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Mr. Sebastian Webel

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Pictures of the Future
The Magazine for Research and Innovation
 

Medical Imaging

Taking X-Rays with a Raisin Loaf

In the DiCoMo project Siemens is working with a number of partners to develop a new x-ray detector through to readiness for practical use. In the new detector, the scintillator layer consists of a light-absorbing polymer in which the scintillator material is embedded in a pattern resembling the raisins in a raisin loaf.

Digital x-ray systems are the state of the art now, but for many they are still too costly. Less expensive digital detectors could change all that. The breakthrough may come thanks to the EU grant project DiCoMo. Siemens is once again playing the coordinating role.

Today digital devices are the state of the art in x-ray imaging. For developing countries and emerging markets, however, they are often too costly, and x-ray films are still widely used in these locations as a result. Cheaper digital detectors would make digital x-rays affordable in these markets. The results from the HOP-X (Hybridorganische Photodetektoren für die Radiographie, support code: 13N12377) project offer good prospects of being able to reduce these costs. As part of this German grant project, Siemens, Merck, the Leibniz Institute for New Materials and CAN GmbH devoted three years to researching materials and manufacturing processes for improved and lower-cost detectors.

“What we discovered proved so promising that we now have funding to develop these products to the point where they can be put into practical use,” report organic electronics experts Oliver Schmidt and Sandro Tedde. They have been involved in this project from the outset, initially for Corporate Technology and now for Healthcare. As they did with HOP-X, they are also coordinating the new DiCoMo (Direct conversion hybrid-organic X-ray detectors on metal oxide backplane, support code: 643920) project, but this time with EU funding.

Sectional view of an image sensor element using a scanning electron microscope. The light-absorbing polymer appears here as the dark areas and the scintillator material embedded in it forms the lighter elements. Actual image width approx. 25 microns.

More details

Today’s digital x-ray detectors consist mainly of a thick scintillator layer that converts the x-ray into light, and below it an image sensor that in turn converts the light into electrical signals. These detectors are not only expensive to manufacture, but also have the disadvantage that the light propagates so strongly in all directions as it passes through the scintillator layer that it hits a large number of pixels on the image sensor. “The result is a real big spot,” says Tedde. “And so we lose detailed information that was still present in the x-ray.” This problem no longer exists in the solution developed in the HOP-X project. Here the scintillator layer consists of a light-absorbing polymer in which the scintillator material is embedded in a pattern resembling the raisins in a raisin loaf. This gives the light no opportunity to become widely dispersed. In fact, the light patches on the image sensor are now even smaller than the pixels.

A low-cost procedure has also been found to manufacture the new detectors. “It is similar to sintering ceramics,” Schmidt explains. “A powder mixture with the desired characteristics is pressed into a compact layer, but without the high temperatures used with ceramics. The light-absorbing polymer melts easily, so it needs only a small amount of heat and pressure to create a pore-free layer. That’s why the process is known as ‘soft sintering.’” Although the process has been fully patented, it’s still completely new territory, and a technical solution must still be found to manufacture large-scale image sensors. This is where DiCoMo is expected to deliver the ideas. “I am very confident that we will find a solution in the next three years,” says Schmidt. “We are working with top-level partners on this project, just as we did with HOP-X.”

Ambitious goals

DiCoMo is about more than just refining the manufacturing process, however. “The image sensor rests on a matrix of thin-film transistors that enhance and pass on the electrical signals from the sensor,” explains Tedde. “This matrix also needs to be further improved. The goal is to have detectors that not only display greater detail and are cheaper to manufacture but also require less radiation to produce the x-ray images. That would be a huge gain for the patients, since that would further reduce their level of radiation exposure.” The project team – comprising, besides Siemens, BASF Switzerland, Belgian microelectronics center IMEC, Dutch research company TNO, Belgian chip designer ICsense NV and Italian simulation specialist MorphwiZe – has been working hard on development since January.

Frank Krull