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Imaging

“Photon-counting CT will become the new standard in chest imaging”

In pulmonology, photon-counting computed tomography (CT) enables physicians to precisely evaluate function thanks to highly detailed spectral maps.

3min
Doris Pischitz
Published on 6. Februar 2023

Professor Frank Wacker, MD1, and Professor Jens Vogel-Claussen, MD1, report their experiences in clinical practice.

When did you start using photon-counting CT and what were your expectations?

Frank Wacker: We started using NAEOTOM Alpha2 in the Department of Diagnostic and Interventional Radiology at Hannover Medical School in fall 2021. We were very excited about the dose efficiency of the new system, since CT scans are the main source of radiation exposure for patients in radiology. We had a lot of clinical applications in mind for it. Lung imaging is a scientific focus here at the school and we had high expectations for the novel photon-counting technology in this area: We hoped it would help us provide useful information for our lung disease patients thanks to high spatial resolution and high-quality spectral information.

Bio Frank Wacker

Frank Wacker is chairman of radiology at Hannover Medical School in Germany, and head of the Imaging Unit at the Clinical Research Center Hannover. His research focuses on image-guided therapies, interventional oncology, and quantitative clinical and preclinical imaging. He is principal investigator of the German Center for Lung Research and the Research Campus STIMULATE, and a board member of the German Society for Interventional Radiology.
Frank Wacker likes the dose efficiency of photon-counting CT.

We were very excited about the dose efficiency of the new system.

Professor Frank Wacker, MD, Chairman of Radiology, Hannover Medical School, Germany

Looking at pulmonology specifically, what were the limitations of traditional CT scanners?

Jens Vogel-Claussen: With the traditional dual-source CT scanner, we couldn’t use the dual-energy information for the high pitch acquisitions [FLASH mode] needed for CT chest angiography—especially in patients who are short of breath. Another problem was the image resolution in the lung parenchyma. We need that to adequately depict the intralobular structures of the lung parenchyma.

Bio Jens Vogel-Claussen

Jens Vogel-Claussen is section chief of cardiopulmonary imaging, and vice chair of the Department of Radiology at Hannover Medical School. His research interests include novel technical developments in cardiopulmonary imaging and their translation into clinical practice. He is principal investigator of the German Center for Lung Research, board member of the Thoracic Imaging Section of the German Radiological Society, and editorial board member of Radiology: Cardiothoracic Imaging.

Where and how has photon-counting been able to overcome these limitations?

Jens Vogel-Claussen: The new photon-counting detector technology can convert X-ray photons directly into electrical signals, which results in much higher image resolution and less image noise. Also, the spectral information is inherent and the quality is better than with conventional detector systems. We also found that it reduced radiation exposure for our patients.

How do improved image contrast and higher spatial resolution affect your diagnoses?

Jens Vogel-Claussen: They help improve the image quality, which is very useful for detailed descriptions of lung and pulmonary vascular disease, and for interdisciplinary conferences that require clinical decision-making.

Jens Vogel-Claussen sees the potential of photon-counting CT in lung cancer screening.

Photon-counting CT has huge potential for future CT lung cancer screening programs.

Professor Jens Vogel-Claussen, MD, Vice Chair, Department of Radiology, Hannover Medical School, Germany

Which patients benefit in particular, also with regard to lower radiation dose and less use of contrast media?

Frank Wacker: Children and young adults with chronic lung and heart disease and a clinical need for single or sometimes even serial CT scans. They really benefit from low-radiation and low-contrast photon-counting CT scans that don’t compromise on diagnostic image quality.

Jens Vogel-Claussen: Adults in general benefit from the reduced radiation dose. Plus, ultra-low-dose photon-counting CT with a tin filter brings down radiation almost to the level of a chest radiograph. The technology has huge potential for future CT lung cancer screening programs.

How and in which cases are you using the spectral information now available from a single scan?

Jens Vogel-Claussen: We use the iodine information in our daily clinical routine for assessing perfusion of the lung parenchyma and for evaluating pulmonary masses and nodules. Our pre- and post-operative evaluations of patients with chronic thromboembolic pulmonary hypertension benefit from the improved image resolution in the pulmonary arterial tree and from the assessment of pulmonary parenchymal perfusion [Figure 1].

Photon-counting CT scan of chronic thromboembolic pulmonary hypertension
[Figure 1] Chronic emboli of the pulmonary arterial vessels can result in chronic thromboembolic pulmonary hypertension (CTEPH). Detection and evaluation are challenging with conventional CT because of the size and location of the emboli. Contrast media used to visualize filling defects in the pulmonary vessels can also now be used to extract the distribution within the lung tissue and show the perfusion of the lung. Here, the method was used to visualize the effect of CTEPH and the postintervention outcome. The aim is to remove the fibrotic material that causes the stenosis and occlusions of the pulmonary vasculature. The successful outcome is well visualized here.

How does the availability of monoenergetic images for every scan assist physicians in making a diagnosis or follow-up?

Jens Vogel-Claussen: The ability to reconstruct a wide range of monoenergetic images is very useful in our daily clinical routine. For example, if we reconstruct the images closer to the k-edge of iodine, we get improved vascular contrast. This is helpful when performing CT pulmonary angiography exams to detect pulmonary embolism.

How are you using photon-counting for standard examinations? How does the technology perform in these cases?

Jens Vogel-Claussen: The standard photon-counting CT exam works well. We use a fixed contrast delay of 70 seconds to also assess the vascularity of lung tumors when evaluating treatment response after chemotherapy.

Could you please describe one or two patient cases where photon-counting has been particularly helpful?

Jens Vogel-Claussen: The improved image resolution and quality mean we can depict the pattern of the lung parenchyma in more detail. For example, we can see intralobular septal thickening more clearly than was often possible on CT scanners with conventional detectors. This helps us to classify fibrotic lung disease in daily clinical routine [Figure 2].

 Frank Wacker: I remember one patient who had a lung nodule measuring 8 millimeters. The iodine information and the high spatial resolution allowed us to confidently diagnose it as a malignant nodule during the tumor board.

Fibrotic lung disease image acquired with photon-counting CT

[Figure 2] Anatomical changes of the lung are key to understanding the type of lung disease. Visualizing tissue changes with a much higher resolution and without the radiation dose penalties of conventional CT detectors can help to classify these changes. Here, “intralobar reticulations” indicating lung fibrosis are clearly visible even on a low-dose lung scan.

How do you see the role of CT evolving in your specialty with photon-counting technology?

Jens Vogel-Claussen: Given its high performance over CT scanners with conventional detectors, photon-counting CT has the potential to become the new standard in chest imaging.

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.

  1. 1 Professor Frank Wacker, MD, and Professor Jens Vogel-Claussen, MD, are employed by an institution that receives financial support from Siemens Healthineers for collaborations.

    2 NAEOTOM Alpha is not commercially available in all countries. Its future availability cannot be guaranteed.


    The statements by Siemens Healthineers’ customers described herein are based on results that were achieved in the customer's unique setting. Because there is no “typical” hospital or laboratory and many variables exist (e.g., hospital size, samples mix, case mix, level of IT and/or automation adoption) there can be no guarantee that other customers will achieve the same results.