“The most important step since the advent of multislice CT”

Photon-counting computed tomography (CT) redefines clinical decision-making in oncology by providing physicians with all relevant CT results with one single scan.
Doris Pischitz
Published on January 3, 2023

Professor Jiri Ferda, MD, PhD, talks about the initial steps with the new technology in both research and clinical practice.

Jiri Ferda is head of the Department of Imaging and head of the Institute of Anatomy at the Medical Faculty of Charles University in Pilsen and University Hospital Pilsen in the Czech Republic. He is board-certified in radiology, neuroradiology, vascular interventional radiology, and nuclear medicine. His professional focus is on CT and dual-energy applications, and on hybrid imaging with PET/CT and PET/MRI. Ferda has 28 years of CT experience. Working with colleagues from Pilsen and Forchheim, Germany, he has authored the world’s first clinical publication about the use of virtual noncontrast imaging of intracranial bleeding with dual-energy CT, and the world’s first publication on the use of photon-counting CT in the clinical environment.
<p>We started using photon-counting CT in June 2020. It was a clinical prototype system, which was installed in our department during COVID-19 and used with approval from the Czech State Institute for Drug Control until the end of 2021. In February 2022, the system was replaced by the clinical Dual Source photon-counting system NAEOTOM Alpha<sup>1</sup>. We expected improved resolution of the images and improved image quality thanks to a better signal-to-noise ratio.</p>
If we’re talking about real limitations, traditional scanners are limited in terms of the spatial resolution on thin slices with inappropriate detection of tumor invasion into surrounding structures. They’re also sometimes limited in terms of contrast resolution in soft tissues. An example could be a rectal tumor that invades the rectal wall and goes through the muscular layer into the adventitia and surrounding fatty tissue.
<p>Photon-counting CT improves both the spatial and the contrast resolution. This makes it possible to use very thin slices for evaluation, even below 0.5 millimeters, and increases the attenuation of iodine-containing structures—that is, enhanced tissues and/or vessels contrast.</p>

Jiri Ferda reports an improved tumor delineation with photon-counting CT.

We can better delineate the tumor invasion and can very frequently better visualize the enhanced tumorous tissue due to vascular mimicry. Vascular mimicry is a special behavior in which tumorous cells mimic vascular spaces. The spaces fill with contrast agent, which leads to increased density on low-energy images, meaning the invasion of tumor cells can be better recognized.
We’ve found particular benefits for patients who need staging of gastrointestinal tumors, tumors in the head and neck region, and in the lung. The lower radiation dose could benefit patients who have been successfully treated and now require follow-ups. Lower contrast agent dose could be valuable by enabling less invasive imaging and by improving cost-effectiveness.
Spectral imaging promises to be essential for assessing tumor enhancement and for following up on tumors after therapy. Interesting applications include evaluating tumor evolution and assessing less perfused zones within the tumor, which would allow us to predict poor drug penetration and limited therapeutic effect.
Using monochromatic images and iodine quantification in every scan benefits us because it optimizes the image quality. Follow-up studies in oncology imaging are crucial. The standardization of the enhancement evaluation is very important for assessing the tumors themselves, and for evaluating the involvement of lymph nodes.
Photon-counting CT scan of the renal collection system
One of our six CT systems is a photon-counting CT scanner used in a routine clinical environment. Selected patients are scheduled for photon-counting CT imaging – particularly patients with liver tumors, pancreatic tumors, or kidney tumors.
A typical example of a patient where photon-counting CT was decisive in the diagnostic setting was a middle-aged woman with an ulcerous lesion in the antrum of her stomach. Photon-counting CT allowed us to determine the extent of the tumor to the serosa and to exclude dissemination outside the stomach. Another patient was a woman with hematuria and enhancement of a very small papillomatous urothelial tumor. This tiny finding could be identified only by using super-high spatial resolution and with the improved detection of enhancing tumorous tissue.
Photon-counting CT scan of the stomach
Better insight into the pathological anatomy and pathological physiology of diseases could be a game-changer.
<p>Since I had the opportunity to observe the evolution of CT from SOMATOM DRH to NAEOTOM Alpha, I can safely say that this is the most important step since the advent of multislice CT in 1998. And I am proud and honored to have the privilege of collaborating with Thomas Flohr, Stefan Ulzheimer, Bernard Schmidt, Christoph Panknin, and others to develop this amazing technology.</p>

By Doris Pischitz
Doris Pischitz is an editor in corporate communications at Siemens Healthineers. The team specializes in topics related to healthcare, medical technology, disease areas, and digitalization.