Land Mines & Breast CancerBy Cecilia Vigliaturo
Electrical engineering professors Fred Barlow and Magda El-Shenawee are trying to apply technology used to detect land mines to screen for breast cancer.
“You can apply one solution for similar problems or devise similar solutions for diverse problems,” said El-Shenawee, associate professor of electrical engineering in the College of Engineering. “Sometimes those diverse problems have more in common than you might think.”
El-Shenawee’s initial research focused on developing and using a unique, incomparably fast technique called the steepest descent fast multilevel multipole method, or SDFMM, an algorithm that analyzes how electromagnetic waves scatter as they bounce off rough surfaces. Essentially, SDFMM combines rigorous mathematical equations that calculate the electric and magnetic currents on the surface of an object. After learning this technique at the University of Illinois-Urbana, she applied it to study radar scattering from rough surfaces, specifically a situation known as a “low grazing angle.” Her work resulted in finding better ways for ships to track missiles over large distances on the sea.
Field and Stream
El-Shenawee first connected land and sea as a visiting scholar working with the Sub Surface Sensing and Imaging Center at Northeastern University, Boston, Mass. “I thought ‘Why don’t we modify this technique for landmine detection?’ It was perfect,” she said. So she repositioned SDFMM to develop models that make the mud as clear as the ocean – incorporating the presence of hidden targets as a part of the mathematical model to study the radar signature of small, buried anti-personnel landmines.
“After you spend years working on these huge mathematical equations, you don’t just throw them away,” she said. “You look around to see what else you might apply them to.”
These images show the location of a sphere that represents a landmine buried under a a rough surface. The technique, used by El-Shenawee with her colleague Carey Rappaport at Northeastern University in Boston, subtracts the "signature" of the ground leaving behind the weaker signature of the land-mine, which can then be seen.
“A simplified assumption made by other researchers was that the ground is flat,” said El-Shenawee. One of the biggest challenges in detecting these buried boobytraps is the dirt that surrounds them. That dirt can be gritty, sandy, muddy or even frozen. Further muddying the waters, junk objects might be buried as well, which presents many possibilities.
“Is it a rock? A clump of dirt? Or is it a landmine?” asked El-Shenawee. “It’s far too expensive and time-consuming to consider every option.”
So she drew upon her background in computational and theoretical electromagnetics and research in rough surface scattering, adapting her equations and applying them to accommodate the natural irregularities of the soil’s surface, taking in all possible combinations of peaks, valleys and hollows. She completed hundreds of simulations that held only soil and hundreds that held a buried mine. When placed side by side, the two types of images looked identical.
“But when I subtracted the dirt from the model with the mine and used the model of just the ground as a reference, the hidden landmine suddenly popped up,” she said.
The researchers had successfully highlighted the issue of the “signature” of the ground. “Signature” refers to any signal that indicates the presence of an object.
“The signature of the landmine is very small and weak, so subtracting out the very large signature of the ground made the landmine apparent,” said El-Shenawee. She then measured and recorded the distinguishing features of the waves that scattered when they collided with a mine.
“Our analysis proved the benefit of inventing a technique to remove the signature of the rough ground,” said El-Shenawee. One large problem: the conventional methods used to measure the profile of the ground surfaces cannot be used in a field full of hidden landmines.
Though the ultimate goal is to develop sensors to detect those mines, every step forward in theory can mean the difference between actual life and death. Consider: in poverty-stricken countries littered with landmines, the most common method of detection is to crawl on the ground, poking a stick at arm’s length.
Unfortunately, funding for research into landmine detection has dried up, stalling further discoveries. El-Shenawee views such setbacks as an inevitable, albeit disappointing, aspect of research.
“My work will be a building block for someone else,” said El-Shenawee. “You start from other people’s work and you leave your work for others. Long after I die, I might still make a contribution. That’s the beauty of research.”
Finding Common Ground
How in the world did El-Shenawee link landmines with breast cancer?
“I realized that they’re both hidden, they’re both dangerous and they both cause death,” she said. “All I needed to do was change the parameters of my equations from geological to biological.”
El-Shenawee, and Fred Barlow, associate professor of electrical engineering, are about halfway through developing, designing, building and testing a microwave imaging system to work with physics-based imaging algorithms to detect breast cancer – as early as possible while the tumor is still as small as possible. The system, or the hardware, is Barlow’s specialty, with the algorithms, or the software, El-Shenawee’s, who also contributes her expertise in physics and analysis.
El-Shenawee has received support from NASA, while the Arkansas Biosciences Institute has funded their efforts to develop what might be an alternative or a complement to traditional mammography.
They’re planning future collaborations with Vasu Varadan, a world-renowned researcher who recently relocated to the University of Arkansas College of Engineering as the George and Boyce Billingsley Chair and Distinguished Professor. And El-Shenawee is working with John Lusth, associate professor of computer science and computer engineering, to develop artificial intelligence software to indicate whether abnormal tissue is benign or malignant.
“We’re definitely not trying to replace mammography,” said El-Shenawee. “But this system might offer additional benefits.”
Breaking New Ground
Mammography, which is an X-ray picture of the breast, is by far the most common and reliable detection method currently available. Indeed, though the total number of women diagnosed with breast cancer has increased, the number of deaths has decreased, which is largely the result of better screening methods, like mammography, which reveal tumors while they’re small.
So why bother coming up with another way to detect breast cancer? And what’s the difference between mammography and microwave imaging, anyway?
Mammograms are usually done in special clinics or radiology centers. The procedure involves squishing the breast between two plates while an X-ray image is made. As any woman who has had the test knows, it’s not painful but it’s not exactly comfortable either. Radiologists sometimes have difficulties distinguishing dense normal tissue from possible tumors, which generates a fair amount of false alarms. In addition, mammograms aren’t cheap, show the breast in two dimensions and emit ionizing radiation, which means they produce an electrical charge that can lead to unnatural chemical reactions inside cells.
“Being exposed to a very small dose of radiation is definitely a safer bet than to risk breast cancer,” said Barlow. “But not being exposed to any radiation would be better yet.”
Microwave imaging, on the other hand, would produce a sharp, three-dimensional image without changing the breast’s natural geometry. A clearer picture could mean fewer false alarms. And since the procedure is non-ionizing, women might be screened earlier and more frequently throughout their lives. The system also would be small and therefore mobile. That mobility, along with a potentially cheap price tag, would be particularly important for women in third-world countries without access to expensive, complicated-to-build mammography clinics.
Perhaps one of the most exciting differences is the possibility of finding the smallest of tumors. It’s possible to detect tumors approximately 3 mm in diameter, but only using a very advanced imaging test, magnetic resonance imaging or MRI, which is expensive and unavailable in some parts of the world. The goal of this research is to spot tumors that are approximately 5mm in diameter in a cheap, efficient manner. As every oncologist preaches, earlier discovery means less invasive treatment and better survival rates.
From Research to Reality
So how would this system actually work?
“We would send electromagnetic waves that would penetrate the breast,” said El-Shenawee. “If nothing is there, the waves will proceed. But if a mass is detected, the waves would be deflected and proceed in a different pattern or direction.”
Simply put, the microwave imaging system would use a probe and a source – or a transmitter and receiver – to gather information about the tumor.
Barlow uses a cell phone to explain how signals processing functions.
“We’re all bathed in an electromagnetic energy,” he said. “Basically, a cell phone is a transmitter and a cell phone tower is a receiver. When you talk on a cell phone, the sound of your voice is encoded and that information, in the form of electromagnetic waves, is radiated to the tower. The cell phone tower also transmits the other voice, which is received by your phone.”
The team is developing a system that uses a transmitter and receiver, each roughly the size of a large muffin, on either side of the breast. The transmitter would send out electromagnetic waves, just like a cell phone, that would pass through the breast tissue. The receiver on the other side would collect that information.
“Those waves would interact with the breast tissue,” said Barlow. “And that interaction would be detected and interpreted.”
The way those waves interact with healthy tissue and the way they interact with cancerous tissue are radically different thanks to a measurement called the “dielectric constant.” The dielectric constant of a certain material refers to the measurement of the speed and strength of a wave within that material, specifically how much speed and strength the wave loses.
“When the waves interact with normal vs. abnormal tissue, there’s a dielectric constant difference of more than five, which is huge,” said Barlow. “Normal tissue is very conducive to conductivity, making the waves travel about three times slower, while abnormal tissue makes the waves travel about 10 times slower.”
Think about the difference between light waves traveling through salt water and peanut butter.
Even more exciting, there is a significant dielectric constant difference between benign and malignant tissue.
“Eventually, we may be able to use this technology to not only reveal whether a tumor is present, but to find out what type of tumor it is,” said Barlow.
Before the team could approach the drawing board, however, they had to prove their idea would work, which highlights the value of virtual reality. “Before we spent a lot of time or money on building the actual hardware, we had to prove that our theory would work,” said El-Shenawee. “You can’t build a system without knowing that it will work.”
Among many possible stumbling blocks, one loomed largest: as the waves hit abnormal tissue, the signals scatter unpredictably. How to capture that “backscatter?”
On the basis of El-Shenawee’s theoretical analysis and computational studies and simulations, Barlow is designing the hardware to rotate, capturing those scattering waves as they bounce off at any angle.
“Using a rotating system lets us measure different angles, and using a sweeping-over frequency lets us measure different frequencies,” he said.
“Collecting the data from all directions around the breast makes the imaging algorithm extract information about the size, shape and location of the tumor,” said El-Shenawee. Those mathematical algorithms allow the software to draw a three-dimensional image of the tissue and the tumor.
“The hardware gathers the data and the software interprets, or translates, that information,” said Barlow. “You might say the hardware gathers the hay and then the software reveals whether there’s a needle, how big it is and where it is.”
Barlow, who has an undergraduate degree in physics and advanced degrees in electrical engineering, works with a sense of urgency.
“Whether it’s your wife, mother, sister, aunt or friend, it seems everyone knows someone with breast cancer,” he said. “The work we’re doing could benefit a lot of people.”
The humanitarian impact also motivates El-Shenawee, who holds this research particularly close to her heart.
“I’m a woman and I’m over 40, so I know and understand the fear as well as the need to find a better way to detect breast cancer.”