Nanotube-Powered X-Rays

Tiny electron emitters inside an x-ray generator could improve medical imaging and cancer therapy.

Carbon nanotubes are at the heart of a new x-ray machine that is slated for clinical tests later this year at the University of North Carolina (UNC) Hospitals. The machine could perform much better than those used today for x-ray imaging and cancer therapy, say the UNC researchers who developed the technology. They have shown that it speeds up organ imaging, takes sharper images, and could increase the accuracy of radiotherapy so it doesn't harm normal tissue.

Capturing the heart: In a new scanner, carbon nanotubes fire electrons instantly to generate x-rays. This gives sharp, high-resolution pictures, such as this one of a fast-beating mouse heart. Credit: Otto Zhou, University of North Carolina

Conventional x-ray machines consist of a long tube with an electron emitter, typically a tungsten filament, at one end and a metal electrode at the other. The tungsten filament emits electrons when it is heated to 1,000 degrees Celsius. The electrons are accelerated along the tube and strike the metal, creating x-rays.

Instead of a single tungsten emitter, the UNC team uses an array of vertical carbon nanotubes that serve as hundreds of tiny electron guns. While tungsten requires time to warm up, the nanotubes emit electrons from their tips instantly when a voltage is applied to them.

The researchers presented work on their nanotube scanner at the meeting last week of the American Association of Physicists in Medicine.

Physics and materials science professor Otto Zhou cofounded a company called Xintek in Research Triangle Park, NC, to commercialize the technology. Xintek has teamed with Siemens Medical Solutions to form a joint-venture company, XinRay Systems, which has developed the prototype system that will be clinically tested this year.

Taking clear, high-resolution x-ray images of body organs is much easier with the new multi-beam x-ray source, Zhou says. Conventional computerized tomography (CT) scan machines take a few minutes to create clear 3-D images using x-ray. "Because the radiation is coming from one point in space, the machine has to move the [electron] source and detector around the object," Zhou says. The x-ray emitter fires while the tube moves. The motion of the heart and lungs can blur images, so a CT scanner takes hundreds of pictures that are synthesized to reconstruct a 3-D image.

The new machine, by contrast, turns multiple nanotube emitters on and off in sequence to take pictures from different angles without moving. Because the emitters turn on and off instantaneously, says Daniel Kopans, director of breast imaging at Massachusetts General Hospital, the system should be able to take more images every second. This faster exposure, Kopans says, should reduce blur, much as a high-speed camera captures ultrafast motion. Zhou and his colleagues have been able to take breast images at nearly twice the resolution of commercial scanners, using 25 simultaneous beams in a few seconds.

Fast, real-time imaging will in turn improve cancer treatment. "State-of-the-art radiation therapy is highly image-based," says Sha Chang, a professor of radiation oncology at the UNC School of Medicine who is working with Zhou. Pictures of the tumor area are taken so that radiation can be focused on the tumor, sparing the normal tissue surrounding it. But since today's scanners are slow, Chang says it isn't possible to take 3-D images and treat the patient at the same time. "Using the [nanotube] x-ray imaging device allows [us] to collect 3-D imaging while we're treating the patient, to make sure high-dose radiation and heat [are] delivered to the right place," she says.

The clinical test results will determine if Xintek can enter the medical-imaging market. Meanwhile, the company is also selling its nanotube emitters to display manufacturers. Companies such as Samsung and Motorola are making displays based on nanotube emitters that promise to consume less power than liquid-crystal displays or plasma screens while providing the brightness and sharpness of bulky cathode-ray-tube TVs because they work on the same principle: shooting electrons at a screen coated with red, green, and blue phosphors.

Xintek's imaging technology is also proving useful for research on laboratory animals. It can take sharp cardiac images of mice, which is hard because of their rapid heartbeats. Zhou says that biomedical researchers at UNC are already using the system and are installing a second unit at the medical-school research facility.

How to Land Safely Back on the Moon

A hazard-detection system promises safe landings for next-generation lunar explorers.
Engineers at the Charles Stark Draper Laboratory in Cambridge, MA, are developing a guidance, navigation, and control system for lunar landings that includes an onboard hazard-detection system able to spot craters, slopes, and rocks that could be dangerous to landing craft. In the Apollo missions of 40 years ago, astronauts steered the lander to a safe spot by looking out the window; the lander itself "had no eyes," says Eldon Hall, a retired Draper engineer and one of the original electronics designers for Apollo's navigation computer.

That meant there were some close calls with Apollo, says Tye Brady, the technical director for lunar landing at Draper, who demonstrated his team's automated-landing and hazard-avoidance technology at last week's celebration of the 40th anniversary of Apollo 11. "They were really close," Brady says, "and one- to two-meter craters are deadly. You don't see them till the last minute." Apollo 11 astronaut Neil Armstrong had to steer past a field of rocks that didn't show up on any recon photos beforehand, and Apollo 14 landed at a precarious tilt with one footpad resting about a meter away from a crater.

The new navigation and guidance system is being developed for NASA's Altair lunar lander, which is scheduled to land on the moon by 2020 as part of the Constellation program. The project is headed by NASA's Johnson Space Center, with support from other NASA research facilities in addition to Draper Laboratory. The Jet Propulsion Laboratory recently completed a field test of the sensors and mapping algorithms, and it plans to begin full systems tests in May 2010.

Brady says that the best image resolution today, such as the cameras on the orbiter now circling and photographing the moon, cannot resolve smaller holes or boulders at projected landing sites, even in smooth, well-lit areas--which aren't the targets for NASA's future landings. Altair aims to land capably at any site on the moon's surface, and the lunar terrain will vary. For that, Brady says, "you need real-time hazard detection" to adjust as you go.

Draper's system will use LIDAR laser technology to scan an area for hazards like craters or rocks before the lander touches down on the moon's surface. Raw data from LIDAR is processed and assembled into a 3-D map of the moon's surface, using algorithms developed by the Jet Propulsion Laboratory. One advantage of using LIDAR is that "it's the only type of sensor that measures the 3-D shape of what's on the ground at high resolution and from high altitude," says Andrew Johnson, the JPL lead for the hazard-detection system. That allows the system to build a terrain and elevation map of potential landing sites onboard the spacecraft, but from high enough up that there is time to respond to obstacles or craters at the landing site.

Landing in a pinch: Draper Laboratory’s simulated guidance, navigation, and control system prioritizes landing sites (areas 1, 2, 3, 4) in this representative display. Astronauts may designate a first-choice site or default to site number 1. Hazards such as boulders and craters are highlighted in red for real-time decisions about safe landing sites.
Credit: Draper Laboratory

Once the map is built, the system designates safe sites based on factors like the tilt angle of the surface, the distance and fuel cost to get to a site, the position of the lander's footpads, and the crew's margin for safe distance from hazards. Based on that information, the navigation system presents astronauts with a prioritized list of three to four safe landing sites. The astronauts can then designate any of the sites as first choice, or if they are incapacitated, the system will navigate the lander automatically to the first site on its list.

The ability to land autonomously will enable both crewed and robotic missions to land safely, Brady says (while Apollo's lunar module had an automatic landing mode, it was never used). In addition to NASA's Altair, the system could be integrated into vehicles landing on near-Earth asteroids, Mars, and other planets, or used with other lunar vehicles built by private groups.

Another advantage of using LIDAR, Johnson says, is that it works under any lighting conditions. To deal with light at the moon's equator--where a "day" is equivalent to 14 Earth days, and a "night" lasts 14 Earth nights--Apollo missions had to be timed exactly, with just one launch opportunity per month, so NASA could control the craft's exposure to light and heat. But because lighting conditions are more varied and extreme at the moon's poles, with patches of light and dark from the shadows of mountains and deep craters, it will be difficult for astronauts to see to navigate. LIDAR allows the craft to "land at night, or in shadowed regions, because the light is provided by the LIDAR sensor, not the sun," Johnson says. With real-time hazard detection, he says, the launch and landing limitations of Apollo won't apply to future missions.

The challenge for a landing system, says Brady, is getting everything to happen in about 120 seconds, including hazard-detection scans to get the data, human interaction for site approval, and then hazard-avoidance maneuvers and touchdown. His team has developed a simulator to create realistic image maps of the moon's surface, in addition to using computer code from NASA for the guidance and navigation portion of the system. So far, about 20 astronauts have sampled the Draper simulation. "They're good at going slow and easy, and they're very patient," Brady says. "They do a good job relying on the system." That's a long way from the early days when the Apollo astronauts "wanted to fly the whole thing themselves," Hall says.

The Draper team continues to develop high-fidelity models of LIDAR and terrain maps, while coordinating with NASA's crew office to determine the best way to display information for astronauts. They aim to have the technology ready by 2012.

A Better Way to Shoot Down Spam

Junk mail can now be identified based on a single packet of data.

New software developed at the Georgia Institute for Technology can identify spam before it hits the mail server. The system, known as SNARE (Spatio-temporal Network-level Automatic Reputation Engine), scores each incoming e-mail based on a variety of new criteria that can be gleaned from a single packet of data. The researchers involved say the automated system puts less of a strain on the network and minimizes the need for human intervention while achieving the same accuracy as traditional spam filters.

Credit: Technology Review

Separating spam from legitimate e-mail, also known as ham, isn't easy. That's partly because of the sheer volume of messages that need to be processed and partly because of e-mail expectations: users want their e-mail to arrive minutes, if not seconds, after it was sent. Analyzing the content of every e-mail might be a reliable method for identifying spam, but it takes too long, says Nick Feamster, an assistant professor at Georgia Tech who oversaw the SNARE research. Letting spam flow into our in-boxes unfiltered isn't a sensible option, either. According to a report released by the e-mail security firm MessageLabs, spam accounted for 90.4 percent of all e-mail sent in June.

"If you're not concerned about spam, I would suggest you turn off your spam filter for about an hour and see what happens," says Sven Krasser, senior director of data-mining research at McAfee. The Santa Clara, CA, company provided raw data for analysis by the Georgia Tech team.

The team analyzed 25 million e-mails collected by TrustedSource.org, an online service developed by McAfee to collate data on trends in spam and malware. Using this data, the Georgia Tech researchers discovered several characteristics that could be gleaned from a single packet of data and used to efficiently identify junk mail. For example, their research revealed that ham tends to come from computers that have a lot of channels, or ports, open for communication. Bots, automated systems that are often used to send out reams of spam, tend to keep open only the e-mail port, known as the Simple Mail Transfer Protocol port.

Furthermore, the researchers found that by plotting the geodesic distance between the Internet Protocol (IP) addresses of the sender and receiver--measured on the curved surface of the earth--they could determine whether the message was junk. (Much like every house has a street address, every computer on the Internet has an IP address, and that address can be mapped to a geographic area.) Spam, the researchers found, tends to travel farther than ham. Spammers also tend to have IP addresses that are numerically close to those of other spammers.

Dean Malmgren, a PhD candidate at Northwestern University whose work includes identifying new methods for identifying spam, says he finds the research interesting. But he wonders how robust SNARE will be once its methodology is widely known. IP addresses, he notes, are easy to fake. So, if spammers got wind of how SNARE works, they might, for example, use a fake IP a

The Georgia Tech researchers also looked at the autonomous server (AS) number associated with an e-mail. (An AS number is assigned to every independently operated network, whether it's an Internet service provider or a campus network.) Knowing that a significant percentage of spam comes from a handful of autonomous server numbers, the researchers decided to integrate that characteristic into SNARE, too.

The end result was a system capable of detecting spam 70 percent of the time, with a 0.3 percent false positive rate. Feamster says that's comparable to existing spam filters but notes that when used in tandem with existing systems, the process should be far more efficient.

"Consider SNARE a first line of defense," says Shuang Hao, a PhD candidate in computer science at the Georgia Institute of Technology and a SNARE researcher. Each of the characteristics in the SNARE system contributes to the overall score of an e-mail. So far SNARE has been implemented only in a research environment, but if used in a corporate setting, the network administrator could set rules about what happens to e-mail based on its SNARE score. For example, e-mail that scores poorly could be dropped before it even hits the mail server. Hao says this can save considerable resources, as many companies have a policy that requires they retain a copy of every e-mail that hits the server, whether or not it's junk. Messages with mediocre scores could be further assessed by traditional content filters.

Hao is currently helping Yahoo improve its spam filter, based on what he's learned developing SNARE. He says that Cisco has also expressed interest in the work.

"It is fairly clever in the way that they combine a bunch of data that's cheap to use," says John Levine, president of the Coalition Against Unsolicited Commercial Email and a senior technical advisor to the Messaging Anti-Abuse Working Group, a consortium of companies involved in fighting spam. "On the other hand, I think some of their conclusions are a bit too optimistic. Spammers are not dumb; any time you have a popular scheme [for identifying spam], they'll circumvent it."

The research team will present their work on SNARE at the Usenix Security Conference next month in Montreal. In the future, Feamster hopes to able to apply their findings to other computer security problems, such as phishing e-mails, in which the sender pretends to be from a trusted institution to con recipients into divulging their passwords.

ddress close to the recipient's.

HP Announces Digital Print Network Service

In an attempt to tap the growing opportunity of personalized digital printing in the hospitality sector, HP India has announced a digital print network service to educate corporate, hotelier, and printing organization. The move is aimed at addressing the industry's requirement of highly personalization solutions, and to have larger business share.

While offering more insight on this, Puneet Chadha, director (imaging solutions business) of HP India's Imaging and Printing Group said, "Today more than 90% of printing solutions in hospitality vertical is dominated by off-set printing and single digit being driven by digital printing. Digital printing fulfills the four key needs of hospitality sector, such as personalized printing, short run and on demand printing and environment friendly."
"The domestic hospitality sector is expected to see investment of over $11 billion in the next two years with 40 international hotel brands making their presence felt in India by 2012," he added.

Hospitality and many other sectors are gradually opting digital printing to produce marketing collaterals and direct mailers to menu cards, photo merchandise, calendars, personalized itinerary and check -in cards.