Observations on the role of nuclear medicine in molecular imaging

The phrase "molecular imaging" is unquestionably current and is receiving ever increasing use. For example, two organizations, the Institute for Molecular Imaging and the Academy of Molecular Imaging have recently been established with molecular imaging as their focus, with journal entitled "Molecular Imaging" and "Molecular Imaging and Biology," respectively. Furthermore, the two leading journals in the field of nuclear medicine have recently added this phrase to their covers-becoming the "European Journal of Nuclear Medicine and Molecular Imaging" and "The Journal of Nuclear Medicine-advancing molecular imaging." The National Institute of Biomedical Imaging and Bioengineering is the newest institute of the NIH. With this degree of attention, it may be surprising that there is as yet no universally accepted definition of molecular imaging. Numerous diverse definitions, some quite complex, have been proposed. With some exceptions, they all refer to imaging in the living animal of function at the cellular or molecular level. Thus molecular imaging may be defined as the observation of biological function at the molecular level in health and disease through some process involving non-invasive imaging of the living mammals.