Berkeley Lab Radiobiology Researchers Transfer Decades of Know-How to New Brookhaven Facility

February 24, 1996

By Jeffery Kahn, [email protected]

Decades of study on the biological effects of high-energy heavy charged particles all but came to a halt in the U.S. three years ago. That's when this Laboratory, which invented nuclear medicine half a century ago, shut down its Bevalac accelerator.

Although other facilities took up some of the slack when funding ended for the Bevalac, its loss was a severe blow to charged particle radiation research. Now, thanks in no small part to the efforts of Engineering and Life Sciences division staff, much of what was accomplished in turning the Bevalac into one of the world's first and finest facilities for heavy ion radiation biology has been "recycled" into a new facility at Brookhaven National Laboratory.

Life Sciences Division researchers, sponsored by DOE and NASA among others, will be major users of the Brookhaven facility. Berkeley Lab, in collaboration with Colorado State University, is a NASA Specialized Center of Research and Training (NSCORT) in radiation biology, with a mandate to train some of the next generation of radiation scientists.

According to Life Sciences physicist Jack Miller, in addition to its value as basic science, research in this field has particular importance to two groups of people -- cancer patients and astronauts.

Says Miller, "We have a lot to learn about the biological effects of densely ionizing radiation such as cosmic ray heavy ions. The knowledge we gain will not only help protect astronauts but will also improve our understanding of both the basic biology and the therapeutic uses of these particles."

Brookhaven's Alternating Gradient Synchrotron (AGS), a dedicated particle and nuclear physics facility, had never before been used for radiobiology, and to do so presented significant technical challenges, similar in many respects to those encountered over many years of development at the Bevalac.

Miller says creating the new Brookhaven research facility -- in a sense, resurrecting the Bevalac radiobiology facility -- was a two-year-long labor of love for Bevalac veterans such as Engineering's R. P. Singh and Mark Nyman and Life Sciences' Bernhard Ludewigt, some of whom worked nights and weekends on their own time, transferring knowledge and hardware to Brookhaven.

Computer and electronic systems and monitoring devices for dosimetry that evolved and were refined over decades at the Bevalac were located, refurbished or rebuilt as necessary, and moved to Brookhaven. These systems monitor the radiation dose delivered to experimental targets as well as the uniformity and composition of the particle beam, and are critical to the success of accelerator-based biology experiments. Singh was responsible for the software, while Nyman accounted for much of the electronics engineering. Ludewigt, as he had at the Bevalac, acted as the liaison between biologists and accelerator specialists.

Miller and Life Sciences physicists Lawrence Heilbronn, Cary Zeitlin and Ken Frankel were responsible for installing and running the dosimetry system at the AGS, and Life Sciences biologists Amy Kronenberg and Priscilla Cooper helped design the facility for staging biological samples at the accelerator.

The Bevalac was both a pioneering facility in the treatment of cancer with heavy ions, and one of a very few accelerators in the world -- and at the time of its shutdown, the only one in the U.S. --which routinely accelerated heavy ions to the energies most commonly observed in space.

Up until now, astronauts have not traveled much beyond the Earth. Due to the protection provided by the Earth's magnetic field, the radiation environment near the Earth is dramatically different than that encountered in interplanetary space. Heavy ions are of relatively little concern near the Earth, but may turn out to be a major hazard on interplanetary missions. For instance, it has been estimated that during a three-year mission to Mars, up to one third of an astronaut's cell nuclei would be traversed by a heavy ion. The very long lead times for mission planning dictate that research into the consequences of such traversals be conducted now, in anticipation of a return to the Moon and voyages to Mars during the first decades of the next century.

Heavy ions can also be harnessed to attack cancerous tissue. Charged particle radiotherapy -- the targeting of a beam of charged particles on a tumor -- was pioneered at this Laboratory and at the Harvard cyclotron, and has now spread to facilities in more than ten countries. Like x-rays, charged particles are able to pass through tissue. However, whereas x-rays begin to give up their energy immediately when they first encounter tissue, charged particles deposit almost all of their energy or radiation dose where they stop. This stopping point can be precisely manipulated to coincide with the location of a tumor through the use of a beam delivery system developed here.

Miller says that the effort to transfer know-how and hardware to Brookhaven really made him appreciate the breadth of resources available here. "In addition to engineers and scientists," he said, "we needed computer technicians, electronics specialists, riggers, carpenters and the shipping department, some times on pretty short notice, and everyone came through."

He also praised the staff at Brookhaven for its efforts. "Just as pushing an accelerator to its upper energy limit is a challenge, so is running it at its lower limit. The AGS is optimized for high energy nuclear physics. For radiobiology, the beam had to be dialed down to about 1 GeV/nucleon, well below its comfort zone. You can think of this in terms of getting an internal combustion engine to idle at 20 r.p.m. rather than at 700. The accelerator people called this `running in the mud', but they made it work very well."

The first AGS radiobiology run took place this past October, with beams of iron ions. (Iron was chosen because it is the heaviest ion present in significant numbers in cosmic rays.) Forty-one scientists from 12 institutions took part in the highly successful run. Life Sciences Division principal investigators participating included Kronenberg (mutagenesis in human and rodent cells); Cooper and Bjorn Rydberg (DNA damage and repair in human and rodent cells); Mary Helen Barcellos-Hoff (epithelial cell transformation); and Miller (heavy ion fragmentation related to astronaut exposures and shielding).