Path Found to a Combined MRI and CT Scanner

Omni-tomography could add together the advantages of several medical imaging technologies

Image: Mehau Kulyk/Science Photo Library/Getty Images

A technology that better targets an X-ray imager’s field of view could allow various medical imaging technologies to be integrated into one. This could produce sharper, real-time pictures from inside the human body, says a researcher who hopes to one day build such a unified imager.


Ge Wang, the director of Rensselaer Polytechnic Institute’s Biomedical Imaging Cluster, in Troy, N.Y., calls his vision omni-tomography. Mixing and matching imaging techniques, such as computed tomography, magnetic resonance imaging, and single-photon emission computed tomography, could improve biomedical research and facilitate personalized medicine, says Wang, an IEEE Fellow.


To fit these imaging methods together, Wang and his collaborators have been developing a technology called interior tomography. In standard CT, X‑rays pass through two-dimensional slices of the body, and then a computer processes the data to build up a picture. If the scanner is trying to image the aorta, for instance, it will X-ray a whole section of the chest, including the points where the body ends and the open air begins. That boundary provides the image-building algorithm with defined edges and the background information it needs to operate. But interior tomography focuses only on structures inside the body, which reduces the patient’s radiation exposure. “If you’re only interested in the heart, why bother to cover your whole chest with X-rays?” says Wang. 


Narrowing the view, however, eliminates the usual reference points needed to create an image conventionally. Interior tomography relies on a different set of hints. The new technique uses information about how substances within the body (such as blood) and air pockets alter X-rays to provide the algorithm with a base for reconstructing the image. It can even use old X-ray images of the same patient to help out. 


Focusing on a specific region has advantages, particularly with patients too big for conventional scanners. “If an object is wider than the X-ray beam width, classic theory says you cannot do an accurate reconstruction,” says Wang. That’s not a concern with interior tomography, he says. 


Images: Hao Gao & Ge Wang

Seeing Both Sides: A CT scanner’s X-rays [left side] provide good structural detail; MRI images [right] are good for seeing functional flaws. Omni-tomography could combine the two technologies in the same machine.

What’s more, Wang’s team has shown that this concept can be generalized for use in imaging methods other than CT scanning, including MRI. And that could lead to a true fusion of major medical imaging techniques. In part that’s because the technique allows the use of smaller X-ray detectors, which in turn makes it possible to fit more scanners into the same machine. 


There are already systems that combine two imaging methods—PET and CT or SPECT and CT, for instance. But those systems usually apply different methods in sequence rather than simultaneously, making it harder to see biological processes in action. The combination of CT and MRI has never been attempted before, but Wang says it’s possible now.


In fact, he and his collaborators in Australia, China, and the United States recently came up with a top-level engineering design for a CT-MRI scanner. They hope to present their design in June at the International Meeting on Fully Three-Dimensional Image Reconstruction in Radiology and Nuclear Medicine, in California. Applying interior tomography to MRI imaging allows the use of a weaker magnetic field, which is one way the design compensates for the incompatibility between powerful magnets in the MRI and rotating metal parts in the CT scanner. 


Wang’s team does not yet have the funding to build a combination CT-MRI scanner, but putting the two technologies together could prove useful. MRI gives high contrast and allows doctors to measure functional and even molecular changes; CT provides greater structural detail. Together, they might allow doctors to get a superior picture of processes in action, such as changes during a heart attack, or serve as a guide to a surgical procedure. The technology would be ideal for imaging vulnerable plaques, suggests Michael Vannier, one of Wang’s collaborators and a radiology professor at the University of Chicago. Vulnerable plaques are buildups on artery walls that are particularly unstable and prone to causing heart attack or stroke. A combination of structural, functional, and molecular information is needed to tell just how dangerous the plaque may be. “In the long run, we think putting many imaging modes together will give you more information,” Wang says.


Interior tomography “is certainly an interesting concept that takes the interest in combining modalities to the ‘ultimate’ level of a single device,” says Simon Cherry, director of the Center for Molecular and Genomic Imaging at the University of California, Davis. While omni-tomography is technically feasible, Cherry wonders whether it will make sense from a clinical and economic perspective. “There are some that say too many of our health-care dollars are spent on imaging, especially in the pursuit of defensive medicine. This will be an expensive machine,” he says. “These are the issues that may well determine whether this approach is successful.” 


About the Author

Neil Savage describes IEEE Fellow Ge Wang’s research on interior tomography, which he first came across while reporting on how medical device firms were trying to reduce the X-ray dosage produced by their imagers. Savage, a longtime Spectrum contributor, says, “With the growing popularity of scanning, finding ways to limit radiation exposure is important.”

The World's Most Powerful MRI Takes Shape

• Biomedical
• Imaging
• News

Medical researchers expect unprecedented resolution from 11.75-Tesla imager

•  

 

Illustration: Emily Cooper

This one goes to 11: The main superconducting coil for the INUMAC imager is made from 170 kilometers of niobium-titanium. When bathed in liquid helium and charged, it produces a magnetic field of 11.75 teslas.

An MRI scanner equipped with a superconducting magnet strong enough to lift a 60-metric-ton battle tank will offer unprecedented images of the human brain when it comes on line a little more than a year from now, say its builders.

The imager’s superconducting electromagnet is designed to produce a field of 11.75 teslas, making it the world’s most powerful whole-body scanner. Most standard hospital MRIs produce 1.5 or 3 T. A few institutions, including the University of Illinois at Chicago and Maastricht University, in the Netherlands, have recently installed human scanners that can reach 9.4 T. Superconducting magnets used in the Large Hadron Collider, which last year was used in the discovery of the Higgs boson, produce a field of 8.4 T.

The development of the scanner, known as INUMAC (for Imaging of Neuro disease Using high-field MR And Contrastophores), has been in progress since 2006 and is expected to cost €200 million, or about US $270 million. The project reached a key milestone this summer with delivery of more than 200 kilometers of superconducting cable, which is now being wound into coils that will produce the scanner’s magnetic field.

“We’re pretty proud of having met all the requirements, plus given them a little extra,” says Hem Kanithi, vice president of business development atLuvata, in Waterbury, Conn., which built the superconductor.

Standard hospital scanners have a spatial resolution of about 1 millimeter, covering about 10 000 neurons, and a time resolution of about a second. The INUMAC will be able to image an area of about 0.1 mm, or 1000 neurons, and see changes occurring as fast as one-tenth of a second, according to Pierre Védrine, director of the project at the French Alternative Energies and Atomic Energy Commission, in Paris. With this type of resolution, MRIs could detect early indications of brain diseases such as Alzheimer’s or Parkinson’s and perhaps measure the effects of any methods developed to treat those illnesses. It would also allow much more precise functional imaging of the brain at work than is currently available. “You cannot really discriminate today what is happening inside your brain at the level of a few hundred neurons,” Védrine says.

High-field MRI could also allow scientists to explore different methods of imaging. Most MRI machines rely on imaging the nuclei of hydrogen atoms, but stronger scanners might gain useful physiological information by looking for weaker signals from sodium or potassium nuclei.

Improved superconducting wire is key to making such a powerful machine. The wire in the INUMAC magnet is made from niobium-titanium, a common superconductor alloy. But it will experience some uncommon conditions as part of INUMAC. To reach the required field strength, the electromagnet must be able to carry 1500 amperes at 12 T and be cooled by superfluid liquid helium to 1.8 kelvins. That requires specialized manufacturing and precise control of the dimensions of the wire, allowing it to be coiled so the cables are aligned to within a few micrometers of precision. “We are pushing the superconducting material niobium-titanium very close to its limits,” Védrine says.

Another material, niobium-tin, can produce magnetic fields stronger than 20 T, but it was passed over for the job because it’s more expensive than niobium-titanium and very brittle, making it difficult to wind.

Ultimately, Luvata produced 170 km of wire for the main superconducting coil. The company made another 58 km for two secondary coils, which will produce an opposing magnetic field to shield the area outside the machine from stray magnetic fields.

Instead of winding the wire into one long coil, as is standard in systems with lower fields, engineers are using a “double pancake” design, in which the wire is coiled into two reels that are spliced together, one on top of the other. The whole magnet will consist of 170 of these double pancakes connected in series. Védrine explains that this reduces the chances for error: Making a mistake in the winding phase using a single helical coil could ruin the whole magnet. However, a miswound pancake can simply be swapped out for a new one. The design provides space for the liquid helium bath to reach all of the coil and keep the temperature low, and it also allows engineers to place the best-performing coils at the center of the system, which improves the precision of the magnetic field.

The inner diameter of the magnet will be 90 centimeters, wide enough for a human body. Patients getting scanned will lie entirely inside the machine, but the region where the field is precise enough to get maximum resolution will be only 22 cm long. “The very good field region is only in the middle of the magnet,” Védrine says. While patients could be situated so that other body parts would fit inside that region, “first we are concentrating on the brain,” he says. It would take an even more massive machine to enlarge the high-resolution area.

Védrine expects to deliver the fully assembled magnet by September of next year. Other parts of the imaging system will then be added in and around the magnet, followed by about three months of testing. “Probably we’ll have the first images by the beginning of 2015,” he says.

New Pacemakers Prove MRI-Proof

With some precautions, modern models are immune to scanner's deadly influence

According to both medical wisdom and regulatory decree, magnetic resonance imaging (MRI) scans and implanted heart devices such as pacemakers do not mix. Henry Halperin, an associate professor of medicine, radiology, and biomedical engineering at Johns Hopkins University School of Medicine in Baltimore, bluntly sums up the problem: "It is feared that the electromagnetic fields of the MRI may heat up metal components or pull on and dislodge the device, causing tissue damage, device malfunction, or possibly death."

Still, forgetful or comatose patients have inadvertently gotten scans, with more than two dozen deaths thought to be associated with the procedure. How many deaths were really due to the scan is anybody's guess; then again, nobody knows how many lives might be saved if patients with implants could get diagnostic MRI scans, which are regarded as the best imaging technology for the diagnosis of many cancers; diseases of the brain, head, and neck; and many cardiovascular conditions. It is estimated that half of patients with pacemakers become candidates for scanning at some point in their lives [see photo, " Safe Inside"].

For those who need it most, an option is now at hand. As part of an industry-supported study published in the 3 August issue of Circulation, Halperin and his colleagues reported that pacemakers made after 2000 can go through MRI machines safely if a team of specialists, including a cardiologist, supervises, following a specific safety protocol.

In a typical MRI, a 1.5-tesla magnet strings the body's protons tautly along the magnet's lines of force. Then radio frequency waves twang the protons out of alignment; when they snap back, they produce an RF signal from which an image of the body's organs is constructed. With all those electromagnetic fields, an electronic device that has an antenna-like electrode lead running into a human heart would seem, on the face of it, a dangerous thing.

The evolution of pacemaker technology and the way that new implants interact with an MRI is what makes scanning possible now, according to the researchers. At about 40 grams, modern pacemakers are, on average, just a fifth the weight of their ancestors, and the pull they're subjected to from a 1.5-T machine is only about the weight of two golf balls--hardly enough to dislodge the device.

But more striking was the discovery, in both animal and human subjects, that when the electrodes absorbed energy from the scanner's RF field, their temperature rose just 5 degrees C--hardly the flesh-cooking inferno doctors feared. According to the Johns Hopkins study, the lead, which runs from the pacemaker to the heart, is too short to couple well with the RF field, and capacitors in the device filter out a good deal of the energy that would cause heating.

All this good news isn't exactly welcome at Biophan Technologies Inc., a West Henrietta, N.Y., company founded in the late 1990s with the sole purpose of developing technologies that can make implants MRI-friendly. Michael Weiner, the company's chief executive officer, finds fault with the Johns Hopkins study, saying the heating result depends on where and when you measure the temperature. The researchers took the temperature at the pacemaker's electrode tip, which is metal and "works like a heat sink," Weiner says. "It's the tissue a few millimeters away that heats up." Because the study's subjects had gotten their implants just four weeks previously, he adds, not enough fibrous scar tissue had formed around the tip to furnish a potential hot spot.

Besides heat and the pull of the magnet, there are at least two other potential problems with the scanning of pacemakers. First, the RF wave front that sweeps over the body 200 to 300 times per second can set up a heart-quickening voltage gradient along the lead to the heart. Second, the current the RF field induces in the device could also, in principle, reset the pacemaker's rate. The Hopkins researchers found no evidence of either problem but acknowledged that they examined pacemakers in only 24 volunteer patients.

The safety protocol outlined for the Johns Hopkins study begins with the conventional remote testing of the implanted device--a pacemaker or a defibrillator. Next, doctors explain the potential risks to the patient and then turn off the device or put it in safe mode, using the device's built-in wireless link. They then scan the patient with an MRI machine in the presence of a cardiologist. Finally, the cardiologist uses the wireless link to check the implant, to make sure it still functions properly.

Johns Hopkins's Halperin says his group's study doesn't threaten Biophan's business. "We tested existing models, but the problem isn't solved, because each new device that comes out would have to be tested separately," he notes. "Besides, the monitoring protocol we use is fairly involved, and with what Biophan is talking about, you wouldn't have to do any of it. Everybody who needed an MRI could get one anywhere, instead of having to go to a special center that can take precautions."

Biophan's safety technologies include an in-lead RF filter--developed, by the way, at Johns Hopkins and licensed exclusively to Biophan--that reduces heating of the electrode in the heart by more than 95 percent. It also has what the company calls an anti-antenna. Normally, the pacemaker's lead makes a circuit, called the primary loop, by conduction from the electrode in the heart, through the patient, and back to the pacemaker. The anti-antenna, a structure in the lead, provides a reverse loop to cancel out any voltage gradient that might build up along the primary loop.

Other companies are working on similar technologies. Minneapolis-based Medtronic Inc., the leading pacemaker company and a backer of the Johns Hopkins research, says its pacemakers and defibrillators will be fully safe for MRI scanning by next year.

RFID Systems May Disrupt the Function of Medical Devices

• Computing
• Embedded Systems
• Article

Researchers ask whether hospitals should adopt new guidelines for medical electronics' interoperability

PHOTO: Andrei Malov/istockphoto

24 June 2008—The use of radio-frequency identification (RFID) systems in hospitals may not be entirely safe, new research suggests. According to a study published this week in the Journal of the American Medical Association, RFID tags and the devices they communicate with can disrupt the performance of medical equipment, including pacemakers and dialysis machines, potentially endangering the patients who depend on those devices.

Erik Jan van Lieshout and Remko van der Togt, along with their colleagues at the University of Amsterdam’s Academic Medical Center, tested whether the presence of RFID transponders and the readers they transmit to could interfere with the function of 41 different electronic medical devices. The team examined both an active RFID system, in which the tags have batteries that allow them to transmit continuously, and a passive system, whose tags are powered only when in the range of a transmitter’s electromagnetic field. In 123 tests, they found 34 incidences of interference.

Of those, the researchers categorized 22 cases as hazardous, meaning that the interference caused an equipment fault that could have direct physical impact on a patient. For example, in two such incidences, a mechanical ventilator and a syringe pump switched off when the RFID system was transmitting near them. The passive RFID tag they used, which had a higher energy output and operated at a frequency of 868 megahertz, induced three times as many disruptions as the active system, which operated at 125 kilohertz.

None of the tests involved patients—just equipment—and no real-life cases have yet been reported of RFID transponders causing a device to malfunction, according to the Dutch research.

The health-care market for RFID systems, according to IDTechEx, a consultancy that focuses on RFID, is about US $121 million, and the tags are increasingly becoming integrated into the hospital environment. They are used, for instance, to track the location of surgical sponges so they are not inadvertently left inside patients. RFID tags are also embedded in bracelets given to newborn babies to prevent kidnapping.

For van Lieshout, who works in his hospital’s intensive care unit, the question of RFID interference arose after he had conducted some similar experiments on the use of cellphones in hospitals. Noticing the growing presence of RFID transponders in the ICU, van Lieshout decided to consult the medical literature and ask his colleagues for guidance on whether the tags’ transmissions could affect the health of his patients. ”They told me, ’Oh yeah, it’s pretty safe.’ But I wanted to know, ’Well, how safe?’ And no one knew,” van Lieshout recalls.

He and his colleagues set out to gain a qualitative sense of their safety: rather than exhaustively testing all the configurations of each available RFID tag and reader, they chose two systems already used in retail and drug-supply chains. They placed a transmitting reader and tag near each medical device and observed the distances at which an electromagnetic field caused disturbances in the devices’ performance. They found that the median distance at which interference occurred was 30 centimeters, with a range extending to 600 cm for several of the devices. ”For a critical-care physician, it was astonishing to find out,” says van Lieshout.

Donald Berwick, president of the Cambridge, Mass.–based Institute for Healthcare Improvement, notes in an editorial accompanying the study that the impact of hospital electronics on patient care has been largely positive but poorly understood. ”Health care is full of tightly coupled, hard-to-see systems, and the naive introduction of a change as apparently isolated as RFID tags…might cause remote and dire consequences far away in space and time,” he writes. Berwick suggests that hospitals look into routinely checking for electromagnetic interference and that regulatory agencies consider updating safety standards for electronic medical equipment.

Setting meaningful standards for testing every existing RFID system with all electronic medical equipment might be a near-impossible task, however. ”RFID means a lot of different things—a lot of different frequency bands, and a lot of ways to use it,” says Ralph Herkert, a senior researcher at Georgia Tech Research Institute’s Medical Device Test Center. As Herkert explains it, tags can operate with readers from different manufacturers at the same carrier frequency, but each signal may be modulated at a different rate. In some cases, the interference might be due to the modulation rather than the carrier frequency or the energy output.

For years, hospital staff has questioned whether the transmitters in cellphones are dangerously disruptive to medical equipment, and bans have been both imposed and then lifted in hospitals across the developed world. This latest batch of evidence—the first to document the influence of RFID technology on medical devices—is unlikely to revive the contentious debate about the hazards of using transmitting technologies in hospitals, says Marlin Mickle, an electrical engineering professor at the University of Pittsburgh and executive director of its RFID Center of Excellence. ”Cellphones are uncontrolled because visitors with cellphones wander all over the place. But RFID readers are installed by the hospital staff,” Mickle says. ”They just have to be smart about where they put them.”

The question remains of how often those interactions between life-saving devices and RFID transponders would arise in the day-to-day operations of a hospital. ”I’m not hoping there will be a frenetic ban on RFID in health care,” van Lieshout says. ”We just have to know what we’re dealing with.”

Mickle compares the study’s relevance to the warnings that accompany implanted devices and pharmaceutical drugs. ”When companies advertise drugs on television, they also tell you all the things that could go wrong,” Mickle says. ”Many electronic devices have those same kinds of warnings. It doesn’t mean we can’t use them.”

Smartphones: The Pocketable PC

Is Your Phone Smarter Than a Fifth Grader?

Illustration: Frank Chimero

This is part of IEEE Spectrum's special report: Top 11 Technologies of the Decade

Douglas Adams's Hitchhiker's Guide to the Galaxyseries is named after a pocketable device that contains everything worth knowing. But that seems almost quaint today, when you can carry the full contents of the Web in your pocket, as well as a telephone, a camera, a radio, a television, and a navigation system. Today's smartphones are marvels of engineering, crammed with more features than the average PC. They've become the prime driver of innovation for both software and hardware.

It took half a century to shrink the mainframe from the size of a living room to that of a suitcase. It took another decade to make it smaller than a wallet. The smartphone has swallowed and assimilated functionality from music players, remote controls, gaming consoles, even printed maps and news publications. And now that smartphones are serving as Wi-Fi hot spots, they can replace wireless routers and modems, too. Smartphones are becoming as essential as keys or a wallet, and they'll soon replace those as well.

This has some real consequences. Unlike its predecessors, the smartphone is an inherently personal device: Not only is it always on, it's always somewhere on us. Without realizing it, we've let smartphones usher us into an age of ubiquitous, pervasive computing that technologists, as well as science-fiction authors, have been dreaming about for years [PDF].

"Smartphones help users stay connected to information at any given time, any given location," says Dilip Krishnaswamy, a Qualcomm engineer and associate editor in chief of IEEE Wireless Communications. "The information is just there when you need it."

We've come to rely on such connectivity. There's no need to pack a map or directions when an app can guide you in real time, nor to consult a restaurant guide before leaving the house. In these and a thousand other ways, the smartphone, more than any other technology to have emerged in the past decade, is the one that has most changed our lives.

To be sure, back in 1973, Motorola's Martin Cooper didn't set out to build an always-connected, portable computing device. He was simply trying to shrink the car phone down to the size and weight of a luggable brick. But once the cellphone had earned a permanent place in our pockets, it became an unavoidable platform for innovation, upstaging the PC. If Starbucks wants to make it quicker and easier to pay for a cup of coffee, why not do it through the phone? If The New York Times wants to get away from paper, well, everyone's already carrying around a perfectly readable screen.

Smartphones are more than just bells and whistles—they actually change behavior. With a traditional mobile phone, users spend most of their time making calls and sending text messages. On a smartphone, basic communication takes a back seat to Internet browsing, e-mail, entertainment, and games. This difference is due to three key ingredients, each of which has seen tremendous advances in the last decade: hardware, software, and network infrastructure.

The hardware is the most obvious. Thanks to high-resolution displays with touch screens or QWERTY keyboards and tiny camera lenses on the outside and gigahertz processors, radio antennas, and image sensors on the inside, the phones hardly resemble their modest predecessors.

But at least as important is the software. "The operating system is the foundation for everything else in a smartphone," says Donna Dubinsky, a cofounder of Palm, the company that first succeeded in cramming computer functionality into a pocketable device. Every major smartphone operating system now supports third-party applications that extend the phone's capabilities far beyond what any one manufacturer can do.

And in addition to using the resources of the phone itself, these apps can off-load data storage and processing to the cloud [see "It's Always Sunny in the Cloud"] in the form of server farms around the world, thanks to ever increasing wireless bandwidth—the third key development behind the smartphone. "People naturally want to focus on the device itself," says Dubinsky, "but what's important is the complete system, including hardware, software, and application development environment."

Current smartphones quietly shift between Wi-Fi and 3G so that users are always connected to the best available network. Remember that the iPhone, still less than four years old, didn't even access 3G networks when it launched. By October of last year, you could get a 3G signal at the top of Mount Everest, and now the first 4G networks are emerging.

Today we're seeing only hints of how a smartphone world will be different. With their numerous sensors, they will form nodes in a vast and unprecedented data collection network. Researchers have already used phones' accelerometers to follow basic health indicators (such as a patient's gait), their GPS to monitor crowd and pedestrian traffic patterns, and their microphones to track bird migrations. Several app developers have created the first useful examples of augmented reality—letting you point your phone at a restaurant and see a bunch of customer reviews, for example.

These capabilities come with strings attached, notably the addictive effects of always-on connectivity. BlackBerries are rightly nicknamed "CrackBerries" for the way they feed a workaholic's addiction. Krishnaswamy notes that we're training ourselves to always be ready for the next e-mail or status update, and we're disappointed when one doesn't arrive. And not everyone likes it when people interrupt dinner to surf the Web to fact-check the conversation.

Some experts even worry about a new digital divide between those who can afford smartphones and data plans and those who can afford only basic mobile phones. In fact, many smartphones cost more than low-end computers, once you take away the subsidized prices that wireless carriers offer for them. Yet in rural and impoverished areas, they represent a much better investment because they're self-contained, needing neither additional network infrastructure nor even reliable power.

In any case, many high-end features will inexorably filter down to low-end phones, as they have in the camera market, and what begins as a luxury will quickly become a necessity. In 2007, sales of smartphones surpassed sales of laptops, and some predict that by 2014 more people will browse the Internet by phone than from traditional computers [PDF].

The drive to communicate on ever-wider scales has shaped many of our technological advances, and these in turn have shaped how we communicate. Moving from text messages to Twitter updates, from voice to video chat seems to be part of our evolution. "The interesting thing is how it's changing human behavior itself," says Krishnaswamy. "Smartphones will become a sixth sense for the user, gathering information from wireless sensors in the user's environment and from the network, interpreting the information, and providing valuable feedback to the user."

This article originally appeared in print as "Smartphones."

For all of IEEE Spectrum's Top 11 Technologies of the Decade, visit the special report.

A Foucault Pendulum on a Chip

A MEMS microgyroscope mimics a 19th-century instrument's mechanism to boost abilities of inertial guidance systems

Photo: Alexander Trusov/University of California, Irvine

1 February 2011—A new type of microscopic gyroscope could lead to better inertial guidance systems for missiles, better rollover protection in automobiles, and balance-restoring implants for the elderly.

Researchers from the MicroSystems Laboratory at the University of California, Irvine (UCI), described what they’re calling a Foucault pendulum on a chip at last week’s IEEE 2011 conference on microelectromechanical systems (MEMS) in Cancun, Mexico. A Foucault pendulum is a large but simple mechanism used to demonstrate Earth’s rotation. The device the UCI engineers built is a MEMS gyroscope made of silicon that is capable of directly measuring angles faster and more accurately than current MEMS-based gyroscopes.

”Historically it has been very pie-in-the-sky to do something like this,” says Andrei Shkel, professor of mechanical and aerospace engineering at UCI.

Today’s MEMS gyroscopes don’t measure angles directly. Instead, they measure angular velocity, then perform a calculation to figure out the actual angle. When something is in motion, such as a spinning missile, keeping track of its orientation requires many measurements and calculations, and each new calculation introduces more error. Shkel says his gyroscope is more accurate because it measures the angle directly and skips the calculation. ”You’re pretty much eliminating one step,” he says.

The gyroscope works on the same principle as does the Foucault’s pendulum you’d find in many museums, demonstrating Earth’s spin. The plane on which the pendulum oscillates stays in one position relative to the fixed stars in the sky, but its path over the floor gradually rotates as the world turns. Similarly, the oscillation of a mass in the gyroscope stays the same with respect to the universe at large, while the gyroscope spins around it.

Of course, the pendulum in Shkel’s two-dimensional device is not a bob on a string. Instead, four small masses of silicon a few hundred micrometers wide sit at the meeting point of two silicon springs that are at right angles to each other. A small electric current starts the mass vibrating in unison. As the gyroscope spins, the direction of the vibrational energy precesses the same way a swinging pendulum would.

The gyroscope operates with a bandwidth of 100 hertz and has a dynamic range of 450 degrees per second, meaning it detects as much as a rotation and a quarter in that time. Many conventional microgyroscopes (at least those of the ”mode matching” variety) operate at only 1 to 10 Hz and have a range of only 10 degrees per second. But inertial guidance systems—such as those that stabilize an SUV when it hits a curb or keep a rapidly spinning missile on track—require both high dynamic range and high-measurement bandwidth to accurately and quickly measure directional changes in such moving objects.

Shkel described and patented the concept for a chip-scale Foucault pendulum back in 2002, but the device’s architecture requires such precise balance among its elements that it is too hard to manufacture, even nine years later. But last week, Shkel’s colleague Alexander Trusov presented a new design, which Shkel says is more complicated in concept but easier to make, requiring standard silicon processes and only a single photolithographic mask.

But it’s just one possible design. Shkel is on leave from his academic post and currently working with the U.S. Defense Advanced Research Projects Agency (DARPA), which has launched a program to create angle-measuring gyroscopes for better inertial guidance systems. Three-dimensional designs that use concepts other than the one behind his 2-D device might be preferable for DARPA’s needs because they’ll take up less space, Shkel says. He hopes the DARPA program will also improve manufacturing processes in general, giving conventional microgyroscopes higher precision for applications that don’t require the bandwidth and dynamic range of a chip-scale Foucault pendulum.

”We will have a new class of devices,” he says, ”but we will also help existing devices.”

About the Author

Neil Savage writes about nanotech, optoelectronics, and other technology from Lowell, Mass. In the February 2011 issue he wrote about efforts to develop rechargeable lithium-air batteries.

ISSCC 2011: Silicon Gets Personal

The 1950s pacemaker: a box that patients had to wheel around on a cart and keep plugged into a wall. Clearly a problem if you wanted to go outside, or if you lost power. This morning, Tim Denison, director of neuroengineering for implant maker Medtronic, asked engineers at the 2011International Solid-State Circuits Conference (ISSCC) to remember that device as he described the ongoing challenge for electrical engineers to make medical devices tinier, more efficient, and capable of treating more ailments. Denison was the first plenary speaker Monday morning at ISSCC which began this week in San Francisco. The theme of this year's conference is "electronics for healthy living."

Denison started his talk with the tale about pacemakers' early days and Medtronics founder Earl Bakken, who invented a battery-operated wearable pacemaker, after adapting a design for a metronome circuit that he saw in a popular science magazine. The device needed manual tuning to adjust the heartbeat's frequency (it's hard to sleep or to go for a jog when your heart rate never changes) and early designs had knobs for self tuning.

Today's pacemakers, thankfully, have come a long way. Completely implantable, they have leads that go into the heart through the patient's veins, and can monitor blood temperature and patient's breathing to adjust the rate. Denison questioned what was next in the pacemaker's evolution and showed a graphic of what looked like a hybrid between a pill and a fishing lure, a future device that could be implanted completely inside of someone's heart. He said that even that device was not the smallest we might see, and that other tiny gadgets could treat a wide range of problems.

In the Sunday tutorial "Interfacing Silicon with the Human Body" that he instructed, he outlined a variety of devices that are commercially available or in development to correct stray electrical signals that mess with our nervous system. These include gadgets for treating obsessive compulsive disorder, Parkinson's disease, dystonia (he showed a video of a patient before and after for this one), depression, migraine headaches, and fecal incontinence. The number of problems isn't limited to those where engineers can detect electrical signals either, he said in the tutorial, noting that small devices can now detect chemical signals and accelerations. He gave a nod to the menagerie of MEMS devices that we've seen wheeled out recently, specifically the Foucault pendulum turned accelerometer on a chip. 

Once we have all of those mini-devices that can correct what ails us, we might need to network them--so that doctors can know of any hitches. Denison mentioned that heart problems can start days before a patient needs to be rushed to the emergency room and a networked device could inform a doctor.

That idea fit well with the talk that followed by Imec Senior VP, Jo De Boeck on wireless personal healthcare. He described a "smart patch" that one day might monitor a variety of general health stats, and specifics depending on the patient. He gave examples including devices that could determine iron levels in a pregnant woman and when a patient has swallowed his pills (a means to improve medication compliance). He noted that one important development has been the proliferation of the smartphone and also pointed to a future need for cheap plastic circuits (such as the plastic microprocessor that his company will unveil later this week). He said that he believed that such circuit design would become increasingly important, pointing to the crowd of 3000 engineers gathered before him and noting that, in the future, half of the room might be working on plastics and half silicon.

A panel discussion this evening will get into some of the details of "Body Area Networks"--including security and protocols to make sure the future's smarter implants don't interfere with one another.

STANFORD ENGINEERS CREATE A TINY, WIRELESSLY POWERED CARDIAC DEVICE

Stanford electrical engineers overturn existing models to demonstrate the feasibility of a millimeter-sized, wirelessly powered cardiac device. The findings could dramatically alter the scale of medical devices implanted in the human body.

By Andrew Myers

A team of engineers at Stanford has demonstrated the feasibility of a super-small, implantable cardiac device that gets its power not from batteries, but from radio waves transmitted from outside the body. The implanted device is contained in a cube just eight-tenths of a millimeter in radius. It could fit on the head of pin.

The findings were published in the journal Applied Physics Letters. In their paper, the researchers demonstrated wireless power transfer to a millimeter-sized device implanted five centimeters inside the chest on the surface of the heart—a depth once thought out of reach for wireless power transmission.

The paper’s senior author was Ada Poon, an assistant professor of electrical engineering at Stanford. Sanghoek Kim and John Ho, both doctoral candidates in Poon’s lab, were first authors.

The engineers say the research is a major step toward a day when all implants are driven wirelessly. Beyond the heart, they believe such devices might include swallowable endoscopes—so-called “pillcams” that travel the digestive tract—permanent pacemakers and precision brain stimulators. The devices could potentially be used for virtually any medical applications for which device size and power matter.

A team of engineers at Stanford has shown that, contrary to earlier models, high-frequency wireless power transmission to a device in the human body is possible. These images show power delivery to the human heart from a 200MHz low-frequency transmitter (left) and a 1.7GHz high-frequency transmitter (right). Red indicates greatest power; blue is least. Note focusing of power on the heart in the right image. Image courtesy John Ho, Stanford Engineering.

A REVOLUTION IN THE BODY

Implantable medical devices in the human body have revolutionized medicine. Hundreds of thousands if not millions of pacemakers, cochlear implants and drug pumps are today helping people live relatively normal lives, but these devices are not without engineering challenges.

First off, they require power, which means batteries, and batteries are bulky. In a device like a pacemaker, the battery alone accounts for as much as half the volume of the device it drives. Second, batteries have finite lives. New surgery is needed when they wane.

“Wireless power solves both challenges,” said Poon.

Last year, Poon made headlines when she demonstrated a wirelessly powered, self-propelled device capable of swimming through the bloodstream. To get there she needed to overturn some long-held assumptions about delivery of wireless power through the human body.

Her latest device works by a combination inductive and radiative transmission of power. Both are types of electromagnetic transfer in which a transmitter sends radio waves to a coil of wire inside the body. The radio waves produce an electrical current in the coil sufficient to operate a small device.

There is an indirect relationship between the frequency of the transmitted radio waves and the size of the receiving antenna. That is, to deliver a desired level of power, lower frequency waves require bigger coils. Higher frequency waves can work with smaller coils.

“For implantable medical devices, therefore, the goal is a high-frequency transmitter and a small receiver, but there is one big hurdle,” explained Kim.

IGNORING CONSENSUS

Existing mathematical models have held that high frequency radio waves do not penetrate far enough into human tissue, necessitating the use of low-frequency transmitters and large antennas—too large to be practical for implantable devices.

Poon proved the models wrong. Human tissues dissipate electric fields quickly, it is true, but radio waves can travel in a different way—as alternating waves of electric and magnetic fields. With the correct equations in hand, she discovered that high-frequency signals travel much deeper than anyone suspected.

Assistant Professor of Electrical Engineering Ada Poon. Photo: L.A. Cicero / Stanford News Service

“In fact, to achieve greater power efficiency, it is actually advantageous that human tissue is a very poor electrical conductor,” said Kim. “If it were a good conductor, it would absorb energy, create heating and prevent sufficient power from reaching the implant.”

According to their revised models, the researchers found that the maximum power transfer through human tissue occurs at about 1.7 billion cycles per second.

“In this high-frequency range, we can increase power transfer by about 10 times over earlier devices,” said Ho, who honed the mathematical models.

The discovery meant that the team could shrink the receive antenna by a factor of 10 as well, to a scale that makes wireless implantable devices feasible. At that the optimal frequency, a millimeter-radius coil is capable of harvesting more than 50 microwatts of power, well in excess of the needs of a recently demonstrated eight-microwatt pacemaker.

ADDITIONAL CHALLENGES

With the dimensional challenges solved, the team found themselves bound in by other engineering constraints. First, electronic medical devices must meet stringent health standards established by the IEEE, particularly with regard to tissue heating. Second, the team found that receive and transmit antennas had to be optimally oriented to achieve maximum efficiency. Differences in alignment of just a few degrees could produce troubling drops in power.

“This can’t happen with medical devices,” said Poon. “As the human heart and body are in constant motion, solving this issue was critical to the success of our research.”

The team responded by designing an innovative transmit antenna structure that delivers power efficiency regardless of orientation of the two antennas.

The new design serves additionally to focus the radio waves precisely at the point inside the body where the device rests on the surface of the heart, increasing the electric field where it is most needed, but canceling it elsewhere. This helps reduce tissue heating to levels well within the IEEE standards.

This research was made possible by funding from the C2S2 Focus Center, one of six research centers funded under the Focus Center Research Program (FCRP), a Semiconductor Research Corporation entity. Lisa Chen also contributed to this study.

Wireless Power Beamed Straight to Your Heart

How many pacemakers can fit on the head of a pin? Just one. But that's pretty impressive if you think about it.

At Stanford University, a team of researchers has built a tiny, implantable cardiac device that measured less than a millimeter in radius. This proof-of-concept device (which didn't actually set the pace for the contraction of living heart muscles) could be so small because it didn't require batteries—instead, it was powered by radio waves transmitted from outside the body.

Lead researcher Ada Poon, an assistant professor of electrical engineering at Stanford, thinks that wireless power transfer could lead to smaller and more precise implantable medical devices, as well as swallow-able devices. For cardiac devices, wireless power could offer big improvements over pacemakers powered by bulky batteries that need to be replaced periodically via surgery. 

Poon's device, described in a paper published in the journal Applied Physics Letters, has an external transmitter that sends radio waves to a coil inside the body, creating enough current to power the tiny implant.

Her big advance was in figuring out what frequency of radio waves to use. Previously, researchers thought that only low-frequency radio waves could travel far enough through human tissue to power an implanted device, but these low-frequency waves required large, impractical coils. Poon's team discovered that high-frequency radio waves, which require only a very small coil, could travel much deeper into the body than anyone realized. The image above shows power delivery to a human heart via low-frequency (left) and high-frequency (right) transmitters. 

Poon's been a busy researcher. We last covered her work in February, when she unveiled a tiny chip that could, theoretically, be propelled and steered through the human body using external magnetic fields. Poon said that chip was suitable for the human digestive tract and larger blood vessels, and could lead to devices for drug delivery and diagnostic imaging. 

Teeny Tiny Pacemaker Fits Inside the Heart

A tiny pacemaker that doesn't need wires to stimulate the heart has been approved for sale in the European Union. It's the world's first wireless pacemaker to hit the market. This device, which is about the size and shape of a AAA battery, is designed to be inserted into the heart in a non-invasive procedure that would take about a half-hour. 

The device was developed by a secretive California startup called Nanostim,which was just acquired by the biomedical device company St. Jude Medical. The company will have to do more clinical trials before the device can be submitted for approval to the U.S. Food and Drug Administration. 

Today's pacemakers are already pretty small—about the size of three poker chips stacked up—but to insert one a surgeon has to cut open a patient to install the device near the heart, and then connect the wires, called leads, to provide electrical stimulation to the heart muscle. Those leads are often the source of the problem when pacemakers fail. The tiny wires can fracture or move as the heart beats continuously, and St. Jude has had several pacemakers recalled as a result of faulty leads.

The Nanostim device is put in place via a steerable catheter that's inserted into the femoral artery. The tiny pacemaker is attached to the inside of a heart chamber, where it can directly stimulate the muscle. The animation below (no audio) demonstrates the insertion procedure. 

http://www.youtube.com/watch?v=VqjMnG2wb5Q

St. Jude says the pacemaker's battery should last for 9 to 13 years, and says that the pacemaker can be removed and replaced in a similar procedure to the insertion. 

The market for such a device is large: More than 4 million people worldwide now have a pacemaker or a similar device to manage their cardiac rhythms, and 700 000 new patients receive such devices each year. http://www.youtube.com/watch?v=VqjMnG2wb5Q

Sunscreen Saves Superhero Gene

Oct. 8, 2013 — Next time your kids complain about putting on sunscreen, tell them this: Sunscreen shields a superhero gene that protects them from getting cancer.

It is widely accepted that sunscreen stops you from getting burnt but to date there has been academic debate about the effectiveness of sunscreen in preventing skin cancers.

Now QUT has undertaken a world-first human study to assess the impact of sunscreen at the molecular level.

Researchers found sunscreen provides 100 per cent protection against all three forms of skin cancer: BCC (basal cell carcinoma); SCC (squamous cell carcinoma); and malignant melanoma.

Lead researcher Dr Elke Hacker, from QUT's AusSun Research Lab, said sunscreen not only provided 100 per cent protection against the damage that can lead to skin cancer but it shielded the important p53 gene, a gene that works to prevent cancer.

"As soon as our skin becomes sun damaged, the p53 gene goes to work repairing that damage and thereby preventing skin cancer occurring.

"But over time if skin is burnt regularly the p53 gene mutates and can no longer do the job it was intended for -- it no longer repairs sun damaged skin and without this protection skin cancers are far more likely to occur."

The study, published in the Pigment Cell & Melanoma Researchjournal, looked at the impact of sunlight on human skin, both with and without sunscreen, and found no evidence of UV-induced skin damage when proper application of sunscreen (SPF30+) had been applied to exposed area.

"Melanoma is the most lethal form of skin cancer with research showing damage of melanocytes -- the pigment-producing cells of the skin -- after sun exposure plays a role in the development of skin cancer," Dr Hacker said.

Dr Hacker said the study, funded by Cancer Council Queensland, involved 57 people undergoing a series of skin biopsies to determine molecular changes to the skin before and after UV exposure and with and without sunscreen.

"Firstly we took small skin biopsies of people's unexposed skin. We then exposed two skin sites to a mild burning dose of UV light, one site was applied with sunscreen and the other was not. We again took biopsies of both sites.

"After 24 hours, we took another set of biopsies and compared the skin samples.

"What we found was that, after 24 hours where the sunscreen had been applied, there were no DNA changes to the skin and no impact on the p53 gene," she said.

Dr Hacker said this was a significant finding.

"In Australia we have strong standards around sunscreens and their ability to protect against erythema (redness of skin)," Dr Hacker said.

"But this research looks beyond the redness to determine whether UV exposure when using sunscreen causes molecular changes to the skin, as these changes have been linked to BCC, SCC and malignant melanoma.

"When there are changes in the molecular structure it can enhance skin cancer development."

Dr Hacker said the study also provided a baseline measurement of molecular responses to UV exposure, which would now be used to investigate post-sun exposure treatments, such as super sunscreens, to assist in the repair of sun damaged skin.

Dr Hacker is a member of the Institute of Health Biomedical Innovation.

Cancer Council Queensland spokesperson Katie Clift said the research reinforced the SunSmart message in Queensland -- which has the highest rates of skin cancer in the world.

"It's imperative that all Queenslanders adopt SunSmart habits every day that they're out and about in the Sunshine State, no matter the season," Ms Clift said.

"Cancer Council Queensland recommends using SPF30 or above broad-spectrum, water-resistant sunscreen, and reapplying sunscreen every two hours.

"Applying sunscreen correctly is important. Adults should apply more than half a teaspoon of sunscreen to each arm and the face, neck and ears -- and just over one teaspoon to each leg, and front and back of the torso.

"It's also important to complement sunscreen with sun protective clothing, a broad-brimmed hat, to seek shade and slide on wraparound sunglasses for best protection."

DNA microarray

A DNA microarray (also commonly known as gene chip, DNA chip, or biochip) is a collection of microscopic DNA spots attached to a solid surface.

Scientists use DNA microarrays to measure the expression levels of large numbers of genes simultaneously or to genotype multiple regions of a genome.

For more information about the topic DNA microarray, read the full article at Wikipedia.org, or see the following related articles:

Protein microarray

A protein microarray is a piece of glass on which different molecules of protein have been affixed at separate locations in an ordered manner thus forming a microscopic array.

These are used to identify protein-protein interactions, to identify the substrates of protein kinases, or to identify the targets of biologically active small molecules.

For more information about the topic Protein microarray, read the full article at Wikipedia.org, or see the following related articles: