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Bruce Wiebusch, Regional Editor -- Design News, June 18, 2001
Attacking cancer with math
Engineers at the Georgia Institute of Technology are using math in the battle against prostate cancer. Mixed-integer programming and computational optimization techniques are helping doctors automate a non-surgical treatment called brachytherapy. Mixed-integer programming is a mathematical/optimization tool in which real problems are modeled into a mathematical formulation. For example, if someone wants to determine the best way to send computers around different routes in the country, you would want the variables to be the flow of the computers along different routes, and this flow has to be integer. In prostate brachytherapy, the treatment requires implanting small radioactive "seeds" in cancerous prostate. Planning treatment and deciding where seeds should be placed is a manual and time-consuming procedure that takes hours of a doctor's valuable time. But Eva Lee, an assistant professor of industrial and systems engineering at the Georgia Institute of Technology and Emory University's school of medicine found a way to reduce the pre-planning to only fifteen minutes. Lee realized that the placement of the radioactive seeds is a binary problem. The problem is a matter of deciding which of 300 possible locations is best for seed implantation. Her use of mixed-integer programming and optimization techniques allows doctors to effectively manipulate the large number of variables involved such as shrinkage of the cancerous tumor over time and distortion of the needles used for delivering the seeds. "In the prostate cancer case, we formulate the treatment planning into a mathematical model which includes all the clinical properties that we would like to see in the plan,' says Lee. "We solve the model and the solution tells us where to place the radioactive seeds inside the prostate." Ultrasound images of the prostate are used for determining optimal placement of the seeds throughout the tumor. Proper coverage of the entire prostate is important, but it is sometimes difficult to carry out a plan because of the many variables involved. Lee's approach uses a dose calculation module, an optimization engine, and a graphical evaluation tool. She explains that her approach frees doctors from having to do the math behind the seed placement. "All they have to do is tell the system what they want in the plan," she says. She also indicates that the new approach should help cut the recurrence rate for prostrate cancer and reduce toxicity in adjacent healthy tissues. The system is ready for commercialization, but has yet to receive FDA approval. In addition to prostate cancer applications, the system may also have applications for planning external beam radiation treatment for brain and other types of cancer. "Every sector in industry can benefit from the use of mixed-integer programming and optimization techniques," says Lee. Outside of medicine, applications include in-vehicle routing and scheduling, and integrated circuit design. For more information, contact Lee at eva.lee@isye.gatech.edu or call (404) 894-4962.Exhibit highlights future space travel
Starship 2040.
Its mission is not "to seek out new life and new civilizations" like those encountered by Captain James T. Kirk in Star Trek, but it does boldly go where no one has gone before. Starship 2040 is a 48-ft traveling display from NASA’s Marshall Space Flight Center that offers its visitors a sneak preview of what might be the future of space travel. Congress has funded the first steps of a 40-year development plan called the U.S. Space Launch Initiative, which provides strategy and funding for next-generation reusable launch vehicles. Visitors walk through a mock-up of the spacecraft’s control, engineering, and passenger compartments, and are shown crew health-monitoring systems, controls for propulsion drives, navigational aids, and emergency and safety systems. Starship2040’s appearance at National Manufacturing Week in March of this year marked the first stop in a nationwide series of public tour. For more information on dates and locations for the exhibit, go to www.starship2040.com.
Telescope seeks new life and new civilizations
Unlike NASA’s Starship2040, a new 1.8m diameter optical telescope being built at Harvard University will search for signs of intelligent life throughout the universe. The telescope searches for pulses of light across the northern sky once every 200 clear nights. It uses an array of 1,024 detectors that can see pulses of light as short as one-billionth of a second. For more information, e-mail infor@optics.org or call Gail Walmsley at (360) 752-1774.
Materials manipulate fluid flow in microdevices
Dr. Jeffrey Moore found a way to direct fluids to their destinations without the walls found in hose and tubing. Instead of walls, the University of Illinois professor of chemistry and researcher at the University’s Beckman Institute for Advanced Science and Technology uses layers of materials that are hydrophilic (having an affinity towards water) and hydrophobic (not having an affinity towards water) for creating virtual walls. The walls are created by an attraction between the liquid and the top and bottom surfaces. As aqueous solution is injected into the multi-layer cartridge, it spans the gap from top to bottom, but confines itself to the hydrophilic pathways and does not spill into adjacent areas. "One advantage of our approach is the simplicity in fabrication and the fact that our devices can be manufactured in parallel via lithography," says Moore. "Our ultimate goal is low-cost, easy-to-make microfluid devices that require no external power supply, but that are still capable of complex functionality," he explains. Applications for the technology include processes that require liquid-gas exchange. The directed flow methods make it easy to create liquid gas interfaces inside microchannels that could be the base for reactions or separations. Moore and other researchers also used their surface-directed flow technique for creating pressure sensitive switches. Contact Moore at (217) 244-4024 or moore@scs.uiuc.edu.
Tightening his nanobelt
Zhong Lin Wang, a professor of materials science and engineering at the Georgia Institute of Technology believes that his "nanobelts" may make practical the mass-production of tiny, nanoscale electronic and opto-electronic devices such as sensors and flat-panel displays. So, what’s a nanobelt? It’s a very thin structure measuring from 30 to 300 nanometers in width that is made from semiconducting metal oxides. The belt-like structures are said to be structurally uniform and defect free, which may make them preferable to nanowires and carbon nanotubes in some optical and electronic devices. "Defects in any nanostructure strongly effect their electronic and mechanical properties," says Wang. He and colleagues Zhengwei Pan and Zurong Dai made nanobelts from oxides of zinc, tin, indium, cadmium, and gallium. They place the metal oxide powders in the center of an alumina tube. The tube is then heated to 1,100 to 1,400C for melting the metal powders to their boiling points while argon or nitrogen gas flow through the tube. When the powders evaporate and then cool, they form crystalline belts, if kept within the proper pressure, temperature, and processing times. The belts bend 180 degrees without breaking. For more information, contact Wang at the Georgia Institute of Technology, 430 Tenth St., NW Atlanta, GA 30318; Tel: (404) 984-8008.
Metal film’s resistance to conductivity limited
Louisiana State University professor Philip W. Adams and researcher Vladimir Y Butko are using beryllium for showing that there is a universal standard for limiting a metal film’s resistance to conductivity. The findings are said to be significant for understanding why metals stop being good conductors when made very thin. Adams says that many scientists have tried researching this question by vaporizing metals and allowing the vapor to settle on surfaces as a thin film. Testing the film’s conductivity of the film deposition is problematic, according to Adams. "The vapors of most metals fall in droplets and create a film that is granular, which makes testing difficult and inaccurate," says Adams. He and Butko discovered that vaporized beryllium makes a smooth film, but does not conduct electricity well. However, when a magnetic field is applied to the film, it’s resistance to conductivity decreased. The more the magnetic field increased, the more the beryllium’s resistance fell, until it stabilized at what is known to physicist call "quantum resistance." Adam and Butko believe other metals react the same way, but the phenomenon was never observed before because the granular films were difficult to test. Adams says the discovery is significant because it shows there is a universal standard for limiting a metal film’s resistance to conductivity and the standard is based on the behavior of electrons in metals when exposed to magnetic fields. For more information, call (225) 578-5985.
Image-guided surgery
Scientists at Iowa State University’s Center for Nondestructive Evaluation (CNDE) are developing surgical techniques employing ultrasound and x-rays that they say will improve surgery success rates and recovery times without increasing the invasiveness of the procedures. They are using their expertise inspecting engineered parts and applying it to surgery techniques. Their investigation includes real-time feedback for brachytherapy, adding a third dimension to ultrasound by combining multiple two-dimensional images, and intravascular ultrasound imaging for measuring differences in how healthy and diseased tissues scatter waves. Contact the CNDE at (515) 294-8152.
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