Heavenly Bodies

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Astronomers at the European Space Agency (ESA), trying to capture better images of far-off celestial bodies, have come up with X-ray technology that will improve detection and treatment of some cancers. Some objects in outer space radiate little visible light, but large amounts of X-rays. Current X-ray telescopes, like the now-orbiting XMM-Newton, can detect only low-energy "soft" X-rays. The next step is a satellite camera that can capture high-energy "hard" X-rays. Toward that goal, scientists at ESA's Science, Technology and Engineering Research Centre (ESTEC) in the Netherlands developed a new microchip made not of silicon, but a compound called epitaxial gallium arsenide, which can pick up the hard X-rays.

"It was really obvious once we broke the back of the material science that we had a very sensitive X-ray detector," explains Tone Peacock, the physicist who heads ESA's Science Payloads Technology Division. And because astrophysics X-ray research is "an area that often overlaps with medicine," the researchers realized that they had a breakthrough with medical implications, as well.

Hard X-rays are the only type that can pass through the human body. So a radioactive tracer that emits hard X-rays can be injected into the body, and the X-ray camera will capture and highlight with pinpoint precision those tissues that are cancerous. The X-ray camera will not only allow detection of some cancers at the earliest stages, but will then guide surgeons when they operate to extract diseased tissues. That should have two benefits. It will enable surgeons to remove only those areas that are cancerous. And it means that some patients will face fewer operations, because the camera eliminates the need for exploratory surgery.

The treatment of breast cancer will initially benefit from this technology. Early on, breast cancer cells often amass in lymph nodes and are hard to detect until they've already spread to other areas of the body. Because the device will show surgeons precisely where the cancer has spread, it may help patients avoid mastectomies or the removal of the entire lymphatic system. The X-ray camera may also help in detecting thyroid cancers. And it can also be used by dentists to hunt for cavities.

Now that the detector has been perfected, ESA scientists are working on a means to transmit the image to a monitor. Each 1 cm x 1 cm chip contains 1,024 pixels, and wiring each of them would not only be difficult, but would require a large and bulky processor. The solution appears to be an ASIC chip, which stands for an Application Specific Intelligent Circuit chip, that bonds precisely to the back of the detector chip and gives each pixel its own integrated process signal. That can be fitted into a palmcorder-sized camera that's connected to a monitor by a coaxial cable.

ESA is a nonprofit agency, and some of the technology has already been turned over to private research and development companies like Metorex of Finland. Eventually, it will be licensed to a large medical equipment maker. That won't take light years to occur, either. Peacock estimates that a commercial product could be ready within three to five years.