Optical Data Communication The First Wireless Endoscope Works by Light

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Cables can quickly become a hygiene problem in a medical environment. The use of conventional wireless systems usually fails due to the strict latency and safety requirements. Researchers have now developed an endoscope that transmits 4K video data via LiFi without delay.

Imaging medical devices such as endoscopes are sometimes connected to monitors and the hospital information system via massive cable harnesses. Commercially available endoscopy systems usually require two connections: an optical waveguide for light guidance and a cable for power supply and data transmission.

This causes problems in everyday clinical practice, as the cables have to be laboriously insulated with sterile sheaths. They also severely restrict the surgeon's freedom of movement during laparoscopic procedures (laparoscopies). Dispensing with cables would speed up work processes and make it easier to clean the equipment.

However, the switch to wireless in medical electronics is complex: standard wireless technologies such as WLAN or Bluetooth reach their limits when it comes to medical technology requirements in terms of reliability, data security, electromagnetic compatibility (EMC) and, above all, the latency of uncompressed or slightly compressed high-resolution video streams.

Light Waves Instead of Radio Frequencies

The BMBF-funded project OWIMED (Optical Wireless Communication for Medical Imaging Devices) is therefore taking a different approach. Under the leadership of the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI), the developers are focusing on optical wireless communication (LiFi).

"Instead of radio waves, we use modulated LED light," explains Dr. Anagnostis Paraskevopoulos, project manager at Fraunhofer HHI. "The localized light propagation makes LiFi ideal for medical technology. We can already meet the requirements for high data rates over short distances today."

Batteries, Microprocessors And Hemispherical Radiation

For a completely wireless endoscope, the developers at IT Concepts and Fraunhofer HHI had to fundamentally redesign the system architecture. The optical light source (LED) for illuminating the abdominal cavity was integrated directly into the endoscope and is powered by a rechargeable battery.

A very compact LiFi module, which is also battery-operated, is located on the endoscope for communication. An integrated modulator switches the LED signals for data transmission up and down at a frequency that is invisible to the human eye. To ensure a robust connection, even when the surgeon is moving, the LiFi modules have been designed to achieve a homogeneous, hemispherical radiation in a radius of 180 degrees.

The receiver counterparts of the LiFi technology are integrated into the operating lights above the table. They use the optimal line-of-sight, i.e. the line of sight to the endoscope. Data is received by light pulses via photodiodes and converted into electrical signals. The electrical data is then forwarded to the monitor. The system is bidirectional: This means that commands can also be sent back to the endoscope from the monitor, for example to adjust camera settings.

Low-Latency Data Compression

Power management is a particular challenge in wireless video transmission. The camera chip integrated in the endoscope therefore works together with a dedicated microprocessor that performs low-latency data compression directly on the device. This allows 4K video streams to be transmitted with minimal energy consumption.

The practical suitability of the prototype was tested intensively on a surgical simulator by the medical staff of the project partner, St. Joseph Hospital Berlin-Tempelhof (Germany). The results are promising: the LiFi endoscope was fully convincing in terms of latency, data rates, reliability and ergonomics. "The feedback from the surgical team was consistently positive. Once our system has been fully developed, the doctors would prefer it to the wired version," concludes Paraskevopoulos. (heh)

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