Molecular imaging in living subjects: seeing fundamental biological processes in a new light

  1. Tarik F. Massoud1,3 and
  2. Sanjiv S. Gambhir1,2,4,5
  1. 1The Crump Institute for Molecular Imaging, 2Department of Molecular & Medical Pharmacology, and Department of Biomathematics, David Geffen School of Medicine at University of California at Los Angeles, Los Angeles, California 90095, USA; 3Departments of Radiology and Oncology, University of Cambridge School of Clinical Medicine, Cambridge CB2 2QQ, UK; 4Stanford University School of Medicine, Stanford, California 94305, USA

This extract was created in the absence of an abstract.

Morphological observations have driven the course of biology ever since the first microscope was built in the late sixteenth century. Molecular imaging is a rapidly emerging biomedical research discipline that extends such observations in living subjects to a more meaningful dimension. It may be defined as the visual representation, characterization, and quantification of biological processes at the cellular and subcellular levels within intact living organisms. It is a novel multidisciplinary field, in which the images produced reflect cellular and molecular pathways and in vivo mechanisms of disease present within the context of physiologically authentic environments. The term “molecular imaging” implies the convergence of multiple image-capture techniques, basic cell/molecular biology, chemistry, medicine, pharmacology, medical physics, biomathematics, and bioinformatics into a new imaging paradigm.

Present imaging technologies rely mostly on nonspecific macroscopic physical, physiological, or metabolic changes that differentiate pathological from normal tissue rather than identifying specific molecular events (e.g., gene expression) responsible for disease. Molecular imaging usually exploits specific molecular probes as the source of image contrast. This change in emphasis from a nonspecific to a specific approach represents a significant paradigm shift, the impact of which is that imaging can now provide the potential for understanding of integrative biology, earlier detection and characterization of disease, and evaluation of treatment.

The emergence of molecular imaging strategies is largely due to recent unprecedented advances in molecular and cell biology techniques, the use of transgenic animal models, availability of newer imaging drugs and probes that are highly specific, and successful development of small-animal imaging instrumentation. These factors, along with continued expansion of scientific horizons in the current postgenomic era, have been pivotal in the drive toward a new standard that allows linking established in vitro and cell culture experimental assays to imaging studies within living subjects. This now creates the possibility of achieving …

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