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The tube is at the heart of X-ray technology. Fritzler and her five-person team in the Power & Vacuum Products department are conducting fundamental research on the subject. 

The team, which is based in her laboratory at the cutting-edge High-Energy Photonics (HEP) Center  in Forchheim in northern Bavaria, develops entirely new X-ray tubes and optimizes existing tubes used in medical devices from Siemens Healthineers.  

Fritzler’s whole career revolves around X-ray tubes. They were even the main focus of her final project for her physics degree. It was while working on this project that she first came into contact with the Innovation department at Siemens Healthineers, which later funded part of her PhD.

Fritzler’s career path at Siemens Healthineers has included four years in Wuxi, China, where she headed up a small team and worked in the X-ray tube production department and the X-ray tube research and development department. She moved to the Innovation department at Power & Vacuum Products in 2014 to work as a simulation engineer and became team leader in 2019. Today she has both physicists and power electronics and design engineers working in her multidisciplinary team. 

It would be a mistake to assume X-ray tubes feature only in traditional X-ray systems: They also serve as the X-ray source that forms an essential part of numerous other medical devices.    

The deeper you dig into the subject, the more it becomes clear why Fritzler describes the field of X-ray tubes as “a giant playground” for physicists: She sees the tube as representing a fascinating interface of different physical principles and challenges that are ripe for experimentation and optimization. The anode design alone offers innumerable opportunities for research and further development.

In her role as a , Fritzler leads the Next Generation Tube Technology (NGTT) project, which Siemens Healthineers has set up to pursue the ongoing innovation and improvement of X-ray tubes: “The project helps ensure we are taking the technology forward continuously,” Fritzler explains.

All research in this area has the objective of continuously improving image quality in medical imaging for patients and medical personnel. Minimizing radiation exposure is also a top priority.

What are the challenges faced in developing X-ray tubes?  “Extrafocal radiation is an issue, including in relation to the development of rotating anode tubes for rotating envelope systems, which are used in applications such as CT scanners,” Fritzler says. 

Extrafocal  radiation is an unwanted form of X-ray radiation, a type of scatter that originates outside the anode focal spot. The focal spot is the point at which the electron beam is intended to strike the anode and generate the required X-rays. However, some of the electrons emitted from the cathode are scattered at the focal spot and go on to strike other parts of the anode or tube housing, where they produce extrafocal radiation in the form of bremsstrahlung, or “braking radiation.”

Because the extrafocal radiation does not come from the defined focal spot, it gives rise to spurious image information that can cause “smearing” — blurring and reduced contrast — of the medical image, Fritzler explains. It also adds to the total radiation dose to which the patient is exposed, without providing any diagnostic benefit.

Fritzler and her team have been investigating special anode structures to reduce off-focus radiation. Although these structures on the anode are microscopic, just micrometers in size, they are able to change the path of electrons at the focal spot and help to redirect them more systematically. 

This, Fritzler explains, reduces the unwanted off-focus radiation and increases the photon yield per electron. The resulting improvement in image quality could subsequently help to facilitate more accurate diagnoses and better treatment, thereby benefiting both patients and medical personnel. 

Fritzler and her team have been developing the idea of the structured anode in close collaboration with Product Development. The technology has now reached level four maturity, which means it will shortly be ready for use in actual products.

����ӰԺ presents another significant challenge in X-ray tube development. Fritzler and the team are researching techniques for joining glass and metal in a way that will allow them to be separated again later on. The conventional method, which essentially amounts to fusing the metal into the glass, cannot be reversed, preventing these valuable materials from being reused.  

The researchers are also investigating ways to minimize the use of rare materials such as cobalt in X-ray tubes.  Progress here not only helps to conserve scarce resources, but also saves money, which is a significant consideration when a single X-ray tube can cost tens of thousands of euros (depending on size, design, and the combination of materials). 

The field of X-ray tubes still harbors very substantial potential for further development, says Fritzler. One of the areas in which she anticipates exciting future research is X-ray fluorescent imaging, a technology that effectively makes chemical elements visible by measuring their specific fluorescence under X-ray radiation.

In her leisure time, Fritzler very much enjoys painting. “My art teacher at school even tried to persuade me to study art,” she recalls with a laugh. Fortunately, she decided to go with physics instead — and today, 130 years on from the invention of the first X-ray tube, she works as a modern artist in the field of X-ray tube innovation.

© Video: Lisa Fiedler (camera and editing), Alexander Goryachok (camera and sound), Katja Gäbelein (concept and direction) 
© Photography: Walther Appelt
© Image processing: Paul Linssen
© Illustrations and motion graphics: Viola Wolfermann
© Archive: Katharina Schroll-Bakes