Innovation culture

When you count photons, you need partners you can count on

Throughout the 20 years of research and development in "photon-counting," it was not always clear that the work of the physicists and engineers would be successful and that a computed tomography system would ever come into being. Where did the confidence that this could succeed come from then?

6min

Andrea Lutz

Published on October 1, 2021

German Federal President Frank-Walter Steinmeier describes the German Future Award as an "award that inspires us with confidence." In particular, it means that "we do not have to let the major challenges of our time simply wash over us, but can shape them thanks to the findings of basic and cutting-edge research."

For the "photon-counting computed tomography system"¹ project, Björn Kreisler, PhD, Stefan Ulzheimer, PhD, and Professor Thomas Flohr, PhD, representing a team at Siemens Healthineers, have now been nominated for this award. The computed tomography (CT) system developed by them and their colleagues provides detailed insights into the human body and is a proverbial "quantum leap" in medical imaging. The core of the system is a new detector principle, based on counting and evaluating individual photons. The X-ray detector comprising a crystalline material enables a resolution of CT images that has hitherto not been achieved and provides valuable additional information. Thomas Flohr, who heads CT Physics at Siemens Healthineers, says: "Our innovation provides additional information to physicians that may allow them to diagnose diseases early, but beyond diagnosis it also enables therapy decisions to be derived and patients to be involved in their own future."

Photon-counting CT will advance medical diagnostics in cardiology, pulmonology, oncology, and emergency medicine.

CT Photon Counting Heart Imaging

And he provides an example to illustrate exactly this point: One of the most frequent causes of death in western industrialized nations are heart attacks. Photon-counting CT, also known as quantum-counting CT, enables reliable detection of arterial stenoses, which indicate an increased risk of a heart attack, even in patients that until today had to undergo a cardiac catheter examination. This way, the mostly elderly patients may be spared this invasive procedure. But other groups of patients will also benefit from the invention from Forchheim: In emergency medicine, the innovation can provide an especially fast and reliable overview of injuries. In oncology, preliminary stages of tumors and metastases may be easily and precisely detected. All of this is what President Steinmeier is referring to when he says: "… we do not have to let the major challenges of our time simply wash over us, but can shape them."

For the "photon-counting computed tomography system" project, Björn Kreisler, PhD, Stefan Ulzheimer, PhD, and Professor Thomas Flohr, PhD, representing a team at Siemens Healthineers, have now been nominated for the German Future Award.

The destination was clear, but the road was rocky

More confidence is what can be offered to patients in this case. And confidence in the future was also needed at times during the 20 years of research and development work because it was not always clear that the work of the physicists and engineers would be successful and that a market-ready CT system would ever result from it. But where did this confidence of success come from? Who had it first? And how did it impact the work over time? Thomas Flohr remembers the beginnings of the project in 2001: "At that time, the advantages of cadmium telluride as a detector material were known in principle. We knew that it would help us achieve a higher resolution and better contrast in CT images. It was clear to us that we could also separately detect individual X-ray quanta and the energy that they carry. In this way, anatomical structures could be better identified, and we would be able to distinguish different types of tissue more reliably than had been possible so far." The problem the team had, however, was that cadmium telluride had not met the requirements for medical imaging by that time and it had also not been available in sufficiently large quantities.

What is cadmium telluride?

A crystalline compound formed from cadmium and tellurium.

The project hung by a thread

The project team started its work with material screenings – and soon identified the company Acrorad in Japan as a strong partner for the task. Together, a technology was developed to produce cadmium telluride artificially and the partnership has continued ever since. "In the first decade, we optimized crystal growth further and further in order to better achieve the properties required for medical CT," Stefan Ulzheimer, program manager for counting technology, recalls. In 2008, the first prototypes of CT components were built: An important milestone. However: "We also quickly saw how many issues still had to be worked on. At some point, we were even on the verge of canceling the project..." And how did the team regain its confidence?

Sometimes it helps if someone who is not directly involved takes a fresh look at things.
Stefan Ulzheimer, PhD, Program Manager for photon-counting CT, Siemens Healthineers

Analysis from an external perspective helped the researchers out of their creative crisis. The colleagues from the central research and development department of Siemens evaluated the technologies for their market opportunities. The team followed a systematic testing process and specific issues were revealed that required some readjustment. Björn Kreisler, senior key expert for detectors, remembers that stamina was required at that time.

People tell us: this doesn't work. And that is why farsightedness and stamina had to be greater than any doubts.
Björn Kreisler, PhD, Senior Key Expert for detectors, Siemens Healthineers

Even outstanding technology must remain affordable

From that moment onward, progress was fast. In 2014, the first clinical tests using prototypes were performed in the U.S .and Germany. "Our network of clinical partners proved to be our special strength," says Thomas Flohr. Once again, the progress of the project was evaluated externally and confidence was there.

The day came when we were sure we would be able to build a marketable product.
Professor Thomas Flohr, PhD, Head of CT Concepts, Siemens Healthineers

In terms of technology, the path there was now clear, but "the initial approaches were exorbitantly expensive," says Stefan Ulzheimer, "and because we were developing a commercial product, technical feasibility was not the sole consideration. However wonderful an invention is, whatever benefits it brings – budgets on the market are limited." The team gradually succeeded in growing cadmium telluride of a high quality and prepare the crystal for the detectors in an economically viable way. At the same time, the engineers developed an innovative technique for image evaluation by which the vast volumes of data produced by counting photons could be processed fast. Feedback from the installation of the second generation of prototypes in 2020 helped to optimize the system for clinical practice.

CT Photon counting Team

For two decades, several teams worked together in an interdisciplinary way and remained confident that something special would be created. Thomas Flohr describes the result in one sentence: "We translated a project originally seen as doomed to failure into a medical CT system that can be produced in series and sold at marketable prices."

Making clinical benefit quantifiable

Regardless of whether the candidates receive the Future Award in November, their journey continues and the team has already set itself new goals. "We would like to see quantum- or photon-counting CT being used more widely. We hope that it will provide a good decision-making basis for physicians and, as digitalization progresses, that it will be able to analyze images independently," says Thomas Flohr. The focus is clearly on making the clinical benefit of the technology quantifiable. Stefan Ulzheimer describes a vision of the physicists: "In five to ten years, diagnostic catheter examination of coronary arteries will no longer be used to exclude significant stenoses."

Product image CT Photon Couting

Since 2021, CT systems with photon-counting detectors have been in routine clinical use. This makes Siemens Healthineers the global pioneer, and the company even wants to increase its lead by introducing a completely new product line. For this purpose, a system for growing cadmium telluride crystals is currently being built and the production installations for CT systems in Forchheim are being expanded.

Dive deeper into photon-counting technology

Siemens Healthineers announces FDA 510(k) clearance of Naeotom Alpha, the world’s first photon-counting CT

“About 15 years ago, work on photon-counting and its clinical vision started at Siemens Healthineers. We always believed in the tremendous clinical value and relentlessly worked on it together with our partners. We are excited that we have received FDA 510(k) clearance,” says André Hartung, Head of Diagnostic Imaging at Siemens Healthineers.

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By Andrea Lutz

Andrea Lutz is a journalist and business trainer specialized on medical topics, technology, and healthcare IT. She lives in Nuremberg, Germany.

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