Magnetic robotic fetoscope improves precision of twin transfusion surgery

In Switzerland, around 2,400 children are born as twins every year. When the fetuses share a placenta, they are connected to one another via blood vessels. If the blood circulation becomes unbalanced, this can be life-threatening for both, as too much blood flows from one fetus to the other. The condition known as 'twin-to-twin transfusion syndrome' (TTTS) affects around twenty to thirty women a year in Switzerland. To date, the only effective treatment is a highly complex operation that is performed by only a handful of specialists worldwide.

Researchers at ETH Zurich and doctors at the University of Zurich have set themselves the goal of making this operation easier and lifting its success rate. Currently, surgeons use a fetoscope for this purpose – a delicate endoscope designed for procedures on pregnant women. It contains a small camera and a channel through which a thin fibre guides laser light to the blood vessels in the placenta. In this way, surgeons are able to seal the vessels in the placenta that connect the two fetuses.

The fetoscopes in use today, however, are rigid. Depending on the position of the placenta, it can therefore be extremely difficult to reach all the affected blood vessels and seal them with the laser.

Magnetic control for greater maneuvrability

In response to this situation the researchers and doctors have developed a flexible fetoscope with a diameter of just 3.2 millimetres, featuring a tip containing magnets. Three large electromagnets outside the patient's body generate a controllable magnetic field, enabling them to bend the tip of the fetoscope, whereby the magnetic field is entirely innocuous.

Navigating with a panoramic view 

The new system combines the individual endoscopic images in real time to form a panoramic image, enabling the surgeon to now select a target on this two-dimensional map. The fetoscope then navigates there automatically. Doctors, however, can take control at any time and steer the fetoscope manually using a PlayStation game controller. Software then translates the desired movement in the camera image into the corresponding change in the magnetic field.

Mattille was surprised by the extent to which the robotic procedure differed from conventional laser surgery. "Even the very steady hand of an experienced surgeon causes the fetoscope to wobble slightly. Our robotic platform, on the other hand, stabilizes the tip and holds it much more steadily at the desired location to coagulate the vessels precisely," as the researcher relates.

In experiments, the participants hit simulated targets far more accurately using the robotic system. "With the robotic system, the deviation was typically 140 micrometres, meaning it is more than four times more precise than conventional comparable instruments," Mattille states.

Critical testing outside the laboratory 

An experiment on a pregnant ewe represented a key step towards the clinical application of the robotic platform. This marked the first time the researchers had left the controlled laboratory environment behind and tested the device under real-world conditions. They now had to contend with the animal's breathing and heart rate, cloudy amniotic fluid, as well as suspended particles and a moving fetus.

Also conceivable for other procedures 

The successful in vivo animal trial represents an important milestone on the path to robot-assisted procedures in fetal surgery: for the first time, researchers have succeeded in demonstrating the key steps of an TTTS procedure in a realistic environment. For Mattille, the motivation is clear: "Although TTTS affects only a small share of twin pregnancies, the procedure is a matter of life and death for these children."

Source:

ETH Zurich

Journal reference: