Functional MRI (fMRI) is widely used in the research of the small animal neuroimaging. Mouse is the most frequently utilized animal model in the neuroscience. A variety of mouse models was generated to investigate many kinds of diseases by the genetic manipulation. Therefore, if the neural activity of the mouse brain can be visualized, we can obtain the invaluable information about the pathogenesis of many neuro-psychiatric disorders. A NMR magnet is widely installed in many institutions, although MRI instrument is very expensive. If the NMR magnet can be utilized as MRI system, many researchers can perform MRI study more easily.
In this study, we proposed "the mouse fMRI unit" using a vertical 600 MHz NMR magnet (14.1 tesla, Bruker) which equipped with the hand-made gradient coil (Gradient strength = 1 T/m, Inner diameter = 24 mm, Outer diameter = 39 mm) and the surface RF coil attached with a mouse bed (Takashima Seisakusyo CO., Ltd., Japan). The tailor-made gradient coil can be designed by Tesla Engineering Ltd., UK and manufactured by Tecno Electric Industry CO., Ltd., Hadano, Kanagawa, Japan. This MRI unit was interfaced to AVANCE console (Bruker) and MRI experiment was executed with ParaVision 5 software (Bruker).
In order to confirm whether this MRI unit can detect blood oxygenation level-dependent (BOLD) signal from mouse, we measure the BOLD signal at the somatosensory cortex after electrical stimulations on mouse forepaw. Taking advantage of ultra-high filed magnet, a multislice gradient echo (FLASH) sequence (TR/TE = 45/1.8 ms, FA = 20, 8 slices) can be utilized for the functional imaging with high space resolution (0.18Χ0.18Χ0.3 mm3). Time resolution for 8 slices was 3.2 seconds.
As a result, the elevation of BOLD signal detected at the somatosensory cortex, according to the electrical stimulation. In previous reports, fMRI study using a FLASH sequence demonstrated the increment of BOLD signal associated with the task (Tsurugizawa et al., 2010; Abe et al., 2012).
The result indicated that this fMRI unit successfully detected the BOLD signal from mouse. We suggest that the fMRI unit have a potential that the mouse MRI study can be performed in many institutions where a NMR magnet has been installed.