Siemens Healthineers Paves the Way in Photon Counting CT

Computed tomography (CT) scans are ubiquitously used to noninvasively diagnose stroke, traumatic injuries, lung cancer, cardiovascular disease, and almost any other condition you can think of. That modality is now even more powerful with the advent of photon counting CT (PCCT), thanks to the US introduction by Siemens Healthineers of the NAEOTOM Alpha in November 2021.

Photon counting CT is a paradigm shift in imaging; offering superior resolution that enables clinicians to see things they couldn’t see before: smaller cancers, better structural detail, and spectral information that allows them to discriminate between different materials. “That is important,” says Matthew Fuld, PhD, director, photon counting CT, Siemens Healthineers North America, “because a lot of diseases are material-specific. Being able to accurately separate materials allows you to qualify and quantify a variety of different disease states.” For example, Fuld describes the ability of PCCT to distinguish calcium from the wall of a coronary artery, so the clinician can see how much of the vessel is really occluded. It can also show clinicians what type of arterial plaque they’re looking at: lipid rich and vulnerable, or calcified and stable. With high resolution and spectral detail, PCCT might enable gout or kidney disease to be more accurately diagnosed, with the ability to depict the small crystals causing pain or impaired function.

Conventional CT uses energy integrating detectors, which convert X-ray impacts into light using a ceramic scintillator; light is then measured by a photo diode and converted to an electrical signal used to create a CT image. This two-step process creates inherent inefficiencies, noise, and artifacts, and the requirement for higher doses of radiation.

In contrast, PCCT uses a crystal semiconductor material (cadmium telluride in Siemens’ platform) instead of a ceramic scintillator to directly generate an electric charge enabling high resolution while eliminating electronic noise, and with a reduced radiation dosage. Detected photons are counted individually, providing a more accurate image signal, and sorted according to their energy levels, enabling spectral discrimination at the detector level.

Siemens Healthineers has been in the US market for about two and a half years, and installations are growing at a pace that is only limited by how quickly hospitals can prepare their facilities to house the new equipment

For its initial approach to market, Siemens Healthineers is targeting the most advanced users, the kinds of research institutions that already have the company’s state-of-the-art product based on dual source CT, “because these are the institutions that are asking the interesting questions and pushing the boundaries,” Fuld states. It’s a strategy designed to show just what PCCT is ultimately capable of, and how the information helps clinicians gain new insights about their patients’ diseases.

“High-end” doesn’t necessarily mean exorbitantly expensive, Fuld emphasizes. “We always get the question, ‘Is this going to be 2 or 3 times the cost of the previous technology?’ It is not. There is a premium, but it is less than double. We wanted to make sure to offer it at a price point at which people could attain it because we believe in this technology and see the value for patients.”

Meanwhile, the company continues to invest in deploying photon counting across more scanners in its portfolio. “We are heavily investing in the technology, and in new crystal growing factories so we can scale up and deliver this, not just in one scanner, but in all scanners,” Fuld reports.

Siemens Healthineers’ research team began developing PCCT in 2003. To get where the researchers are today, they’ve had to solve many problems, not the least of which was accessing a steady supply of the high-purity cadmium telluride crystals that act as detectors.

Another advantage the company brings to the product is its depth of experience in artificial intelligence, The company has AI applications for ensuring that the patient is in the right position, and for helping the operator to choose the right scan protocols and parameters to get the best image acquisition. “It’s not just about ‘I have acquired an image, now let’s throw AI at it,’” says Fuld.

Finally, there are post-processing algorithms that make sure that users can interpret data quickly and efficiently, and specific applications designed to answer particular clinical questions.

Siemens Healthineers clearly has a first-mover advantage in photon counting CT, and due to the above-noted technical challenges of getting to this point, that lead won’t rapidly evaporate. “We see this as the future of CT. For Siemens Healthineers, the future is here now. Everyone else is chasing that dream,” Fuld says.

Excerpted from Siemens Crystallizes a First-Mover Advantage in Photon Counting CT, MedTech Strategist, April 9. 2024.