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Posts Tagged ‘accelerator-driven applications’

This article appeared in symmetry on Jan. 7, 2014.

Accelerator technology could be key to developing an effective treatment for a type of brain tumor currently considered incurable.

Accelerator technology could be key to developing an effective treatment for a type of brain tumor currently considered incurable.

One of the most common and aggressive types of malignant tumor originating in the human brain is called a glioblastoma multiforme. Patients diagnosed with this kind of tumor are told they have, on average, a little more than a year to live.

Because standard treatments, including surgery and radiation therapy, cannot completely eradicate glioblastomas without fatally damaging the surrounding healthy tissue, these tumors are considered incurable. But Narayan Hosmane, a boron chemist from Northern Illinois University, is working with a team of scientists from Fermilab to try to rid them of that classification.

The group is exploring the capabilities of an experimental treatment called Boron Neutron Capture Therapy. The key to making BNCT work, they think, could lie in particle accelerator technology.

Daniel Silbergeld, a University of Washington neurosurgery and neuropathology professor based at UW Medical Center and Harborview Medical Center in Seattle, operates on more than 200 tumors in a year, at least half of which are glioblastomas.

“Our goal is to help that person live as long as possible and as well as possible,” Silbergeld says. “We never know how well an individual is going to do.”

Silbergeld, who is an affiliate of Seattle Cancer Care Alliance, says patients who undergo aggressive therapy tend to be the ones who live longer.

Here’s an overview of how BNCT works: A medical professional injects into the patient’s bloodstream a tumor-seeking compound containing non-radioactive boron. Normally, blood does not come in contact with the brain, thanks to a bodily structure called the blood-brain barrier. But due to the relatively low molecular weight of the compound, and the fact that tumors often compromise the blood-brain barrier anyway, the drug can bypass this membrane and enter the glioblastoma, which is filled with blood vessels. The drug accumulates there and in some of the surrounding tissue.

Next, scientists send a beam of neutrons through the patient’s brain. Compared to other elements, boron (specifically, boron-10) is one of the best at capturing neutrons; because of the structure of its nucleus, it acts like a specialized, larger-than-average baseball mitt. When a neutron is caught, the boron atom fissions into two particles called an alpha particle and a lithium ion. These particles, due to their relative heaviness, deposit a lot of energy locally—in this case, in the cancer cells. The deposited energy is equivalent to a hefty dose of radiation to the tumor, meant to eradicate it.

So far, the most successful BNCT trials have yielded results that are about the same as standard therapies. The technique has been attempted around the world for decades and has even reached clinical trials in Japan.

But, until now, researchers have generated their beams of neutrons using nuclear reactors. Patients at research facilities, such as MIT’s Fission Converter Beam, or hospitals, such as the Helsinki University Central Hospital, would lay with their heads positioned directly against a nuclear reactor that generates neutrons by a fission chain reaction. Hosmane and the group from Fermilab have another idea.

They think they can improve results by creating epithermal neutrons using higher energy beams from a linear particle accelerator instead, says Tom Kroc, head of neutron therapy at Fermilab. In the past, Fermilab’s fast neutron therapy facility used beams of 66 million electronvolts. While BNCT trials would not require nearly that much energy, the capabilities are much higher than the 2 million electronvolts or less that reactors provide.

Low-energy neutrons have more of a propensity for causing boron atoms to fission; however, they cannot penetrate tumors located deep within the brain, Kroc says.

“With the neutrons from the reactors, they can only treat tumors that are about 2 centimeters deep,” Kroc says. “Our hope is that since we have a higher energy beam we will be able to treat tumors that are deeper.”

He says they must “try to find some sweet spot,” slowing down their beam just enough to penetrate deeply while also giving the boron atoms a fighting chance at fission.

An added benefit of using a particle accelerator instead of a nuclear reactor could be the reduced amount of security required at treatment facilities, Kroc says. And, while treatments using a reactor took a number of hours to complete in the past, the use of an accelerator could speed up a patient’s visit to about 10 to 20 minutes.

In addition to changing the way the neutron beam is generated, the NIU-Fermilab team is working to improve the way the boron is administered.

“The biggest challenge is to get that boron into the tumor,” says Jim Welsh, chief medical coordinator for the development of BNCT at Fermilab.

Hosmane is in the process of getting approval for a different compound that he hopes would work in a similar way, but more effectively. For example, Welsh says, to get to the tumor, some of the compounds would emulate the function of amino acids, which are able to bypass the blood-brain barrier using special carrier proteins. But for now, the team’s efforts are still mostly ground-level.

“It’s beyond the early stage, but I’d say it’s still in the experimental and exploratory stage,” Welsh says.

Silbergeld’s colleague, Radiation Oncologist Jason Rockhill, is well versed in BNCT research. He says that, beyond getting enough boron to the target cell, an added challenge is to then inflict enough cellular damage to destroy the cancer.

“BNCT is a really cool idea, but it’s complex,” Rockhill says.

He estimates that, between drug development and gaining access to the proper type of accelerator, getting to the point of clinical trials is likely to take much time and effort—plus upwards of multiple millions of dollars.

If Welsh’s team pulls together proper funding, receives access to Fermilab’s linear-accelerator-derived neutron beam facility and purchases the necessary computer software, they could start pursuing clinical trials in a few years, Welsh says.

Fermilab is the only place in the United States considering using linear accelerator-based neutrons for BNCT and would be the only lab using the new drugs being developed at NIU.

“There is so much potential,” Kroc says. “The questions are still unanswered as to whether we can make it work, and I want to see it through to its conclusion.”

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A version of this article appeared in symmetry on Nov. 5, 2013.

From new medicines to cancer treatment, the tools of particle physics play an important role in hospitals around the world. Image: Sandbox Studio

From new medicines to cancer treatment, the tools of particle physics play an important role in hospitals around the world. Image: Sandbox Studio

The same particle-physics technology used to understand the universe is also used to improve health and medicine. Accelerators and detectors play an important role in diagnosing disease, shrinking tumors and sterilizing medical equipment. Large-scale computing makes it possible to determine which potential new drugs are most likely to work before starting large-scale human trials. And particle-physics-trained scientists serve as medical physicists, making sure it all works as planned.

Sterilizing instruments and supplies

Particle physics technology can be used to disinfect syringes, bandages, scalpels, stethoscopes and other tools without damaging them. Medical equipment is sent through a series of small particle accelerators and bombarded with beams of electrons or X-rays. In a matter of seconds, the beams eradicate any surface microbes.

Distributed and grid computing

The World Wide Web is not the only computing advancement to come out of particle physics. In order to cope with the huge amount of data produced by experiments, particle physicists developed a network of grids allowing multiple users to share computing power and storage capacity. The grid concept has a number of uses in the medical field, including screening drug candidates to determine which ones are most likely to fight disease.

Simulation

Practice makes perfect, and when it comes to our health, the closer to perfect, the better. So some doctors and medical physicists are designing treatment plans using modeling tools developed for particle physics to predetermine the electromagnetic and nuclear interactions of particles with tissue. In radiation therapy, this software can help doctors understand what will happen when a beam of particles passes through a patient’s body.

Semiconductors

In the heart of particle physics detectors around the world, hundreds of detectors made with silicon semiconductors splay out around particle collision points, tracking charged particles to create pictures of their paths. Physicians make use of this semiconductor technology in many medical devices, including semiconductor lasers. These discrete beams of high-intensity light are perfect for delicate operations like eye surgery.

Particle-physics-trained staff

Many particle physicists can be found inside hospitals and clinics. Particle physicists who cross over into the medical field often come with extensive training in the operation and maintenance of accelerators. With their thorough understanding of particle beams, these scientists are highly valued as specialists who manage the medical imaging systems that detect tumors and who operate the accelerator beams that kill cancer cells.

PET

PET scanners are common tools that let medical professionals examine organs and tissues inside the body. The PET scanner’s genealogy traces back to detector technologies developed in the 1980s to identify individual photons in particle physics experiments. It may sound strange, but PET scanners use antimatter produced inside the body. When a special tracer is injected into a patient, a type of radioactive decay occurs, emitting positrons—the antimatter counterparts to electrons. These positrons annihilate with nearby electrons, releasing bursts of photons. The photons are detected and compiled into three-dimensional images.

MRI

Magnetic resonance imaging, the basic principles of which emerged from early research in physics, is more discerning than traditional screening, which sometimes can’t make out tumors hidden within dense tissue. When a patient is subjected to the powerful magnetic field inside an MRI machine, atoms inside his body line up in the direction of the field. A radio frequency current is temporarily switched on, causing the protons inside those atoms to flip around until the radio frequency is removed. At that point, the protons pivot back into place—each at a different rate. The varying rates are measured, allowing scientists to determine what’s happening inside the living tissue.

Cancer treatment

One of the most effective techniques to fight cancer uses the same technology particle physicists employ to accelerate particle beams to nearly the speed of light. There are more than 17,000 particle accelerators worldwide used for the diagnosis and treatment of disease. Doctors exchange a scalpel for a beam of charged particles, which they aim at cancerous tissue, killing malignant cells by destroying DNA strands in the nuclei while sparing the surrounding healthy tissue.

Kelly Izlar

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View this animation to see how Fermilab's Project X would be integrated into the laboratory's Accelerator Complex.

This story first appeared in Fermilab Today April 12.

According to the Nuclear Energy Institute, U.S. nuclear power plants have produced roughly 70,000 tons of radioactive waste over the last four decades. By 2025, scientists expect the amount of wa ste to be roughly 100,000 tons. The nuclear industry faces an ever-increasing waste problem, and Fermilab’s proposed Project X is developing the technologies that may contribute to a solution.

Last week at AccApp’11, an accelerator applications conference hosted by the American Nuclear Society and the International Atomic Energy Agency, Fermilab’s David Johnson explained how Project X could demonstrate the technologies required for accelerator-driven nuclear waste treatments.

“Fermilab has proposed the construction of a high-power proton linac for support of our high-energy physics program, and we are exploring the possibility to expand the application of the project to nuclear physics and energy applications,” Johnson said.

Project X is a proposed high-intensity proton accelerator complex that would support experiments in neutrino and rare processes physics. By using highly efficient superconducting radio frequency cavities, the technology of choice for next-generation accelerators, Project X would create a continuous-wave beam of protons. While the Project X mission is focused on particle physics, the beam that will be produced has uses that go beyond particle physics. The continuous-wave beam—as opposed to a pulsed one—makes it possible for Project X to also support experiments validating assumptions that underlie accelerator-driven waste treatment concepts. It would also demonstrate the associated accelerator and target technologies, Johnson said.

By hitting a lead-bismuth target with protons, a high-power, continuous-wave linac would create fast, or highly energetic neutrons. These fast neutrons would burn up the dangerous radioactive elements in nuclear waste, significantly reducing its half-life. In order to meet the requirements for treating nuclear waste on the industrial scale, the accelerator must operate reliably with virtually no downtime. Johnson explained that by advancing technologies and producing stable accelerator operations, Project X could serve as a proof of concept for the application.

“We would like to get the nuclear community excited about this potential facility,” Johnson said. “We welcome any and all participation.”

- Elizabeth Clements

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