Steady as She Goes

When Steven Dubowsky saw the details of Massachusetts General Hospital’s (MGH) planned proton beam therapy center several years ago, he immediately realized that its high-tech robotic apparatus for positioning patients was not nearly precise enough.

Dubowsky, a robotics expert at MIT and an advisor to the MGH facility, spent the next two and half years solving the problem. By writing an elaborate algorithm that compensates for imprecision inherent in the equipment and designing an array of sensors to detect the different sizes and shapes of patients, Dubowsky and coworkers at MIT improved the system’s accuracy by an order of magnitude. When the MGH facility, which will treat patients with inoperable brain tumors, opens within the next year, it will use software for the patient positioning apparatus based on Dubowsky’s work.

Proton treatment is favored over conventional X-ray radiation in treating some tumors precisely because it can target cells far more accurately. “The goal [of the facility] is to point a beam of radiation at the tumor and avoid treating nearby material,” says Michael Goitein, MGH’s project director. At least three other dedicated proton centers are being built in the United States. “I’m sure they’ll use this or similar software,” says Goitein.

While the facility’s initial plans called for targeting the proton beam with an accuracy within a half-millimeter, Dubowsky says early tests confirmed his hunch: The system, which is being built by Ion Beam Applications, a Belgium-based company, was actually achieving accuracy no better than 5 millimeters.

Dubowsky holds his forefinger and thumb slightly apart. “That’s about 5 millimeters.” Then he closes the gap, nearly touching his finger to the thumb. “And that’s about 0.5 millimeters.” It’s not a huge difference. But it could be the difference between life and death.