In this MEDICA-tradefair.com interview, Professor Nikolaou explains how photon-counting computed tomography (PCCT) works, details its advantages, and reveals how research and the healthcare industry benefit from digital CT images.
Prof. Nikolaou, what is the technology behind photon-counting CT?
Prof. Konstantin Nikolaou: Unlike conventional CT scanners, photon-counting CT technology uses an entirely different detector material. These semiconductor detectors are made of high-purity cadmium telluride crystals, which directly transform x‐ray photons into electrical signals. In contrast, current CT detectors first convert the X‐rays into visible light and subsequently convert the light into an electrical signal using photodiodes. That means the photon-counting CT signal always remains fully digital. The first scanners for clinical application featuring the innovative detectors have been on the market since 2021.
What are the benefits?
Nikolaou: The technology enables physicians to control the X-ray radiation dose more accurately, which also leads to better image quality. An X-ray source emits photons with different energy intensities that we can now filter more precisely – examples include low energy photons that do not contribute to the image structure. We can also take away individual photons and virtually split up the X-ray spectrum, thus distinguishing and visualizing different materials from others in the image.
Take cardiac imaging, for example: we can subtract calcified plaque in the heart's arteries, i.e., the build-up within the walls of the coronary arteries. Prior to this, severe calcification made it difficult to view the affected vessel. If we subtract the calcification, we get a better view of the remaining vessel lumen, allowing a more accurate assessment of any narrowing in calcified blood vessels. Early research is available, but studies have not yet been extensive enough. We still need additional multicenter research trials to demonstrate the potential.
However, research has already shown that PCCT facilitates a radiation dose reduction since the technology counts photons more efficiently. Obviously, this benefits patients since it allows us to reduce CT scan radiation exposure while maintaining image quality.
The detector material also enables better contrast on CT images because the detector is no longer divided into individual detector elements but can count the photons on every square millimeter of the detector. Current CT scanners have a spatial resolution of 0.5 millimeter, whereas PCCT allows a higher spatial resolution by a factor of two or more. This is especially exciting and beneficial when you examine smaller vessels such as the coronary arteries, tiny bone structures in the inner ear, or small fibrotic changes in lungs or infiltrates.