Light and sound combined for better images of inside the body

With ultrasound, the body's interior can be examined and with photoacoustics, pulsed laser light has begun to be used for similar purposes. Now, researchers at Luleå University of Technology want to combine both into a new technology, providing high-resolution images of the body's interior – a technique that could be useful in diagnostics in healthcare.

“In short, we will use light and sound in combination to get better images of tissue than you can get with traditional ultrasound technologies. Through this combination we get the best of both worlds; high contrast, good resolution and large penetration depth,” says Torbjörn Löfqvist, Associate Professor of Electronic Systems.

In a laboratory on the university campus in Luleå, the first round of experiments has recently been completed. Now, PhD student Manne Segerlund is working on developing algorithms, based on basic equations for the propagation of light and sound, that convert measurement data into an 2D image of the tissue. This is basic research that may also have applications in other research fields.

“The measurements give us a lot of data, from which we want to extract information. Using clever algorithms, we want to work out what the tissue looks like inside by measuring on the surface of the skin. The model that does the job is called an inversion algorithm. What I'm doing now is a wonderful mix of physics, mathematics, statistics and numerics,” says Manne Segerlund.

New possibilities in health care

In healthcare, ultrasound is a well-known technique. Sound is sent into the body, absorbed and scattered by different types of tissue, some of it bounces back, and by recording when, and the properties of the returning sound, an image is generated. However, resolution and contrast are low. There is also a new technology, photoacoustics. Using pulsed laser light, tissue is heated and cooled very rapidly. The small but rapid expansion caused by the heat creates sound waves that can be detected with a sensitive sensor, similar to ultrasound. What the researchers now want to do is combine both in a single sensor. For those working in a clinic, the new instrument would look similar to existing ultrasound equipment but would offer new possibilities for detailed examinations.

The image generated by the algorithms is given by the combination of the ultrasound and the laser light. One challenge is the combination problem. Which data comes from which of the different methods?

“We want to be able to show that our algorithms do not mix up the information from the ultrasound and the laser light. This is easier said than done. If we find a solution, it can be used in other fields as well, such as geology. Seeing what's under the surface of the earth is basically the same problem as seeing what's under the skin,” says Manne Segerlund.

Foundation for useful technology

The project is still in its early stages. The researchers plan to conduct studies on tissue-like models later on and there may be clinical collaborations at a later stage.

“We are going into unknown territory, we have a compass but no map. Some problems that arise are unforeseen and some steps may be bigger or deeper than we anticipated, that's the elegance and charm of basic research, and the foundations are needed before you can apply the knowledge wisely. If you start with a seemingly simple problem, you will find a depth. I am confident that the technology we are developing will be used in health care in the future. We hope to get to the point where we have the foundation for a complete and useful technology. We will not build the clinical device ourselves, but we will be able to show how,” says Torbjörn Löfqvist.

• The project is a part of PRECISE – innovative precision health.
  
• Read more about the project.