Space walk for the cure

OTTAWA-A Canadian-designed experiment aboard the International Space Station (ISS) is using technology that is helping to advance the treatment of cancer patients on earth. Since February 2002, nine astronauts aboard ISS have worn a .04-inch square silicon chip dosimeter that measures the levels of radiation they are exposed to during space walks.

Similar devices are being used now in 400 cancer clinics worldwide to measure the radiation that patients receive. The chip is attached at the end of a strip of 1/16- inch-wide circuit-board tape that leads to instruments that record the radiation levels. "The tape is small enough that it doesn't absorb, deflect, or change the radiation beam at all," says Ian Thomson, president of the Ottawa-based company Thomson Nielsen that developed the device. In recent experimental cases, the chip even has been inserted inside patients through catheters to measure radiation levels in sensitive internal organs. "It's a quality assurance thing," Thomson says. "It helps fine-tune the treatment." And what about those astronauts? So far, results have shown that astronauts receive 4.5 milliSieverts (mSv) per month-more than double what a radiation worker is allowed on Earth.