Molecular imaging: dream or reality?

Abstract

Imaging has witnessed considerable advances during the last 20 years. Morphological imaging with computed tomography (CT) and magnetic resonance (MR) has benefited from the improvement of spatial and temporal resolution, which revitalized especially the role of CT in diagnostic imaging. Multislice CT (MSCT) imaging has become an important tool for staging and restaging of oncological diseases as well as a new diagnostic modality to detect calcifications of the coronary arteries. At the same time, functional imaging has expanded its role in the clinical assessment of severity and extent of disease processes with documented prognostic value. MR imaging as well as tracer techniques using single photon emission computed tomography (SPECT) and positron emission tomography (PET) have added an important new dimension to the functional characterization of pathophysiological processes by providing regional information on perfusion, metabolism, and cell integrity. More recently, with the increasing knowledge in molecular biology, new imaging targets have been identified. Specific receptor families as well as cell surface proteins have been proposed as targets for various imaging approaches using radiolabeled peptides, antibodies, or MR contrast agents. The specific noninvasive visualization of protein expression has become possible for diagnosis and therapy guidance. Using transgenic approaches, specific proteins can be expressed, providing reporter gene imaging for the visualization of gene expression. In this lecture I shall address the characteristics of established and emerging imaging technologies as well as discuss possible applications of molecular imaging (Phelps 2000).