Simultaneous Acquisition of Multislice PET and MR Images: Initial Results with a MR-Compatible PET

PET and MRI are powerful imaging techniques that are largely complementary in the information they provide. We have de-signed and built a MR-compatible PET scanner based on ava-lanche photodiode technology that allows simultaneous acquisition of PET and MR images in small animals. Methods: ThePET scanner insert usesmagnetic field–insensitive, position-sensitive avalanche photodiode (PSAPD) detectors coupled, via short lengths of optical fibers, to arrays of lutetium oxyortho-silicate (LSO) scintillator crystals. The optical fibers are used to minimize electromagnetic interference between the radiofre-quency and gradient coils and the PET detector system. The PET detector module components and the complete PET insert assembly are described. PET data were acquired with and with-out MR sequences running, and detector flood histograms were compared with the ones generated from the data acquired out