Evaluation of brain metabolism in steno-occlusive carotid artery disease by proton MR spectroscopy: a correlative study with oxygen metabolism by PET.

UNLABELLED: Carotid occlusive diseases may cause ischemic changes in both the gray matter and the white matter as a result of hemodynamic compromise. To validate the use of proton magnetic resonance spectroscopy (MRS) in evaluating the carotid occlusive diseases, we compared changes in peaks of choline, in the sum of creatine and phosphocreatine, and in N-acetyl-aspartate (NAA) of the white matter with cortical oxygen metabolism measured by PET. METHODS: Eleven patients with unilateral steno-occlusive carotid artery disease underwent PET and MRS. Ten age-matched healthy volunteers underwent MRS. No subjects had cortical infarction. MRS was performed bilaterally in the centrum semiovale. Regional blood flow, regional metabolic rate of oxygen (rCMRO2), and regional oxygen extraction fraction (rOEF) of the cerebral cortex were measured by the steady-state method with 15O gas. RESULTS: The asymmetry index of the ratio of NAA to the sum of creatine and phosphocreatine (NAA/Cr) correlated positively with the asymmetry index of rCMRO2 (r = 0.77; P < 0.01). Because rCMRO2 is a marker of tissue viability, the NAA/Cr of the centrum semiovale may reflect viable neuronal cells. The asymmetry index of the ratio of choline to the sum of creatine and phosphocreatine (Cho/Cr) showed a significant positive correlation with the asymmetry index of rOEF (r = 0.65; P < 0.05). All but 1 patient with an increased Cho/Cr (>1.03) showed an increase in rOEF of the ipsilateral cortex (>0.56). This finding may indicate membrane damage caused by ischemia, because the centrum semiovale is the deep watershed zone. CONCLUSION: The metabolic changes in the centrum semiovale detected by proton MRS reflect a hemodynamically compromised state and are useful in evaluating tissue viability.

"Ivy sign" on fluid-attenuated inversion-recovery images in childhood moyamoya disease.

We report on MR studies of a 15-year-old girl with moyamoya disease in whom diffuse leptomeningeal enhancement ("ivy sign") was revealed by fluid-attenuated inversion-recovery (FLAIR) and contrast-enhanced imaging. We speculate that the mechanism behind this enhancement is caused by a retrograde slow flow of engorged pial vasculature via leptomeningeal anastomosis. Nevertheless, it remains unknown whether the precise source of a high signal on FLAIR images is attributable to pial vessels themselves or congested thickening of the leptomeninges or both.

Crossed cerebellar diaschisis: assessment with dynamic susceptibility contrast MR imaging.

The authors investigated the feasibility of using T2-weighted, half-Fourier rapid acquisition with relaxation enhancement, or RARE, dynamic susceptibility contrast magnetic resonance (MR) imaging to depict crossed cerebellar diaschisis. In 10 patients after unilateral supratentorial stroke, crossed cerebellar diaschisis was demonstrated in the relative regional cerebellar blood volume maps obtained with MR imaging. Cerebellar blood volume values for the nonaffected cerebellar hemisphere were significantly larger than those for the affected side (P = .0003).

Quantitative analysis of cerebral microvascular hemodynamics with T2-weighted dynamic MR imaging.

The purpose of this study was to quantify cerebral microvascular hemodynamics with T2-weighted dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI) using a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence. We performed T2-weighted DSC-MRI with HASTE sequence in 19 normal subjects. After bolus injection of gadopentetate dimeglumine, HASTE images of two sections were acquired for the simultaneous creation of concentration-time curves in the internal carotid artery and in brain tissue. Absolute regional cerebral blood volume (rCBV), regional cerebral blood flow (rCBF), and mean transit time (MTT) values of brain tissue were calculated on a base of the indicator dilution theory, and all values were corrected on the assumption that rCBF of white matter is constant in 22 mL/100 g tissue/min without age-dependent alteration. A decrease in rCBV and rCBF of gray matter was age dependent, while rCBV of white matter did not show significant change with aging. The mean rCBF value in gray matter was 37.3 +/- 8.4 mL/100 g tissue/min. The mean rCBV value was 4.1 +/- 0.8 mL/100 g tissue in gray matter and 2.9 + 0.4 mL/100 g tissue in white matter. The rCBV and rCBF values of gray and white matter obtained from T2-weighted DSC-MRI with HASTE sequence were slightly lower than the published data calculated by gradient-echo sequence. We were able to perform absolute quantifications of the capillary blood volume and flow, using a HASTE sequence, which would not have been possible with a gradient-echo sequence. This technique provides a new method for estimating cerebral microvascular hemodynamics.

Evaluation of peri-infarcted hypoperfusion with T2*-weighted dynamic MRI.

The purpose of this study was to evaluate cerebral perfusion with T2*-weighted dynamic MRI in the area around the infarcted core. We examined seven patients with subacute cerebral infarction. After bolus injection a gadopentetate dimeglumine, a series of gradient-echo images were recorded in a selected slice. From these images, concentration-time curves were created on a region-of-interest (ROI) basis around infarction for calculating relative regional cerebral blood volume (rrCBV). Brain perfusion single photon emission computed tomography (SPECT) study also was performed with intravenous injection of 123I-labeled N-isopropyl-p-iodoamphetamine (123I-IMP). All patients showed prolonged signal decrease in the area around the infarcted core. ROI analysis showed significantly increased rrCBV compared to the normal side (P < .01, paired t test). The 123I-IMP SPECT study showed that these areas had decreased cerebral blood flow. Theses findings suggest compensatory vascular dilatation due to decreased perfusion pressure. T2*-weighted dynamic MRI is a useful method for detecting compensatory vasodilatation of ischemic insult in the peri-infarcted area.

[Dynamic susceptibility contrast MRI with echo planar imaging using 1.0T system: comparison of different EPI sequences].

Dynamic susceptibility contrast MRI has been performed using the gradient echo sequence on conventional MR imagers. On echo planar imaging (EPI) devices, not only gradient-echo EPI but also spin-echo EPI allow for the monitoring of contrast agent-induced changes in susceptibility. The purpose of this study was to evaluate the contribution of each EPI pulse sequence to susceptibility-induced delta R2(*) through the first pass of a bolus of Gd-DTPA. Thirty healthy volunteers were examined with a 1.0T superconducting MRI unit (IMPACT, Siemens) using EPI. For dynamic susceptibility contrast MRI, we used gradient echo EPI (TE = 60), spin echo EPI (TE = 60) and asymmetric spin echo EPI (TE = 88). Regional relative CBV (rrCBV) maps were generated. On the rrCBV map generated with gradient echo EPI, the high-intensity area of the brain surface was more conspicuous than that generated with spin echo EPI. The rrCBV map generated with asymmetric spin echo EPI represented the contrast between those generated with spin echo EPI and gradient echo EPI. The rrCBV rate between gray matter and white matter with gradient echo EPI was significantly higher than that with spin echo EPI. We suggest that the rrCBV map calculated with spin echo EPI tends to reflect capillary blood volume and the rrCBV map calculated with gradient echo EPI tends to reflect total blood volume.

Age, menopause, bone turnover markers and lumbar bone loss in healthy Japanese women.

The change in lumbar vertebral bone mineral density (BMD) during a 2-year study period was examined in 167 healthy middle-aged and elderly Japanese women with reference to age, menopausal status and bone turnover markers at baseline. The perimenopausal and postmenopausal groups of the subjects showed a significant loss of BMD during the study period but the premenopausal women did not. The annual percent decrease of BMD (delta BMD) in the perimenopausal women (-2.40% in average) was significantly greater than that in either of the premenopausal (-0.01%) or over-all postmenopausal women (-0.85%). The subjects who had been postmenopausal for less than 10 years showed a significant bone loss. delta BMD in the postmenopausal women became less marked as the postmenopausal duration increased. The bone loss was accelerated for about 10 years after menopause. The pattern and magnitude of bone loss of Japanese women seemed to be similar to those of Caucasian women. The regression equation for delta BMD based on the bone turnover markers at baseline was shown to be significant in the postmenopausal women and the serum level of bone-specific alkaline phosphatase isoenzyme had a significant relation to delta BMD. However, this equation accounted for only 17.3% of the total variance of delta BMD and, hence, its validity was not sufficiently high for the prediction of bone loss in clinical settings.

Relative contributions of age and menopause to the vertebral bone density of healthy Japanese women.

The relative contributions of age and menopause to vertebral bone mineral density were evaluated based on the estimated weights for age- and menopause-related bone loss components using a mathematical model in 177 healthy female volunteers ages 35-81 years, living in a community in Fukui, Japan. Bone mineral density was determined by dual X-ray absorptiometry. The model used was that which afforded the best fit among the eight possible models to the data observed. Each model was composed of a linear function for the age-related component and a different type of function for the menopausal component, without interaction between them. The weights for these components in each model were estimated by the least-squares method. The coefficient of determination and Akaike information criterion disclosed that among the eight models tested, the model affording the best fit was composed of a logarithmic decrease in bone density with an increase in years since menopause, up to 10 years postmenopausal, with no further decline thereafter. In this model, the weights for both components were statistically significant and the type III sum of squares of the menopausal component was greater than that of the age-related component. We suggest that both age and menopause made significant contributions to the decline in vertebral bone mineral density, with the contribution of menopause being greater than that of age.

Fluid attenuated inversion recovery (FLAIR) imaging in acute Wernicke encephalopathy.

We report a case of Wernicke encephalopathy in which the FLAIR sequence could reveal involvement of the mammillary bodies. FLAIR imaging was useful in monitoring the lesions as well as in diagnosing Wernicke encephalopathy.

[Bone mineral density of the lumbar spine and its relation to biological and lifestyle factors in middle-aged and aged Japanese women (Part 3). Relationships of physical fitness and lifestyle factors to bone mineral density in premenopausal and postmenopausal women].

We recruited community-dwelling women for participation in a study to investigate the effects of risk factors in lifestyle on bone mineral density (BMD). The subjects were 177 women aged 35 years and over living in a rural area in Fukui Prefecture. Their BMD of the lumbar spine (L2-L4) was determined by dual energy X-ray absorptiometry (DXA). In addition to measurements of height, body weight and grip strength, the lifestyles of the women, including physical load in work, sporting activities, smoking habits, calcium intake, and history of bone fracture were interviewed in detail. Adjusted for age, the BMD significantly correlated to body weight (r = 0.337, p < 0.05 for premenopausal women and r = 0.289, p < 0.01 for postmenopausal women) and body mass index (kg/m2) (r = 0.291, p < 0.05 for premenopausal women and r = 0.190, p < 0.05 for postmenopausal women). These results indicated the lower body weight to be a risk factor for the osteoporotic process in middle-aged and aged women. With respect to the grip strength as a physical fitness indicator, a significant correlation coefficient (r = 0.267, p < 0.01) with BMD was obtained for postmenopausal women independent of age and body weight. In univariate analysis, BMD showed no significant correlations with sporting activities, smoking habits, lower back pain and history of bone fracture for either premenopausal women or postmenopausal women.(ABSTRACT TRUNCATED AT 250 WORDS)

MR imaging of monostotic fibrous dysplasia of the clivus. A case report.

We describe the MR appearance of a case of monostotic fibrous dysplasia confined to the clivus. The lesion showed intermediate signal intensity on T2-weighted images which is uncommon among clival diseases.

Autoreactive blood cells and programmed cell death in growth and development of protochordates.

The tunicate Botryllus is a marine protochordate whose clonal colonies undergo regulated natural transplantations when they come into contact in nature. The outcome of these transplantations (fusion or rejection) is controlled by genes of a highly polymorphic histocompatibility system that resembles in many respects the mammalian major histocompatibility complex (MHC). While fusion or rejection reactions are often completed within 24 hr after transplantation, resorption of one partner of a pair of fused semiallogeneic colonies may occur days to weeks after initial contact. The latter process is similar to the degeneration of old individuals, or zooids, that precedes maturation of each new generation of asexual buds. Here we describe comparisons of in vitro reactions of a) mixtures of cells from allogeneic animals and b) cells taken from animals at the zooid-resorption ("takeover") stage of colony development. In vitro autoreactivity of cells from resorbing colonies may reflect in vivo responses to senescent cells, which in turn may be related to allorecognition events that govern fusion or rejection between colonies.