Image caption: One of the team’s computer-generated 3D images of the experimental object using the ghost imaging approach.
A new study led by the Australian National University has discovered a way to significantly lower doses of x-rays—something, researchers say, that could make screening for early signs of disease cheaper and safer. The research team, which involved the European Synchrotron Radiation Facility and Monash University, built upon an unconventional imaging approach known as “ghost imaging” to take 3D x-ray images of an object’s interior that is opaque to visible light.
Lead researcher Dr. Andrew Kingston says the study was the first to achieve 3D x-ray imaging using the ghost imaging approach, which has the potential to make 3D medical imaging much cheaper, safer, and more accessible.
“The beauty of using the ghost imaging technique for 3D imaging is that most of the x-ray dose is not even directed towards the object you want to capture — that’s the ghostly nature of what we’re doing,” says Kingston from the ANU Research School of Physics and Engineering. “There’s great potential to significantly lower doses of x-rays in medical imaging with 3D ghost imaging and to really improve early detection of diseases like breast cancer.”
Since too much radiation can increase cancer risk, there are limits to using CT systems, 3D mammography, and other 3D x-ray approaches on patients. “A variation of our approach doesn’t require an x-ray camera at all, just a sensor—this would make a 3D medical imaging setup much cheaper,” Kingston says.
The proof-of-concept approach took a 3D ghost image of a simple object of 5.6mm diameter at a relatively low resolution of about 0.1mm. The researchers devised a new ghost imaging measurement system that used a series of x-ray beams with patterns.
Each beam was then split into two identical beams. The pattern was recorded in the primary beam, which acted as a reference since it never passed through the object that the researchers were imaging. The secondary beam passed through the object, with only the total x-ray transmission measured by a single sensor. The researchers then used a computer to create a 2D x-ray projection image of the object from these measurements.
This process was repeated with the object at different orientations to construct a 3D image, researchers reveal. “Our most important innovation is to extend this 2D concept to achieve 3D imaging of the interior of objects that are opaque to visible light,” Kingston says. “3D x-ray ghost imaging, or ghost tomography, is a completely new field, so there’s an opportunity for the scientific community and industry to work together to explore and develop this exciting innovation.”
Co-researcher Professor David Paganin from Australia’s Monash University says the team’s achievement could be compared to the early days of electron microscopes, which could only achieve a magnification of 14 times. “This result was not as good as could be obtained with even the crudest of glass lenses using visible light,” he says. “However, the microscope using electrons rather than light had the potential—realized only after decades of subsequent development—to see individual atoms, which are much tinier than an ordinary microscope using visible light can see.”