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Supersonic Imagine

Tumor Detection and Destruction

Since their discovery of the time reversal mirror (TRM), Mathias Fink and his team have been actively diversifying its industrial applications. Among the most promising is an ultrasonic camera that can detect tumors before destroying them.

fink

© F. Jannin/CNRS Photothèque


You have come up with a solution that could prove revolutionary in the field of medical imaging. What is it going to change?

Mathias Fink: At the moment, using conventional ultrasonic scanner techniques, ultrasounds can be used to visualize different organs, the shape of a fetus or amniotic liquid, because their propagation speed (around 1500 meters/second) varies slightly from one medium to another. However, this variation in propagation speed is not sufficient to allow detection of tumors even though they are denser than their surrounding environments. Our technique should overcome this obstacle.

 

How exactly does it work?

MF: To detect a tumor, we create something called a 'shear' wave, similar to what a physician does when he palpates areas of a patient's body. For this, the probe of our ultrasonic scanner focuses the ultrasounds on a single point of the patient's body to trigger a 'microseism.' The resulting shear wave propagates at speeds of 1 to 5 meters/second, depending on the elasticity of the medium through which it passes. By moving the source of the 'microseism' at a supersonic speed that can attain Mach 10, we subsequently amplify the shear wave. The probe then immediately switches to 'time reversal' camera mode (see below), at a rate of 5000 images a second–a hundred times faster than a traditional ultrasonic scanner. An algorithm computes the velocity of the shear wave at each point of the image. The contours of any tumor that may be present are then clearly outlined, with a resolution close to one millimeter. The device is principally intended for detecting cancers of the breast, the prostate, the kidney, the thyroid and fibrosis of the liver, but it can also be applied to imaging the heart, an organ that produces its own shear wave when it contracts.

 

This device is based to a large extent on your work on time reversal mirrors (trM). How do they work?

MF: trMs are electronic devices predominantly made up of sensors, which record and digitize a signal, then send it back to its source, but in the reverse order–starting with the end. Consequently, when a sound wave encounters a trM, it retraces its path back to its source step by step. It follows whatever path it has taken and passes through whatever media it had encountered previously. It's as if we were playing the 'movie' of the wave backwards. This makes it possible to return to the source with a very high degree of precision and therefore to 'target' it, if necessary, with other signals created this time by the trM. And there are numerous applications: undersea imaging, telecommunications–even home automation systems–but also medical imaging and above all ultrasonography.

 

What therapeutic solutions do these devices provide?

MF: With current techniques, we can already destroy tumors or stones in the prostate using high powered ultrasounds. But organs like the liver are difficult to treat because they move during the treatment. Hence the interest for trMs which always send the initial wave back to its source. trMs also allow non-intrusive brain surgery with no need to open the skull. In our laboratory,1 we have developed a type of 'time reversal helmet' equipped with 300 small ultrasound emitters which, when a tumor is detected, instantly sends the received wave back to the tumor, but amplified by a factor of one million to burn it.

 

The Supersonic Imagine start-up2 is now developing this project. How was it created?

MF: In the last twenty years, there were no medical imaging manufacturers based in France. Most specialists in the field had left for the United States. But three years ago, I convinced Jacques Souquet, who had been based in the States for 22 years, to return to France. He left his job as R&D Director with Philips Medical System and founded the Supersonic Imagine start-up on the basis of the technological innovations developed by our LOA team. The company negotiated an exclusive license for six patents held by CNRS and, on this strong technological basis, venture capitalists backed us by injecting €10 million in the very first round. Ten more French researchers brimming with enthusiasm for the adventure have returned from the States, bringing with them several American colleagues.

 

How is the development of the actual devices coming along?

MF: The time reversal helmet has been successfully tested on ewes and monkeys. The ultrasonic scanner is currently being tested on hundreds of patients at the Institut Curie. We are determining its degree of precision on tumors that have already been detected. A prototype, scheduled to be up and running by the end of 2007, will be installed in ten cancer detection centers throughout the world. In the near future, Supersonic Imagine will bring out a dual-purpose device for both diagnostic and therapeutic use.

 

Interview by Emmanuel Thévenon

Notes :

1. Laboratoire “Ondes et acoustique” (LOA) (CNRS / Ecole supérieure de physique et de chimie industrielle / Université Denis Diderot Paris-VII).
2. www.supersonicimagine.fr

Contacts :

Mathias Fink
LOA, Paris.
mathias.fink@espci.fr


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