Device Combines Ultrasound and Photoacoustics to Improve Imaging

University of Twente Enschede,
The Netherlands
www.utwente.nl

In collaboration with various companies, scientists at the University of Twente's MIRA biomedical research institute have recently developed a prototype for a handheld device that combines ultrasound technology with photoacoustics.

The device integrates pulsating diode lasers in the ultrasound probe to produce better images than either technology can do alone.

Where ultrasound offers images of structures, photoacoustics offers images that contain more functional information, such as where blood is located in the body. By combining both technologies in one device, images are generated that offer considerably more information. The combination of ultrasound technology and photoacoustics was made possible through the integration of pulsating diode lasers in the ultrasound probe. The result is a compact, handheld and relatively inexpensive system.

Doctoral candidate Pim van den Berg tested the technology for a variety of applications as part of his PhD research. His research shows that the device can be used to see a clear difference between arthritic fingers and healthy fingers and to detect fibrosis of the liver in laboratory animals. In the future, fewer mice will probably be necessary in research into liver fibrosis.

Potential Applications

The combination of ultrasound and photoacoustics in a compact device means that the applications of

this technology include a simpler and more accurate diagnosis of the degree to which patients with rheumatoid arthritis are suffering from inflammation of the joints.

Another potential application is fibrosis of the liver. Fibrosis of the liver means damage to liver tissue due, for example, to Hepatitis A or B or alcohol. This combination device can help detect the disease in laboratory animals. It would allow researchers to track a single mouse for a longer period of time, for the purposes of discovering how the illness is progressing and learning more about the effects of medication. Fewer mice will be needed with the use of this technology.

Working with University College London, van den Berg also tested the device for measuring the flow rate of blood, which provides physicians with information about inflammation. “The test has been very successful,” he says. “We would like to find out how fast the blood flows, how many blood vessels there are near the site of the inflammation, and the levels of oxygen and nutrients. This information will tell us more about the inflammation.”

In the future, the device could also be tested for use in mapping other ailments, such as skin cancer, burns, or hardening of the arteries. “In a new European project with the same partners, we will be conducting measurements to greater depths to detect hardening of the carotid artery,” says Prof. Wiendelt Steenbergen, van den Berg's thesis supervisor.

How It Works

In photoacoustics, short laser pulses are emitted into a patient's body. When the laser hits a blood vessel, for example, the light is converted into heat, causing a small increase in pressure. This increase in pressure then moves through the body in the same way a sound wave would. This sound wave on the skin can be measured. Photoacoustics technology is an extension of ultrasound imaging. In ultrasound imaging, the sound is transmitted into the body, where it bounces off of various tissues in a variety of ways and produces waves that can also be detected on the skin. Photoacoustics does not measure echo, but rather it measures the sound that is produced through the absorption of light. This means a much greater sensitivity to substances that absorb light — such as blood — is needed. The method is primarily suitable for measuring waves in relatively superficial parts of the body, up to 15 mm under the skin.

This research was conducted by the Department of Biomedical Photonic Imaging at University of Twente's MIRA Institute in collaboration with Ruchi Bansal and Jai Prakash from the Department of Biomaterials Science and Technology (MIRA) and with Thore Bucking, Joanna Brunker, and Paul Beard from University College London. The study was partly funded by the European Commission (FP7/318067).