Abstract
In the functional MRI (fMRI) scan with visual stimulation, a mirror mounted on the radio-frequency (RF) coil or goggles has been used for stimulus presentation, which partly restricts the view angle. The development of a transparent RF coil would enable more realistic stimulations for higher brain functions. In this study, RF coils for a 7-T MRI system were fabricated from transparent conductors. Square-shaped surface coils with a 5-mm side length and 3-mm width were fabricated using three types of conductors (copper sheet, ITO and metal-mesh film). The resistances of the copper sheet and metal-mesh film coils were 0.1 and 0.8 Ω, respectively. On the other hand, the ITO coil had a relatively high resistance of 3.1 kΩ. The signal-to-noise ratios of the images acquired with the copper sheet and metal-mesh film coils were 41.8 and 6.05, respectively. The image acquired with the ITO coil was too noisy for SNR evaluation. These results show that the metal-mesh film is suited for the fabrication of a transparent RF coil. In the future, a birdcage volume coil with a metal-mesh conductor will be developed and applied with visual stimulation to fMRI scans of a small animal.
