Four things to consider when designing endoscopes
The big goal that all endoscope makers share is this: how can scopes get smaller and smaller while light output ideally grows and grows. At SCHOTT, the application engineer Elisabeth Y. Han works on a team of scientists and engineers who collaborate intensively with the customers’ technical teams to reach this goal. Here she talks about four things that should be considered.
Together, we help increase patient comfort and enable surgeons to perform diagnoses and therapies with more precision than ever before, ultimately leading to better results and faster recovery times for the patient. However, tackling this challenge involves more than meets the eye. Designing the optical path of a fiber-based endoscope involves juggling many aspects in terms of physics, mechanics, and even glass chemistry. Fibers are extremely thin and flexible, yet powerful and performant. Let’s take a closer look at four things to consider for optimal light path design:
1. The light spectrum of glass optical fibers
In medtech, classic white-light endoscopy operates in the visible wavelength range between about 400 and 780 nm. In addition, there are interesting applications at the “left and right edges” of this spectrum that our SCHOTT PURAVIS® fibers help enable. This includes photodynamic diagnostics at 405 nm which makes tumor markers visible with blue light, and fluorescence diagnostics at around 800 nm which enables high-contrast imaging with color markers like ICG.
2. Space constraints of smaller scopes
As instruments used in surgery shrink in size to minimize incisions and maximize patient comfort, creativity is key. I have seen a lot of “funky” shapes at the distal end such as moon or halo shapes to achieve an overall reduced housing while maximizing light output. By working with designers and product developers early on, we can better understand what elements, such as working channels or the camera module, our fibers need to thread through.
3. Advantages of fusing over gluing fibers
End surface conditions of the fibers also affect how much light is transported to the point of surgical focus inside our bodies. One way to improve the transfer of light from one element to the next is by choosing to fuse the fibers together at the ends rather than gluing them. Fused fibers are joined together at the proximal and/or distal end of the bundle by modifying the individual fiber cross-sections using temperature and pressure. Compared to a glued fiber bundle, a fused bundle offers a homogeneous and closed glass surface and is more densely packed with fibers. This has several advantages which all lead to the desired high level of light output.
4. Long-term autoclavability
Autoclaving has two big key factors that affect the performance of a part: the high temperature of up to 138 degrees Celsius and the steam factor (i.e., moisture). These two aspects can damage a lot of different materials, whether it's the fibers inside the scope or any other components going into the system. That is why it is important to choose high-quality glass fibers that don’t weather during reprocessing, meaning that they can withstand thousands of autoclave cycles during their lifetime without deteriorating.
Together with my colleague Jan Steigleder, Senior Product Manager Medical, we explored these four topics in more detail (see links below). We are proud to say that years of experience and deep expertise allow our teams to collaborate with scope designers on unique solutions to provide more dependable views inside the body and allow for improved patient safety.
Text: Elisabeth Y. Han, SCHOTT North America Inc., Lighting and Imaging
March 2024
Links
The Light Spectrum of Glass Optical Fibers and the Effects of Solarization
Dealing with Space Constraints when Designing Smaller Scopes
Why “Fused” Beats “Glued” in Endoscopic Light Guides
Designing for Long-term Autoclavability in Endoscopes
