Correction Of Fmri Signals By Using The Vessel Diameter Extracted From Mra Images

Functional MRI (fMRI) is already one of the most useful tools to investigate brain activities. Normally, activations are defined by the significant difference between distributions of signal intensities on the two kinds of conditions. However, intensities of these signals depend on the vessel diameter because they reflect blood flow volume. Correction using vessel diameter will be needed when we compare signal intensities at two different areas accurately. In this study, we measured the vessel diameter by magnetic resonance angiography (MRA) and correct the fMRI signals by using the diameter. We then evaluated the signals at different areas. Here, we considered the spatial resolution of MRA images and focused on the thick vessel around motor area.In our experiment, we chose a visual oddball paradigm accompanied with a button pushing task. We paid attention to the motor area as a first step because this area is definitely activated when subjects push a button on target detection. In the experiment, MRA images were acquired before fMRI measurement. As a result, variation of fMRI signal was suppressed and similar hemodynamic responses were acquired at close two pixels by the correction. We therefore considered that correction process is very important when we compare two different fMRI signals.