Out of the designs for weapons of mass destruction has come the foundation for a new software system that could save the lives of thousands of cancer patients every year.
Drawing on some of the computer algorithms used for the Manhattan Project -- which developed the atomic bombs used by the United States in World War II -- a group of scientists at Lawrence Livermore Laboratories in California has produced the Peregrine system, a promising new tool that refines the treatment of cancer with radiation therapy.
"The Peregrine system should have a significant effect on the success rate of treating cancer with radiation therapy," said Lynn Verhey, a medical physicist at the University of California at San Francisco.
Radiation treatment uses gamma and X-rays to zoom in on and kill cancer cells, preventing their reproduction. The Peregrine system tells physicians how the radiation doses will be absorbed by the patient's body, which helps them determine where to aim the radiation beams, how many beams to use, and how to shape them.
According to Edward Moses, who manages the Peregrine project, about 60 percent of the cancer patients in the United States -- around 750,000 a year -- are treated with radiation therapy. About half these people can reasonably expect to be cured, because their tumors are localized and more sensitive to high-energy light. Nevertheless, of these potentially curable patients, some 120,000 die with their primary tumors intact, said Moses.
Until now, it's been very difficult to efficiently calculate how much radiation an X-ray or gamma-ray beam will deposit into the tumor itself and how much into the healthy tissue around the tumor, Verhey said. This is because different parts of the body have different densities and atomic compositions. X-ray photons behave differently each time they encounter materials in the patient's body such as air, muscle, or bone, Verhey explained.
Some of the research surrounding radiation therapy is rooted in work that was done in the early 1940s with the Manhattan Project.
"The brains sitting around in the Manhattan Project had some questions they wanted to answer, such as 'How does radiation go through matter?' or 'How does heat move?'" said Moses. "They came up with equations that produced the Monte Carlo system of analysis. Using that system, they were able to simulate what would happen in little chunks of time, with radiation, heat, and so on."
For years, doctors administering radiation treatment simply used a bag of water as a model for the patient's body -- a model that was not very precise. More recently, computed tomographic, or CT, scans of the area around the patient's tumor have been used to get a realistic view of the anatomy of each patient. But there were still problems in calculating doses at different tissue boundaries, such as where muscle meets bone or where air meets tissue.
Consequently, in order to prevent delivering toxic overdoses to normal tissue, radiation therapy has had to be administered in very conservative doses, which has made it less effective, Moses said.
But scientists have known for years how to calculate radiation doses more accurately, says Christine Hartmann-Siantar, the project's principal investigator. The technique is called the Monte Carlo analysis, and it traces the life of a single proton, from the X-ray machine through a 3-D CT scan of the patient's body. Everything that happens to the photon as it meets with tissue, blood, bone, and so on, is calculated.
This procedure is repeated with more than 100 million randomly generated photons in order to get an accurate representation of how a radiation dose will impact the patient. But this takes time.
"As recently as 1995, doing a Monte Carlo analysis on a patient could take 200 hours or more, which would never be practically possible," Hartmann-Siantar said.
In marked contrast, the Peregrine system software can conduct a Monte Carlo analysis on a patient and produce a 3-D dose calculation in about 30 minutes. The scientists figured out a way to streamline the old Monte Carlo algorithms, and then coupled that with some jazzed-up hardware of their own design: a single platform, multiprocessor system that runs on 24 Intel Pentium chips.
The Peregrine system interfaces easily with commercial therapy-planning systems, so there is very little training required to use it in the clinical environment. Moses said that the whole patented system should add only 10 percent to 15 percent to the cost of typical radiation treatment systems.
The Lawrence Livermore Labs will be submitting Peregrine to the Food and Drug Administration shortly and anticipate that the system should show up in hospitals in early 1999.
Meanwhile, the impact Peregrine will have on the treatment of cancer patients is invaluable, the Livermore scientists believe.
"This is the greatest thing I’ve ever worked on," said Hartmann-Siantar. "Peregrine 'simulates reality,' a technique which is going to eventually affect all areas of medicine. 'Simulation' is going to revolutionize the way doctors make decisions in treating their patients."
