Photon-counting helps both patients and researchers

One of the world’s first photon-counting computed tomography imaging devices has been installed in the Center for Medical Image Science and Visualization (CMIV) at Linköping University Hospital. Images from the Siemens NAEOTOM Alpha are twice as clear as those from previous machines. This ensures that more patients can be given a correct diagnosis.

Photo of men looking through a  photon counting CT (PCCT). Great joy at the inauguration. There are high expectations of what both healthcare and research can achieve with the photon counting computed tomography. Emma Busk Winquist

There were joyous scenes at the Center for Medical Image Science and Visualization (CMIV) for the official inauguration of the CT scanner on Monday 15 November. Siemens held a similar event in Germany at the same time. The first series-produced photon-counting CT scanner has been installed at only a few locations around the world and is expected to have great significance for both medical care and research.

“This is a technological paradigm shift in computed tomography. It will be a huge benefit to patients, giving faster examinations and much clearer images, but with significantly less radiation exposure”, says Anders Persson, director of CMIV and professor of medical imaging.

Development at Siemens

“The difference is amazing. It is the clinical issues that will provide impetus to the research”, says Mats Ulfendahl, director of research at Region Östergötland.

The innovative computed tomography imaging device is the result of nearly 20 years’ development. One of three research machines (which lacked CE labelling) was installed at CMIV in 2020. This was replaced in August 2021 with a CE-labelled machine, approved for clinical examinations. Confidential research exams have been carried out, and only now has it been possible to hold a public inauguration, after Siemens introduced the technology commercially.

Benefits in research and medical care

The radiation in a conventional CT scanner is converted to light, which is then collected to give a signal that forms an image. One important innovation in the photon-counting machine are the detectors, which collect the radiation. When photon-counting is used, it is not necessary to convert the radiation to visible light: each individual X-ray quantum (or photon) is counted, and the information used to produce an image.

The noise introduced by the conversion in a conventional CT scanner is avoided, giving a clearer image. 

“The noise introduced by the conversion in a conventional CT scanner is avoided, giving a clearer image. And we can measure the energy of each photon. We know which photon passed through a particular tissue in the body. We will have even greater benefit from this with the aid of research and clinical work at CMIV”, says Lars Karlsson, Nordic manager for diagnostic imaging at Siemens Healthineers.

“There can hardly be a better place than CMIV to investigate in more detail how we can apply this technology in medical care”, he adds.

Avoiding invasive procedures

One example is suspected angina, for which conventional angiography is normally carried out. This is an invasive procedure in which a catheter is inserted through an artery in the groin or arm, to reach the coronary arteries and inject a contrast agent for imaging. It may be possible to avoid this invasive procedure in the future.

We want to be able to use the data we have collected to gain more knowledge. 
“Around half of these procedures are unnecessary”, says Anders Persson. “It’s not possible to determine who should be treated until the procedure has been carried out. However, the photon-counting computed tomography technique gives very detailed images, and it is possible to determine, for example, whether a coronary artery requires treatment for a build up of plaque or calcification.”


Linköping was a pioneer in the field. It has the world’s longest follow up of coronary artery data from CT scans, stretching back as far as 2003. Last year, around 1,000 such exams were carried out on patients in Östergötland.

“We want to be able to use the data we have collected to gain more knowledge. We want to visualise the flow in the coronary arteries and create unambiguous tools, making it possible for a doctor to decided whether surgery is necessary, rapidly and without using an invasive procedure”, says Anders Persson.

(Translated by George Farrants)

Brief facts: CMIV

The Center for Medical Image Science and Visualization (CMIV) is a research centre that collaborates closely with Region Östergötland. It is located centrally in clinical operations at Linköping University Hospital.

CMIV carries out research
together with clinical specialists from Region Östergötland. It also collaborates in technical development with companies such as Sectra, Siemens, Philips and Bayer, and conducts research in several fields.

In 2019, Professor Kajsa Uvdal, in collaboration with Anders Persson and others, was awarded nearly SEK 18 million from the Swedish Research Council for a project investigating the body’s endogenous molecular contrast agents. This interdisciplinary project will use the new photon-counting CT scanner.


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