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Space spin-offs – better cancer therapy

Artist's impression of a black hole

Safer, lower-dose medical scans are on their way, thanks to astronomers' studies of radiation from astronomical bodies such as black holes.

ASTRONOMERS ARE WORKING with medical physicists and radiation oncologists to develop a potential new radiation treatment—one that is intended to be tougher on tumours, but gentler on healthy tissue.

In studying how chemical elements emit and absorb radiation inside stars and around black holes, the astronomers discovered that heavy metals such as iron emit low-energy electrons when exposed to X-rays at specific energies.

Their discovery raises the possibility that implants made from certain heavy elements could enable doctors to obliterate tumours with low-energy electrons, while exposing healthy tissue to much less radiation than is possible today.  Similar implants could enhance medical diagnostic imaging.

Last month, at the International Symposium on Molecular Spectroscopy, Ohio State University senior research scientist Sultana Nahar announced the team’s computer simulations of the elements gold and platinum, and the design of a prototype device that generates X-rays at key frequencies.

Their simulations suggest that hitting a single gold or platinum atom with a small dose of X-rays at a narrow range of frequencies—equal to roughly one tenth of the broad spectrum of X-ray radiation frequencies—produces a flood of more than 20 low-energy electrons.

“As astronomers, we apply basic physics and chemistry to understand what’s happening in stars. We’re very excited to apply the same knowledge to potentially treat cancer,” Nahar said.

“We believe that nanoparticles embedded in tumours can absorb X-rays efficiently at particular frequencies, resulting in electron ejections that can kill malignant cells,” she continued. “From X-ray spectroscopy, we can predict those energies and which atoms or molecules are likely to be most effective.”

CT scanner

The space spin-off will hopefully lead to better, life-saving scans.

Reducing patient’s radiation exposure

“From a basic physics point of view, the use of radiation in medicine is highly indiscriminate,” Pradhan added. “Really, there has been no fundamental advance in X-ray production since the 1890s, when Roentgen invented the X-ray tube, which produces X-rays over a very wide range.”

No fundamental advance, that is, until now.

Nahar and Anil Pradhan, professor of astronomy at Ohio State, discovered that particular frequencies of X-rays cause the electrons in heavy metal atoms to vibrate and break free from their orbits around the nucleus, creating what amounts to an electrically charged gas, or plasma, around the atoms at the nanometer scale.

“Together with long-time collaborator and medical physicist Yan Yu from Thomas Jefferson University Medical College, we’ve developed the … methodology, which we hope will have far-reaching consequences for X-ray imaging and radiation therapy,” Pradhan said.

While typical therapeutic X-ray machines such as CT scanners generate full-spectrum X-rays, hospitals could employ the new technique to greatly reduce a patient’s radiation exposure.

That’s the function of the proof-of-principle device that the team has constructed. Though the working tabletop prototype needs to be further developed, these first experiments show that the effect can be used to deliver specific frequencies of X-ray radiation to heavy metal nanoparticles embedded in diseased tissue for imaging or therapy.

“This work could eventually lead to a combination of radiation therapy with chemotherapy using platinum as the active agent,” Pradhan said.

Adapted from information issued by Ohio State University.

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Space travel could kill you

EXPOSURE TO COSMIC RADIATION outside the Earth’s magnetic field could be detrimental to astronauts’ arteries, according to a study by University of Alabama at Birmingham (UAB) researchers.

Using mice as test animals, researchers assessed the affect of iron ion radiation commonly found in outer space to see if exposures promoted the development of atherosclerosis, as terrestrial sources of radiation are known to do.

They found it accelerated the development of atherosclerosis, independent of the cholesterol levels or circulating white blood cells of the mice. It also worsened existing atherosclerotic lesions.

“It’s well known that prolonged exposure to radiation sources here on Earth, including those used in cancer treatment, excessive occupational exposure and atomic bombs, are associated with an increased risk for atherosclerosis,” said Dennis Kucik, associate professor in the UAB Department of Pathology.

“But cosmic radiation is very different from X-rays and other radiation found on Earth. The radiation risks of deep-space travel are difficult to predict, largely because so few people have been exposed.”

Apollo astronaut

Only 27 Apollo astronauts have travelled beyond Earth's protective magnetic field.

Irreversible damage

X-rays can be blocked by lead shields. But cosmic radiation ions can become more dangerous when they interact with metals, generating secondary particles that also may have biological effects.

Although it’s possible to use other materials to shield against ion radiation, incorporating these into spacesuits presents significant challenges.

The only people who’ve been exposed to high levels of cosmic radiation are the 27 Apollo astronauts who travelled as far as the Moon in the late 1960s and early 1970s.

Kucik said that because many people have early atherosclerosis—whether they travel in space or not—they could not draw any conclusions from the small number of astronauts who have been outside the Earth’s magnetic field.

Instead, they examined atherosclerosis development in mice following targeted exposure to a particle beam of high-velocity iron ions—similar to those found in space.

They tested the mice after 13 and 40 weeks to assess the development of atherosclerosis in the aorta and carotid arteries. They concluded there was a biological response to radiation injury.

“At 13 weeks it was surprising and quite remarkable that we already could see permanent damage—an irreversible thickening of the artery wall where it had been exposed to radiation,” said co-author Janusz Kabarowski, assistant professor in the UAB Department of Microbiology.

Artist's impression of a mission to Mars

Astronauts on future manned missions to Mars will need to be protected from deadly radiation.

Potential cancer spin-off

Knowing the effects of cosmic radiation on the heart health of deep-space astronauts will help meet the unique challenges of treatment and prevention posed by missions of long duration, Kabarowski said.

“Our future research will look at the mechanisms causing the damage, and we will try to find a way to target those mechanisms to correct the damage or prevent it altogether.”

Kucik said the team’s findings also may help cancer treatment. Newer proton radiation therapies can be targeted to stop and deposit all of their energy in a tumour, much like iron ions from space stop in the body.

“No one knows the atherosclerotic risk of this therapy,” Kucik said. “Anything we learn through these studies on deep-space travel will be useful for cancer patients.”

The research has been published online in the journal Radiation Research.

Adapted from information issued by Jennifer Lollar, University of Alabama. Images courtesy NASA / Pat Rawlings (SAIC).

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