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11.02.2022 13:44
Seeing through blood with a microscope
Middle ear infections are often triggered by cholesteatomas, a chronic bone suppuration. The new cooperation project “BetterView” is working on a special surgical microscope so that cholesteatomas and other bacterial contamination can be better recognized and safely eliminated: The so-called SWIR microscope system uses short-wave infrared light. It is intended to screen blood, bacterial biofilms, cartilage and soft tissue, display them spatially and make them distinguishable from one another. Seven partner institutions are cooperating in the project, including the University of Bielefeld and the Klinikum Bielefeld, one of the sponsoring clinics of the Universitätsklinikum OWL.
The research is coordinated by the medical technology company Munich Surgical Imaging. A total of 4.1 million euros will be spent on the project. The Federal Ministry of Education and Research is funding the new research.
Minimally invasive surgery works with the smallest skin incisions – the tissue is therefore hardly injured during the operations. Optical microscopes help to examine the area to be operated on. They illuminate the surgical field and transfer the view to a screen in high resolution. So far, however, light from the visible spectral range has been used almost exclusively in surgical microscopy. The microscopes used reach their limits when the surface is covered by bleeding or bacterial colonization. The new project “BetterView” is developing the new SWIR surgical microscope so that doctors have a clear view in such situations. SWIR stands for ShortWave InfraRed.
Shortwave infrared light sensors have only recently become readily available
“A new generation of image sensors now makes it possible to equip surgical microscopes with the function of processing and displaying images in the short-wave infrared light spectrum in real time,” says Professor Dr. Thomas Huser from the Faculty of Physics at Bielefeld University. Huser is a specialist in biomedical photonics, which deals with the development of novel microscopy methods. Together with his team, he constructs and uses high-resolution microscopes and develops the software for image processing.
In microscopes with sensors such as the SWIR surgical microscope, the recorded image signal must first be automatically analyzed and processed.
In order for the surgical microscope to be able to display the shortwave infrared signals, Huser and his team are developing their own software that filters out light outside of the shortwave infrared range and calculates a three-dimensional view of the image. “The software also has to generate color contrasts. Such colored markings make it easy to distinguish between nerves and soft tissue, for example,” explains Huser. The software must display the video image in real time so that the surgeons can work precisely in the operating room and see what their intervention is doing in the operating field without delay.
Study with the new microscope in Bielefeld University Hospital
In order to test the SWIR surgical microscope in practice, the project will initially use it in the treatment of cholesteatomas – a chronic purulent inflammation of the middle ear. The microscope is being tested in the University Clinic for Ear, Nose and Throat Medicine, Head and Neck Surgery at the Bielefeld Clinic. The most cholesteatoma operations in Germany are carried out at the clinic – 650 operations per year.
“If a cholesteatoma is left untreated, it can lead to serious damage,” says Professor Dr. medical dr Holger Sudhoff, Director of the University Clinic for Ear, Nose and Throat Medicine, Head and Neck Surgery at the Bielefeld Clinic and member of the OWL Medical Faculty. “In such a case, the chronic inflammation destroys the three auditory ossicles, with the result that the affected person becomes hard of hearing in the ear,” explains Sudhoff. In late stages, the inflammation can also lead to paralysis of the facial muscles, meningitis and cranial abscesses. A cholesteatoma, also known as bone suppuration, can be caused by a middle ear infection or by the eardrum growing into the middle ear.
Common surgical microscopes are reaching their limits
Surgical microscopes that only use the light range that is visible to humans are generally used for diagnosis, in the operation and in aftercare. “They help us to determine whether a bacterial biofilm has formed,” says Sudhoff. If a cholesteatoma becomes inflamed by bacteria, it grows faster and causes more damage to the affected bones. How much the bacterial colonization has spread is often not recognizable with the usual microscopes because, for example, hemorrhages cover the biofilm.
In addition to microscopy, the specialists also use computed tomography (CT) to diagnose cholesteatomas. This means that any fluid in the middle ear cannot be distinguished from a cholesteatoma. Magnetic resonance imaging is also used to prepare for an operation. It provides a higher resolution than CT. The disadvantage, however, is that it cannot display the details of the auditory ossicles precisely enough either.
Completely eliminate bacterial infestation with the help of the microscope
Those responsible for the project expect a number of advantages from the new SWIR microscope. The focus here is on the microscope’s ability to see through blood and distinguish between bacterially populated tissue, bones, nerves and soft tissue. “In this way, surgeons can already see during the procedure where there is still bacterial colonization in the middle ear,” says project coordinator Dr. Hans Kiening from the medical technology company Munich Surgical Imaging (MSI). “This allows them to completely remove infected areas that could otherwise lead to a cholesteatoma developing again.” MSI comes from a surgical microscope that is already used in surgery and delivers high-resolution images. The new project builds on this development.
Because the future SWIR microscope can also see through soft tissue compared to conventional microscopes, it should also be able to examine areas that are optically hidden. In this way, it can be seen, for example, whether bone material in the inner ear has also been colonized by bacteria or has been damaged. In addition, the microscope should increase patient safety. Because if surgeons can precisely identify and differentiate the inside of the ear, the risk of injuring sensitive structures such as the facial nerve or the labyrinth of the inner ear is reduced.
The Federal Ministry of Education and Research is funding the BetterView joint project as part of the “Photonic methods for detecting and combating microbial contamination” funding initiative with 2.73 million euros (funding number: 13N15827). Of this, 374,000 euros will go to the University of Bielefeld and 478,000 euros to the Klinikum Bielefeld. The project runs from January 2022 to December 2024. The medical technology company Munich Surgical Imaging (MSI) coordinates the network. In addition to the University of Bielefeld and the Klinikum Bielefeld, the Helmholtz Pioneer Campus at the Helmholtz Zentrum München, the Leibniz Universität Hannover, the camera system manufacturer PCO AG and the laser manufacturer Omicron-Laserage Laserprodukte GmbH are also involved.
Chronic diseases play an important role in the research of the OWL Medical Faculty. These are diseases that last a long time and are often difficult or not completely curable. Chronic diseases are among the most common health problems in Germany and other industrialized countries. The Medical Faculty OWL deals with them as part of their research profile “Medicine for people with disabilities and chronic diseases”.
Scientific contacts:
Prof. Dr. Thomas Huser, University of Bielefeld
Faculty of Physics
Phone: 0521 106-5451
Email: [email protected]
Further information:
https://www.photonikforschung.de/projekte/lebenswissenschaften/projekt/bettervie… Project profile in the Photonics Research Germany portal
https://www.physik.uni-bielefeld.de/biopho/index.php/en/ Website of the working group of Prof. Dr. Thomas Hauser
https://bit.ly/3LlvXih Website of the University Clinic for Ear, Nose and Throat Medicine, Head and Neck Surgery
https://www.uni-bielefeld.de/fakultaeten/medizin/forschung/profil/ Research profile of the medical faculty OWL
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