Cerebral blood flow by arterial spin labeling in poststroke dementia.

OBJECTIVE: To investigate the relationship between cerebral blood flow and dementia in older stroke survivors and subjects with Alzheimer disease (AD). METHODS: This cohort study used arterial spin labeling MRI at 3 T to examine cerebral blood flow (CBF). We scanned 39 patients 6 years after stroke. They were older than 75 years at the time of stroke and free of dementia 3 months poststroke, with 8 subsequently developing dementia. We also scanned 17 subjects with AD and 29 healthy control subjects. We determined the perfusion in regions of interest (ROIs). Hippocampal volume was also measured using a previously validated automated procedure. RESULTS: The gray matter/white matter CBF ratio was reduced globally in the poststroke dementia (PSD) group (1.55 SD = 0.12) relative to control subjects (1.78 SD = 0.18; p = 0.03). The CBF ratio in a parietal ROI was reduced in the AD (1.34 SD = 0.31; p = 0.003), PSD (1.32 SD = 0.22; p = 0.041), and poststroke no-dementia (PSND) (1.44 SD = 0.34; p = 0.014) groups relative to that of control subjects (1.70 SD = 0.32). In subjects without stroke, the best predictor of dementia was hippocampus volume, whereas in the stroke group, it was the global CBF gray matter/white matter ratio. Hippocampus volume was not significantly different between the AD and PSD groups, and both had reduced hippocampi relative to those of control subjects and the PSND group. CONCLUSIONS: We found evidence for both vascular and AD pathology in PSD, suggesting that both the direct impact of the stroke and subsequent development of AD-type changes play a role in the etiology of PSD.

Determination of activity concentration levels of (238)U, (232)Th, and (40)K in drinking water in a gold mine in Ghana.

The study of the activity concentration levels of uranium, thorium and potassium in drinking water from different locations in a gold mine in the Ashanti Region of Ghana was conducted using gamma spectrometry. The mean outdoor absorbed gamma dose rates at 1 m from the water were 0.524 nGy h, 0.422 nGy h, and 0.252 nGy h for groundwater, surface water, and treated water, respectively. The results obtained for the activity concentration levels of U and Th are found to be within the maximum acceptable concentration levels of 3.0 Bq L and 0.6 Bq L, respectively, recommended by the World Health Organization. The overall mean outdoor gamma dose rate is 0.41 nGy h and the corresponding outdoor annual effective dose obtained for adult members of the public for drinking water from the mines is 3.58 muSv y. This value is found to be within the 10.0 muSv per annum (0.01 mSv per annum) for public exposure control set by the World Health Organization. Therefore, the mining activities on drinking water studied did not show any significant radiological health implications on the public.