Molecular imaging in gastrointestinal endoscopy

Imaging of cellular therapies

Cellular therapy promises to revolutionize medicine, by restoring tissue and organ function, and combating key disorders including cancer. As with all major developments, new tools must be introduced to allow optimization. For cell therapy, the key tool is in vivo imaging for real time assessment of parameters such as cell localization, numbers and viability. Such data is critical to modulate and tailor the therapy for each patient. In this review, we discuss recent work in the field of imaging cell therapies in the clinic, including preclinical work where clinical examples are not yet available. Clinical trials in which transferred cells were imaged using magnetic resonance imaging (MRI), nuclear scintigraphy, single photon emission computed tomography (SPECT), and positron emission tomography (PET) are evaluated from an imaging perspective. Preclinical cell tracking studies that focus on fluorescence and bioluminescence imaging are excluded, as these modalities are generally not applicable to clinical cell tracking. In this review, we assess the advantages and drawbacks of the various imaging techniques available, focusing on immune cells, particularly dendritic cells. Both strategies of prelabeling cells before transplant and the use of an injectable label to target cells in situ are covered. Finally, we discuss future developments, including the emergence of multimodal imaging technology for cell tracking from the preclinical to the clinical realm.

Targeted imaging of flat and depressed colonic neoplasms

Molecular imaging is a rapidly growing new discipline in gastrointestinal endoscopy that involves the development of novel imaging probes and instruments to visualize the molecular expression pattern of mucosa in the digestive tract. Several platforms for imaging agents, including antibody and peptide, are being developed to target over expressed biomolecules in cancer. In addition, novel imaging instruments, including fluorescence endoscopy and confocal microscopy, are being developed to provide wide-area surveillance and microscopic examination, respectively. These methods are being applied to detect the presence of flat and depressed colonic neoplasms and to identify tumor margins.

Exogenous Molecular Probes for Targeted Imaging in Cancer: Focus on Multi-modal Imaging

Cancer is one of the major causes of mortality and morbidity in our health care system. Molecular imaging is an emerging methodology for the early detection of cancer, and the development of exogenous molecular probes that can be labeled for multi-modality imaging is critical to this process. Today, molecular imaging is at crossroad, and new targeted imaging agents are expected to broadly expand our ability to detect pre-malignant lesions. This integrated imaging strategy will permit clinicians to not only localize lesions within the body, but also to visualize the expression and activity of specific molecules. This information is expected to have a major impact on diagnosis, therapy, drug development and understanding of basic cancer biology. At this time, a number of molecular probes have been developed by conjugating various labels to affinity ligands for targeting in different imaging modalities. This review will describe the current status of exogenous molecular probes for optical, nuclear and MRI imaging platforms. Furthermore, we will also shed light on how these techniques can be used synergistically in multi-modal platforms and how these techniques are being employed in current research.

Advances of endomicroscopy for gastrointestinal physiology and diseases

Confocal endomicroscopy is a novel technique that permits in vivo microscopy of the human gastrointestinal mucosa during ongoing endoscopy, thereby providing optical virtual biopsies. Endomicroscopy has been demonstrated to reveal histological information in a multitude of diseases in the upper and lower gastrointestinal tract in vivo. Most studies have focused on inflammation and neoplasia, such as Barrett's esophagus, gastric cancer, celiac disease, Crohn's disease and ulcerative colitis, or colorectal neoplasias. Endomicroscopy allows obtainment of "smart," targeted biopsies from regions with microscopic alterations rather than having to rely on random untargeted tissue sampling. This reduces the number of biopsies while increasing the diagnostic yield. In addition, immediate histological information is available, enabling immediate therapy. Apart from morphological visualization, endomicroscopy offers a unique possibility to study pathophysiological events in their natural environment (functional imaging). Molecular imaging with endomicroscopy applied in clinical and basic science will permit advances in understanding of the cellular basis of gastrointestinal physiology and pathophysiology.

[Molecular imaging of the small intestine]

Molecular imaging uses the molecular signature of cells for targeted minimally-invasive detection and characterization of gastrointestinal pathologies. Exogenous fluorescent agents serve as molecular beacons for visualization of specific surface markers or metabolic activity in the target tissue. Molecular imaging with radioactively labeled substances is well established in nuclear medicine for wide-field detection of lesions in the small intestine. In gastrointestinal endoscopy, both macroscopic detection by endogenous or exogenous fluorescence and microscopic visualization by endomicroscopy have been investigated in clinical trials, however have not yet been evaluated in larger patient cohorts. Still, molecular imaging has the potential to greatly enhance our understanding of gastrointestinal pathology and to impact on future clinical algorithms and science in gastroenterology.