Emerging Technologies
Molecular Imaging: A Primer for Interventionalists and Imagers

https://doi.org/10.1097/01.RVI.0000235746.86332.DFGet rights and content

The characterization of human diseases by their underlying molecular and genomic aberrations has been the hallmark of molecular medicine. From this, molecular imaging has emerged as a potentially revolutionary discipline that aims to visually characterize normal and pathologic processes at the cellular and molecular levels within the milieu of living organisms. Molecular imaging holds promise to provide earlier and more precise disease diagnosis, improved disease characterization, and timely assessment of therapeutic response. This primer is intended to provide a broad overview of molecular imaging with specific focus on future clinical applications relevant to interventional radiology.

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IMAGING MODALITIES

Molecular imaging encompasses a broad set of technologies that couple imaging modalities and contrast agents with molecular specificity. Analogous to stains used in histopathology, these agents, called molecular probes or tracers, consist of a signaling component that emits a detectable signal and a targeting component that confers localization. This latter component can be a peptide, receptor ligand, enzyme substrate, oligonucleotide, or antibody. The imaging instrumentation must then be able

MOLECULAR IMAGING STRATEGIES

The four imaging systems and their respective contrast agents having been discussed, our focus turns to how molecular imaging is specifically practiced. The imaging strategies most widely used can be classified as direct and indirect. Direct molecular imaging is characterized by the direct and specific interaction of the molecular probe with a target, resulting in probe localization, accumulation, and/or activation. As shown in Figure 2, the target can be a cell surface receptor, antigen,

CLINICAL APPLICATIONS

In its capacity to noninvasively interrogate cellular, molecular, and genetic processes fundamental to diseases, molecular imaging has the potential to affect all disciplines of clinical medicine. A survey of the molecular imaging literature reveals that its application to human ailments is being explored in a range of disparate fields from neurology and psychiatry to infectious diseases and drug resistance. Fortuitously, cardiovascular disease and cancer, the leading causes of mortality and

CONCLUSIONS

The advent of molecular imaging has brought about fundamental paradigm shifts in our approach to research and patient care. In the laboratory setting, molecular imaging provides innovative tools for dissection of the cellular and molecular features of various biologic processes within the milieu of living organisms.

In clinical practice, molecular imaging holds promise to ultimately allow earlier and more precise disease diagnosis, disease characterization, and assessment of therapeutic

APPENDIX I: GLOSSARY OF TERMS

Angiogenesis: formation of new blood vessels.

Antisense: sequence of DNA or RNA that is complementary to and binds target DNA or RNA.

Apoptosis: programmed cell death. Autofluorescence: the inherent fluorescence of tissues.

Cell surface receptor: protein and/or polysaccharide structure on the surface of a cell that selectively binds certain molecular messengers.

Clone: production of multiple copies of a single gene.

Dendrimer: branching polymer used to transfer genetic material into cells.

Enhancer:

APPENDIX II: WEB SITES

The Academy of Molecular Imaging: http://www.ami-imaging.org

The Society for Molecular Imaging: http://www.molecularimaging.org

Molecular Imaging Central: http://www.mi-central.org

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