In vivo small animal imaging is a cornerstone in the study of human diseases by providing important clues on the
pathogenesis, progression and treatment of many disorders. Molecular tomographic imaging can probe complex biologic
interactions dynamically and to study diseases and treatment responses over time in the same animal. Current imaging
technique including microCT, microMRI, microPET, microSPECT, microUS, BLT and FMT has its own advantages and
applications, however, none of them can provide structural, functional and molecular information in one context.
Multi-modality imaging, which utilizes the strengths of different modalities to provide a complete understanding of
the object under investigation, emerges as an important alternative in small animal imaging. This article is to introduce
the latest development of multimodality systems for small animal tomographic imaging. After a systematic review of
imaging principles, systems and commerical products for each stand-alone method, we introduce some multimodality
strategies in the latest years. In particular, two dual-modality systems, i.e. FMT-CT and FMT-PET are presented in detail.
The end of this article concludes that though most multimodality systems are still in a laboratory research stage, they will
surely undergo deep development and wide application in the near future.