Dose Efficient Dual Energy: The New Standard in Chest X-rays

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Overcoming the complexities of CXR without a dose penalty.

Chest X-rays (CXR) are one of the most difficult radiographs to interpret. The dense chest structure includes complex overlying and underlying patient anatomy, and the ever-present motions of the lungs and heart. Ideally, radiologists would like to view separate images – one of soft tissue and another of bone – in order to make a more accurate diagnosis.

Duel energy chest image with Carestream logo in the bottom right corner.
Carestream’s patented dual energy subtraction method utilizes differential filtration that enables high quality dual energy images to be captured at a similar entrance exposure as a standard PA chest X-ray.

In order to achieve this separation, imaging providers have explored dual energy image-capture technology that captures two radiographic images of a patient in rapid succession. However, the benefits of the technology brought with it increased radiation dose. (Two exposures are required; one at a relatively lower energy X-ray exposure, and a second at a relatively higher energy.) Also, imaging providers had difficulty overcoming the artifacts and misregistration resulting from patient motion (due to heartbeat and breathing) between the capture of the high- and low-energy image.

Fortunately, Carestream has achieved a patented, technology breakthrough.Our Dual Energy method delivers excellent image quality at a similar entrance exposure as a standard PA chest X-ray. Our innovative differential filtration imaging subtracts rapidly-acquired, low- and high-energy exposures for the generation of bone and soft tissue images – and it has automatic patient motion correction. We believe that Dual Energy has the potential to become the new standard of care in chest imaging.

Our Dual Energy image capture software is built on our Eclipse imaging processing engine that uses powerful, proprietary algorithms to provide automated and robust image processing that delivers superb image quality and consistent presentation. It is one of several Imaging Intelligence capabilities for robust processing and images of optimal quality — while reducing quality errors and increasing dose efficiency.

Providing radiologists with more information – without a dose penalty

Dual Energy provides radiologists with more information for diagnosis. It improves the visualization of overlying and underlying patient anatomy and provides enhanced detection of subtle features that can be difficult to visualize in traditional 2D radiographs.

Dual Energy takes advantage of the differential, energy-dependent absorption properties of bone and soft tissue structures in human anatomy. By capturing two radiographic images of a patient in rapid succession, one at a relatively lower energy X-ray exposure and a second at a relatively higher energy, it is possible to mathematically derive a soft tissue-only image with bone structures removed, and a corresponding bone-only image (1) – but the dose is the same as a standard chest X-ray thanks to the innovative differential filtration design. This gives radiologists the ability to remove or emphasize structures. For example, a radiologist can emphasize bone to see a rib fracture that might otherwise be missed. Or conversely, remove bone from the image to see the underlying anatomy.

Duel energy with 4 chest views.
High and low energy images captured of a patient in rapid succession (on left) are transformed using image processing to create a soft tissue-only image and a corresponding bone-only image (on right).

“In order to have effective dual energy, you need a clean separation of high-and low-energy beams in order not to pay a dose penalty. It also needs to be very quick in switching the two exposures. If there is too long a gap between the two acquisitions, the patient will either breath or move,” explains Dr. Narinder Paul, BM, MRCP (UK), FRCR (UK), FRCPC, the Professor of Cardiothoracic Imaging, City Wide Chair-Chief of the Department of Medical Imaging, Western University; and Scientist at the Robarts and Lawson Research Institutes. (2)

Dual Energy software is currently available as an optional purchase on Carestream’s DRX-Evolution Plus.

Applications for dual energy

Numerous studies have been reported in scientific literature regarding the diagnostic benefits of dual energy imaging, in particular for chest radiography. For example, the detection sensitivity for abnormalities in the lung is improved because features that are often difficult to visualize in standard chest radiographs become more conspicuous when overlying rib structures are subtracted (3,4).

Dual energy imaging additionally enables a degree of quantification for certain material properties that can help to improve specificity. For example, calcified lung nodules appear more pronounced in bone-only images, which is usually indicative that the lesion is benign. Other published scientific papers have reported that dual energy soft-tissue images provide overall increased sensitivity for the detection of infectious consolidations, interstitial lung changes, and aortic or tracheal calcification. Dual energy further allows for the assessment of bone abnormalities that can simulate disease, such as bone islands, costochondral osteophytes, or healing rib fractures, each of which may mimic a solitary pulmonary nodule.

“As a cardiac thoracic radiologist, I see two applications for dual energy,” said Dr. Paul. One is removing overlying bony structures – so I can look at underlying nodules or lung architecture that is obscured by the bone. Or second, I can emphasize bony structure. If someone comes in with trauma, I could pick up rib fractures that would possibly be missed with conventional imaging.”

Carestream’s image-capture breakthrough

How did Carestream achieve this breakthrough in image capture?

Currently, other commercially available digital radiography systems that offer dual energy employ a fixed filtration approach. This means that the X-ray beam filtration remains constant for the exam, and that only the kilovoltage setting (kV) is changed between the high- and low-energy exposures.

Put AI to work today.


The Carestream dual energy subtraction method utilizes differential filtration that enables high quality dual energy images to be captured at a similar entrance exposure as a standard PA chest X-ray. Further, the Carestream patient motion compensation software has been demonstrated in clinical studies to be effective in reducing patient respiration-induced motion artifacts.

An ever-present goal of digital radiology is to acquire the most information possible at the least possible dose. Our Dual Energy is one of our latest innovations that provide enhanced image quality that enables improved visualization of buried pathology, and improved dose efficiency. It is one of several advanced imaging applications we are delivering to the market – leveraging technologies for faster image acquisition.

Learn more about CXR:

Eclipse Imaging Processing

Improving the Quality of Mobile Chest X-rays

A Guide to Mobile Chest X-rays for Thoracic and Cardiac Care

Photo of Xiaohui (Ed) Wang.
Xiaohui (Ed) Wang.

Xiaohui (Ed) Wang, Ph.D. is the Director of Imaging Systems, R+D Innovation and Platforms at Carestream Health. He has 26 years of experience in research and development of medical imaging systems, including digital radiography and computed tomography.


1. “Development and characterization of a dual-energy subtraction imaging system for chest radiography based on CsI:Tl amorphous silicon flat-panel technology, “ John M. Sabol; Gopal B. Avinash; Francois Nicolas; Bernhard E. H. Claus; Jianguo Zhao; James T. Dobbins III, Proceedings Medical Imaging 2001: Physics of Medical Imaging, vol 4320.

2. YouTube interview with Dr. Paul. Dr Paul is a member of the Carestream Advisory Board.

3. “Dual-energy subtraction chest radiography: what to look for beyond calcified nodules,” Kuhlman JE1, Collins J, Brooks GN, Yandow DR, Broderick LS, Radiographics, 2006, 26(1).

4. “Dual-energy chest radiography with a flat-panel digital detector: revealing calcified chest abnormalities,” Fischbach F, Freund T, Röttgen R, Engert U, Felix R, Ricke J, American Journal of Roentgenology, 2003, 181(6).

5. “Optimization of image acquisition techniques for dual-energy imaging of the chest,” Shkumat NA, Siewerdsen JH, Dhanantwari AC, Williams DB, Richard S, Paul NS, Yorkston J, Van Metter R, Med Phys. 2007, 34(10).


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