Multi-energy detectors, or what do you think about changing to color tomography?

 

Improvement versus Innovation

Is it time to change and go from improvement to innovation? This is the question that is starting to be asked in the sector of x-ray detectors. Over the past 20 years, we have changed from linear detectors to flat-panel detectors and to flat-panel detectors with a surface that keeps on getting bigger and a pixel size that keeps getting smaller, making images that are ever larger with even better resolution. It is not unusual to see industrial tomography systems with 8 000*8000 pixel detectors. This is a considerable improvement compared to the 500*500 sized images from fifteen years ago. So, projections whose quality is constantly improving, which, incidentally, can pose problems in terms of storage and calculation.

More advanced and better quality…but not really different. So, without going into detail (the bravest and most curious will do that), we need to look at the new techniques in the field of electronics. When we do this, we often see the term ‘photon counting” coming up in relation to the new-generation x-ray detectors. This scaling up makes it possible to know the energy characteristics of every photon. Detectors no longer simply make images, they offer valuable and individual information on the spectrum of each photon.

Photon counting?

There are many photo-counting detector prototypes and fully developed products available on the market.  Obviously, history is being re-written and is going through the same stages. This first generation of photo-counting detectors often comes in the form of linear detectors rather than flat-panel, offering less resolution compared to the current generation of conventional detectors. Prices are also still high and for 2D radiography, the investment can be considerable, knowing that this type of detector must also be used with a more powerful calculator. Our expertise and experience in the field of 2D does not allow us to have a clear-cut opinion on the question.  Is there a major gain in image quality, is the investment justified? We can’t really answer this question. On the other hand, by integrating this type of detector in a CT system, we move right into another dimension for tomography. The tube will be the same, as will the mechanics and the geometry (if your system allows tomography with a linear detector), the detector alone is responsible for the considerable improvement of your CT system. In this way, you have color tomography.

Seeing life through rose-tinted glasses

Of course, the software and the reconstruction must be adapted to this new type of detector. In short, we are going to carry out a multi-channel reconstruction that directs and combines the information from each pixel. At Digisens we are able to assist you from the early stage of your project to the full software multi energy CT solution. Please see our consulting and engineering page to have more information about that and don’t hesitate to contact us.

So why color? We’re talking about color tomography because we are capable of a degree of discrimination never previously reached, and the information on the energy level at each point and the thickness of the materials allow us to identify the material very definitely and very precisely and thereby affect a color to it. A key application for tomography is detecting explosives. Without photon-counting detectors, it is impossible to differentiate a laptop battery from an explosive material. Color tomography, on the other hand, can assign a different color. This color tomography therefore opens up considerable scope for improvement in detecting and differentiating metals, plastics or biological materials in the three main fields of tomography: the sectors of industry, medicine and security. The color revolution has begun.