Spectral imaging yields clinical, financial benefits

By Anna Colvin, AuntMinnie.com contributing writer

February 7, 2023 -- Detector-based multienergy spectral imaging and photon-counting CT technology opens up a myriad of possibilities in countless clinical scenarios, according to Prof. Philippe Douek, PhD, chairman of the Imaging Department at Lyon University Hospital in France.

Spectral imaging brings fundamental benefits. Prof. Douek, who is also a researcher at the Creatis Biomedical Imaging Research Laboratory, noted that to his knowledge Philips Healthcare's Spectral CT 7500 scanner is currently the only equipment on the market that combines spectral imaging on an 8-cm-wide detector with rapid advancement of the table. This combination enables significant reductions in contrast agent dose, Prof. Douek explained.

"We can do complete examinations of the aorta and arteries of the lower limbs by injecting only 20 cc of contrast agent, which is a real revolution," he said. "Before that, we used to inject doses in the 100-120 cc range. For the patient, this is a major advance. We have also reduced dose flow rate by a factor of 3 to 4, with doses of just 1.5 or 2 cc per second."

Being able to reduce dose flow is a huge step for patient comfort, echoed Philippe Coulon, PhD, director of CT Clinical Science Radiology at Philips.

"We can decrease the pressure in the vein, so it won't collapse," he said. "We're avoiding the risk of having the contrast spread in the muscle, which can be really painful."

Prof. Douek and his team are obtaining breathtaking images with the system.

"The combination of these different technologies allows us to follow the bolus as closely as possible," he said. "And if the bolus doesn't lead to sufficient enhancement, the contribution of spectral imaging will strongly improve contrast."

These advances benefit cardiovascular applications at large: heart disease as well as peripheral cardiovascular pathology, neurovascular pathology, and vascular disease. In addition, the Spectral CT 7500 scanner enables radiologists to automatically acquire a chest scan in less than one second, and a chest-abdomen-pelvis scan in less than two seconds.

Spectral technology also pushes the boundaries of oncology imaging, as contrast enhancement enables detection of smaller cancers. It characterizes lesions with new material maps that Philips can produce -- e.g., electron density, Prof. Douek said.

"You also have a better characterization of abscesses and uric acid crystals that are deposited either in the joints or in the cavities of the kidneys," he added.

"Spectral CT is like adding color to a black-and-white TV. It adds a completely new dimension in how you look into CT scans and translate those," said Shani Shalev, head of Clinical Science for CT/AMI Global. "We can do more material decomposition and separate different tissues in a better way."

The clinical benefits of detector-based spectral technology are tremendous, with initial studies showing wonderful outcomes, such as prediction of treatment outcome and better improvement on cost as fewer follow-up scans are needed.

Researchers in Denmark recently showed that using spectral CT triggered a 25% reduction in follow-up scans in 400 oncological patients.

"Spectral could become the standard of care because there is no compromise anymore: You don't irradiate more and you get more information." Coulon said.

Chest, abdomen, and pelvis CT angiography performed in less than 2 seconds
Chest, abdomen, and pelvis CT angiography performed in less than 2 seconds. This nongated exam demonstrates fast scanning and Spectral Results from a single 100 kVp scan. Scan parameters: 100 kVp, 102 mAs, CTDIvol 4.9 mGy, DLP 349 mGy*cm, Scan time 1.79 seconds. Image courtesy of Philips.

Photon counting: Taking CT to the next level

In addition to the work he does day to day with Spectral CT 7500, Prof. Douek has also had an opportunity to work on Philips' prototype photon counting CT system.

"We've improved spatial resolution by a factor of eight on a volume at 200 µm isotropic, which opens a lot of possibilities, especially in cardiac imaging," said Prof. Douek, who has recently published a study on the topic in Radiology.

"Photon-counting CT brings improvement in spatial resolution, reduction of x-ray dose by 30%, and better spectral characterization because instead of having one point we have five," he added.

The technology will also benefit musculoskeletal imaging, helping to better visualize the cartilage, as well as respiratory diseases such as pulmonary embolism and pulmonary interstitial disease, recent research has shown.

"Eventually all the territories of the human body will benefit from this technology," he said. "It has a lot of clinical potential."

And photon counting will expand the benefits of spectral CT even further, Shalev agreed.

"Photon counting will take us to a different level of energy differentiation, with more levels of energy that we can distinguish between," she said. "The main benefits will be dose reduction and increasing spatial resolution and contrast for the short term."

In the future, photon-counting CT combined with artificial intelligence (AI) will offer a new type of image that will allow radiologists to differentiate between specific materials that can be injected with a specific K-edge signature, from which a very specific image can be obtained.

"K-edge imaging will enable us to track heavy material contrast products such as gadolinium in the body," said Douek, who has managed to obtain excellent K-edge images in atherosclerosis, which he published in Radiology in 2021.

Photon-counting CT helps to uncover some of the already existing, yet unseen capabilities in spectral CT. The next step for the technology's development will be to preserve the workflow, as spectral imaging already brings 10 to 100 times more data than a conventional scanner, Coulon explained.

"Hospital networks are not ready for that yet, so we're working on it," he said.

Further optimizing the workflow

With photon-counting CT, spectral imaging is going to amplify the data, making imaging interpretation more complex. AI technology will be key to help physicians get through all the studies, Frans Venker, senior vice president and global business leader for CT/AMI at Philips, explained.

"You need AI backup to assist physicians in order to make sense of all the data that's going to come from future systems," he said. "That will be critical."

Philips is developing performance bridge solutions to help departments be more efficient with key performance indicators. The company also offers vendor-agnostic training on different modalities in so-called radiology operational command centers.

"We can improve care with those solutions linking with our modalities but also with the overall solutions at the department level, to further optimize workflow," he concluded.

The comments and observations expressed are those of the author and do not necessarily reflect the opinions of AuntMinnie.com.


  1. Andersen MB, Ebbesen D, Thygesen J, Kruis M, Rasmussen F. Impact of spectral body imaging in patients suspected for occult cancer: a prospective study of 503 patients. Eur Radiol. 2020;30(10):5539-5550. doi.org/10.1007/s00330-020-06878-7
  2. Andersen MB, Ebbesen D, Thygesen J, et al. Economic impact of spectral body imaging in diagnosis of patients suspected for occult cancer. Insights Imaging. 2021;12(1):190. doi.org/10.1186/s13244-021-01116-0

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