Photon-counting CT – added value in cardiovascular imaging


The University Hospital of Zurich has produced impressive results since introducing the photon-counting CT scanner NAEOTOM Alpha to their radiology department, according to radiology Professor Hatem Alkhadi.1

Since its installation in March 2021, more than 9,000 examinations with the photon-counting CT scanner NAEOTOM Alpha have been conducted at the University Hospital of Zürich. Once the first tests had been run, the number of daily scans was gradually increased up to between 35 and 50, says Hatem Alkhadi, professor in radiology at the leading Swiss hospital’s Institute of Diagnostic and Interventional Radiology.

One and a half years on, Professor Alkhadi could not be more enthusiastic about the new technology. “We have a higher diagnostic gain from every single CT scan we conduct. The image quality is better than ever.”1 Especially in the field of cardiovascular medicine, he sees many important applications.

As one of the main advantages, Alkhadi mentions the ultra-high-resolution mode, which provides “fantastic high-quality information” of the heart, coronary arteries, plaques, or coronary stents. 1 Then there is spectral imaging, or multi-energy information, available in every scan, adding clinically relevant functional information in examinations of the myocardium. 

Another big advantage is the reduction of image noise. The contrast-to-noise (CNR) ratio improved by 70 percent in an early study by Alkhadi2 conducted on the same patients using the same contrast media protocol and the same radiation dose. He points out: “As a consequence, you can translate the lower CNR into a lower radiation dose or a reduction in the contrast medium used.” Especially in elderly patients with kidney problems this is a more than welcome side-effect, the radiologist says.

The CNR gain is pronounced in overweight and obese patients, according to Alkhadi. The bigger the patient, the higher the CNR gain is compared to older energy-integrated detectors. 2

Another major benefit is offered by the PURE Lumen option, which removes all the calcifications from the image while keeping iodine enhancement completely intact.3 There are countless potential applications in cardiovascular imaging, says Alkhadi, most importantly arteriosclerosis and its early detection. With this option, the lumen of affected vessels can be seen with high resolution and close to no artifacts. A study with 60 patients under his supervision is still ongoing, but first results indicate that NAEOTOM Alpha's capability to remove calcium based on spectral material decomposition might soon become the new standard protocol for arteriosclerosis examination, says Alkhadi.1

Not only patients with high calcium levels but also coronary stent patients stand to benefit significantly. “Of course, we have to gather more data first, but I foresee there will also be a change of paradigm regarding coronary stent follow-up imaging,” says the expert. 1 

Even one and a half years after the installation of the system, the team at the University Hospital Zurich continues to explore and discover new clinical applications where photon-counting CT can add value to clinical decision making. “We are still learning about the many new possibilities with NAEOTOM Alpha. It continues to get better and better,” Alkhadi says. In general, the radiologist sees a continuation of the trend towards more individualized patient care and diagnosis. “The days are gone where we had ‘one for all’ – one protocol with one contrast media setting which was supposed to work for everyone. With this machine, we are prepared.” 1

Florian Bayer, journalist in Vienna