Showing papers by "Paulo Loureiro de Sousa published in 2007"

Manganese-enhanced magnetic resonance imaging (MEMRI) of rat brain after systemic administration of MnCl2: changes in T1 relaxation times during postnatal development.

Abstract: Purpose To measure regional T1 changes in the postnatal rat brain following systemic administration of the contrast agent manganese chloride (MnCl2). Materials and Methods MnCl2 (120 mM) was administered intravenously (i.v.) at 1.25 mL/hour to a dose of 175 mg/kg body weight. MRI experiments were performed on anaesthetized animals (32 male Wistar rats, postnatal days (PDs) 11, 16, 21, and 31) at 2.0 T. Regions of interest (ROIs) were drawn in sagittal slices and placed over five brain regions: olfactory bulb, cerebellum, cortex, thalamus, and hypothalamus. The signal intensities of each ROI were measured and fitted to a three-parameter function to estimate T1 values. Results In the brains of animals who did not receive the contrast agent (control group), we observed a consistent age-dependent decrease in T1 values. In the brains of manganese-infused animals (manganese group), however, T1 values were significantly lower than in the control group, indicating the uptake of manganese, but no dependence of T1 on age was found. Conclusion Our T1 measurements indicate that the relative Mn2+ concentrations are higher in neonates and decrease with brain development. An estimate of the relative cortical concentration of manganese shows a two-fold drop from PD 11 to PD 31. J. Magn. Reson. Imaging 2007. © 2006 Wiley-Liss, Inc.