Background: We describe the fabrication and performance of a chronic in situ coil system designed to allow focal brain stimulation in rats while acquiring functional MRI data.
New method: An implantable receive-only surface radiofrequency coil (iCoil) was designed to be fitted subcutaneously, directly onto to the rat skull surface during the intracerebral cannulation procedure. The coil is fixed in place using acrylic dental cement anchored to four screws threaded into the skull. To demonstrate the use of this coil system in situ, whole-brain functional MRI scans were acquired during various stimuli, including intracranial microinfusions of bicuculline and morphine in the prefrontal cortex and ventral tegmental area, respectively.
Results/comparison to other methods: SNR performance of the iCoil was superior to three commercially-available coils, in some instances by a factor of two. Widespread BOLD activation was observed in response to bicuculline and morphine microinfusions.
Conclusion: A new approach was demonstrated for high-SNR MR imaging of the brain in rats with intracranial implants using an implantable surface coil. This approach enables mapping the functional response to highly targeted stimuli such as intracranial microinfusions.
Keywords: Animal imaging; BOLD; Cranial implant; Implantable RF coil; SNR.
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