circumstances and trials; and 3) reproducible quantitative MR measures should ideally be used for the assessment of patients but are essential for clinical trials

BACKGROUND AND PURPOSE: This study was designed to determine whether neuropsychological function in HIV-infected persons is correlated with loss of brain volume (as measured by percentage of brain parenchymal volume [PBV]). We hypothesized that whole-brain parenchymal volume might correlate with neuropsychologic performance, even before overt clinical dysfunction is apparent. METHODS: A computer-assisted segmentation technique with thin section MR imaging was used for 15 patients with HIV infection (seven symptomatic, eight asymptomatic) and for five HIV-negative control participants to quantify whole brain and CSF volumes. To determine the degree of brain atrophy, the PBV relative to that of intracranial content was calculated. Neuropsychological performance was assessed by using a standard battery of eight tests (NPZ-8 test battery). RESULTS: HIV-infected patients had significantly lower NPZ-8 scores (t[18] = 2.26, P <.05) and lower PBV (t[18] = 1.79, P <.01) than those of healthy control participants. With the Spearman rank order correlation coefficients, data analyzed for all 20 study participants (15 HIV-infected patients and five noninfected control participants) showed a significant (r = -0.50, P <.05) negative correlation between PBV and NPZ-8 test battery score. In addition, there was a significant negative correlation between subtest score of motor impairment and PBV (r = -0.69, P <.01) and between AIDS dementia complex score (r = -0.64) and PBV (P <.01). CONCLUSION: These correlations suggest that quantitation of PBV may offer an objective, easily acquired surrogate predictor of neuropsychological impairment and clinically apparent cognitive/motor dysfunction among HIV-infected persons

BACKGROUND AND PURPOSE: The T2-weighted MR imaging total lesion volume and Expanded Disability Status Scale (EDSS) score are two common measures of relapsing-remitting multiple sclerosis disability and pathologic abnormality. Because the whole-brain N-acetylaspartate concentration is considered to be a new marker of the disease burden, the purpose of this study was to evaluate the relationship among these three measures. METHODS: The whole-brain N-acetylaspartate concentration and T2-weighted lesion volume were quantified by using MR imaging and proton MR spectroscopy in 49 patients with relapsing-remitting multiple sclerosis (36 female and 13 male patients; average age, 39 years; age range, 24-55 years; average EDSS score, 2; range of EDSS scores, 0-6). Correlations among whole-brain N-acetylaspartate concentrations, T2-weighted lesion volumes, and EDSS scores were obtained. RESULTS: No correlation was found between whole-brain N-acetylaspartate levels and either T2-weighted lesion volumes or EDSS scores. A weak correlation was found between the EDSS scores and T2-weighted lesion volumes (P =.043, r(s) = 0.292). CONCLUSION: Despite the lack of correlation between whole-brain N-acetylaspartate concentration and the clinical disability reflected in the EDSS score, only the former evaluates the global neuronal cell disease in the entire brain, including those lesions that are occult to conventional imaging techniques