Significant improvements and developments in fast scanning tech-niques for functional magnetic resonance (MR) imaging of the brain have occurred during the past year. By taking advantage of improved hardware configuration on the MRI unit, LDRR has developed a new pulsed spin- labeling MR perfusion technique, known as FOCI FAIR, that allows for improved definition of blood transit time into the brain parenchyma. The FOCI pulse is a 180 degree hyperbolic secant pulse with wave profile that allows for a better defined acquisition volume of interest. This results in an improvement in the cere-bral perfusion maps and allows for a more accurate assessment of blood flow throughout the imaging volume of interests. The new development in proton magnetic resonance spectroscopic imaging (MRSI) involves the acquisition of cerebral metabolites without suppression of the water signal. MRSI without water suppression makes use of the high dynamic range that recently became available with state-of-the-art MRI instrumentation. This new technique allows for reliable quantitation of the concentration of brain metabolites by using the water signal as a reference. With this approach, corrections can be made to effect the instrumental variation and subject motion on the measured metabolite intensities. A study on the reproducibility was performed in six healthy controls, demonstrating a high intrasubject reliability and a low coefficient of variation between the multiple experiments. In addition to the hardware demands, this new proton MRSI requires dedicated post-processing techniques of the data, involving reliable time-domain fitting routines. Future plans are to install this non- water-suppressed MRSI technique on all MRI units at the NIH to be used by investigators interested in using proton magnetic resonance spectroscopy to study cerebral metabolism.
