The world's first photon-counting computed tomography in clinical use at Karolinska University Hospital


The world's first clinically approved photon-counting computed tomography (CT) scanner has been put into operation at Karolinska in Huddinge. The technology improves image quality to such an extent that the radiation dose in many cases can be halved. It will also be possible to perform advanced lung examinations in patients who have had severe COVID-19.

A computed tomography scan, or a CT scan, is a technique that is useful for taking pictures of small details in the human body. With a photon-counting CT scan, it is possible to zoom in even further on the images.

- The resolution is so good that it is possible to detect blood clots and signs of inflammation in very small vessels in the brain, vessels that we cannot see with a standard CT scan, says Tobias Granberg, Section Manager at the Neuroradiology Medical Unit.

The new technology enables advanced vascular examinations and the study of blood flow in the lungs of people with COVID-19, a research project being conducted at Karolinska in Huddinge. It will be possible to reduce the amount of contrast media for patient groups with sensitive kidneys, such as elderly patients and patients, who have undergone kidney transplants.

The examination can be done very quickly, which is convenient for the patient and reduces the risk of movements affecting the diagnosis. The technology also makes it possible to halve the radiation dose in many cases, which is particularly important for pregnant women and children.

In the examination room, the patient is met by a sound and light show on the top and the sides of the scanner, made possible by a donation from the Astrid Lindgren Children's Hospital Foundation. The patient to be examined can choose between different scenarios; an animated children’s movie, a jungle with the sound of waterfalls and the song of exotic birds, a starry sky with the northern lights, and more. Originally a paediatric adaptation with good results at Karolinska Hospital in Solna, where it is used for similar examinations.

- Patients and families can get a break from illness and the sterile hospital environment. The examination room is perceived as calmer and safer. With the light show and sound effects, we have captured the attention of children from 4 months to 2-3 years so that they are able to lie still, which means that we can reduce the number of examinations needed to be performed with sedation or anaesthesia. In addition, the equipment is good for adults with claustrophobia, says Christin Ekestubbe, X-ray nurse.

In simple terms, a photon-counting computed tomography scan can not only detect photons after they have passed through the human body, but also measure their energy, making it better at detecting what substances are present in the body. Disturbances from plaques in the blood vessels disappear and it becomes possible to see obstructions in the thin coronary arteries of the heart. Comparability between examinations is also improved, providing more reliable tumour follow-up.

In addition to Karolinska, Linköping and Lund also have the same type of clinically approved photon-counting CT scanner.  According to Tobias Granberg, it is no coincidence that technology at the forefront of radiology is being installed in Sweden.

- Radiological research is strong in Sweden. We are used to handling new technologies, are good at radiation protection and at developing new examination methods with contrast media. Here at Karolinska University Hospital, we are also skilled in medical specialties where this new technology is particularly beneficial to the patient, he says.

The photon-counting technology is something Karolinska is researching extensively in. Recently, the world’s first photon-counting CT scanner based on silicon technology was installed at Karolinska in Solna.

Photos by: Catarina Thepper and Torkel Brismar