High resolution endoscopy

Typical OCT systems provide a axial resolution of around 10 pm, ultra-high resolution is of the order of 1 pm. OCT systems typically use near infrared light with penetration depths in soft tissue of the order of a few millimetres. The mode of contrast in OCT is based on boundaries between zone of differences in refractive index within a specimen specifically, layers of different types of tissue can show up prominently on OCT images. Since the mid-1990s OCT has been suggested to be promising for real-time optical biopsy [42, 43], State-of-the-art probe systems have dimensions of a few millimetres and can be readily used at endoscopy. 

Very high resolution systems (voxel diameters of 1 mm or less) may replace exploratory procedures such as endoscopy. The scan data can be processed interactively to give the physician views corresponding to a virtual endoscopic examination under his control. However, parallel studies in which hundreds of patients receive literal or virtual visualization procedures with comparison of diagnostic accuracy, and long term outcome will be necessary before virtual examinations can be accepted as the standard of medical care, see also Nuclear Magnetic Resonance Spectroscopy. 

The technical aspects of virtual endoscopy (VE) have been introduced in Chapter , to which the reader should refer. The application of VE to the study of the middle ear is quite simple, but requires, as for the other image processing methods, the availability of volumetric and high-resolution data. The optimal CT acquisition protocols have already been discussed. 

Davis RE, Levoy M, Rosenman JG et al (1991) Three-dimensional high-resolution volume rendering (HRVR) of computed tomography data applications to otolaryngology-head and neck surgery. Laryngoscope 101 573-582 De Nicola M, Salvolini L, Salvolini U (1997) Virtual endoscopy of nasal cavity and paranasal sinuses. Eur J Radiol 24 175-180... 

OCT is an optical imaging technique that has been coupled successfully with endoscopy to allow scanning inside the body at depths of typically a few millimeters [31,32]. OCT is a high-resolution, non-destructive optical technique used for cross-sectional imaging of biological tissue [33]. Most conventional endoscopic OCT probes use lenses with fixed focal lengths as the focusing objectives. 

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