Future challenges of multimodality imaging.

During the last decade, positron emission tomography/computed tomography (PET/CT) and single-photon emission computed tomography/computed tomography (SPECT/CT) have procured advances in research and clinical application of fusion imaging. The recent introduction of systems that combine PET and MRI opens new horizons for multimodality molecular imaging. These systems offer simultaneous morphologic, functional, and molecular information of a living system. Moreover, other combinations of anatomic and functional imaging modalities (for example CT and MRI or PET and optical imaging) are emerging, holding promise in basic medical research or in clinical medicine. These developments are paralleled by advances in the field of biomolecules and particles, to provide new agents useful for more than one imaging modality and to facilitate the study of the same target by different imaging devices. In the near future PET/MRI may emerge as a new powerful multimodality technique in clinical oncology, offering considerable potential for imaging applications beyond correlation of functional and anatomic images. Future developments should include the simultaneous acquisition of multifunctional data such as PET tracer uptake, MR spectroscopy, or fMRI along with high-resolution anatomic MRI.