In this paper, we present the development of implantable microcoils specifically dedicated to 7Tesla MRI of the rat brain for the diagnosis and monitoring of tumors and neurodegenerative diseases. These coils are flexible and wireless, with an easy batch fabrication. We also present for the first time a study of the packaging effects on the characteristics of the coil, f 0 and Q factor. The optimization of the packaging with PDMS allows us to realize the first in vivo image of the rat brain using an implanted flexible microantenna.