Next-Generation Medical X-rays

Next-Generation Medical X-rays

By Mark Anderson

NOTE: This is an overview of the entire article, which appeared on IEEE Spectrum Online.
Click here to read the entire article.

An extremely tiny X-ray, in the form of an electron-emitting chip, is at the heart of a new type of X-ray source that can replace large particle accelerators in phase-contrasting imaging. In short, this new technique, called X-ray phase-contrast imaging (XPCI), allows doctors to see more with less light.

X-rays cannot image the body’s soft tissues, except with the use of contrast-enhancing agents such as iodine or barium that must be swallowed or injected, and their resolution is limited. These agents bind to a tumor or other structure the doctor wants to examine, but the effects of these contrast agents on the kidneys alone can harm or even kill an already weakened patient. Other risks associated with these contrast agents include increased cancer rates and damage to DNA.

XPCI uses a technique that measures the change in an X-ray’s phase as opposed to measuring the X-ray’s intensity. For example, because X-rays move slower through muscle mass than through blood, a chest X-ray wave front that passes through a lung sac (mostly air and blood vessels) will arrive sooner than a wave front that passes through the heart. XPCI can therefore image not only bones and cartilage, but also internal organs, internal bleeding, tumors, and much more. An additional advantage is that XPCI involves no toxic contrast agents and a substantially lower X-ray dosage.

According to Mark Eaton, president and CEO of Stellarray, an X-ray company based in Austin, Texas, “People are getting more and more CT scans. The doctors love them because they can get a better diagnosis, but the radiation dose is getting to be too high. Phase-contrast imaging is fundamentally different. What you’re detecting is the phase change, not the absorption. It is a profound level of dose reduction, by one to two orders of magnitude.”

The catch right now is that XPCI has been available only from extremely powerful, laser like X-ray sources (such as particle accelerators) the size of a warehouse. X-ray sources formerly based on particle accelerators have been shrinking, and a tabletop chip-based system is being developed by Luis Fernando Velasquez-Garcia and his colleagues at MIT and Massachusetts General Hospital in Boston.

Extremely Tiny X-ray: An electron-emitting chip is at the heart of a new type of X-ray source. It can replace large particle accelerators in phase-contrast imaging. Photo: Microsystems Technology Laboratories/MIT

Velasquez-Garcia says that the technology could have applications that go beyond the medical field. Not only would there be new applications, such as airport baggage screening and other applications for homeland security, but safer applications as well which will have many benefits throughout the medical world.