Endoscopic Molecular Imaging in Gastrointestinal Oncology

Abstract

Gastrointestinal (GI) endoscopy has been widely used for detection, differentiation and staging for neoplasia in the digestive tract, and has made great progress during the last decade (Sivak, 2006). Diagnostic accuracy can be enhanced by better training, more efficient techniques, and the development of new image-processing technologies (Cotton et al., 2006; Tajiri, 2007); however, diagnosis using conventional endoscopy with optical characteristics is essentially limited because it is based on morphological changes and/or discoloration. Chromoendoscopy can enhance surface structure and to determine demarcation borders but is not enough for screening out of early cancer because it is still depending on endoscopists’ expertise and biopsy. Auto-fluorescence imaging system has been applied for lesions which have been difficult to morphologically recognize or are indistinct with conventional endoscope and this system has potential application for the diagnosis of dysplastic lesions and early cancers in the gastrointestinal tract. Optical digital enhancing method such as narrow band imaging (NBI), flexible spectral imaging color enhancement (FICE) and iSCAN are novel endoscopic techniques which can distinguish neoplastic and non-neoplastic lesions without the dye. Magnifying endoscopy in combination with optical digital method has an obvious advantage; the analysis of the epithelial pit pattern and the vascular network. Some of other techniques are allowing us to visualize cell morphology on the micro level reflection of microscopic characteristics. However, we should solve these problems; how to combine these technologies in diagnostic strategy, how to apply them into the algorithm for therapeutic decision and how to standardize several classifications of morphology surrounding them. ‘Molecular imaging’ is a concept representing the most novel imaging methods in medicine, and the definition of the word is controversial. It is broadly defined as ‘the in vivo characterization and measurement of a biological process at the cellular molecular level’ (Weissleder & Mahmood, 2001) or as the technique that ‘directly or indirectly monitor and record the spatiotemporal distribution of molecular and cellular processes for biochemical, biological, diagnostic, or therapeutic application’ (Thakur & Lentle, 2005). Positron emission tomography (PET) might be included in a wide concept of molecular imaging methods: the detection, spatial localization, and quantification of specific molecular targets and events that form the basis of pathologies (Mahmood & Wallace, 2007). In the clinical setting of medical fields, a major paradigm shift has been rapidly taking place in imaging technology represented by PET. Similarly, in the field of GI endoscopy, the authors propose rapid