Researchers in Switzerland have improved the ability of x-rays to help early diagnosis of breast cancer. The new x-ray technique, called “phase contrast imaging” (PCI), has been in development as a medical imaging technology since the 1990s, and it's a more sensitive kind of camera that can examine soft tissue inside the body without requiring a person to swallow kidney-compromising “contrast agents” like iodine or barium.
As IEEE Spectrum reported earlier this year, PCI compares the propagation speed of X-ray wavefronts as they pass through a subject, using algorithms that infer the composition of the X-rayed material from the signal delays the device detects along each beam. So while old-fashioned X-rays could only take photo negative pictures of hard and dense objects that stopped x-rays cold — like bones — PCI instead examines X-rays that pass through its subject. That gives it the soft tissue sensitivity and imaging precision of CT scans but at a fraction of CT scans’ high X-ray doses.
The catch to date has been that the best PCI methods require X-ray sources that produce a wavefront that is well synchronized. And this has traditionally meant only the kind of (synchrotron) x-rays that giant particle accelerators can produce, which of course limits the number of patients that can use PCI and makes it really expensive and inaccessible to boot.
Yet new, cheaper and more compact X-ray sources are being developed now that could enable synchrotron-like X-ray PCI without the need for any big, rare, and expensive particle accelerators.
Spectrum previously reported on an X-ray chip developed at MIT and Massachusetts General Hospital. The new effort, led by researchers at ETH Zurich, the Paul Scherrer Institute, and the Kantonsspital Baden, instead relies on a more traditional X-ray tube but one whose rays pass through a series of fine metal grates, providing coherence enough for PCI. (A 2010 review of the various experimental techniques in x-ray PCI mammography described this “grating interferometry” method as “promising” though still time consuming and technically challenging.)
For a patient, PCI would enable earlier and more accurate cancer detection, though it remains unclear if the new development will offer the most effective X-ray source for real-world mammograms. (The researchers explain that they have, to date, only run their PCI method on tissue samples and not yet on human patients.),