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Current Directions in Biomedical Engineering

Joint Journal of the German Society for Biomedical Engineering in VDE and the Austrian and Swiss Societies for Biomedical Engineering

Editor-in-Chief: Dössel, Olaf

Editorial Board Member: Augat, Peter / Buzug, Thorsten M. / Haueisen, Jens / Jockenhoevel, Stefan / Knaup-Gregori, Petra / Kraft, Marc / Lenarz, Thomas / Leonhardt, Steffen / Malberg, Hagen / Penzel, Thomas / Plank, Gernot / Radermacher, Klaus M. / Schkommodau, Erik / Stieglitz, Thomas / Urban, Gerald A.

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2364-5504
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“Hands free for intervention”, a new approach for transoral endoscopic surgery

A. Boese
  • Corresponding author
  • Department of Medical Engineering, Otto-von-Guericke University, Magdeburg, Germany, tel.: +493916719366
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/ M. Detert / Chr. Stibbe / M. Thiele / Chr. Arens
Published Online: 2015-09-12 | DOI: https://doi.org/10.1515/cdbme-2015-0039

Abstract

A standard method for transoral diagnostic and dissection of tumour is the endoscopic examination plus microscopic and laser supported surgery. For endoscopic examination a set of rigid endoscopes with different angles of view are on the market and in use. To simplify the diagnostic examination, a first idea was to use an endoscope with flexible angles of view. A further step of this approach is the electrical angulation of the endoscopic view to enable an adaption on the surgery site without using the hands. Thus the hands are free for intervention. This paper shows a first implementation of a prototype of an electrical operated endoscope for a free hand imaging in transoral interventions.

Keywords: Endoscopic surgery; movable camera; ear nose and throat (ENT); transoral; free hand imaging

1 Introduction

For diagnosis of the upper throat and larynx endoscopes were used [1]. These endoscopes are rigid with a stack of lenses and optics inside [2]. For imaging a high resolution camera system and light sources featuring further options of diagnostic like fluorescent imaging [3] can be connected. A direct view into the interesting region of interest is possible. For transoral examination endoscopes with different angles of view are in use. For full examination the endoscopes have to be changed to view the region of interest from all directions. This is time consuming and requires a set of different endoscopes. A new strategy to enable a variable view is the ENDO-CAMELEON (Karl Storz, Tuttlingen, Germany). A mechanical steerable lens system provides a change of view from straight to 110° backward [4]. By rotation of the endoscope a 360° surround view is possible. In an extended approach we developed an endoscope with an integrated camera system and light source on the tip. The camera is rotatable, swiveling and the movements are electrical operated. This idea is the base of a complete new approach for endoscopic transoral surgery in the field of ENT. By combining the electrical operated endoscope with a holder and a manipulator (e.g. foot pedal), a “hands free” imaging is possible. The endoscope can be fixed in a proper position to give a good overview of the surgery site. Adaption of the field of view can be made by the manipulator during intervention. So the hands can be used for grapping and cutting tissue for dissection. In this paper we introduce a first prototype of an electrical operated endoscope.

2 Methods

For understanding the need of optimisation of the endoscopes for transoral access, a workflow observation in a surgery situation was performed (Figure 1). Here the basic facts for a new design were collected as described in [5].

Endoscopic surgery on the larynx (Curtesy Prof. Chr. Arens, Magdeburg)
Figure 1

Endoscopic surgery on the larynx (Curtesy Prof. Chr. Arens, Magdeburg)

In intense interviews with the user the specifications were clarified. The operation of the endoscope should be close to the movement of the human eye. The diameter of the final prototype should not be larger than the state of the art endoscope STORZ ENDO-CAMELEON (10 mm). We decided to use a micro camera and to be integrated into a movable setting. The Nane Eye image sensor (Awaiba GmbH, Nürnberg, Germany) provides a RGB image with a resolution of 250×250 pixels [6]. It is available in combination with 4 white LEDs as a light source and an USB connectable module. The size of the image sensor including lights is 2.4 × 2.4 × 1.7 mm. To realize a wide range of movement a cardaniac operated camera module with a slider crank was chosen for the first design. In a next step the camera module was designed as a ball. The swiveling of this ball was operated by a linear piezo motor. For transfer of the movement, a flexible Bowden cable with a PTFE tube as cover was chosen. For rotation, a stepper motor with a high precision was integrated. After selection of the main parts, a general construction of the endoscope was performed. Beside the main features, the endoscope has a fast changeable cover for a separate sterilisation. The camera module is covered by a transparent glass dome (Figure 2) to provide a large field of view.

Tip of the endoscope with integrated camera and range of view
Figure 2

Tip of the endoscope with integrated camera and range of view

A control panel for manual steering was integrated in the proximal end of the endoscope. All electrical parts were connected over a self-made printed circuit board and a common interface wire for PC connection (Figure 4).

After manufacturing and assembly the endoscope was tested successfully in the main functions (imaging, light intensity, movements, handling and heat development). The final prototype is shown in Figure 3.

Prototype of the electrical operated endoscope
Figure 3

Prototype of the electrical operated endoscope

Electrical operated endoscope a) manual steering panel, b) rotational power unit, c) translational power unit
Figure 4

Electrical operated endoscope a) manual steering panel, b) rotational power unit, c) translational power unit

3 Results

An endoscope with an electrical movable image sensor was build up. The final outer diameter is 8 mm. The properties of movement were tested. A rotation of the field of view of 380 degrees is possible, also a swivelling of 120° from straight view. Figure 2 shows the range of the field of view. The movement can be easily operated over the integrated steering panel or via pc control (Figure 4a). Thus any other manipulator can be connected.

Also a continuous test of the power units was performed by operating the system via pc control. Beside the movement, the image quality and power of light source are important factors for the endoscope. Figure 5 shows the images of the camera under different light conditions.

Test of the light intensity and image quality according to power supply
Figure 5

Test of the light intensity and image quality according to power supply

Because the light sources lead to a warming of the system up to 45 °C, the former tip cover out of glass was changed into a poly carbonate dome after testing. Thus the cover is more robust and the temperature transfer is less. Finally the endoscope was tested in a phantom to estimate image quality. Due to the low resolution the image quality is poor but acceptable for the first step.

4 Conclusion

We showed that a realisation of an electrical operated endoscope with a wide range of view is possible in an adequate size. Thus the “hands free” imaging approach is feasible. The movement of the chosen power units is very precise. The operation of the camera ball works reliable. For the first prototype the weight (945 g) is still too high but can be optimized by the change of materials and wall thicknesses. The biggest drawback is the poor image quality. The intensity of light source is satisfactory. Here the use of an image sensor with higher resolution is mandatory. The use of LED light sources enables an easy integration of additional LED to provide different wave lengths for spectral imaging in future. To follow the “hands free imaging” approach, also the standard endoscope STORZ ENDO-CAMELEON can be electrified. In combination with an external power unit an operation of the direction of view can be realized. This could be integrated in a fixation arm to hold the endoscope in place during intervention. This will be our next step to realize a “hands free” imaging approach in transoral surgery. This technique is not limited to this field of ENT. Also in urology, gynaecology laparoscopy or other fields of endoscopic applications, an electrical operation of the angle of view could be advantageous [7].

Acknowledgement

The work of this paper is partly funded by the Federal Ministry of Education and Research INKA (FKZ 03IP710, 03IPT7100X) and by the Land Sachsen-Anhalt KOMET (FKZ AZ: 48-76120).

References

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About the article

Published Online: 2015-09-12

Published in Print: 2015-09-01


Author's Statement

Conflict of interest: Authors state no conflict of interest. Material and Methods: Informed consent: Informed consent has been obtained from all individuals included in this study. Ethical approval: The research related to human use has been complied with all the relevant national regulations, institutional policies and in accordance the tenets of the Helsinki Declaration, and has been approved by the authors’ institutional review board or equivalent committee.


Citation Information: Current Directions in Biomedical Engineering, ISSN (Online) 2364-5504, DOI: https://doi.org/10.1515/cdbme-2015-0039.

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