New computational imaging method cuts X-ray dose while preserving high resolution: Study

Researchers have shown that it’s possible to take clear, high-resolution X-ray images using very little radiation. With more development, the new approach could eventually make medical X-ray diagnostics less risky and more accessible.

“While traditional X-ray imaging relies on enough X-ray photons reaching a detector to form a clear image, our approach uses computational techniques to reconstruct an image from fewer photons,” said research team leader Tiqiao Xiao from the Shanghai Advanced Research Institute, Chinese Academy of Sciences. “We were able to show the low-dose potential of this approach by achieving megapixel radiology with ultra-low-light.”

In Optica, Optica Publishing Group ’s journal for high-impact research, the researchers demonstrate X-ray ghost images with nearly 2-megapixel resolution using only ‌0.48%‌ of the X-ray photons typically required for X-ray imaging. The proof-of-concept study suggests that comparable X-ray image quality may eventually be achievable with far lower radiation doses than are used today.

“Our technology could be combined with routine hospital imaging equipment such as chest X-rays and CT scans,” said Xiao. “It would make medical X-ray imaging‌ safer, which is especially important for children, pregnant patients and people needing frequent scans.”

High-resolution with less radiation

Ghost imaging is a computational imaging approach that works by correlating two beams, in this case, X-rays. One beam encodes a random pattern that acts as a reference and never directly probes the sample while the other passes through the sample. Because very little X-ray power comes into contact with the object being imaged, ghost imaging has the potential to reduce radiation exposure when used for medical imaging.

Although various research teams have been working to implement X-ray ghost imaging, it hasn’t been fully demonstrated experimentally. The primary challenge has been obtaining high-resolution images while keeping X-ray exposure extremely low. The researchers overcame this limitation by reengineering the imaging system to maximize both image quality and dose efficiency.

In the new approach, which the researchers call ultra-low-light X-ray ghost imaging, the X-ray beam is split into a weak beam that interacts with the sample and a much stronger reference beam, allowing more information to be gathered from every X-ray photon. This was accomplished using highly uniform and strongly correlated X-ray crystal splitting, which enabled synchronous signal acquisition in both beams.

The researchers also incorporated detectors that are optimized for each beam — one designed to capture faint signals and another designed to record fine spatial details. Another key was a synthetic-aperture imaging approach that uses an intelligent algorithm to reconstruct a full high-resolution image from ‌dozens of measurements‌, far fewer measurements than conventional ghost imaging methods require.

“Together, these advances balance three key performance indicators simultaneously: a large field of view, ultra-low photon consumption and high imaging resolution,” said Xiao. “This provides a more practical and effective solution for X-ray ghost imaging.”

Demonstrating ultra-low-dose imaging

The researchers demonstrated their new ghost imaging method in a controlled comparative experiment using the X-ray test beamline (BL09B) at the Shanghai Synchrotron Radiation Facility. Using identical ultra-low-photon conditions, they imaged a sample area using the new method and conventional direct X-ray radiology. The results showed that the new method delivered much higher quality than direct imaging.

The new technique was able to produce X-ray images measuring 1992 × 944 pixels with the same contrast-to-noise ratio (CNR) as conventional radiology while using 0.48% of the photons. It also achieved the maximum CNR attainable with conventional radiology using 100 times fewer photons.

The researchers note that further development is needed before the new imaging method can be used clinically. They plan to improve the image quality and demonstrate the method with laboratory X-ray sources, such as X-ray tubes, a key step toward translating the technology from synchrotron-based experiments to real-world medical imaging.

Reference:

C. Zhao, H. Zhang, J. Tang, N. Zhao, J. Wu, Z. Li, T. Xiao, “Ultra-low-light megapixel X-ray ghost imaging”, Optica, DOI:10.1364/OPTICA.598975.