A Gentler Look at Tumors

Lower radiation exposure in the diagnosis and treatment of cancer: Fraunhofer researchers are drawing on a technology from a completely different field.

X-rays are fascinating for Victoria Heusinger-Hess: They tell us quickly and in detail what is present or taking place under a surface. Nor can she avoid this topic as a research scientist at the Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMI: X-rays play an important role at the Efringen-Kirchen site. For example, the research scientists are able to use high-speed X-ray imaging to study dynamic processes taking place over periods of milliseconds or microseconds. They can do this at speeds of up to 1000 frames per second. “An X-ray video like this,” explains the mathematician, “enables us to directly observe what happens inside a vehicle and what happens to the occupants during a high-speed car crash, for example.”

In contrast, X-ray examinations in medicine are both a blessing and a hazard: the longer and more frequently a person is exposed to the ionizing radiation used, the greater the probability of damage to cells and tissue. In just a single CT scan, a person receives two to five times the average radiation dose that they naturally experience in a year.

“As little as possible, as often as necessary” is therefore the medical motto when using imaging procedures such as X-rays or computer tomography. The benefits and risks must be weighed especially carefully for people who are genetically predisposed to cancer or already have a tumor. So researchers at Fraunhofer EMI asked: Is there a technical solution that provides meaningful image data while simultaneously working so quickly and effectively that the patients are exposed to as little X-ray radiation as possible?

Electromagnetic waves provide a glimpse inside

In a joint project with researchers from the Fraunhofer Institute for High Frequency Physics and Radar Techniques FHR and the Fraunhofer Institute for Digital Medicine MEVIS, the Fraunhofer EMI team decided on a surprising solution: radar. This technology has thus far been used more in shipping and air traffic or for gathering weather data. The principle is simple: A radar unit emits electromagnetic waves that cannot penetrate certain materials (such as an airplane), but are instead reflected back to the radar. Based on the time of flight and the change in frequency of the reflected waves, conclusions can then be drawn about the shape, material and movement of the detected object. The so-called “body scanners” at the airport also work with radar waves: They make the body and any suspicious objects under the clothing visible.

The advantage of radar technology is that electromagnetic waves can also penetrate the body at a suitable frequency and image tissue changes without being harmful to health. The disadvantage: Image resolution is somewhat coarse. “If we limit ourselves to radar, we could see that a tumor is there,” explains Heusinger-Hess. “But precise localization is not possible.” To compensate for this drawback, the Fraunhofer researchers are combining radar and X-ray technology. “By integrating additional information from a previous X-ray scan,” says Heusinger-Hess, “the subsequent radar image can be enhanced to a higher level.” For example, in practice, an X-ray CT scan of a tumor would be taken at the start of cancer treatment, as has been the case up to now. Subsequent examinations could then be replaced by less harmful radar technology, using intelligent algorithms to incorporate prior information from the initial X-ray image.

A phantom breast made from gelatine and fat

The research at Fraunhofer EMI is currently focusing on breast and lung tumors. There are very practical reasons for this. Unlike the abdominal region, for example, breasts and lungs are relatively compact areas of the body where there are not too many different organs and types of tissue. And unlike in the skull, for example, there is no massive bone plate to impede the passage of radar waves.

The patent for combined radar and X-ray tomography has already been granted, and the next step is to further develop the technology. To achieve this, Heusinger-Hess and her team have developed so-called breast phantoms made primarily of gelatine and fat. The algorithms are being further developed on the one hand, but different scan variants are also being tested. For example, can X-ray and radar images be created simultaneously, or does it make more sense to capture images with a time delay? Can radar measurements be used to change or compensate for artifacts in X-ray images? And can artificial intelligence, trained with simulation data and real measured values, enable neural networks to draw the right conclusions from the image data in a further step?

Applications outside medicine are also conceivable, such as for a quick check of containers in a shipping port or for hand luggage scanning at an airport. This takes the Fraunhofer team full circle back to the initial question of their research in security: “X-ray technology gives us the quick information that there is a square object in a suitcase,” explains Heusinger-Hess. “But the radar gives us the important details: Is it explosives, or just a bar of chocolate?”