In minimal invasive surgery, rigid endoscopes are used to view inside the body through natural or artificial
made orifices. As the price of a rigid endoscope is high, they are being constantly re-used after a cleaning and steam
sterilization procedure at the Department of Central Sterilization. However, due to mechanical, chemical and thermal
stresses, endoscopes degrade over time. To determine whether an endoscope still provides sufficient quality, personnel
of the Department of Central Sterilization visually inspect the outside and inside of an endoscope. In practice this check
is hard as it appears difficult to tell whether an image is good enough as it should be compared to the image of an new
endoscope of the same type. Because of the large diversity in endoscopes, the variation of image quality of new
endoscope is already so large, that it is difficult to perform this manual check objectively.
In this paper we describe the results of using an experimental test bench to measure the optical quality of
endoscopes over the years 2007-2011. The system is based on measuring the illumination pathway using a white LED
and photo cell and the viewing pathway using a LCD generated test pattern and high resolution camera. The
measurements show that endoscopes roughly degrade 20% per year, but also that the variation in degradation is so high
and uncorrelated to the type of endoscope that structural measurement of the quality of endoscopes may be a prerequisite.
Looking at the system itself, it appeared that although the system had sufficient stability over these years to
allow conclusions, it has too much drawbacks to be used at the Department of Central Sterilization, like the stability of
the LCD screen, loosing track of endoscopes when they are placed in another basket and the large number of manual
steps needed to perform a measurement.
For this reasons we present a new design of an endoscope measurement system, called the MDE, a
Measurement Device for Endoscopes. It is based on comparing the endoscope image of the inside of a marker sphere
with that of a new one. After a test run at the St Jansdal clinic in Harderwijk, the Netherlands, from March to December
2011, the system will be re-designed the coming months to include endoscope labeling with a data matrix, detection of
broken illumination fibers and lenses and scanning of water and dust particles. Aimed to be commercially available
from the end of 2012, we hope that this system will be a valuable device for assuring the optical quality of endoscopes
in clinical practice.