Where Next for the Endoscope?

Ricardo A. Natalin; Jaime Landman

In This Article

Beyond Imaging

From the perspective of imaging alone, the change from fiberoptic endoscopy to distal sensor endoscopy represents an important but limited advance in the history of endoscopy. However, distal sensor technologies offer additional capabilities that are just beginning to be explored. The intrinsic abilities of CCD and CMOS chips to stratify and process information have engendered a revolutionary change in the nature of the endoscope.

The first step beyond endoscope imaging was made in 2008 by Gyrus-ACMI (Southborough, MA, USA), who offered a software update known as the endoscope protection system (EPS; Figure 3) for use with their Invisio (DUR-D) digital flexible ureteroscope. The EPS exploited the ability of the CMOS sensor incorporated into the DUR-D ureteroscope to detect colors in different portions of the optical field in order to detect the blue cladding of a Dornier DURHL-20 laser fiber. When the EPS is active, the CMOS chip continuously detects the presence of the laser fiber as a blue color in a specific portion of the optical field. When the laser fiber is retracted (or obscured), information is transmitted from the CMOS chip to the computer control unit. This control unit is connected to the laser and is able to initiate shutdown of the system within milliseconds, which prevents the laser from functioning 'blind' and reduces endoscope damage and probably procedure costs.

Figure 3.

Endoscope protection system (EPS). Constantly tracking the presence of the laser fiber via the CMOS chip avoids blind functioning of the laser, reduces endoscope damage and probably decreases procedure costs. Abbreviations: CCU, camera control unit; CMOS, complementary metal oxide semiconductor.

This system was highly effective in vitro,[18] and was similarly efficacious in a pilot clinical trial.[19] False-positive shutdown of the laser did occur when the part of the field of view occupied by the laser fiber was obscured by stone fragments, but the system remained highly valuable. As a complement to standard good laser policy, the EPS system is likely to prevent a substantial proportion of ureteroscope malfunctions caused by laser damage. As such, the EPS system might help to diminish the cost of ureteroscopy and diminish the risks associated with training.[19]

Another technology made possible by information stratification, this time by the CCD chip, is narrow-band imaging (NBI), which was introduced by Olympus to work in association with their cystoscopes and ureteroscopes. NBI employs optical interference filters that restrict the wavelengths of light used for imaging to a narrow portion of the spectrum used in conventional white light endoscopy. Use of NBI improves the definition of the epithelial surface and emphasizes the mucosal microvessels, which appear as dark brownish structures (Figures 4 and 5). NBI might improve the identification of neoplastic tissue, which has high microvessel density and usually appears darker than the normal mucosa. The system is operated by simply pressing a switch on the endoscope to activate the optical filters and change from conventional imaging to NBI.[20] NBI has demonstrated superior sensitivity for identifying recurrent flat and papillary superficial bladder tumors in a surveillance setting, when compared with standard white light cystoscopy.[21] NBI technology might also improve diagnosis and early identification of recurrence for high-grade tumors and carcinoma in situ, but this capability has yet to be definitively established.

Figure 4.

NBI system. a | Rather than utilize the entire white light spectrum, NBI employs optical interference filters to detect specific wavelengths of light. b | This approach improves the definition of the epithelial surface and emphasizes the mucosal microvessels, which appear as dark brownish structures. Abbreviation: NBI, narrow-band imaging.

Figure 5.

Improved visualization of bladder lesions with NBI. a | Lesions seen with white light cystoscopy. b | The same lesions seen with NBI. Abbreviation: NBI, narrow-band imaging.

Similar improvement in the sensitivity of detection of upper urinary tract transitional cell carcinoma (TCC) might be achieved through NBI-enhanced ureteroscopy. Rabbani and colleagues[22] studied patients with bladder cancer who were undergoing long-term surveillance for upper urinary tract TCC, and found a relatively constant incidence of such disease over time, even 10 years after the initial cancer diagnosis. NBI achieves a higher detection rate of bladder cancer recurrence during surveillance than does white light cystoscopy.[23] Thus, the advanced imaging techniques offered by distal sensor endoscopes might enhance early diagnosis and long-term survival in these patients, although further clinical assessment is required in this setting.