Radiation Therapy for Moving Targets

Researchers have combined two devices for real-time tumor tracking and treatment.

Normal tissue often gets caught in the crossfire during radiation therapy. Damage is caused by the high-energy beams of radiation used to kill tumor tissue--particularly when the patient's breathing causes the tumor to shift.

Odd couple: A prototype device combines a magnetic resonance imager with a linear accelerator, two technologies that ordinarily interfere with each other. The blue cylinders facing each other are the imaging magnets. The metal circle visible to the left at the back is a magnetic and radiation shield that protects the accelerator’s waveguide. Credit: University of Alberta Cross Cancer Institute

To better track a tumor's position in real time and adjust the radiation accordingly, researchers at the University of Alberta in Canada have combined a linear accelerator with a magnetic resonance imager. Today in Anaheim, CA, at the annual meeting of the American Association of Physicists in Medicine, researchers will present evidence that a device that combines these technologies can accurately track and irradiate a moving target.

Radiation therapy uses high-energy x-rays from a medical linear accelerator to damage tumor tissue and treat nearly every type of cancer. In the United States, half of all patients with cancer receive this form of treatment, which typically requires 10 to 15 sessions lasting from about 15 to 30 minutes each. In order to make sure the entire tumor is irradiated, doctors have to irradiate a margin of healthy tissue around it, which leads to side effects including nausea, pain, and skin-tissue damage. In between sessions, the healthy tissue regenerates, but the tumor does not. One way to minimize the side effects is to lower the radiation dose and increase the number of sessions, sometimes to as many as 35.

"We would like to decrease the margins and increase the radiation dose, in order to control the tumor better without side effects," says Gino Fallone, director of the medical physics division at the University of Alberta department of oncology.

Another challenge is posed by tumor movement during treatment. Tumors in the lungs and the prostate especially may move by about two centimeters during treatment. Current radiotherapy deals with this challenge by combining the radiation source with a computed tomography (CT) scan. This helps doctors reduce damage to healthy tissue, but CT scans are not very good at showing soft tumor tissue, and they are too slow to track tumor movement in real time. Fallone's group has turned to magnetic resonance imaging (MRI), which provides crisp pictures of soft tissues such as tumors, in the hopes of doing better.

Until now, it hasn't been possible to use MRI to guide radiotherapy. This is because MRI machines and the linear accelerators that supply high-energy x-rays for radiotherapy interfere with each other. MRI uses a strong magnet and pulses of radio-frequency waves to excite and read a signal from protons in the water molecules inside soft tissues in the body. Medical linear accelerators also use radio-frequency pulses, in their case in order to accelerate electrons through a waveguide toward a metal target. When the electrons hit the target, high-energy x-rays come out the other side; these x-rays are then aimed at tumor tissue. If these two machines are in the same room, the magnetic field from the MRI interferes with the waveguide, preventing the electrons from being accelerated, and the radio-frequency pulses from the linear accelerator interfere with the imager's magnetic field, degrading picture quality.

To combine the technologies, the Alberta researchers had to reengineer both components. "The whole machine is designed differently," says Fallone. Special shielding is employed. And instead of using a high-strength magnetic field generated by superconducting-wire coils, as in clinical MRI, the machine uses a weak permanent magnet. The weak magnet interferes much less with the accelerator and is smaller and less expensive to operate. This December, Fallone's group published the results of imaging studies that showed it was possible to generate MRI images while running the linear accelerator without interference.

The weak magnet imposes a different challenge, however: the image quality is much lower. So researchers at Stanford University are working on computational methods for getting the necessary information from these lower-resolution images. "Diagnostic MRI requires a very high image quality, but for radiotherapy you don't need to see the tumor in exquisite detail," says Amit Sawant, an instructor in radiation oncology at the Stanford School of Medicine. "You can afford to lose [image] signal, and still get enough information to know when the tumor is moving." What's important to see during radiotherapy, says Fallone, are the edges of the tumor.

Fallone and Sawant will present initial results of image-tracking studies done with the prototype combined device at the conference in Anaheim. Sawant's group will describe imaging software that allows the machine to acquire five two-dimensional MRI images per second--much faster than conventional MRI. The Stanford researchers increased the imaging speed by decreasing the imaging area and using a technique called compressive sensing. When images are stored, about 90 percent of the data is thrown out; using compressive sensing, it's possible to acquire only the most important 10 percent of the image data in the first place.

Fallone will present results demonstrating that such real-time guidance can be used to redirect the prototype device's x-ray beam. "So far, only CT has been available for image guidance," says Bhadrasain Vikram, chief of the clinical radiation oncology branch of the National Cancer Institute's Radiation Research Program. "It's exciting that [MRI] is becoming available to start asking whether it can provide more accurate information." Better guidance for radiotherapy, says Vikram, might speed up the treatments or even "cure some cancers you can't cure today."

But before the system can be tested on patients, the researchers caution that the image-acquisition process needs to be sped up even more, so that it's possible to make 3-D images. The device will also need to be tested on animals. Fallone estimates that human tests are at least five years away.

Microsoft, Yahoo team up to ding Google with Bing

SAN FRANCISCO (AP) -- Microsoft Corp. has finally roped Yahoo Inc. into an Internet search partnership, capping a convoluted pursuit that dragged on for years and finally setting the stage for them to make a joint assault against the dominance of Google Inc.

The 10-year deal announced Wednesday gives Microsoft access to the Internet's second-largest search engine audience, adding a potentially potent weapon to the software maker's Internet arsenal as it tries to better confront Google, which is by far the leader in online search and advertising. Microsoft didn't have to give Yahoo an upfront payment to make it happen, as many Yahoo investors had hoped.

Google tried to stop Yahoo from falling into Microsoft's camp. Last year it formed its own proposed search advertising deal with Yahoo, only to be forced to retreat from that alliance after U.S. antitrust officials threatened to sue.

The extended reach will allow Microsoft to introduce its recently upgraded search engine, called Bing, to more people. The Redmond, Wash.-based software maker believes Bing is just as good, if not better, than Google's search engine. Taking over the search responsibilities on Yahoo's highly trafficked site gives Microsoft a better chance to convert Web surfers who had been using Google by force of habit.

"Microsoft and Yahoo know there's so much more that search could be," said Microsoft Chief Executive Steve Ballmer. "This agreement gives us the scale and resources to create the future of search."

Even with Yahoo's help, Microsoft still has its work cut out. Combined, Microsoft and Yahoo handle 28 percent of the Internet searches in the United States, well behind Google's 65 percent, according to online measurement firm comScore Inc. Google is even more dominant in the rest of the world, with a global share of 67 percent compared to a combined 11 percent for Microsoft and Yahoo.

In return for turning over the keys to its search engine to Bing and promoting it, Yahoo will get to keep 88 percent of the revenue from all ads that run alongside search requests on its site for the first five years of the deal. Yahoo also will have the right to sell ads on some Microsoft sites.

Yahoo estimated the deal will boost its annual operating profit by $500 million and save the Sunnyvale, Calif.-based company about $275 million on capital expenditures a year because it won't have to invest in its own search technology. An unspecified number of Yahoo engineers will lose their jobs as the company scales back, Yahoo Chief Executive Carol Bartz told analysts in a Wednesday conference call.

But the deal isn't expected to close until early next year, and then it could take another two years before all the pieces of the partnership are in place worldwide. The companies first will give antitrust regulators time to review the proposed partnership's effects on the Internet ad market and then it will take time to stitch together their different technologies.

Shares of Yahoo slid $1.68, or 9.8 percent, to $15.54, as investors expressed disappointment over the fact that the company won't be getting an immediate windfall. Microsoft shares advanced 14 cents to $23.61. Google shares fell $5.51, 1.3 percent, to $434.34.

The alliance could give Yahoo a chance to recoup some of the money it squandered in May 2008, when it turned down a chance to sell the entire company to Microsoft for $47.5 billion. Yahoo's market value currently stands at about $22 billion.

The two rivals began talking about a possible partnership as far back as 2005 before Microsoft intensified the courtship with last year's attempt to buy Yahoo.

It took Bartz just six months to strike a deal with Microsoft -- something that neither of her predecessors, Terry Semel and Yahoo co-founder Jerry Yang, seemed interested in doing.

Shortly after her arrival, Bartz made it clear she was willing to farm out Yahoo's search engine for "boatloads of money" as long as she as thought the company would still receive adequate information about its users' interests. Although Yahoo won't get any immediate cash, Bartz predicted the deal will still be a boon for the company.

"This agreement comes with boatloads of value for Yahoo, our users, and the industry, and I believe it establishes the foundation for a new era of Internet innovation and development," Bartz said Wednesday.
Under the agreement, Yahoo will have limited access to the data on users' searches -- which yield insights that can be used to pick out ads more likely to pique a person's interest. The value of that information is why Microsoft wants to process more search requests.

Like Yahoo, Microsoft has invested billions in its search technology during the past decade, yet remained a distant third in market share while its online losses piled up. The company's Internet services division lost $2.3 billion in the fiscal year ending in June, nearly doubling from the previous year.

Microsoft is counting on Bing, unveiled in early June, to turn things around.

Bing has been getting mostly positive reviews and picking up slightly more traffic with the help of a $100 million marketing campaign. Analysts believe Bing's successful debut pushed Microsoft to reopen negotiations so it could expose its search engine improvements to a wider audience more quickly.

"The reason the deal happened now is the recent success of Bing. I think it put pressure on Yahoo, as well as Yahoo not being able to turn it around on its own," said Gartner Inc. analyst Neil MacDonald.

Microsoft and Yahoo are bracing for antitrust scrutiny into whether the combination would have an adverse effect on competition in the online ad market.

The U.S. Justice Department spent five months dissecting last year's proposed search advertising partnership between Google and Yahoo before concluding that it would give Google too much control over the market. And under the Obama administration, the Justice Department is promising to pore over deals far more rigorously than it did when the proposed Google-Yahoo partnership came up.

Microsoft used its lobbying muscle to spearhead the campaign against Google teaming up with Yahoo, so it wouldn't be a surprise if Google turned the tables.

"There has traditionally been a lot of competition online, and our experience is that competition brings about great things for users," Google spokesman Adam Kovacevich said. "We're interested to learn more about the deal."

A key lawmaker on antitrust issues said the Yahoo-Microsoft plan "warrants our careful scrutiny." Sen. Herb Kohl, a Wisconsin Democrat, said the Senate antitrust subcommittee he chairs will review the deal "because of the potentially far-reaching consequences for consumers and advertisers and our concern about dampening the innovation we have come to expect from a competitive high-tech industry."

Peter Kaplan, a spokesman for the Federal Trade Commission, declined to comment. A spokeswoman for the Justice Department couldn't immediately be reached for comment.

Ballmer expects that support from online advertisers and Web publishers who would like a stronger rival to Google will eclipse any objections that Google might raise.

"We think this is one of these cases where the coming together will produce more effective market competition, not less," he told analysts in Wednesday's conference call.

Just getting Yahoo to succumb to its latest advance represents a coup for Microsoft and the boisterous Ballmer, who was rebuffed for so long.

Microsoft is doubling down on Internet search at the same time Google is attacking Microsoft's bread-and-butter business of making software for personal computers.

Google is working on a free operating system for inexpensive personal computers in a move that could threaten Microsoft's ubiquitous Windows franchise. If it gains traction, Google's alternative, called Chrome OS, could divert some revenue from Microsoft while the software maker is trying to grab more of the money pouring into search advertising.

Chrome OS, though, isn't supposed to hit the market until the second half of next year. That means Microsoft could get a head start on Google in the duel to steal each other's financial thunder.

Search Spammers Hacking More Websites

The head of Google's Web-spam-fighting team warns that spammers are increasingly attacking websites.

The head of Google's Web-spam-fighting team, Matt Cutts, warned last week that spammers are increasingly hacking poorly secured websites in order to "game" search-engine results. At a conference on information retrieval, held in Boston, Cutts also discussed how Google deals with the growing problem of search spam.

Credit: Technology Review

Search spammers try to gain unfair prominence for their Web pages in search results, thereby making money from the products that these sites offer or from advertising posted on them. The practice, also known as "spamdexing," exploits the way search engines' algorithms figure out how to rank different pages for a particular search query. Google's page-rank algorithm, for instance, in part gives prominence to pages that are heavily linked to other material on the Web. Spammers can exploit this by adding links to their site on message boards and forums and by creating fake Web pages filled with these links. Garth Bruen, creator of the Knujon software that keeps track of reported search spam, says that some campaigns involve creating up to 10,000 unique domain names.

"We're getting better at spotting spammy pages," said Cutts after his talk, adding that spammers are increasingly hacking legitimate websites and filling their pages with spam links or redirecting users to other sites.

"As operating systems become more secure and users become savvier in protecting their home machines, I would expect the hacking to shift to poorly secured Web servers," said Cutts. He expects "that trend to continue until webmasters and website owners take precautions to secure Web-server software as well."

"I've talked to some spammers who have large databases of websites with security holes," Cutts said. "You definitely see more Web pages getting linked from hacked sites these days. The trend has been going on for at least a year or so, and I do believe we'll see more of this."

Bruen agrees. "We've seen an increase in spam e-mail and spam domains that not only sell illicit products, but that attempt to download malware and infect the visitor's PC," he says. Such malware could use an unknowing victim's computer to send out e-mail spam.

"It really is an arms race," says Daniel Tunkelang, one of the conference organizers and the chief scientist at search company Endeca.

To prevent such attacks, Cutts recommended that anyone running her own website regularly patch the Web server and any software running on it. "In the same way that you wouldn't browse the Web with an unpatched copy of Internet Explorer, you shouldn't run a website with an unpatched or old version of WordPress, cPanel, Joomla, or Drupal," said Cutts. He also suggested that users hand over management of Web software. "Using a cloud-based service where the server software is managed by someone else can often be more secure," he said.

During his talk, Cutts also explained that Google's efforts to identify dubious Web sites now include parsing the JavaScript code that underlies pages. Code may contain hidden instructions that record users' data, for example.

"It wasn't obvious to me that Google can do this," says Endeca's Tunkelang. "And apparently some spammers were saying that Google can't do that."

Cutts noted that spammers and hackers are also finding new ways to spam, with the rise of social networking sites like Facebook and Twitter. These sites "bring identity into the equation, but don't really have checks to verify that a profile or person sending you a message is who you think they are," said Cutts.

"Authentication [across the Web] would be really nice," says Tunkelang. "The anonymity of the Internet, as valuable as it is, is also the source of many of these ills." Having to register an e-mail before you can comment on a blog is a step in this direction, he says, as is Twitter's recent addition of a "verified" label next to profiles it has authenticated.

Danah Boyd, a Microsoft Research scholar who studies social media, suggests that spammers take advantage of the fact that people don't always adhere to the rules on social-networking sites--for example, they sometimes provide fake information about themselves. "The variability of average users is precisely what spammers rely on when trying to trick the system," says Boyd. "All users are repurposing systems to meet their needs, and the game of the spammer keeps changing. That makes the work that Matt does very hard but also very interesting."