by Cate House

efore he was a physician, Julian Rosenman was a physicist. It’s no wonder, then, that as he races around checking patient x rays and answering questions about treatment options, his mind is also racing to figure out ways to use the basic research of physicists to help cancer patients.

Rosenman, a professor of radiation oncology who specializes in lung cancer, explains that the three major ways to treat lung cancer are surgery, removing part or all of one lung; chemotherapy, using drugs to kill cancer cells; and radiation therapy, using high-energy beams to kill cancer cells and shrink tumors. Usually, doctors use a combination of the three.

As a radiation oncologist, Rosenman is interested in making radiation doses more accurate and faster to calculate. The idea behind radiation therapy is simple: find the tumor and aim a bunch of radiation beams at it from different angles. But the difficulty, especially with the lung and all of its air pockets, is making sure that the tumor gets a high dose of radiation without causing damage to the surrounding tissue.

To make targeting tumors easier, Carolina’s computer science department helped develop a software program that models a patient in three dimensions, so technicians can find the exact placement of the tumor. Called 3D-conformal therapy, the software came out in the 1980s and is being used not only at Carolina but also at many other medical institutions to help treat prostate and lung cancers.

More recently, radiation oncologists have been able to take radiation beams and break them up into hundreds of little beamlets. This technique, known as intensity modulation, allows the oncologists to assign different weights to each beamlet, so they can add more strength to specific areas. "The clinical value of this is just beginning to trickle in," Rosenman says. "And it’s showing that you can give higher radiation doses with fewer complications, and that’s good."

While these techniques are proving helpful, the methods used to calculate radiation doses are still very approximate. There is a way to do the calculations correctly, Rosenman explains, but even with today’s computers, the calculations are so complex that they can’t be counted accurately in a reasonable amount of time. "One calculation could run for months on a computer, and the patient could die in that amount of time," he says.

Next: photons, electrons, and Monte Carlo

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