Radiation is heavy artillery against tumors: It can obliterate cancerous cells, but nearby tissue often suffers collateral damage. Now, a group of researchers has developed a new technique that helps calculate the path the radiation takes, potentially enabling oncologists to target tumors far more precisely.

Therapeutic radiation usually involves shooting beams of x-rays or electrons at a tumor. At its most basic, the beam is rectangular in cross-section. Tumors tend to be lumpy and don't conform to simple geometries, however, and the parts of the beam that miss the tumor can damage healthy cells.

A second beam can shine simultaneously from another direction. Where the two beams intersect, the power is heightened. This composite beam can be precisely fitted to cover the entire tumor.

Controlling the beams isn't easy, though. X-rays and electrons don't follow predictable paths through the body, and they interact with tissues unpredictably, making it hard to calculate exactly how much radiation is zapping the tumor versus wreaking havoc elsewhere.

To obtain better precision, physicists Jinsheng Li and Chang-Ming Ma at the Fox Chase Cancer Center in Philadelphia, Pennsylvania, developed a fast, accurate computer program that simulates billions of trips for each beam of radiation through a map of the patient's body. The program then analyzes the data statistically and reads out the "best bet" beam design, which a radiation oncologist can use to configure the equipment.

Not only is the new technique more precise, but it's faster as well. Previous programs took days to calculate a single radiation dose. Li and Ma's program can do the calculations in about an hour. The team will report its findings 1 August at the American Association of Physicists in Medicine meeting in Orlando, Florida.

What's exciting about the technique is that it's flexible enough to treat tumors anywhere in the body, says Eric Klein, a physicist in radiation oncology at Washington University School of Medicine in St. Louis, Missouri. But he cautions that modulated radiation therapy for electrons has not been approved by the Food and Drug Administration, nor has combined x-ray/electron IMRT, and it may take 3 to 4 years before the team's approach is used in the clinic.

"Getting the dose right. The colored outlines show the intensity of IMRT radiation: the tumor bed (red) gets the most, the breast (orange) receives less, and the heart (green) and other areas receive as little as possible. Credit: Jinsheng Li/Fox Chase Cancer Center"

Source: Science Daily News