Performance evaluation of a PET/MR detector based on the ClearPEM technology

We present performance results for a PET detector prototype in simultaneous operation within a 7 T MR system. The detectors are based on ClearPEM technology, a dedicated PET scanner for high-resolution breast imaging, and suitable for integration into combined PET/MR systems at ultra-high magnetic fields. To demonstrate simultaneous PET/MR detection with minimal electromagnetic interference between the two systems, the PET detectors and front-end electronics were carefully shielded and a new dedicated RF volume coil was constructed to mitigate electromagnetic coupling with the shielded electronics. Noise measurements at the level of the PET front-end electronics and the MR RF receiver have shown the mutual interference of RF power and digital noise, and demonstrated the excellent shielding effectiveness achieved. Simultaneous data acquisitions with a Ge-68 source and a saline phantom have shown no distortions or artifacts on MR images caused by the detector modules, and no degradation on the detector performance and energy resolution. Therefore we conclude that both systems can be operated simultaneously with negligible or no electromagnetic interference.