The fourth Biomedical Imaging Research Opportunities Workshop (BIROW IV) was held in February, 2006 in Bethesda, Maryland. The workshop explored four promising areas of imaging research: Imaging of rodent models; Imaging in drug development; Imaging of chronic metabolic disease – diabetes; and Image-guided intervention in the 4th dimension – time. These explorations uncovered multiple research opportunities that have the potential of enhancing the discovery of new knowledge, providing more efficient pathways for drug development, yielding improvements in the management of chronic metabolic diseases such as diabetes mellitus, and guiding medical interventions such as surgery, radiation oncology, and ablation therapy. Research challenges were identified in each of these areas of opportunity that must be resolved through scientific exploration and technology development. The meeting concluded with the observation that research in biomedical imaging offers the potential of improving patient care in many ways, and the promise of exciting and rewarding careers to young research aspirants.