Ghostly Images


A pioneering new x-ray imaging technique may make x-rays cheaper, safer, and more detailed. Su Wei Ng investigates.


In the digital era, new technology and innovations could change the world by bringing better, safer medical equipment and improving the quality of patient care. New technology could make x-rays cheaper, and perhaps more importantly, safer. Recently, a team of physicists in China used “ghost imaging” to make detailed x-ray images they claim have decreased the radiation dose by a “million times.” This is undeniably great news for people who require routine x-ray imaging due to health conditions.

“Recently, a team of physicists in China has used “ghost imaging” to make detailed x-ray images they claim have decreased the radiation dose by a “million times.””

In conventional radiography, x-rays, a form of electromagnetic radiation, are used to visualize the internal structures of a patient. The x-rays are passed through the body and captured behind the patient by a multipixel detector; film sensitive to x-rays or a digital detector. There is variance in absorption of the x-rays by different tissues within the body – dense bone absorb more radiation, while soft tissue allows more to pass through. As a result, bones appear white on the x-ray, soft tissue shows up in shades of grey, and air appears black. This variance produces contrast within the image to give a 2D representation of all the structures within the patient.

Ghost imaging constructs images of objects using information from light detected at two detectors. The idea is to use correlations in intensities between an object beam that strikes the object and a reference beam that does not, similar to the use of intensity correlations from starlight to determine the diameter of a star.

Wu and his team have made a prototype using a smaller, cheaper, and more portable imaging system created by connecting a single-pixel camera to a patterned light source to produce x-ray images following thousands of successive pictures taken with a sandpaper filter. A computer is then used to calculate the image from the dissimilarities in the sequence of grey pixels to produce the final image. This statistical technique is believed to cause less noxious radiation than conventional radiography techniques.

The main advantages of this system are exactly those which medicine seeks: cost reduction and increased safety. Nevertheless, further improvement on the image quality is required to make this system available for diagnostic purposes in the medical field.