OPTIMAL COMBINATION OF SPIRAL-IN/OUT BOLD SIGNALS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Acquisitions with the spiral-in/out technique result in two separate image timeseries obtained during the spiral-in and spiral-out trajectory, respectively. In uniform brain regions the two components have comparable signal and BOLD contrast and can be averaged, but in regions compromised by susceptibility effects where both signal and noise can differ in the two images other combination methods may be more effective. Here, several weighting schemes are compared for signal and activation contrast recovery in whole brain and prefrontal cortex using verbal working memory (7 subjects) and breath-holding tasks (6 subjects) scanned at 3T. It is found that a statistically-weighted combination based upon activation maps derived separately from the spiral¿in and spiral-out images provides activation volumes with increases over second-choice signal-weighted combination and over spiral-out acquisition alone, and that simple averaging is inferior to signal-weighted combination.