Molecular imaging within the lower gastrointestinal tract: From feasibility to future

Abstract

Molecular imaging is based on the labelling of defined molecular targets through the utilization of fluorescently linked probes and their subsequent detection with high-resolution endoscopic devices, thereby enabling visualization of single molecules including receptors. Whereas early studies have used molecular imaging for improved visualization and detection of early dysplasia and cancer as well as for assessing intestinal inflammation and inflammation-associated cancer within the gastrointestinal (GI) tract, more recent studies have impressively demonstrated that molecular imaging can also be used to characterize and visualize the molecular fingerprint of cancer and inflammation in vivo and in real time. With this, molecular imaging can be used to guide expression-tailored individualized therapy. With the rapid expansion and diversification of the repertoire of biological agents utilized in inflammatory bowel disease and cancer, this approach is gaining increasing attention. Within this review, we first summarize the technical components commonly used for molecular imaging and then review preclinical and clinical studies and evolving clinical applications on molecular imaging within the lower GI tract. Molecular imaging has the potential to significantly change endoscopic diagnosis and subsequent targeted therapy of gastrointestinal cancer and chronic gastrointestinal diseases.

Molecular Endoscopy for the Diagnosis and Therapeutic Monitoring of Colorectal Cancer

“…In most instances, exogenous labeling is required, as endogenous molecules cannot be detected specifically and with sufficient contrast. Exogenous labeling is usually performed with contrast agents that contain a ligand specific for the target of interest, which is linked to a reporter molecule (12). As optical molecular imaging is usually achieved through fluorescence detection, fluorochromes are used as reporter molecules.…”

“…Furthermore, it is not restricted to endogenous fluorochromes. In contrast to AFI endoscopes, where fluorescence is detected in the visible light spectrum, endoscopes for molecular imaging of exogenous fluorochromes were mostly developed to detect fluorescence in the near-infrared (NIR) light spectrum (12,29). This approach offers two advantages.…”

“…In contrast to widefield fluorescence endoscopes, CLE devices were built to deliver microscopic information about suspect lesions during endoscopy. Initially, two different systems have been developed and used in preclinical as well as clinical trials (12). In one system, the CLE device was integrated into the tip of a clinical videoendoscope (eCLE, Pentax, Tokyo, Japan, no longer for sale).…”

Innovative Diagnostic Endoscopy in Inflammatory Bowel Diseases: From High-Definition to Molecular Endoscopy

“…More specific and distinct molecular imaging in advanced gastrointestinal endoscopy is the real-time visualization and binding of labeled-molecules to targeted structures on the surface of epithelial cells and the detection of this conjunction by in vivo histology. Probes usable for molecular imaging could be labeled antibodies, peptides, enzymes, affibodies or lectins, respectively ( 36 ). Molecular imaging is far away from widespread clinical use.…”

Biomolecular Imaging of Colorectal Tumor Lesion Using FITC Labeled scFv-Cκ Fragment Antibody

“…In the past years, for the sensitive diagnosis of colorectal cancer lesions, advanced molecular imaging techniques such as auto uorescence imaging, near-infrared imaging, and confocal endomicroscopy/pCLE have emerged 19,20 . As molecular imaging is based on externally derived probes labeled with a uorescent dye or other markers, various probes for molecular imaging in the gastrointestinal tract have been studied.…”