The specific absorption rate (SAR) above regulation levels is considered a significant risk in MRI scanners1. Indeed, the strength of the static magnetic field (B0) and the radiofrequency (RF) electromagnetic field can lead to local heating of tissues. To ensure patient safety, it is therefore important to estimate the local SAR in addition to the global SAR. Various methods are used to assess the local SAR: dipole probes that measure electrical field (E), or thermal sensors. This work presents an optical probe based on Pockels effect and developed to measure precisely the E-field. Previous works have demonstrated the ability of this probe to perform E-field measurements in an unloaded birdcage coil. Here, in vitro E-field measurements are presented at different B0-fields strengths and RF coil geometries.