Posts tagged implants
Articles and news from the latest research reports.
(Image caption: A blue light shines through a clear implantable medical sensor onto a brain model. See-through sensors, which have been developed by a team of UW-Madison engineers, should help neural researchers better view brain activity. Credit: Justin Williams research group)
See-through sensors open new window into the brain
Developing invisible implantable medical sensor arrays, a team of University of Wisconsin-Madison engineers has overcome a major technological hurdle in researchers’ efforts to understand the brain.
The team described its technology, which has applications in fields ranging from neuroscience to cardiac care and even contact lenses, in the Oct. 20 issue of the online journal Nature Communications.
Neural researchers study, monitor or stimulate the brain using imaging techniques in conjunction with implantable sensors that allow them to continuously capture and associate fleeting brain signals with the brain activity they can see. However, it’s difficult to see brain activity when there are sensors blocking the view.
“One of the holy grails of neural implant technology is that we’d really like to have an implant device that doesn’t interfere with any of the traditional imaging diagnostics,” says Justin Williams, a professor of biomedical engineering and neurological surgery at UW-Madison. “A traditional implant looks like a square of dots, and you can’t see anything under it. We wanted to make a transparent electronic device.”
The researchers chose graphene, a material gaining wider use in everything from solar cells to electronics, because of its versatility and biocompatibility. And in fact, they can make their sensors incredibly flexible and transparent because the electronic circuit elements are only 4 atoms thick—an astounding thinness made possible by graphene’s excellent conductive properties. “It’s got to be very thin and robust to survive in the body,” says Zhenqiang (Jack) Ma, a professor of electrical and computer engineering at UW-Madison. “It is soft and flexible, and a good tradeoff between transparency, strength and conductivity.”
Drawing on his expertise in developing revolutionary flexible electronics, he, Williams and their students designed and fabricated the microelectrode arrays, which — unlike existing devices — work in tandem with a range of imaging technologies. “Other implantable microdevices might be transparent at one wavelength, but not at others, or they lose their properties,” says Ma. “Our devices are transparent across a large spectrum — all the way from ultraviolet to deep infrared.”
The transparent sensors could be a boon to neuromodulation therapies, which physicians increasingly are using to control symptoms, restore function, and relieve pain in patients with diseases or disorders such as hypertension, epilepsy, Parkinson’s disease, or others, says Kip Ludwig, a program director for the National Institutes of Health neural engineering research efforts. “Despite remarkable improvements seen in neuromodulation clinical trials for such diseases, our understanding of how these therapies work — and therefore our ability to improve existing or identify new therapies — is rudimentary.”
Currently, he says, researchers are limited in their ability to directly observe how the body generates electrical signals, as well as how it reacts to externally generated electrical signals. “Clear electrodes in combination with recent technological advances in optogenetics and optical voltage probes will enable researchers to isolate those biological mechanisms. This fundamental knowledge could be catalytic in dramatically improving existing neuromodulation therapies and identifying new therapies.”
The advance aligns with bold goals set forth in President Barack Obama’s BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative. Obama announced the initiative in April 2013 as an effort to spur innovations that can revolutionize understanding of the brain and unlock ways to prevent, treat or cure such disorders as Alzheimer’s and Parkinson’s disease, post-traumatic stress disorder, epilepsy, traumatic brain injury, and others.
The UW-Madison researchers developed the technology with funding from the Reliable Neural-Interface Technology program at the Defense Advanced Research Projects Agency.
While the researchers centered their efforts on neural research, they already have started to explore other medical device applications. For example, working with researchers at the University of Illinois-Chicago, they prototyped a contact lens instrumented with dozens of invisible sensors to detect injury to the retina; the UIC team is exploring applications such as early diagnosis of glaucoma.
Chinese Doctors Use 3D-Printing in Pioneering Surgery to Replace Half of Man’s Skull
Surgeons at Xijing Hospital in Xi’an, Shaanxi province in Northwest China are using 3D-printing in a pioneering surgery to help rebuild the skull of a man who suffered brain damage in a construction accident.
Hu, a 46-year-old farmer, was overseeing construction to expand his home in Zhouzhi county last October when he was hit by a pile of wood and fell down three storeys.
Although he survived the fall, the left side of his skull was severely crushed and the shattered bone fragments needed to be removed, which has led to a depression of one side of his head.
Due to his injuries, Hu cannot see well out of his left eye, experiences double vision (diplopia) and is also unable to speak and write.
Making artificial vision look more natural
In laboratory tests, researchers have used electrical stimulation of retinal cells to produce the same patterns of activity that occur when the retina sees a moving object. Although more work remains, this is a step toward restoring natural, high-fidelity vision to blind people, the researchers say. The work was funded in part by the National Institutes of Health.
(Image caption: Chichilnisky and colleagues used an electrode array to record activity from retinal ganglion cells (yellow and blue) and feed it back to them, reproducing the cells’ responses to visual stimulation. Credit: E.J. Chichilnisky, Stanford.)
Just 20 years ago, bionic vision was more a science fiction cliché than a realistic medical goal. But in the past few years, the first artificial vision technology has come on the market in the United States and Western Europe, allowing people who’ve been blinded by retinitis pigmentosa to regain some of their sight. While remarkable, the technology has its limits. It has enabled people to navigate through a door and even read headline-sized letters, but not to drive, jog down the street, or see a loved one’s face.
A team based at Stanford University in California is working to improve the technology by targeting specific cells in the retina—the neural tissue at the back of the eye that converts light into electrical activity.
"We’ve found that we can reproduce natural patterns of activity in the retina with exquisite precision," said E.J. Chichilnisky, Ph.D., a professor of neurosurgery at Stanford’s School of Medicine and Hansen Experimental Physics Laboratory. The study was published in Neuron, and was funded in part by NIH’s National Eye Institute (NEI) and National Institute of Biomedical Imaging and Bioengineering (NIBIB).
The retina contains several cell layers. The first layer contains photoreceptor cells, which detect light and convert it into electrical signals. Retinitis pigmentosa and several other blinding diseases are caused by a loss of these cells. The strategy behind many bionic retinas, or retinal prosthetics, is to bypass the need for photoreceptors and stimulate the retinal ganglion cell layer, the last stop in the retina before visual signals are sent to the brain.
Several types of retinal prostheses are under development. The Argus II, which was developed by Second Sight Therapeutics with more than $25 million in support from NEI, is the best known of these devices. In the United States, it was approved for treating retinitis pigmentosa in 2013, and it’s now available at a limited number of medical centers throughout the country. It consists of a camera, mounted on a pair of goggles, which transmits wireless signals to a grid of electrodes implanted on the retina. The electrodes stimulate retinal ganglion cells and give the person a rough sense of what the camera sees, including changes in light and contrast, edges, and rough shapes.
"It’s very exciting for someone who may not have seen anything for 20-30 years. It’s a big deal. On the other hand, it’s a long way from natural vision," said Dr. Chichilnisky, who was not involved in development of the Argus II.
Current technology does not have enough specificity or precision to reproduce natural vision, he said. Although much of visual processing occurs within the brain, some processing is accomplished by retinal ganglion cells. There are 1 to 1.5 million retinal ganglion cells inside the retina, in at least 20 varieties. Natural vision—including the ability to see details in shape, color, depth and motion—requires activating the right cells at the right time.
The new study shows that patterned electrical stimulation can do just that in isolated retinal tissue. The lead author was Lauren Jepson, Ph.D., who was a postdoctoral fellow in Dr. Chichilnisky’s former lab at the Salk Institute in La Jolla, California. The pair collaborated with researchers at the University of California, San Diego, the Santa Cruz Institute for Particle Physics, and the AGH University of Science and Technology in Krakow, Poland.
They focused their efforts on a type of retinal ganglion cell called parasol cells. These cells are known to be important for detecting movement, and its direction and speed, within a visual scene. When a moving object passes through visual space, the cells are activated in waves across the retina.
The researchers placed patches of retina on a 61-electrode grid. Then they sent out pulses at each of the electrodes and listened for cells to respond, almost like sonar. This enabled them to identify parasol cells, which have distinct responses from other retinal ganglion cells. It also established the amount of stimulation required to activate each of the cells. Next, the researchers recorded the cells’ responses to a simple moving image—a white bar passing over a gray background. Finally, they electrically stimulated the cells in this same pattern, at the required strengths. They were able to reproduce the same waves of parasol cell activity that they observed with the moving image.
"There is a long way to go between these results and making a device that produces meaningful, patterned activity over a large region of the retina in a human patient," Dr. Chichilnisky said. "But if we can handle the many technical hurdles ahead, we may be able to speak to the nervous system in its own language, and precisely reproduce its normal function."
Such advances could help make artificial vision more natural, and could be applied to other types of prosthetic devices, too, such as those being studied to help paralyzed individuals regain movement. NEI supports many other projects geared toward retinal prosthetics.
"Retinal prosthetics hold great promise, but this research is a marathon, not a sprint," said Thomas Greenwell, Ph.D., a program director in retinal neuroscience at NEI. "This important study helps illustrate the challenges of restoring high-quality vision, one group’s progress toward that goal, and the continued need to for the entire field to keep innovating."
(Source: nei.nih.gov)
Εngineer invents safe way to transfer energy to medical chips in the body
A Stanford electrical engineer has invented a way to wirelessly transfer power deep inside the body, and then use this power to run tiny electronic medical gadgets such as pacemakers, nerve stimulators or new sensors and devices yet to be developed.
The discoveries reported May 19 in the Proceedings of the National Academy of Sciences culminate years of efforts by Ada Poon, assistant professor of electrical engineering, to eliminate the bulky batteries and clumsy recharging systems that prevent medical devices from being more widely used.
The technology could provide a path toward a new type of medicine that allows physicians to treat diseases with electronics rather than drugs.
"We need to make these devices as small as possible to more easily implant them deep in the body and create new ways to treat illness and alleviate pain," said Poon.
Poon’s team built an electronic device smaller than a grain of rice that acts as a pacemaker. It can be powered or recharged wirelessly by holding a power source about the size of a credit card above the device, outside the body.
Infants Benefit from Implants with More Frequency Sounds
A new study from a UT Dallas researcher demonstrates the importance of considering developmental differences when creating programs for cochlear implants in infants.
Dr. Andrea Warner-Czyz, assistant professor in the School of Behavioral and Brain Sciences, recently published the research in the Journal of the Acoustical Society of America.
“This is the first study to show that infants process degraded speech that simulates a cochlear implant differently than older children and adults, which begs for new signal processing strategies to optimize the sound delivered to the cochlear implant for these young infants,” Warner-Czyz said.
Cochlear implants, which are surgically placed in the inner ear, provide the ability to hear for some people with severe to profound hearing loss. Because of technological and biological limitations, people with cochlear implants hear differently than those with normal hearing.
Think of a piano, which typically has 88 keys with each representing a note. The technology in a cochlear implant can’t play every key, but instead breaks them into groups, or channels. For example, a cochlear implant with 22 channels would put four notes into each group. If any keys within a group are played, all four notes are activated. Although the general frequency can be heard, the fine detail of the individual notes is lost.
Two of the major components necessary for understanding speech are the rhythm and the frequencies of the sound. Timing remains fairly accurate in cochlear implants, but some frequencies disappear as they are grouped.
More than eight or nine channels do not necessarily improve the hearing of speech in adults. This study is one of the first to examine how this signal degradation affects hearing speech in infants.
Infants pay greater attention to new sounds, so researchers compared how long a group of 6-month-olds focused on a speech sound they were familiarized with —“tea”’ — to a new speech sound, “ta.”
The infants spent more time paying attention to “ta,” demonstrating they could hear the difference between the two. Researchers repeated the experiment with speech sounds that were altered to sound as if they had been processed by a 16- or 32-channel cochlear implant.
The infants responded to the sounds that imitated a 32-channel implant the same as when they heard the normal sounds. But the infants did not show a difference with the sounds that imitated a 16-channel implant.
“These results suggest that 6-month-old infants need less distortion and more frequency information than older children and adults to discriminate speech,” Warner-Czyz said. “Infants are not just little versions of children or adults. They do not have the experience with listening or language to fill in the gaps, so they need more complete speech information to maximize their communication outcomes.”
Clinicians need to consider these developmental differences when working with very young cochlear implant recipients, Warner-Czyz said.
FDA approves first-of-a-kind sleep apnea implant
Sleep-deprived Americans have a new option to address hard-to-treat nighttime breathing problems: a first-of-kind device that keeps airways open by zapping them with an electrical current.
The Food and Drug Administration approved the pacemaker-like device from Inspire Medical Systems for sleep apnea patients who have trouble with the current standard of care: machines that blow air through a bedtime mask.
Coming soon: a brain implant to restore memory
In the next few months, highly secretive US military researchers say they will unveil new advances toward developing a brain implant that could one day restore a wounded soldier’s memory.
The Defense Advanced Research Projects Agency (DARPA) is forging ahead with a four-year plan to build a sophisticated memory stimulator, as part of President Barack Obama’s $100 million initiative to better understand the human brain.
The science has never been done before, and raises ethical questions about whether the human mind should be manipulated in the name of staving off war injuries or managing the aging brain.
Surgical implants are widely used in modern medicine but their effectiveness is often compromised by how our bodies react to them. Now, scientists at the University of Cambridge have discovered that implant stiffness is a major cause of this so-called foreign body reaction.
This is the first time that stiffness of implant materials has been shown to be involved in foreign body reactions. The findings – published in the journal Biomaterials – could lead to major improvements in surgical implants and the quality of life of patients whose lives depend on them.
Foreign bodies often trigger a process that begins with inflammation and ends with the foreign body being encapsulated with scar tissue. When this happens after an accident or injury, the process is usually vital to healing, but when the same occurs around, for example, electrodes implanted in the brain to alleviate tremor in Parkinson’s disease, it may be problematic.
Despite decades of research, the process remains poorly understood as neither the materials from which these implants are made, nor their electrical properties, can explain what triggers inflammation.
Instead of looking for classical biological causes, a group of Cambridge physicists, engineers, chemists, clinical scientists and biologists decided to take a different tack and examine the impact of an implant’s stiffness on the inflammatory process.
According to Dr Kristian Franze, one of the authors of the study: “Electrodes that are implanted in the brain, for example, should be chemically inert, and these foreign body reactions occur whether or not these electrodes are switched on, so it’s not the electrical signalling.
“We thought that an obvious difference between electrodes and brain tissue is stiffness. Brain tissue is as soft as cream cheese, it is one of the softest tissues in the body, and electrodes are orders of magnitude stiffer.”
To test their hypothesis that mechanical signals trigger inflammation, the team cultured brain cells on two different substrates. The substrates were chemically identical but one was as soft as brain tissue and the other two orders of magnitude stiffer, akin to the stiffness of muscle tissue.
When they examined the cells, they found major differences in their shape. “The cells grown on the stiffer substrate were very flat, whereas those grown on the soft substrate looked much more like cells you find in the brain,” he explained.
To confirm the findings they did genetic and other tests, which revealed that many of the inflammatory genes and proteins known to be involved in foreign body reactions had been upregulated on stiff surfaces.
The team then implanted a tiny foreign body into rats’ brains. The implant was made of a single material but one side was as soft as brain tissue and the other as stiff as muscle. They found much greater foreign body reaction around the stiff part of the implant.
“This strongly indicates that stiffness of a material may trigger foreign body reactions. It does not mean there aren’t other triggers, but stiffness definitely contributes and this is something new that hasn’t been known before,” he said.
The findings could have major implications for the design of implants used in the brain and other parts of the body.
“While it may eventually be possible to make implants out of new, much softer materials, our results suggest that in the short term, simply coating existing implants with materials that match the stiffness of the tissue they are being implanted into will help reduce foreign body reactions,” said Dr Franze.
Brain Implants Hold Promise Restoring Combat Memory Loss
The Pentagon is exploring the development of implantable probes that may one day help reverse some memory loss caused by brain injury.
The goal of the project, still in early stages, is to treat some of the more than 280,000 troops who have suffered brain injuries since 2000, including in combat in Iraq and Afghanistan.
The Defense Advanced Research Projects Agency is focused on wounded veterans, though some research may benefit others such as seniors with dementia or athletes with brain injuries, said Geoff Ling, a physician and deputy director of Darpa’s Defense Sciences office. It’s still far from certain that such work will result in an anti-memory-loss device. Still, word of the project is creating excitement after more than a decade of failed attempts to develop drugs to treat brain injury and memory loss.
“The way human memory works is one of the great unsolved mysteries,” said Andres Lozano, chairman of neurosurgery at the University of Toronto. “This has tremendous value from a basic science aspect. It may have huge implications for patients with disorders affecting memory, including those with dementia and Alzheimer’s disease.”
At least 1.7 million people in the U.S. are diagnosed with memory loss each year, costing the nation’s economy more than $76 billion annually, according to the most recent federal health data. The Department of Veterans Affairs estimates it will spend $4.2 billion to care for former troops with brain injuries between fiscal 2013 and 2022.
Accidentally cut your ear off? Just 3D print a new one
It’s way too late for Vincent van Gogh, but cutting off your ear is a much less impressive gesture now you can get a new one printed.
This week, researchers at Hangzhou Dianzi University in China unveiled their Regenovo 3D printer. Unlike more familiar 3D printers, which work with plastic or metal dust, Regenovo prints living tissue – such as these little ears.
The Hangzhou team aren’t the only ones 3D-printing spare parts for people. Earlier this year, a team at Cornell University in Ithaca, New York, also demonstrated an ear printer, and Organovo in San Diego, California, are on the way to building fresh human livers.
Meanwhile a team at Heriot-Watt University in Edinburgh, UK, has turned human embryonic stem cells into 3D-printer ink. Things are more advanced when it comes to making new bones, as a woman with a 3D-printed titanium jawbone could tell you.