July 1, 2014

Optical Fiber 3D Navigation for Medical Technology

Ultra-short Light Pulses for tomorrow’s Surgical Technology

Precise, minimally invasive surgical procedures have a number of advantages for patients such as shorter post operative recovery times, less pain and smaller scars. But clinics and hospitals benefit as well. Passive capture of 3D profiles and shapes with optical fiber sensor systems opens a new dimension of possibilities in medicine for the navigation and positioning of surgical instruments within the human body. 

The coordinates of a catheter can be tracked with optical fiber 3D navigation when inserted in a blood vessel in real-time. Light is fed through optical fibers the breadth of a human hair. Strain and temperature impact on the fiber changes the light and thus gives information about the type, place and extent of the effect of the catheter in the blood stream.

Technical Background

Fraunhofer HHI in Goslar has developed a method based on femtosecond (ultrashort) laser technology by which waveguides and periodic modulations of the refractive index can be directly written in both the core and the cladding of optical fibres. This method enables fabrication of a large array of microscopically small, freely adaptable optical strain sensors both outside the core and inside a single fibre. This technology has been adapted for use in the medical field by Fraunhofer HHI in association with the Klinikum rechts der Isar and the Technical University Munich.

Advantages of the Technology

  • Offers a compact and light sensor system
  • Immune against electromagnetic fields
  • Integrable in existing superordinate systems
  • Uses novel femtosecond laser technology 
  • Free setting of the range of sensor dynamics 
  • Uses standard optical fiber Telekom plugs
  • Real-time monitoring

Fiber Bragg gratings (FBG) can be used to measure not only the temperature and stretching of the stent at various places but also its inclination, acceleration and vibration. The sensors are placed at pre-defined points so that up to several hundred sensors in a single fiber can be read. This enables measurement of three dimensional information about the position and movement of the stent. As this renders precise coordinates about all the positions and movements of the object, the term “shape sensing” has been given to this particular measurement technique.  

A future technique for the visualization of measurement data in three dimensional blood vessel imaging gives surgeons an inuitive understanding of the interaction of often complex intertwined blood vessels. This enables them to plan operations in the smallest detail and minimize the risk of uncontrolled bleeding and other complications during surgery.

Further Application Fields

A whole raft of applications are also feasible for shape sensing outside the field of medical technology, including such uses as: 

  • Monitoring temperature and pressure in the oil and gas industries
  • 3D profiling 
  • Structural Health Monitoring, e.g. for wind power stations
  • Condition monitoring of structures like bridges
  • Lifetime prediction of critical structural components (such as wire ropes and power cables)
  • Mapping of motion sequences, e.g. in computer games and animations