High-resolution and magnification endoscopes offer image quality that is significantly better than that of first-generation video endoscopes or the older fiber-optic systems. The resolution of an endoscopic image is a different quality from the magnification, and is defined as the ability to distinguish between two points that are close together. High-resolution imaging improves the ability to discriminate details while magnification enlarges the image. In digital video imaging, resolution is a function of pixel density. By incorporating high-pixel density charged-coupled devices (CCD) , high-resolution endoscopes provide slightly magnified views of the gastrointestinal tract with greater mucosal detail. Magnification endoscopy utilises a movable lens controlled by the endoscopist to vary the degree of magnification, which ranges from ×1.5 to ×150. Newly designed magnification endoscopes provide high-resolution and magnification features [4].

Super magnifying endoscopes provide magnification up to 1100-fold. These endoscopes are called endocytoscopes . Endocytoscopy allows in conjunction with intravital staining identification of cellular structures [5].

High definition endoscopes are currently broadly available. Here, CCDs convert light information into an electronic signal. This signal is processed in the video-processor into an image. The standard analogue broadcasting systems (PAL or NTSC) generate approximately 480–576 scanning lines on a screen. The new high definition endoscopes can generate up to 1080 scanning lines on a screen, which further increases the resolution. Surface analysis on distinct lesions can be done even before magnification (see Fig. 17.2). There are convincing data about screening colonoscopy emerging showing that high definition endoscopy lead to an increased detection of patients having at least one adenoma [6].

The so-called FUSE-colonoscope (Endoschoice, USA) has three optics at the distal tip of the colonoscope. Fuse colonoscopes feature cameras at the tip as well as on the sides of the scope providing a panoramic 330° view of the colon. The wide view facilitates navigation to the cecum as well as intubation of the terminal ileum. Studies have demonstrated that the adenoma detection rate can be significantly increased and the miss rate of adenomas can be significantly reduced [7].

Balloon assisted colonoscopy (G-EYE Colonoscopy ) allows straightening colonic folds during withdrawal. Furthermore, endoscope slippage is reduced and the insufflated distal ballon of the colonoscope canters the endoscopic image and facilitates polyp removal by “anchoring” the endoscope in front of the polyp.

The silicone balloon is permanently mounted on any desirable colonoscope. The balloon is insufflated during withdrawal and pressure of the balloon is automatically controlled.

Studies have proven the benefit of the G-EYE system . Adenoma detection rates are significantly improved and adenoma miss rates are significantly reduced [8].

However, the benefit of wide viewing colonoscopy and balloon-assisted colonoscopy for IBD patients is not determined yet.

Chromoendoscopy or tissue staining is a relatively “old” endoscopic technique that has been used for decades. It involves the topical application of stains or pigments to improve localization, characterization, or diagnosis of lesions [9]. It is a useful adjunct to endoscopy; the contrast between normally stained and abnormally stained epithelium enables the endoscopist to make a diagnosis and/or to direct biopsies based on a specific reaction or enhancement of surface morphology (see Fig. 17.2).

The technique for staining is simple and easy to learn. Chromoendoscopy can be done in an untargeted fashion of the whole segment (Panchromoendoscopy ) or directed towards a specific lesion (targeted staining). While spraying dyes in the colon in an untargeted fashion, the endoscopist needs to direct the endoscope and catheter tip towards the colorectal mucosa and use a combination of rotational clockwise-counter clockwise movements with simultaneous withdrawal of the endoscope tip.

Surface analysis of stained colorectal lesions was a new optical impression for the endoscopists in the nineties. First, Kudo et al. described that some of the regular staining patterns are often seen in hyperplastic polyps or normal mucosa, whereas unstructured surface architecture was associated with malignancy. Also the kind of adenoma (tubular vs. villous ) can be seen by detailed inspection. This experience has lead to a categorization of the different staining patterns in the colon: The so-called pit-pattern classification [10] differentiated five types and several subtypes. Types 1 and 2 are staining patterns predicting non-neoplastic lesions, whereas types 3–5 are predicting neoplastic lesions. With the help of this classification the endoscopist may predict histology with good accuracy. Although the pit-pattern classification was developed by the help of magnifying endoscopes the question arises whether an endoscopic differentiation of different staining patterns can also be done with the help of the more common high-resolution endoscopes.

Chromoendoscopy has shown significant advantages in the detection of flat colorectal neoplasia and in colitis associated neoplasia [11].

Magnifying chromoendoscopy using either methylene blue or indigo carmine is a valid and proven tool for improving endoscopic detection of intraepithelial neoplasia in patients with long-standing ulcerative colitis. Chromoendoscopy increased the diagnostic yield of intraepithelial neoplasia as compared with conventional colonoscopy 3- to 4.5-fold. Differentiation of non-neoplastic from neoplastic lesions is possible with a high overall sensitivity and specificity. Chromoendoscopy is endorsed in multiple guidelines as a superior and recommended alternative to conventional colonoscopy with random biopsies [12].

An international guideline (SCENIC) was published 2015 underlining the importance of chromoendoscopy with guided biopsies as the standard for surveillance in patients with IBD [13].

Conventional white light endoscopy uses the full visible wavelength range to produce a red-green-blue image. In contrast, narrow band imaging, in combination with magnification endoscopy, illuminates the tissue surface using special filters that narrow the respective red-green-blue bands. This enhances the tissue microvasculature mainly as a result of the differential optical absorption of light by haemoglobin in the mucosa associated with initiation and progression of dysplasia, particularly in the blue range. To some extent, the resulting images look like “chromoendoscopy without dyes” (see Figs. 17.3 and 17.4).

Alternatively, the light which is reflected from the mucosal can be modified using post processing computer algorithms (FICE, i-Scan, SPIES). This can modulate different forms of enhancement, which leads to an accentuation of the vasculature, the surface architecture or the pattern visualisation (see Figs. 17.3 and 17.4). However, none of these filters has proven so far any benefit diagnosing colitis associated neoplasia [14, 15].

Autofluorescence imaging systems are available that use video endoscopes with two CCDs: one for high-resolution white light endoscopy and one for autofluorescence imaging (AFI). The autofluorescence image is a pseudo-colour image composed from three integrated images: (1) the total autofluorescence after blue light excitation (395–475 nm); (2) the green reflectance (540–560 nm); and (3) the red reflectance (600–620 nm).

A new system has become available that incorporates high-resolution endoscopy, AFI and NBI in one single system: endoscopic tri-modality imaging (ETMI) . This system has a new autofluorescence algorithm in which the fluorescence image is composed of two integrated images instead of three images: total autofluorescence after blue light excitation (395–475 nm) and green reflectance. Autofluorescence in conjunction with NBI can help to unmask colitis-associated neoplasias [16].

Optical coherence tomography (OCT ) is a high-resolution cross-sectional imaging technique. It is analogous to B-mode high-resolution endosonography but uses light waves instead of acoustic waves. As a result, OCT has a high resolution, up to ten times higher than high-frequency ultrasound, enabling microstructural features of tissue to be identified, but it has a limited sampling depth of 1–2 mm [17] OCT measures the intensity of back scattered light from tissue at various depths using low-coherence interferometry.

OCT is a probe-based technique in which the probe is passed through the accessory channel of an endoscope. Unlike endosonography, OCT can be performed without a coupling media (e.g. water). The OCT catheter has to be positioned adjacent to the mucosa within the system’s focal distance (1-5 mm), which may be difficult due to the movement of the oesophagus by peristalsis and heart beat. In addition, compression artefacts may be seen when the probe comes in contact with the mucosa. OCT can easily differentiate normal epithelium from abnormal tissue with high accuracy. However, the detection and grading of high-grade dysplasia and early cancer remain still challenging [18].

Future developments in OCT, such as ultra-high resolution OCT, spectroscopic OCT, Doppler OCT and optical frequency-domain imaging, may enhance the accuracy of OCT for the detection of dysplasia and give rise to other applications.

Endocytoscopy is based on the principle of light contact microscopy. The first studies using this system were performed in the field of otolaryngology. After application of methylene blue the tip of a rigid endoscope was placed in direct contact with the surface. With this method cytological details can be directly visualised, making direct observation of living cells feasible [5, 19]. The first endocytoscopy system was, however, a rigid instrument, which is not practical for use in the gastrointestinal tract. Therefore, a novel endocytoscope system has been developed, the Endocytoscope. This system consists of two flexible endoscopes with a diameter of 3.2 mm that can easily pass through an accessory channel with a diameter of 3.7 mm: one low-magnification endocytoscope with a maximal magnification of 450× and a high-magnification endocytoscope with a maximal magnification of 1100×. Recently, the integration of the endocytoscope within an otherwise conventional endoscope could be achieved.