The "Iceberg Phenomenon": As Soon as One Technological Problem in NOTES Is Solved, the Next One Appears!

PURPOSE: Though already proclaimed about 7 years ago, natural orifice transluminal endoscopic surgery (NOTES) is still in its early stages. A multidisciplinary working team tried to analyze the technical obstacles and identify potential solutions. METHODS: After a comprehensive review of the literature, a group of 3 surgeons, 1 gastroenterologist, 10 engineers, and 1 representative of biomedical industry defined the most important deficiencies within the system and then compiled as well as evaluated innovative technologies that could be used to help overcome these problems. These technologies were classified with regard to the time needed for their implementation and associated hindrances, where priority is based on the level of impact and significance that it would make. RESULTS: Both visualization and actuation require significant improvement. Advanced illumination, mist elimination, image stabilization, view extension, 3-dimensional stereoscopy, and augmented reality are feasible options and could optimize visual information. Advanced mechatronic platforms with miniaturized, powerful actuators, and intuitive human-machine interfaces could optimize dexterity, as long as enabling technologies are used. The latter include depth maps in real time, precise navigation, fast pattern recognition, partial autonomy, and cognition systems. CONCLUSION: The majority of functional deficiencies that still exist in NOTES platforms could be overcome by a broad range of already existing or emerging enabling technologies. To combine them in an optimal manner, a permanent dialogue between researchers and clinicians is mandatory.

Spatial orientation in translumenal surgery.

"Natural Orifice Translumenal Endoscopic Surgery" (NOTES) is assumed to offer significant benefits to patients, such as reduced trauma as well as reduced collateral damage. But the potential advantages of this new technology can only be achieved through safe and standardized operation methods. Several barriers, which have been identified during clinical practice in flexible intra-abdominal endoscopy, can only be solved with computer-assisted surgical (CAS) systems. In order to assist the surgeon during the intervention and enhance his visual possibilities, some of these CAS systems require 3-D information of the intervention site, for others 3-D information is even mandatory. Therefore it is evident that the definition and design of new technologies for CAS systems must be strongly considered. A 3-D endoscope, called "Multisensor-Time-of-Flight" (MUSTOF) endoscope, is actually being developed. Within these developments, an optical 3-D time-of-flight (TOF) sensor is attached to the proximal end of a common endoscope. The 3-D depth information obtained by this enhanced endoscope can furthermore be registered with preoperatively acquired 3-D volumetric datasets such as CT or MRI. These enhanced or augmented 3-D data volumes could then be used to find the transgastric or transcolonic entry point to the abdomen. Furthermore, such acquired endoscopic depth data can be used to provide better orientation within the abdomen. Moreover it can also prevent intra-operative collisions and provide an optimized field of view with the possibility for off-axis viewing. Furthermore, providing a stable horizon on video-endoscopic images, especially within non-rigid endoscopic surgery scenarios (particularly within NOTES), remains an open issue. Hence, our recently presented "endorientation" approach for automated image orientation rectification could turn out as an important contribution. It works with a tiny micro-electro-mechanical systems (MEMS) tri-axial inertial sensor that is placed on the distal tip of an endoscope. By measuring the impact of gravity on each of the three orthogonal axes the rotation angle can be estimated with some calculations out of these three acceleration values, which can be used to automatically rectify the endoscopic images using image processing methods. Using such enhanced, progressive endoscopic system extensions proposed in this article, translumenal surgery could in the future be performed in a safer and more feasible manner.

[Orientation of endoscopic images: rectification by gravity]. / Orientierung endoskopischer Bilder: Rektifizierung durch Schwerkraft.

A known problem in endoscopic surgery (especially with flexible video endoscopes) is the absence of a stable horizon in endoscopic images displayed on a monitor. With our "ENDOrientation" approach, image rectification, even in non-rigid endoscopic surgery (particularly NOTES), can be realized with a tiny MEMS tri-axial inertial sensor placed on the tip of an endoscope. This sensor measures the impact of gravity on each of the three orthogonal accelerometer axes in real time. After an initial calibration and temporal filtering of these three data steams, the rotation angle of an endoscope can be estimated directly. The achievable sampling rate of the inertial sensor is above the usual endoscopic video frame rate of 25 Hz; the rotation accuracy is approximately one degree. The image rectification can be performed in real time by digitally rotating the endoscopic video signal. Improvements and benefits have been evaluated in animal studies: coordination and movement of different instruments was rated to be much more intuitive with a stable horizon on endoscopic images. The recorded time stamps and position tracks clearly support this observation.

Endoscopic orientation correction.

An open problem in endoscopic surgery (especially with flexible endoscopes) is the absence of a stable horizon in endoscopic images. With our "Endorientation" approach image rotation correction, even in non-rigid endoscopic surgery (particularly NOTES), can be realized with a tiny MEMS tri-axial inertial sensor placed on the tip of an endoscope. It measures the impact of gravity on each of the three orthogonal accelerometer axes. After an initial calibration and filtering of these three values the rotation angle is estimated directly. Achievable repetition rate is above the usual endoscopic video frame rate of 30 Hz; accuracy is about one degree. The image rotation is performed in real-time by digitally rotating the analog endoscopic video signal. Improvements and benefits have been evaluated in animal studies: Coordination of different instruments and estimation of tissue behavior regarding gravity related deformation and movement was rated to be much more intuitive with a stable horizon on endoscopic images.

Time-of-Flight 3-D endoscopy.

This paper describes the first accomplishment of the Time-of-Flight (ToF) measurement principle via endoscope optics. The applicability of the approach is verified by in-vitro experiments. Off-the-shelf ToF camera sensors enable the per-pixel, on-chip, real-time, marker-less acquisition of distance information. The transfer of the emerging ToF measurement technique to endoscope optics is the basis for a new generation of ToF rigid or flexible 3-D endoscopes. No modification of the endoscope optic itself is necessary as only an enhancement of illumination unit and image sensors is necessary. The major contribution of this paper is threefold: First, the accomplishment of the ToF measurement principle via endoscope optics; second, the development and validation of a complete calibration and post-processing routine; third, accomplishment of extensive in-vitro experiments. Currently, a depth measurement precision of 0.89 mm at 20 fps with 3072 3-D points is achieved.

Parameters of humoral and cellular immunity following vaccination of pigs with a European modified-live strain of porcine reproductive and respiratory syndrome virus (PRRSV).

Parameters of humoral and cellular immunity were investigated in pigs experimentally infected with a modified-live European porcine reproductive and respiratory syndrome virus (PRRSV, strain DV). PRRSV was detected by real-time RT-PCR and PRRSV-specific antibodies by a commercial ELISA test-kit, respectively. Interleukins IL-1alpha, IL-2, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor (TNF-alpha) and interferon-gamma (IFN-gamma) as well as IL-2 receptor (IL-2R) were quantified at mRNA level using RT-PCR. Subpopulations of blood lymphocytes were assayed using flow cytometry. No significant changes neither in cytokine expression nor in shifts of CD4 and CD8 markers could be found, but similar curve diagrams concerning CD8 single positive T cells could be observed in all vaccinated animals with an initial decrease and an increase between post-infection days (PIDs) 7 and 14. In the vaccination group, TNF-alpha and IL-6 tended to be increased at PIDs 22 and 40, whereas no increase could be seen in IFN-gamma. When comparing the in vivo immune response to that being seen in in vitro experiments, similar shifts of CD4/CD8 lymphocyte subpopulations may be seen. Cytokine curve diagrams, however, do not reflect the in vitro findings to that extent.