No abstract

Previous in vivo proton magnetic resonance spectroscopic imaging ((1)H-MRSI) studies have found reduced levels of N-acetyl-aspartate (NAA) in multiple sclerosis (MS) lesions, the surrounding normal-appearing white matter (NAWM) and cortical grey matter (CGM), suggesting neuronal and axonal dysfunction and loss. Other metabolites, such as myoinositol (Ins), creatine (Cr), choline (Cho), and glutamate plus glutamine (Glx), can also be quantified by (1)H-MRSI, and studies have indicated that concentrations of these metabolites may also be altered in MS. Relatively little is known about the time course of such metabolite changes. This preliminary study aimed to characterise changes in total NAA (tNAA, the sum of NAA and N-acetyl-aspartyl-glutamate), Cr, Cho, Ins and Glx concentrations in NAWM and in CGM, and their relationship with clinical outcome, in subjects with clinically early relapsing-remitting MS (RRMS). Twenty RRMS subjects and 10 healthy control subjects underwent (1)H-MRSI examinations yearly for two years. Using the LCModel, tNAA, Cr, Cho, Ins and Glx concentrations were estimated both in NAWM and CGM. At baseline, the concentration of tNAA was significantly reduced in the NAWM of the MS patients compared to the control group (-7%, p = 0.003), as well as in the CGM (-8.7%, p = 0.009). NAWM tNAA concentrations tended to recover from baseline, but otherwise tissue metabolite profiles did not significantly change in the MS subjects, or relatively between MS and healthy control subjects. While neuronal and axonal damage is apparent from the early clinical stages of MS, this study suggests that initially it may be partly reversible. Compared with other MR imaging measures, serial (1)H-MRSI may be relatively less sensitive to progressive pathological tissue changes in early RRMS.

Diffusion tensor imaging (DTI) parameters such as mean diffusivity (MD) and fractional anisotropy (FA) assess aspects of structural integrity within tissue. In relapsing-remitting (RR) multiple sclerosis (MS), abnormalities in normal appearing brain tissue (NABT) have been shown cross-sectionally. The evolution of these abnormalities over time is unclear. We present a longitudinal study investigating early RR MS subjects. The aims were to determine DTI changes over two years and assess the potential of DTI as a longitudinal quantitative marker at this stage of MS. Fifteen controls and 28 patients with RR MS (median disease duration 1.9 years; median EDSS 1.5) had DTI yearly for two years. NABT and whole brain tissue (NABT plus lesions) FA and MD histograms analysed. At baseline, differences in FA were noted between patients and controls (mean [p = 0.042] and peak height [p = 0.008]), while at two years differences in MD were observed (mean [p = 0.008] and peak location [p = 0.024]). However there were no significant DTI differences in longitudinal rates of change between patients and cohorts. In conclusion, although subtle NABT abnormalities were detected in early RR MS, the absence of longitudinal change suggests a limited role for global DTI assessment of NABT in following the early disease course.

Blending PVC with other polymers has proven to be a viable approach in developing higher performance flexible PVC-based materials with a potential for more extensive applications, traditionally dominated by rubbers and thermoplastic elastomers. Miscibility in polyvinyl chloride (PVC)/thermo-plastic polyester polyurethane (TPU)/poly(ethylene-co-normal butyl acrylate-co-carbon monoxide) (ENBACO) ternary polymer blends, was assessed by means of dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM) analysis techniques. Experimental design was performed by using a software program called "ECHIP" that makes it possible to perform statistically designed experiments with a minimum number of trials. The results confirmed total miscibility in the composition range examined: 30% <%PVC < 60%, 0% <%TPU < 40% %ENBACO = 100 - (%PVC +%TPU) Because of the differences in the physical properties of polymer materials used to blend with PVC, research on the most suitable process parameters to achieve miscible blends without degrading them revealed a rather narrow processing window.