A new visualisation method enables more precise catheter navigation through the vascular system. It is being developed at the Fraunhofer Institute for Digital Medicine (MEVIS) in Bremen, Germany, and one of its ambitions is to reduce physician radiation exposure.
The “intelligent catheter navigation”, or Intellicath method, uses a catheter equipped with an optical fibre containing tiny “mirrors”. When light passes through the fibre, the mirrors reflect a portion of the light. Whenever the fibre bends, the reflected light changes colour. Sensors can measure the change in colour.
“The signal from the sensors gives us information about the intensity and direction of the curvature,” Torben Pätz, a mathematician at Fraunhofer MEVIS, explains in a news release. “To some extent, the fibre knows how it is formed.”
Around the world, millions of endovascular procedures are performed per year, using X-ray guidance to place stents or remove blood clots. This results in radiation exposure for patients and physicians alike, and an additional challenge is that X-rays do not provide the most precise images, according to Pätz.
Before the procedure, physicians obtain computed tomography (CT) or magnetic resonance (MR) images of the patient. Based on this image data, IntelliCath software creates a 3D model of the vessel system and displays it on a monitor. During the endovascular procedure, live data from the fibre navigation is fed into the model. The doctor views the monitor to see how the device moves through the vascular labyrinth live and in 3D.
MEVIS experts have already been able to test the method’s feasibility using a prototype, according to Pätz. “We connected several silicone hoses into a curved labyrinth,” he says. “Then, we inserted our device containing an optical fibre into the labyrinth.” On the monitor, they were able to locate the catheter’s position in real-time with precision approaching five millimetres. The researchers have applied for two patents.
Although several medical device companies work on similar projects, “they expend a great deal of technical effort into trying to reconstruct the shape of the entire catheter, which can be up to two meters long,” Pätz comments. “Our algorithm, however, only needs a fraction of the data to localise the catheter in a known vascular system.”
As a result, the MEVIS approach promises cost-effective technology without special fibres and measurement systems and is less sensitive to measurement errors than previous approaches, according to the institute.
Next, the researchers will test the IntelliCath system on both a full-body phantom of the human vascular system and on a pig lung. Toward the end of the current project phase in 2020, a prototype will be ready to serve as a foundation for a clinical trial.
Pätz and his team are also developing acoustic feedback to relieve doctors of the constant need to look at the monitor. The idea is to employ various indication sounds to signal how far the next vessel junction is and in which direction the catheter should be inserted.
“It is similar to a car’s parking assistance system, where you also receive acoustic indications about the distance to the next obstacle,” Pätz explains.
